Vidyamandir Classes Biomolecules & Polymers Biomolecules & Polymers CARBOHYDRATES Section - 1 Defini ns In olden times, carbohydrates were defined as hydrates of carbon, represented by general formula C,(H,0),, i.e.,hydrogen and oxygen existed in the ratio of 2:1 asin water molecule, ¢.g., Glucose [C,(H,0),], Sucrose [C,(H,) tc, However, a number of compounds such as Rhamnose [C,H,,0,], 2-Deoxyribase [C,H)0g] are known, which are carbohydrates by their chemical behaviour but cannot be represented as hydrates of carbon. Its also important to note that all compounds possessing the formula C, (11,0), ate not necessarily carbohydrates eg., Formaldehyde, HCHO [C(H,0), Acetic acid [C,(H,0),], et. Now, carbohydrates are defined as polyhysiroxy sldehystes or polyhysroxy ketones or substances which give these on hydrolysis and contain atleast one chiral ca"bon ator, Itmay be noted here that aldehydic and ketonic groups in carbohydrates ‘are not present as such but usually exist in combination with one of the hydroxyl groups of the molecule in the form of hhemiacetals. Classification of Carbohydrates : (On the basis of hydrolysis, carbohydrates are divided into three major classes. These arc ()) Monosaccharides : These are polyhydroxy aldehydes or ketones which cannot be decomposed by hydrolysis to give simpler carbohydrates. With few exceptions, they have general formuls, C,H,,0,. (lucose is the mostimportant ‘member in their class. These are crystalline in nature, readily dissolve in water and are sweet in taste (sugars). C4Hh,0, + 1,0 2s wo reaction Glucose or Fructose ((i) Olfgosaccharides : The oligosaccharides are carbohydrates which yield a definite number (2-10) of monosaccharides molecules on hydrolysis The oligosaccharides containing two monosaccharide units are called disaccharides, and those containing three, four ot five units are termed as trisaccharides, tetrasaccharides or pentasaccharides respectively, e.g., Suctose and Maliose, both disaccharides, yield two molecules of monosaccharides on hydrolysis, CyH20,,+1,0 5 c,,0, + Ct, CuO), +0 _#, 2c 9, Maltose Glucose ids three monosaccharide units Rafinose, a trisaccharide, with molecular formula CyqHy,0y,. y Self Stuy Cours or THEE with Online Suppor 1Biomolecules & Polymers 8 Cylly.O 5+ 2H0 > CyB g + C0, + Col, Raffinose Glucose Fructose Galactose Majority of oligosaccharides are colourless crystalline solids, soluble in water and sweet in taste. {li Polysaccharides : The polysaccharides ae carbohydrates ofhigh molecular weight which yield many monosaccharide molecules on hydrolysis. The general formula of polysaccharides is (CqHyo0,),. Storch cellulose, alycogen, ete, are the examples of polysaccharides. (CH), +0 H,0 5 264.0, starch Glucose Polysaccharides are colourless, amorphous solids having no taste and insoluble in cold water. These are also called non-sugars. Sugars and Non-Sugars : All the mono and disaccharides are commonly know as sugar as they possess a sweet taste, while, higher carbohydeates then disaccharides are called non-sugars. Reducing and Non-Reducing Carbohydrates : ‘Carbohydrates that reduce Fehling’s solution or Tollen's reagent are termed reducing carbohydrates while the others are non-reducing carbohydrates, “AI monosaccharides and most of the disaccharides except sucrose are reducing carbohydrates.” Monosaccharide : ‘The monosaccharides are the bass of carbohydrate chemistry, since all carbohydrates are either monosacchatides or are converted into monosaccharides on hydcolysis. The monosaccharides ate either polyhydroxy aldehydes or ketones. 0 i These are, therefore, classified into two main groups, viz., \idoses (containing ~C-If group), and Ketoses ° 1 (containing —C— group) The aldoses and ketoses are further divided into sub-groups, on the basis ofthe numberof carbon atoms in their molecules 48 ioses, etroses, etc. To classify a monosaccharide completely its necessary to specify both, the type of the carbonyl 10up and the number of carbon atom present inthe molecule, Thus monosaccharides ate generally eferredto as aldotioses, ketotrioses,aldotetroses, ketotetroses, otc 2 CETTE, set sesy course for ie with ontine SupportRie ue nee ‘The aldoses and ketoses may be represented by the following general formulas Biomolecules & Polymers cHO CH,OH | I (cHorn, re CH,OH (CHOR),, CH,OH Aldoses Ketoses (n=1,2,3,4,5) — (n=0,2,2,3,4,5) Except ketotriose (dinydroxy acetone), all aldoses and ketoses contain asymmetric carbon atoms and are optically stv, ‘The enantiomers which rotate the plane of plane polatised light to the right are written as (4), the others which rotate to the left are written as (-). The (+) and (-) signs only specify the direction of rotation of the plane polarised light by a particular enantiomer but it does not give any indication of the arrangement of OH and H around the asymmetric carbon atom. Maximum number of optical isomers is 2° where nis the number of asymmetric carbon atoms in the molecule. ‘Note Aldohexoses exist in sixteen optically active forms, ic., Glucose, Mannose, Galactose, Allose, Alttose, Idose, Gulose and ‘Talose and esch existing in two forms, Glyceraldehyde contains one asymmetric carbon atom and can thus oo ono est in wo optically active forms, called the Dform(-OH groupon 4 oH Ho H the ripbi side of lowest asymmetric carbon) and the L-form (OH group on the ese of lowest asymmetric carbon, CH,OH CH,OH D- Giyceraldehyde L-Glyceraldehyde ‘The sugars having same configuration as of D-Glyceraldehyde ate known as D-supis while that of L-Glyeeraldehyde as |L-sagars. Glucose, an aldose, and Fructose, aketose, are most important monosaccharides. The natural form of Glucose and Fructose are D-forms. co exon 46-08 é-o no-0-1 no-G-1 u-6-0n u-¢-on toG OW | peoaigntin —o 1860 dxyon exon ot-cucse Ot rues ‘Note: Epimers: A pair of diastereomers that differ only in the configuration about a single carbon atom are said to be emer, e.g. D(4)-Glucose is epimeric with D(1}-Mannose and D(1)-Galactose. Sel study Course for TEE wih one Support 3Biomolecules & Polymers ne a0 dio bo nt-on ie 01 OE wo-G-w wo-G-mWo-G- a W-G-noW-e-1l0—H-t-n0 énon dion u,on otcaecose —O1-Suese oi anese Glucose [C,H,,0,] (Aldo-Hexose) : ‘As glucose occurs in nature asthe optically active dexto-rotatory isomer, it is known as \ox\sos. Is also called a8 p:3pe ‘gat. Ta combined form, it occurs in eane sugar, polysaccharides such as starch and cellulose, Itis sls present in Various lycosides like Amygdalin and Salicin, Preparation : 4. Laboratory Method = Is prepared in laboratory by acid hydrolysis of cane sugar in presence of alcohol w CuO, HO > C4b.05 + C,H, 0, cane sugar Glucose Fructose (Sucrose) 2, Manufacture :Itis obtained on a large scale by the hydrolysis of starch (com starch or potato starch) with dilute sulphuric acid or HCL we (Chg), +1L0 SP BC Hh0) Starch 2K Ginote Property: 1. Itis acolourless erystalline solid, readily soluble in water, with melting point as 146°C. From aqueous solution, it separates out asa crystalline monohydrate (ClH,;0,,H,0) which melts at 86°C. Itis sparingly soluble in alcohol but insoluble in ether. It shows characteristic of hydroxyl and aldehydic group, Alcoholic Reaction: (Reactions due to -OH group) : (0 Reaction with acid chloride and acid anhydrides : CHO cHO ZnCl, | (CHOM,+5CH,CocL =—25 — (CHOOCCH,), +5 HCL | CH,OH cH,ooccH, Glucose Glucose penta-acetate This shows that a molecules of glucose contains 5~OH groups, 4 ETIFUNEEEEIIIIIIA, ser stcty course for ts with onine SupportVidyamandir Classes Biomolecules & Polymers Reaction with PCI CHO CHO (CHOW), + 5PCls > GeV. SPOCK. st HOH CHC Glucose Penta-chloroglucase (il) Reaction with metallic hydroxides : Glucose behaves as a weak acid, Itreacts with certain metallic hydroxides like Ca(OH, Ba(OH), ete. to form metallic glucosates, which are soluble in water. CHO, OH +HO~Ca~ OH ——> C,H,,0,-0-Ca-OH-H,0 Calcium Glucosate (iv) Formation of Glycosices : When treated with methyl alcohol in presence of dry HCI gas, glucose yields mono- ‘methyl ether which is actually a mixture of ~ and B-forms indicating that one of the -OH group is different from, others, Cals" O1+1- 0 ~ CH, E+ 4,0, OCH, + H,0 “a and B-Methy/ glucoside \< NC I | cu cH B+ Methyl glucoside 6. Reactions of carbonyl Group (Aldehydic group) (Reduction CHLOH CHOW Nowe (CHOR.+2 1H] “Eg? (FHOM, CHO cH,oH Sorbitol On prolonged heating with concentrated HI snd red phosphorus at 110°C, glucose forms a mixture of 2-iodohexane and n-hexane. Oxidation = Glucose undergoes oxidation with various oxidising agents readily, Le, glucose acts as a seducing agent. Sel study Course for TEE with Onine Support 5Biomolecules & Polymers ‘With Febling’s solution, a voc puccipitale of euprous oxide is formed. {a) Reaction with Fehling’s soluti CH,OH cH,oH on com, S225 Com, + C40-+1,0 | | (Red pot.) cHo COONa Sodium salt of ‘luconic Acid {b) Reaction with Tollen’s Reagent : With ammonical AgNO,, ase: misvor or black precipitate is formed. cro cu,0H Hom, + NO, a GHOM, ~ aL M ae éu0 CooNt, Note: Fructose being an @-hydronyl Ketone also gives postive result with Tolen's Reagent and Fehling'ssolwion, Hence irate i alo aredveing sug. cu,0H Hyon i . i co | BS co I I uo, com Sey 0 Gio, Gio, i i dion buon Fructose (c)_ Reaction with Bromine Water : CH,OH CHO Bryil,o cots fo] —— > (CHOH), cHO COOH Gluconiec acid (q) Reaction with Nitric acl: Niue acid or any other strong oxidising agent converts glucose to saccharic acid ‘or slucaric acid containing same number of carbon atoms. CHOW ‘coon HNO) (CHOM, + 310) > (CHoM, + H,0 cHo coon Saccharic acid ‘ Sel study Course for ITEE with online SupportVidyamandir Classes Biomolecules & Polymers (ii) Reaction with HEN : CHLOH + HCN ——> (CHO), HO-CH-CN Glucose cyanohydrin (iv) Reaction with Hydroxylamine : HOH CH,OH (CHO), + NH,OH > (CHOK), + H,0 duo bu=now Glucose oxime (v) Reaction with phenylhydrazine (Fischer's mechanism) : With limited amounts of phenylhydrazine, glucose forms a phenylhyrezone. fist CH,OH—(CHOH), ~CHO 2) CH,OH(CHOH), CH= NNHCgHs Glucose Glucosephenylhydrazone With an excess of phenylhydrazine, the reaction is some what more complicated. Three moles of phenylhydrazine are consumed for each mole of the glucose to form slvicos:vone, a yellow crystalline solid containing two phenylhydrazine residues per molecule, SCH NHN CH,0H(CHOH), cHoHCHO Sos Glucose CH,OH (CHOH), C-CH =NNHCgHs twas suggested that the second molecale of phenylhydrazine 0slise the hydroxyl group adjacent tothe aldehyde ‘group, followed by the reaction of the carbonyl group so generated withthe third molecule of phenylhydrazine, (+ IMPE is intramolecular proton exchange) cHo CH= NHC, GH NE en Lo austin * wee, [0 DENHC AH, nc on SE neon Z C01 iglogentond (cHom, (OH), (chon, | \ 1 cit cron cH,on cuon | Glucose Glucose phenylhydrazone CH=NNHCgs cH=NH cH=NH I Hs NHNH; i Hs NHNH, i CHNNHCH, SHSM CNHs SEEMINE CL c a) c mo (com, (com, (con), 1 1 1 cH,on cH,on cH,on Glucosazone Imino ketone setfstuy Course for DEE wih Once Support Tr rEy —;Biomolecules & Polymers RUC GucUriu oer) (vi) Action of Alkalies-Lobry de Bruyn van Ekenstein Rearrangement : onc ca-on H-C-OH ,2-tuaiation, 0! (cuior, © (cior, CH,oH cH,on D(+}-Glucose a Enedio! cuo cHo cH,oH H-C-on Ho-C-H c-0 | | (CHOH), (CHOH), (CHOH), I | cH,oH cuon cH,oH (+) -Glucose 0 ()-Mannose D(-Frueose (vii) Reaction with HIO, : Being an a-hydroxy carbonyl compound containing a number of vie-hydroxyl groups, glucose undergoes oxidative cleavage with specific oxidising agents like periodic acid (Malaprade reagent) and lead tetra-acetste. CH,OH(CHOH),CHO + sHI0, ——> HCHO + SHCOOH +sHI0, Periodic sid Formaldehyde Formic odie acid acid ‘This reaction has a great potential for application to structure determination of glycols, and it has been extensively used in carbohydrate research for structure determination. ‘Note : Monosaccharides exist as -yclic structures in the form of bemiacetais. Thus glucose forms a six membered ring of five carbon atoms and one oxygen atom (Pyraniose jor) ‘Anomers* Inthe eyele structures of monosaccharides, °, ~0H of glucose combines with © alichyslic group. As axesult (©, becomes cil or asymmetric and thus has two possible arrangements of -Hand—OH groups around it, i.e, -OH group aay be on ili side at, (6-D-Glucose) or onthe lt se of C,()-D-Ciucoss). Such pair of stereoisomers which differ in configuration only around C, are called snomers. C, carbon atom is called someric carbon. H ‘oe OH HO-ChH non nt on no% nO = wn ° n_on nd_on Hot H2t-6-n He “zon txyon ‘txon ohne ocune potciune ihhcucpranan (coencan pot Leucnranoe Fischer projection formula of eyclic form and open chair form. EI, sete study course for rrs£€ with online SupportWiens Biomolecules & Polymers Haworth projection formula of cyclic form ScHOH HA " Ho NOH Won HOH e-D-Glucose po-chucose a-D(+}-Glucopyranose [-D{+}-Glucopyranose: Mutarotation » The ciange in specific sotstion of an optically active compound in solution with time to an equilibrium value is called as mutarotation, e.g,, when either of the stereoisomerie forms of glucose, ie., o-D-glucose and B-D-glucose, is dissolved in water and allowed to stand, it gets converted into equilibrium mixture through a small amount of open chain form. e-D-Giucose, == Openchainform == —_B-D-Glucose (36%) (0.02%) (4%) [ay =+ 112° [oly =+527° a], = 419° Fructose [C,H,,0,] (Keto-Hexose) : Fructose is an important ketohexose, It is obtained along with glucose by the hydrolysis of disaccharide, suerose Open Chain Structure of Fructose : con cron c-0 onc HO: H H OH H OH HO H "1 on 110 Wn CHOW CHLOH DG HFructose L(svFructose > Fructose also undergoes cyclisation process by hemni-ketal formation to result in a five-membered ring like (ur. smh -ou I I rv 2 2C-0 HOH,C~C-OH on 7c—CH,0H no—}— no——n Ho—}— 4] \ 4 ° | ° u—t—on | n—l_on n—t—on u—}— on / 1 By °CH,OH “cHon ‘CH,OH aD )Frucoturanose ———O-/)Fructofranase Selfstuy Course for IEE with Onne Support TTTBiomolecules & Polymers CCUCUCUS cer Reaction of Fructose : w Reaction with Phenylhydrazine : Equimolar amounts of fructose and phenylhydrazine react to form fructose phenylhydrazone, but with excess of phenylhydrazine, fructose yields the saine os.zone as that obtained from glucose Asin the ease of glucose, formation of glucosazone from fructose can be explained as follows: cusohn cuou ncn Le CHgNENH VG me ly ts) CAN-NHCU, SS CNH NUCH, (cHom, (cHom, (CHOW), | | 1 cH,OH HOH CHOH Fructose Fructose phenylhydrazone [eu Gu NNHC C=NNHC(H Guo . caus, | caus GO NNEC Cn NH cao GNM (crow, (crow, (quot, cHon cHon cHou (i). Reaction with NH,OH : cH,OH cH,OH big men, blyon (Guo, (Gu01), 10 cH,on cu,0n Fructose oxime (il) Reaction with HCN : on non oe a be dion, vom, ‘hua baum {iv) Reaction with Acetic anhydride 10 cH,0H CHi,0re b-0 2, boo tow, HoA0y, bu,oH tui,ore Fructose Pentaacetate Self Study Course for IITJEE with Online SupportWiens Biomolecules & Polymers (v) Reaction with Red P and HI gui es ceo “ Gin, (cu01, cH rHerane cuon (vi) Oxidation by Nitric Acid On exidation with HINO,, fructose yields a mixture of acids, namely tribydroxyelutaric acid, tartaric acid and glycollic acid, Each ofthese acids contains s fewer number of carbon stoms then fructose, thereby suggesting thatthe carbonyl group in fructose is a keto group and not an aldehyde group. Hon coon coon I no, cron c=0 = + (HOM, + (HOR), | coon i i quot, coon coon ion Giycollic —Tartaricacid —Trihydroxyglutaric acid (vii) Action of Alkalies on Fructose ‘This reaction is known as Lobry de Bruyn and Alberda Van Elkenstein rearrangement or simply Elkenstein rearrangement On warming with dilute alkali fructose like glucose, gives rise to an equilibrium mixture of glucose, fructose snd mannose, The ability of fructase (a ketose) to reduce Fchling solution and Tollen’s reagent is possibly due to this initial isomerisation of fructose to glucose and mannose which are being aldoses are capable to reduce Fehling solution and Tollen’s reagent. won bos = wb bon kon don vn Sud cours er TRE WA ine Spor) TT iBiomolecules & Polymers RZC) GucUcim cere) Haworth projection formula of Fructose Just lke glucose, D (~) fructose also exists in two forms ct and B forms, which exhibit ns00'at/0». By reasoning similar to that used earlier inthe case of glucose D(-) fructose was assigned a six-membered structure or a p)sanose sing structure ‘and the a, and B-forms can be depicted as follows H H J 4 a q ° ‘cn,on H X98 anomeric carbon a 2 and a “ H o H ou on OH on CH,OH oH OH oH OH c-0(-) Fructose P-0L) Fructose Disaccharides : ‘Carbohydrates which upon hydrolysis give two molecules ofthe same or different monosaccharides are called disaccharides. ‘Their general formu is C,H,,0,,. The three most important disaccharides are sucrose, msl{ose and lactose CQHa20y +H0 4 CHt,206 + CoHy205 Sucrose frinvertase Glucose” Fructose Catto, to 5 2641205 Nolese—orMatase Gcose Ciatt,0,,411,0 + Cett05+ Celle Lactose Gucose Galactose Disaccharides may also be considered to be formed by a condensation reaction between two molecules of the same or different monosaccharides withthe elimination of a molecule of water. This reaction involves the formation ofan acetal from ‘ahemiacetal and alcohol -in which one of the monosaccharides acts asthe hemiacetal while the other acts asthe alcohol. Sucrose [C,,H,20, ScHOH Itis also called cane sugar. It is our common table sugar. Itis obtained from cane-sugar and sugarbeets. It is actually touoseunid found in all photosynthesis plants, Ho\gHH/| tis formed by condensation of one molecule of glucose OHO Shes ooge « 0. ‘and one molecule of fructose. Unlike maltose and Lactose, (rucoreune) HOHLC | it is non-reducing sugar since both glucose (C, ~ o) and L Hg Iructose (C, ~ B) are connected to each other through their cH.OH reducing centres, ono# 22 EEE, sete stucy course for rJ£e with Online SupportRie ou uC eee Biomolecules & Polymers Properties : 1. Iti colourless, edourless crystalline compound, with melting point as 185°—186°C. 2 Ihis very soluble in wate, slightly soluble in alcobol and insoluble in ether. 5. tis dextro-rotatory but does not show mutssotaton, 4. tis a non-reducing sugar as it does not seduce Febling's solution orTollen’s reagent. 5. Onhesting, slowly and eatefully, it melt and then if allowed to cool, it solidifies to pale yellow glassy mass called “Barley Sugar’. When heated at 200°C, it loses water to form brown amorphous mass called caramel. On strong heating, it chars to almost pure carbon giving smell of burt sugar. Inversion of Cane - Sugar : ‘The hyctrolysis of sucrose by boiling with HCI, produces a mixture of equal molecules of D-Glucose and D-Fructose. Ht CyHh,0,, +0 > C4,,0, + CeHt,,0, Sucrose D-Glucose D-fructose (ay =153"fay = 92° [ot]y = + 66.5° + [ollp= (455°) + (92! Taye Sugar ‘Sucrose solution is dextro-rotatory. Its specific rotation is + 66.5°. But on hydrolysis, it's solution become laevorotatery, because D-fructose has a greater specific rotation than D-glucose. Because of this, the hyidrolysis of sucrose is known as the inversion of sucrose, and the equimolecular mixture of glucose and fructose is known as invert sugar or invertose. Maltose HoH CH,OH > Ieis composed of 2 a-D-glucose units joined HA ur WAR H together by C, — ycosidic linkage. < \ OH together by C, ~C, elycose inks HONE mA, > Ieisareducing suger fee-aldehydic group can tn yy bbe produced at the C, of 2nd glucose. u w -0-Glucose e-D-Glucose Lactose : SCH,OH ScH,OH > this formed by glycosidic linkage between C, of — 10_/F W/E on B-D-galactose and C, of B-D-glucose. \on oH & Row a HN, 4 > This also reducing in nataze Hoon HO On -0- Galactose §-0- Glucose Note: > Galactose : $and4 abnormal > Mannose : 2.and3 abnormal > Sucrose: C1-C2(oeD glucose and B-D fructose) > Lactose C1-C4 (B-D galactose and B-D glucose) > Maltose : C1-Cé (oeD glucose and a-D glucose) > Amylose : Polymerof Glucose » Cellulose ; C1-C4 (Polysaccharide of B-D glucose. Self Study Course for IITJEE with Online Support 13Biomolecules & Polymers Polysaccharides : They contain a large number of monosaccharide Starcl (2) Amylose > > > visa water soluble component It constitutes about 15-20% of starch. It is a Jong unbranched chain with a-D-(+)-glucose units joined together by ©,=€, glycosidic linkage Structure of Starch TEMAS cred units joined together by glycosidic linkages. is a polymer of e.-glucose and consists of two components : (b) Amylopectin > > > tis insoluble in water. It constitutes about 80-85% of starch, It is a branched chain polymers of a-D-glucose units in which chain is formed by C, - C, glycosidic linkage whereas branching occurs by C, ~ C, glycosidic linkage Amylose and Amylopectin are both different carbohydrates of high molecular weight and formula (C,H,.0,), polysacchatide amylose is made up of long straight chains each containing about 200 or more D-glucose units join together by a 1,4-linkage. HA oH on AL HWA oH] HAL en ~n~0 \ OH H ‘0 ou H toe ou H 0” OH H/On~ 4, 4-lycoside linkage Structure of Amylose Molecular weight of amylose lies between 30,000 to 40,000, ‘The polysaccharide amylopectin consists of chains of D-Glucose units each unit joined by a glycosidic linkage to C4 of the next unit, Further investigation reveals that amylopectin is highly branched structure consists of several short chains of about 20 glucose units each, one end of each of these chains being joined through C-1 to C-6 on the next chain. chon H é ink Branch aC, cion cuon " OH H Vu Wa ms poKow uP on uog foe Hoon hoon ate A Anopectn 14 Self Study Course for IITJEE with Online SupportRich clucal Classes Biomolecules & Polymers H. Cellulose > Iisa straight chain polysacchatide composed of B-D-glucose units held together by C, ~ C, glycosidic linkage. HOH,C 0, H ° H OH HOH, oO Tt HOH,C H H oH OH Blinks ° Cellulose lil, Glycogen + Carbohydrates are stored in animal body a8 Glycogen. When Body needs glucose, enzymes break the glycogen downto glucose. Itis found in liver, muscles brain, yeast and fungi. Itis also known as animal starch because ts struct s similar to amylopectin and is rather more highly branched Analysis of Carbohydrates : The following reactions characterizes the carbohydrates as a class of organic compounds () Molisch Test : For this test 2,3 drops of « 1% alcoholic solution of c-naphthol is added to a 5% aqueous solution of the organic compound (suspected to be a carbohydrate), followed by a careful addition of about 2 ml of cone, sulphuric acid, ‘Formation of a deep violet rine atthe junction of the liquids indicates the presence of a carbohydrate”. The violet ring formed in this test is believed to be due to the formation of an unstable condensation product of ‘o-naphthol with furfural formed presumably by the cyclodehydration of the carbohydrate with the acid i) A n of Heat When heated strongly in a dry test tube, carbohydrates generally char and ive out the smell of burnt sugar. Action of cone. H,50,: ‘When warmed with conc. H,SO, carbohydrates show immediate blackening. Ifa carbohydrate has been indicated by the above test, the following tests are used to distinguish reducing earbohy- rates from non-reducing carbohydrates, only reducing carbolydrates respond to these tests, () Febling test Tollen’s test ‘These test are already described in an earlier chapter of Aldehyde and Ketones. ST 1sBiomolecules & Polymers CO GuGUn ceed AMINO ACIDS & PEPTIDES Section - 2 Amino Acids : Amino acids are the bifunctional compounds that contain both a carboxyl group, ~COOH, as well as an amine group NH, . They are derivatives of carboxylic avids in which one hydrogen atom of carbon chain is substituted by amino group. They are classified as acidic, basic or neutral according to the number of amino and carboxyl groups in @ molecule. 4L.Acidlic Armino acids : These contain a second carboxyl group or a potential carboxyl group inthe form of carboxamide, COOH Hooc: NH 2.aming Sutin acd 2 Basic Amino acids: These contain a second basie group which may be an amino group. Ny an LN {coon 2,6-Diaminoherante acid 3. Neutral Amino acids : These contain only one amino and one carboxyl group, They are further classified according to the position of amino group in relation of cazboxyl group into 0, B-, y~ and 3— amino acids. H,N-CH,-Coon Amino acetic acid or Glyeine CH,-CHONH -CooH ‘e-Amino propionic acid or Alanine H,N-CH, -CH, -COOH B-Amino propionic acid H.N-CH,-CH,-CH,-COOH 7-Amino butanvie acid Out of these o-amino acids are most important as they are the building blocks of “bio-proteins’. Types of a-Amino acids : (@) Amino acids with Non-polar side chain: Examples are ‘NH, Glycine cy ct, ory Scoot ‘NH 2 Aline (AMY cucu H,N-CH-Coo +H” —> H,N-CH-coo <-Amino acid miter ion ‘The zwiter ion is dipola, charged but overall electically neutral. Therefore, amino acids ate amphoteric. Depending ‘on the pH of the solution, the amino acid ean donate or accept proton. i i i p os ov HCH coon —— HN-cH-coo” 4+ HN-CH-coo Low pH ~witer ion (i) Higher pH Catone form (i) Neutra form Anion form (i) aif Sdy Couns Tori RE Uh Online Sippel 7Biomolecules & Polymers RUC GucUriuoened 5, Iso-Electric point : When an ionized form of amino acid is placed in an electric field it will migrate towards the ‘opposite electrode. Depending on the pH of the medium, following three things may happen: (i) In acidic solution, the positive ion moves towards eathode, (ii) In basic solution, the negative ion moves towards anode. « ‘The zwitter ion does not move towards any of the electrodes, ‘The intermediate pH at which the amino acids show no tendency to migrate towards any of the electric field is known as isoelectric point R R R I or ae oun | — HyN-CH-COOH === HyN-CH-Coo” == H,N-CH-coo w uw w Hh ny In other words, the iso-electric point (pl) of the amino avid is the pH at which it has no net charge. ILis the pH at ‘which the amount of negative charge on an amino acid exactly balances the amount of positive charge. pl 1H at which there is no net ch ge (pH) on the amino acids fan amino acid has amino group and one carboxyl group, it has two pK, values. The isoelectric point (pl) of this amino acid has the average value of both the pK, value, ic. pKa, +pKay 2 For Example: fan amino acid does not have an ionisable side chain, its pl value is average of pKa values of the carboxyl group and the protonated amino group, e.g., Jn alanine, ° I CH,CHC-OH <— pk, el! ®NH, <— pk, =9.69 2.34+9.69 2 @ Ionisable side chain is NH, hence, pls the average of pK, value of both —NII; that change to -NH, (by loss of proton). _8.95+10.79 2 pl 9.87 18 EEE, sete study course for rrs£€ with Ontine SupportRi uEUC ees) Biomolecules & Polymers In glutamic acid, ° ° pk,=425 ——» ll0-C- CH, ~ CH, CH, “CH C- On| H,N—CH, ~CO— NH ~cH- coon cu, cH, Givcine Alanine Giycyalanine Also, the -NH, group of glycine may reaet with “COOH group of alanine resulting inthe formation of different dipeptide, alanylelyeine, IN-CH-CO-OIi =I- NUCH, - COOH j5> H.N-CH-CO=Nil -cHl,-Ccoon cH, cH, Alanine Givcine Alanyigycine Note Since the resulting molecule still has a free amino and a carboxyl group, it may react with other amino acids at either ends to give ahigh + molecular Weight linear or condensation product oT FDBiomolecules & Polymers RUC GucUriuoened 20 wi ing Formula and Nomenclature of Polypeptide : According to conventions, the structutes of polypeptides are written in such a way that amino acid with the free amino (NHL group is written on the left hand side ofthe polypeptide chain while the amino acid withthe free carboxyl (COOH) ‘group is written on the right hand side of the chain. e.g. the tripeptide, alanylgly-cylphenylalanine is represented as terminal residue (Terminal residue H.N CH CNH CH, CNH CH Coon cH, CH,-C, Hy Alanine Glycine Phony! alanine ‘The name of any polypeptide is written from the N-terminal residue. While writing the name, the suffix ine inthe name of the amino acid is replaced by yl for all constituent except the C-terminal residue. Properties : ‘These are amphoteric in nature due to the presence of terminal ammonium and carboxylate ions as well as the ionized side chains of amino acid residues. 2, Like, amino acids, they also neutralise both acids as well as bases and also possess iso-electric point 3. Atisoelecttic point, polypeptides have least solubility and hence can be separated, Structure of Peptides (Proteins) Proteins may have one or more polypeptide chains. The priniary structure of a protein refers to the covalent structure including disulphide bridges of each polypeptide chain, It simply refers to the sequence in which the various amino acids present in a protein are linked to one another. Ro \ZE TM NLS NINE roy A H oO R® HOH Primary structure ofa Protein o=0! ‘The first ever primary structure of a protein i. insulin was determined by the British chemist, Frederic Sanger. The different ‘chemical and biological properties of various proteins are primarily due to the differences in their primary structures. A protein containing 100 amino acids is @ very small protein, yet 20 different amino acids can be combined at one time in 20)!" different ways to give an equal number of proteins each having its own characteristic properties. ‘The importance of the primary structure of a protein in determining its biological activity is shown by the Lact that replacement of just one amino acid in the sequence of a protein destroys its biological activity IA, sets stuay course for 11JEE with ontine SupportWim Biomolecules & Polymers iguration and conformation of the peptide bond in polypeptides : ‘The lone pair of electrons on the N-atom in the peptide bond is delocalised over the >C = O group. As a result, ccarbon-nitrogen bond acquires some double bond character. In other words, the rotation about the C—N bonds hindered and as a result of this hindered rotation, the peptide bond can show ecometrica! isomerism, Further because of much larger steric repulsions between R, and R, groups, in the cis-isomer, the trans-isomer is more stable. i X Resonance Structure of Peptide Bond ‘Thus, the atoms forming the peptide bond, i.c., CONH group lie ina plane with the O and H atoms in trans-orientation. j j | bon. , VAP N\A / ay a’ \y Lo Lda trans (more stable) cis (Jess stable) POLYMERS Section - 3 Introduction : Polymers form the backbone of the modern civilization and are the chief products of the modern chemical industries. Polymers, (Greek poly means many and mer means unit or par) are very high molecular mass compounds, each molecule ‘of which consists a very large number of simple structural units joined together through covalent bonds in regular fashion, ‘The simple molecules from which the repeating structural units are derived are called ts0no1ers and the process by which these simple molecules, ie., monomers are converted into polymers is called polymerisation, Classification of Polymers : 1. Classification of Polymers on the basis of Origin : {A) Natural Polymers : ‘Taey are available in nature (animals or plants). Examples of such polymers are: natural rubber (J, 4-cis-polyisoprene), natural silk, cellulose, starch, proteins, etc. Polymers such as polysacharides (starch, cellulose), proteins and nucleic acids ec., which control various life processes in plants and animals are called b0!ymers {8) Semisynth Polymers : They are chemically modified natural polymers such as hydrogenated, halogenated or hydro-halogenated natural rubber, cellulosics, Le. esters and ethers of cellulose such as cellulose nitrate, methyl cellulose, ete ESSE ESTES ere STBiomolecules & Polymers 22 {C) Synthetic Polymers : They are man made polymers prepared synthetically such as polyethylene, polystyrene, polyvinyl chloride, polyesters, Bakelite, Buna Nylon, Dacronete, Cla ication on the Basis of Thermal Response : (A) Thermoplastic Polymers : Polymers which can be easily softened when heated and hardened with litte change in their properties. They can be softened or plastic 1d repeatedly on application of thermal energy, without much cchange in properties if weated with certain precautions, e.g. polyolefins, polystyrene, nylons, linear polyesters and polyethers, polyvinyl chloride, Teflon etc. They normally remain soluble and fusible after many cycles of heating and cooling, (8) Thermosetting Polymers : Polymers which undergo permanent change on heating. They can be obtained in soluble and fusible forms in early or intermediate stages of their synthesis, but they get packed or cured and become insoluble and infusible when further heated or thermally treated. The curing or packing process involves ‘chemical reactions leading to further growth and cross linking of the polymer chain molecule and producing gisnt molecules, e.g, Bakelite, melamine formaldehyde, diene rubbers, unsaturated polyesters et. Certain plastics do not soften very much on heating. These can be easily softened by the addition of some organic ‘compound which are called pastci-ers, For example, Polyvinyl chloride (PVC) is very stiff and hard but itis made soft by adding plasticizer e.g. Dioctyl phthalate (DOP), (C) Fibres : Polymers which have strong intermolecular forces between chains. These forces are either H-bonds or dipole-dipole interaction. These are closely packed with s high tensile strength and less elasticity. Therefore, they have sharp melting points. These polymers are long, thin and thread like and can be woven in fabrics. Some of the example of these polymers are Nylon-66, Dacron. etc (D) Elastomers : Polymer with elastic character like rubber. In elastomers the polymer chains are bound together by ‘weakest intermolecular forces. These are easily stretched by applying small stress and regains its original shape When stress is emoved. For example, natural rubber. ‘The natural rubber is a gummy material which has poor elasticity, However, when natural rubber is heated with 3.5% sulphur, it becomes non-sticky and more elastic. This process is called \ui-«-«1io and product formed is. vulcaniced rubber whieh has better tensile strength and resistance to abrasion than natural rubber 3. Classification on the Basis of Formation : (A) Addition Polymers : They are formed from olefinic, diolefinic, vinylic and related monomers. They all have ~C-C- linkages along the main chains of the polymer molecules and usually no other atom appears in the main chain, These polymers are formed by simple additions of monomer molecules to each other in quick succession by ‘chain mechanism. This is known a$ ociition poly merication or chaiir—growthpolymericarion. The examples of such polymers are: polyethylene, polypropylene, polystyrene, polybutadiene, polyvinyl chloride, etc. Set Study Course for IIJEE with Onine SupportRi cucu ocd Biomolecules & Polymers 4, (8) Condensation Polymers : A polymer formed by the condensation of two or more than two different monomers ‘with the elimination of the species like water, ammonia, hydrogen chloride or alcohol ete.,is called condensation _polvmers In this type of polymerization generally each monomer contains two functional groups. Besides ~C-C- linkages, they contain atoms such as O. N, S, etc., at regular intervals in the main chain. The process of their formation is called condensation polymerization oF step-growth polymerisation Polyamides, polyesters, polyethers, polyurethanes, terylene, bakelite, epoxy resins and alkyd resins, ete. are examples of condensation polymers. Classification on the Basis of Structur (A) Linear Polymers : These can schematically be represented by lines of finite lengths with well packed structure, hhaving high densities, high tensile (pulling) strength and high melting points. They are formed from olefinic, ‘vinylic or related polymerization under suitable conditions or by condensation polymerization of bifunctional ‘monomers. Linear polymers such as high density polyethylene, polyvinyl chloride, polystyrene, Nylon-6, etc, are soluble and fusible. (8) Branched Polymers : They can be schematically represented by lines of finite lengths with the short or long branch structures of repested units. The branches appear as « consequence of uncontrolled side reactions during polymerization or by design of polymerization, Branched polymers are usually more readily soluble and fusible than linear polymers of comparable chain length or molecular weight. For example, low density polythene, glycogen, starch etc. (©) Cross-linked or Network Polymers : They can be represented by a network structure, planar-network as in ‘graphite or space-network as in diamond. Cross-linked polymers are insoluble and infusible as the molecules in them are giant molecules, often of uausually high or infinite molecular weight. Depending on the nature and frequency of cross-links, such polymers may show different orders of swelling in solvents, These polymers sre hard, rigid, brite because of network structure, Examples are; Phenol—formaldehyde resins, epoxy resins, vulcanized rubber ete. Molecular masses of Polymers : ‘The molecular mass of a polymer can be expressed in two ways. “ (8) Self Study Course for IITJEE with Online Support Number average molecular mass: If N,, Ny, N, ... are the number of molecules with molecular masses M,,M,,M, ...respeetively. — _NiM, +NoMz +NjM, + My Ni +N +N; This may be expressed as Myy where N, is the number of molecules ofthe # type with molecular mass M, Weight average molecular mass :I'm,.m,,m,.....are the masses of species with molecular messes M,.M,. respectively, then the weight average molecular mass is 2BBiomolecules & Polymers AUC) GucUr Ueno) My +:myM +myMy my +m, +m zea) ZUN|Mi) where N;is the number of molecules of mass M, M, so that My, Poly dispersity index : The ratio of weight average molecular mass to the number average molecular mass is called po!) dispersity index, PDI. My PDI= M, This gives an idea about the homogeneity of a polymer. For natural polymers, PDI is usually unity and therefore, natural polymers are monodisperse. For synthetic polymers, the PDI is greater than one and therefore M,, is grester than My ‘The number average molecular mass, Ni, is measured onthe basis of colligtive propenis like osmotic pressure. On the other hand, the weight average molecular mass, My is determined with the help of methods like ultra centifugation, sedimentation ete ‘Some Important Polymers + 1. Polyolefins 2 Rubber 3. Teflon 4. Poly Vinyl Chloride PVC) 5 Nylon 6. Formaldehyde Resins 7. Terylene S Cellulose 1. Polyolefins : These are generally obtained from ethylene or its derivatives. The polymerization normally takes place at a temperature between 473-673 K under high pressure and in the presence of traces of oxygen. (i) Polyethylene or Polyethene : It is a polymer of ethylene. It is manufactured by heating pure ethylene to 465—485 K under high pressure (1500 —2000 atm) in the presence of traces of oxygen (0.03 to 0.1%). 465-485 acl, =cH, (cH) -cH-), Ethylene ‘ere Polyethylene vis whitish, translucent polymer of moderates ength and high toughness, Uses ts major uses are as packing films, pipes, containers, laboratory apparatus, bottles, buckets, toys, mould articles and electrical insulators, Itmay be noted that these days two types of polythene are used which have widely different properties. These are, Jow density polythene (LDPE) and high density polythene (HDPE), The low density polythene is prepared as discussed above. It consists of highly branched chain molecules. Due to branching, the polythene molecules donot pack well and therfore, ithas low density (0.92 g/cm) and low ‘melting point (384 K). Low density polythene is transparent of moderate tensile strength and high toughness. Itis mainly used for, 24 EEE, sett stucy course for JE with Online SupportRic ucUc ieee Biomolecules & Polymers i) a) Self Study Course for IITJEE with Online Support = > Asapacking material in the form of thin plastic film bags. > For insulating wizes and cables. > In the manufactures of pipes, toys, bottles, ete. ‘On the other hand, high density polythene is prepared by heating ethylene at about 333-343 K under a pressure ‘of 6—7 atm in the presence of a catalyst such as triethylaluminium and titamnium tetrachloride (known as Z\sle" Natta eatalys0, CH, = CH (cH, -cH,-) Polyethylene This polymer consists of linear chains and therefore, the molecules can get closely packed in space. It has, therefore, high density (0.97 g/em), and higher melting point (403 K).Icis quite harder, tougher and has greater tensile strength than low density polythene tis used in the manufacture of containers, buckets, tubes, pipes, house wears ete Polypropylene or Polypropene : The monomer unit is propylene. It is manufactured by passing propylene through hexane (an inert solvent) containing Zigler Natta catalyst (a mixture of tiethylaluminium and titanium tetrachloride), . Zeige ) nCH, CH=CH, ES» 2 oy Propylene cH), Polypropylene Itis harder and stronger than polyethylene. Uses : > For packing of textiles and foods, > Formanufacturing liners of bags, lining material for TV cabinets and refrigerators, > Formaking ropes, fibres, heat shrinkable wraps for records and other articles, > Formaking automobile mouldings, seat covers, carpet fibres etc. Polyacrylonitrile (PAN) or Orlon : Ikis a polymerized product of vinyl cyanide (acrylonitrile) nuc=cH-cn —> {cH,-cH Viny cyanide (heron) \ Ja Polyacrylonittile Vinyl eyanide can be prepared by treating acetylene with HCN in the presence of Ba(CN), Be yy 2), ,.0-cH-eN Vinyl eyanice HC It is a hard, homy and high melting substance. It is also known as actilon or orlon, Uses : > For making blankets, sweaters, bathing suits, ete > Formaking synthetic carpets. 25Biomolecules & Polymers Rc) Gucuriu ceed 2. Rubber: Itis of two types, viz. Natural rubber and Synthetic suber > Natural Rubber Itis an addition polymer of isoprene (ic, 2-Methyl-1, 3-butadiene). It is manufactured from latex, a colloidal solution of rubber particles in water, obtained by making incisions in the bark of rubber trees foond in topical and sub-topical counties (o ) rs s{onj-C-cu-ca,) Zobmestion, | cy, acu cn isoprene Pohisoprene ‘Rubber has an average chain length of S000 monomer units of isoprene. Since each repeating units in polyisoprene ‘contains a double bond, it may have either cis-or a trans-orientation, Natural rubber has os-stereochemistry while gutta percha, obtained by free radical polymerisation of isoprene, has irans-configuration. Properties 1. Ithas remarkable elasticity but is sticky in nature. 2, Iwundergoes long range reversible extension even under relatively small applied force, 3. Ithas weak intermolecular forces and occasional cross-linking. With no highly polar substituents, intermolecular attraction is largely limited to van der Waal’s forces. But these are weak because of all cis-configuration about the double bond, 4. The trans-configuration permits highly regular zig-zags that fit together well while the cis-configuration does not. 5. The trans-configuration is highly crystalline and non-clastic. «is, 4 Poisoprene A ADADAKRW Tears, 4Polsoprene > Vulcanized Rubber : ‘Natural ubber is soft and tacky sticky) and becomes cH, cH even mote so at high temperature and britle atlow cy CH CH, CH C= CH CH, temperatures. It has a large water absorption i capacity, low tensile stength and resistance to : ~A~CH-C=CH-cH, cH, organic solvents and is also easily attacked by 1 . abrasion, Tt is also not resistant to the action of cH-CH oxidising agents, These disadvantages are removed cH, by VULCANISATION’ which involves addition of sulphur te rubber and heating the mixture at 373415 K. The vulcanized rubber thus obtained has excellent elasticity, low water absorption tendency and resistant to the action of organic solvents and oxidising agents. During vulcanization, sulphur bridges or cross-links between polymeric chains are introduced through their relative allylic positions 26 EEE DI, set stucy course for rrs€€ with Ontine SupportRie oud Biomolecules & Polymers ‘These crosslinks make rubber hard and stronger and remove the tackiness of natural rubber since the individual chains ‘cannot slip p ich other due to sulphur bridges. Thus rubber can be stretched only toa certain extent and hydrocarbon ‘chains have the tendency to regain their shape when tension is removed, > Synthetic Rubber : ‘To improve the qualities of natural rubber and to meet the ever increasing demands of mankind, a number of forms of synthetic rubber have been prepared. @ ci the same way. It is prepared by the polymerisation of 1, 3-butadiene in the presence of Zeigle-Natta catalyst {ic,,amixture of (C,H) Aland TCL) Polybutadiene : This polymer has properties similar to those of natural rubber and can also be vuleanised in certgyate rien | -M. CHa n(CH, = CH- CH=CH) "Ts, None’ i Ny a Cis, 4Polybutadiene ‘Buna Rubbers : Butadiene polymerises in the presence of sodium to give a rubber substitute viz. BuNa. Itis of ‘wo types (a) Buna-N or GRA : This synthetic rubber obtained by co-polymerisstion of one part of acryl nitrile and two parts of butadiene. n(CH, = CH-CH Hy= CH) » CH CH= CH CH, CH, CH, CN Buna CN tis more rigid responds less to heat and very resistant to swelling action of pettol, oils and other organic solvents. {b) Buna-S or GRS :Itis a copolymer of three moles of butadiene and one mole of styrene and is an elastomer, {cis obtained as a result of free radical co-polymerisation of its monomers. n(C,H,~ CH= CH,) + n(CH,= CH - CH CH) ——> CH; CH= CH CH, CHC Bunas Cys {cis generally compounded with casbon black and vulcanised with sulphur. It is extremely resistant to wear and (car and find use in the manufacture of tyres and other mechanical rubber goods. (ii), Neoprene : Ibis a polymer of chloroprene and is obtained by free radical polymerisation of chloroprene. a a i} I n(CH = C-CH = CH) —+ +CH, -C=CH-CHy35, Chioroprene Neoprene I is an excellent rubber like material. Itis a thermoplastic and need not to be vulcanised. Lis superior to natural rubber as tis esistant (othe reaction of ais, heat, light, chemicals, alkalies and acids below 50% strength. It is used {for making transmission belts, printing rolls and flexible tubing employed for conveyance of oil and petrol Self Study Course for IITJEE with Online Support PaBiomolecules & Polymers RUC GucUriuoened 28 3. Teflon :Itis also called polyterrafluoroethylene (PTET). Itis a polymer of tetrafluoro ethylene (F,C=CF,) which on polymerisation gives Teflon (CR =CR) SE +R CR», ‘Tetrafluoroethylene Polytetrafluoroethylene or Teflon Itis thermoplastic polymer with a high softening point (600 K). Itis very tough and difficult to work. Itis inert to most chemicals except fluorine and molten alkali metals. It withstands high temperatures, Its electrical properties make it an {deal insulating material for igh frequency installation, Due to its chemical inertness and high thermal stability, itis used in making non stick utensils, For this purpose, a thin layer of Teflon is coated on the inner side ofthe vessel. tis also used for making gaskets, pump packings, valves, seals, rnon-lubricated bearings, filter cloth, ete 4, Poly Vinyl Chloride : Itis commonly named as PVC. I's starting material is vinyl chloride (CH, =CH- Cl). Itis prepared by the polymerisation of vinyl chloride in presence of peroxides. Pesondes n(CH, =CH) 8, cH, cH, I I a a Viryichioride Poly Vinylenioride PVC is by and large a linear polymer, colourless and thermoplastic in nature and having a chloride content of about 56.8%. The polymer is thermally unstable and extensive heating transforms it into a dark coloured residue resembling polyacetyline and libersting HCl as the volatile. It is insoluble in all hydrocarbons as events. It possesses flame retardation and self extinguishing characteristics. PVC is a pliable (easily moulded) polymer and thus has a wide range of applications. () When plasticised with high boiling esters such as di-n-butylphthalte, itis used for making raincoats, band bags, plastic dolls, ete (1d) tis @ good electrical insulator and hence is used for coating wires, cables and other electrical goods. (1) Itis also used in making ; gramophone records and hose pipes. 5. Nylon: These are polymers having amide linkage and are known as polyamides. These are prepared by the condensation polymerization of dibasic acid with diamines or their squivalents. (i) Nylon-6, 6 tis a polymer resin, It is condensation polymer formed by reaction between adipic acid and hexamethylene diamine at 525 K under pressure. As both monomer units consist of 6 carbon atoms, so itis known as nylon-66. l Pomenzation , (C8) C08) BN (CH)g—NB) L ae ® 216 2) 395K - 1,0 (CH) 4 ~C-NH—(CHy)g -NH>, It is a thermoplastic polymer when extruded above its melting point (536 K) through spinneret, it gives nylon fibre ‘which is extremely tough and resistant to friction. It possesses greater tensile strength, elasticity and lusture than any natural fibye. Itis chemically inert and is fabricated into sheet, bristles and textile fibres IA, sete stuty course for 11JEE with online SupportWren Biomolecules & Polymers (i) Nylon-6, 10 Teis another type of nylon, obtained by the condensation of hexamethylenediamine and sebacic acid, a dibasic acid containing te carbon atoms. i i S(H,N=(Ci)g NH) (0 = E-(CH)g E04 FEM 5 CN —CH)g=NHE~E“(CH)4 Op =H Iti tough late andhas high tensibl stength.Itis used inthe manufacture of carpets, tet bres and bristles for brushes Nylon-6 : Iti also called Perlon-L. Its manufactured by prolonged heating of caprolactum, having amino group at one end and a carboxyl group at the other, st 530-540 K, ho ¢ 1,0, + A, Polymerises i Hd cry, coo) SESS enn cH, C% Ceprolactum -Aminocaproie acid Nylon-6 The fibres of nylon-6 are obtained when molten polymer is forced through a spinneret and the fibres formed are cooled by the stream of air Itis used in the manufacture of tyre cords, fabric and mountaineering ropes, 6. Formaldehyde Resin + These include polymers like Bakelite and Melamine polymers (i) Phenol formaldehyde resins (Bakelite) : It is a condensation polymer and is obiained from phenol and formaldehyde in the presence of basic catalyst oH ou on ‘ ction wero 25 oO a o-hydroxybenzy buon ‘alcoho! prhydronybenzyl alcohol ‘The condensation of o-hydroxybenzy! alcohol or p-hydroxy benzyl alcohol gives a linear polymer. Linear Polymer [Novolae) ou CHOW potymesen Self Study Course for IITJEE with Online Support 29Biomolecules & Polymers CT CUCUR IoC ‘The ortho and para substituted phenols can undergo polymerization to produce a cross-linked polymer known as bakett. on on HOH Polymer ” - ~a,o cH,OH on on on yy cH, ~~ NS cn, cH, cm, ZA wh La, cH, ~~ ou on ou Balt (Crosslinked polymer Uses : Soft bakelites with low degree of polymerization are used for making glue for binding laminated wooden planks and in varnishes. High degree polymerization gives hard bakelites which are used for making combs, fountain pens, barrels, electrical goods, formica table tops and many other products. (i) Melamine formaldehyde resin: It is a polymer formed by the condensation of melamine which is a heterocyclic diamine with formaldehyde. The polymerization occurs as / HN\AN NH, aN NNN LOY + xc — PYOT aw Oo NH, NH Melamine Melamine polymer 7. Terylene : tis a condensation polymer which is known as polyester. Terylene is a polymer of ethylene glycol and (erephthalic acid, Itis known as terylene or Dacron, COOH) cH, —cH,) - (fe) 20%, 40 cncr,-0-¢-{O-e tba bu] poy (boon ( ) ILis a very strong fibre and is used for making cloth by mixing with cotton, magnetic recording tapes, etc x Self study cours for HEE with Online SupportRie ou uc uee eed Biomolecules & Polymers ‘An important polymer of polyesters clas is glyptal. Glyptal i a polymer of ethylene glycol with phthalic acid. t ) { coon \ cu,-cn, coon a belt lon bn) , Ethylene Geol Phthalic a Ic was commonly used in manufacture of paints, lacquers, building materials such as asbestoss, cement, ete Uses: ‘These films are suitable in electrical applications and packaging and as magnetic recording tapes. The fibre is made by ‘melt spinning process. Poly ethylene terephthalate is the most important synthetic fiber to have found widespread textile applications either alone or more commonly as different blends with cotton or wool. The fibre is widely known as Terylene or Dacron. The polyester fibres possess good crease resistance and wash and wear properties. A sizable fraction of the polyester fibre is used as the reinforcing cord in the tyre and related industzy 8, Cellulose : Cellulose is the most abundant constituent of the vegetables or plant kingdom. More than 50% of all the living matter is cellulose. Itis the chief structural material of cell walls ofall plants. It is also the chief component of wood (45 — 50% cellulose), cotton (90 — 95% cellulose), ete. The molecular mass of cellulose varies from 50,000 to $500,000 suggesting thereby that cellulose may contain 300-3000 glucose units Cellulose is a non-reducing sugar since it does not reduce Tollen’s reagent or Fehling’s solution. It also does not form an osazone and is not fermented by yeast. It also does not undergo hydrolysis easly. ‘Types of Polymers of Cellulos (i) Cellulose Nitrate : Cellulose nitrate is the oldest cellulosic or cellulose derivative known and it is the only inorganic ester of cellulose of commercial importance. Nitration of cellulose is carried out by using a mixture of HINO, and H,SO, over a specific time period under controlled conditions of temperature and mixed acid composition, ‘The transformation of cellulose (R — Cell - 0 H) inte the nitrate may be written as R-Cell-OH+HO- NO, —> R-Cell-ONO, +H,0 Cellulose nitrates for plastics and coating (lacquer) applications have nitrogen (Nitrogen) content in the range of 1.5 12.2%. They are available in alarge number of viscosity grades and they are soluble in esters, Ketones, ether alcohol mixture and glycol ethers. Cellulose nitrates with 10.9 ~ 11.2% nitrogen content find use in fiexographic inks, lacquer coatings for paper, fils. For plastics application cellulose nitrate is invariably plasticized with neatly 25% by weight of camphor. The camphor plasticized product is known as celluloid, Cellulose Acetate : The most important organic ester of cellulose is cellulose acetate, Cellulose acetate is prepared by acylation of cellulose using a mixture of acetic anhydride and glacial acetic acid as the acetylating agent under controlled condition, Small proportion of H,SO, is used as catalyst Self Study Course for IITJEE with Online Support 31Biomolecules & Polymers CO CUCURIR oer ‘A major outlet of cellulose acetate isin the area of sheets, films and membranes. Is exceptional clarity makes it suited for photographic films. Injection moulded items include toothbrush handles, combs, et. Films are useful in packaging and wrapping. The toughness, low flammability (compared to cellulose nitrate), good clarity are advantageous, On the other hand ts high water absorption, por solvent and chemical resistance and limited heat resistance and dimensional stability are its limitations. Mixed organic esters of cellulose also have been developed commercially. The most important mixed esters are cellulose acetate butyrate and cellulose acetate propionate. Cellulose acetate butyrate is more suitable than cellulose acetate for movie films. Its excellent appearance and clarity, toughness and ease of mouldability are of special advantage ‘The mixed esters used in the msking of automobile parts, tool hands, toys, telephone housing and pipes. a2 ETD, st study course or 2 with onine Support