 Describe reactions of Group IV Elements.

GROUP IVA ELEMENTS

Group IVA of the periodic table consist of five elements including carbon (C), silicon (Si),
germanium (Ge), tin (Sn) and lead (Pb).
Electronic configurations and melting and boiling points of group IV-A
Property C Si Ge Sn Pb
Atomic number 6 14 32 50 82
Electronic [He]2s22p2 [Ne]3s23p2 [Ar]3d10 [Kr]4d105s2 [Xe]4f145d10
2 2 2
configuration 4s 4p 5p 6s26p2
Melting points (oC) 3600 1420 937 232 328
Boiling points(oC) 4827 2355 2830 2560 1744
Nature of element Non-metal Non-metal Metalloid Metal Metal
Common properties of group-IVA elements
 All the elements of this group show a valency of four except tin and lead which either show four
or two valency due to inert pair effect.
 All of them form hydrides (MH4)
 They form tetrachlorides (MCl4)
 They also form the dioxides (MO2)
Possible oxidation state
 Oxidation state of group-IV elements may be positive negative depending upon the nature of the
compounds.
 The typical oxidation state shown by elements of group-IV is +4 found in compounds like CCl4,
SiCl4 and SnO2.
 However, down the group there are more and more examples where the oxidation state is +2, such
as SnCl2 and PbCl2
Inert pair effect in formation of ionic bond:
 All the elements in group–IV have valence electronic structure of ns2, np2, where ‘n’ varies from 2
(for carbon) to 6 (for lead).
 The oxidation state of +4 is found where all these outer electrons are involved in bonding.
 But at the bottom of the group there is tendency for the s2 pair not to be used in bonding. This is
called inert pair effect which dominates in lead.
 The nature of compounds M+2 and M+4 cations can be predicted by Fajan’s rule e.g. Sn+4 is smaller
than Sn+2 so the compounds of Sn+4 are covalent while those of Sn+2 are ionic.
CARBON
Uniqueness of carbon
1- Carbon and silicon are non-metals while the other members of the family are metalloids (Ge, Sn)
or metals (Pb).
2- Carbon shows the property of catenation or self-linkage property.
3- Tetravalent, can combine with four same or different elements.
4- Can form multiple bonds.
5- Carbon also forms homocyclic and heterocyclic compounds.
Unit – 11 59
 COMPOUNDS OF CARBON AND SILICON
OXIDES OF CARBON
There are three oxides of carbon
a. CO
b. CO2
c. C3O2 (carbon suboxide)
Structure of the carbon dioxide
 Carbon dioxide exists in the gaseous state.
 The observed C- O bond distance is 115 pm.
 It has linear structure with 180° angle.
 Solid CO2 has a face centered cubic structure.
 Being linear its dipole moment is zero.
 Carbon is sp hybridized.
  
O C O
Comparison between CO and CO2
CO2 CO
Molecule is linear Molecule is linear
Dipole moment is zero Dipole moment is 0.112D.
All electrons of C-atom take part in bond Two valence electrons are inert in C and two form
formation covalent bonds.
σ and π bonds are present σ and π bonds are present
Co-ordinate covalent bond is absent Co-ordinate covalent bond is present
Used in soft drinks and fire extinguishers. Toxic and form carboxy haemoglobin complex in
blood.

Uniqueness of carbon
 Carbon and silicon are non-metals while the other members of the family are
metalloids (Ge) or metals (Sn, Pb).
 Carbon shows the property of catenation or self linkage markedly.
 Tetravalent, can combine with four same or different elements.
 Can form multiple bonds.
 Carbon also forms homocyclic and heterocyclic compounds.

SILICON
It occurs only in combined state.
Compounds of silicon
Silica, Silicates, Silicones
SILICON DIOXIDE (SiO2)
 Every Si atom is tetrahedrally attached with four O atoms.
 Each oxygen atom is attached to two silicon atoms.
 Ratio of atoms Si and O is 1:2
 Both Si and O atoms are sp3 hybridized.
Structure of SiO2: O O O
Polymorphic species:
 In each of the various crystalline forms of silica, there is a special Si Si Si
pattern which is repeated throughout the crystal in a regular
definite crystal lattice. O O O
 The regular tetrahedral arrangement of four oxygen atoms around O O O
each silicon persists in each crystalline form but different
polymorphic species differ in Si Si Si
(i) Si-O-Si bond angles O O
(ii) Rotation about each Si-O bond. O O O
Unit – 11 60
Quartz
 Quartz, the common crystalline form of silicon oxide, is a hard, brittle, refractor, colourless solid
which differs very markedly from carbon dioxide.
 Quartz is found in the following forms: Rock crystal, amethyst quartz, smoky quartz, rose quartz,
milky quartz. Opal is hydrated variety of quartz. Sand is largely silicon dioxide (silica).
Vitreous silica/ silica glass (incorrectly called fused quartz)
 On heating at high temperature, it gives viscous liquid
 On cooling, it becomes rigid without going into a regular crystal pattern.
Interesting and useful properties of vitreous silica
 High transparency to light
 Can withstand very high temperature i.e. 1500ºC-1600ºC
 Very low thermal expansion
 Excellent insulator
 Hard brittle and elastic
 Insoluble in water and inert with other reagents
 Inert towards acids except HF.

Comparison between CO2 and SiO2

CO2 SiO2
Double covalent bonds are present Single covalent bonds are present
C atom is smaller Si atom is larger
Molecule is linear Tetrahedral geometry is present
Structure is one dimensional Structure is three dimensional
CO2 is gas at room temperature. SiO2 is solid at room temperature.
SEMICONDUCTORS
 A substance whose resistance to electric current is different under different condition is called
semiconductor
 Compounds/elements acts as semiconductor are Germanium, Selenium, Silicones, Lead sulphide,
Silicon carbide, Calcium sulphide, Lead telluride, Gallium arsenide, Indium antimonide.
 Electrical conductance depends upon temperature of semiconductor.
 On heating resistance of semiconductor decrease while that of metal increases.
 In light conductance of semi conductor increases
 Semiconductors are used in transistors, photoelectric cell and solar batteries.
 The junction between the different materials forms a boundary. It allows electricity to pass more
properly and is used in transistors.
CHLORIDES OF CARBONS, SILICON AND LEAD
 All these elements give tetrachlorides (MCl4) which are covalent and tetrahedral due to sp3 hybrid orbitals.
 MCl4 are fuming liquids at room temperature. The stability of MCl4 decreases from CCl4 to PbCl4.
PbCl4 decomposes to give PbCl2 and Cl2 gas.
PbCl4 
 PbCl2 +Cl2
Reaction with water
 Silicon react with steam at red heat as follow
Sis  2H 2O g  
 SiO2s   2H 2 g 

Unit – 11 61
 CCl4 does not react with water. This is due to bulky nature of chloride atoms around small carbon
atom. As a result oxygen of water cannot penetrate to reach carbon atom.
 SiCl4 to PbCl4 react violently with water to produce their respective oxides and fumes of HCl.
Superheated steam
CCl 4 + H 2 O   COCl2 + 2HCl
Phosgene gas

SiCl 4 + 2H 2 O 
 SiO 2 + 4HCl
PbCl4 + 2H 2 O 
 PbO 2 + 4HCl
 Except carbon, the tetrahalides of Si, Ge, Sn and Pb react with halide ions and from the hexahalo complex.
2-
 SiF6 
SiF4 + 2F- 
 PbCl2 is ionic in nature and sparingly soluble in cold water but more soluble in hot water.
H O
2 (l)
PbCl 2(s)   Pb +2 
(aq) + 2Cl (aq)

Oxides
 The elements of group-IV form two types of oxides i.e. monoxide (CO, SiO, GeO, SnO, PbO) and
dioxide (CO2, SiO2, GeO2, SnO2, PbO2,) in which these exist in +2 and +4 oxidation states and
some other oxide like C3O2, Pb3O4, Pb2O3.
Their stability order is as follow
Ge2+ < Sn 2+ < Pb 2+
Ge4+ > Sn 4+ > Pb 4+
Ge2+ < Ge 4+ ; Sn 2+  Sn 4+ ; Pb 2+ > Pb 4+
 Silicon burns in oxygen under strong heating as follow
Sis  O2 g  
 SiO2s
Nature of oxides
Co is slightly acidic while all Ge, Sn, Pb are amphoteric
Formula Nature Acid-base reactions
Covalent , slightly
CO CO g  + NaOH g  
 HCOONa  aq 
acidic
CO2 Covalent, Acidic CO2(aq) + H2O() ↽ ⇀ H+ + HCO3– (aq) (Acidic)

SiO2 + NaOH 
 2Na2SiO3 + H2O (Acidic)
SiO2 Covalent, Acidic SiO 2(s) + CaO (s) 
 CaSiO 3( ℓ )
Slag

XO XO(s) + 2HCl(aq) 
 XCl2 +H2O (Basic)
(X = Ge, Sn, Ionic, Amphoteric
Pb) XO(s) + NaOH(aq) 
 Na2XO2 + H2O() (Acidic)
XO2(s) + 2NaOH(aq) + 2H2O() 
 Na2[X(OH)6](aq)
XO2 (Acidic)
(X = Ge, Sn, Ionic, Amphoteric XO2(s) + 4HCl(aq) 
 XCl4(aq) + H2O() (Basic)
Pb)
2
  XCl6 
XCl 4 + 2Cl 

Unit – 11 62
 PRACTICE MCQs
Q.1 Which of the following is semiconductor
A. Aluminium B. Diamond
C. Graphite D. Silicon
Q.2 Diamond is hard because
A. It has a high value of refractive index
B. All the valance electrons of each carbon atom are involved in bonding
C. It is a giant molecule
D. It is a crystalline allotrope of carbon
Q.3 A gas which burns with a blue flame is
A. CO2 B. NO
C. N2 D. CO
Q.4 Which of the following shows inert pair effect
A. Boron B. Carbon
C. Silicon D. Tin
Q.5 In network of silica (SiO2), each silicon atom is surrounded by _______atoms of oxygen
A. 4 B. 2
C. 1 D. 6
Q.6 CO2 is gas while SiO2 is solid at room temperature
A. Carbon is non-metal while silicon is semi-metal
B. CO2 is an independent molecule while SiO2 has network covalent structure
C. Carbon forms multiple bond while silicon does not form multiple bonds
D. Silicon has all sigma bonds.
Q.7 Which pair of elements form acidic oxides
A. Li and Be B. Mg and Ca
C. Na and K D. C and Si
Q.8 Identify the correct statement regarding CO
A. It combines with H2O to form carbonic acid
B. It is a slightly polar molecule
C. It is powerful oxidizing agent
D. It is used to prepare aerated drinks.
Q.9 Which of the following is metasilicic acid
A. H2SnO3 B. H2SiO3
C. H3AsO4 D. H3SbO4
Q.10 The geometry around each Si-atom in SiO2 is
A. Trigonal B. Cubic
C. Linear D. Tetrahedral
Q.11 The empirical formula of quartz, opal and sand is
4 2
A. SiO4 B. SiO3
2
C. SiO4 D. SiO 2
Q.12 Which one of the following is not a semi-conductor
A. Si B. Ge
C. Se D. Sn
Q.13 If temperature of gallium arsenide is increased then its conductivity will
A. Decrease B. Increase
C. Remains constant D. First decreases then increases
Q.14 Silicones differ from silica by a group of
A. –R B. –OH
C. HCO3– D. O2
Unit – 11 63
Q.15 Silicon react with steam at red hot to produce
A. SiO2 + H2 B. Si(OH)4 + H2
C. SiO2 + SiH4 D. SiH4 + O2
Q.16 SiO2 has
A. Diamond like structure B. Giant covalent structure
C. sp3 hybridization on Si atom D. All of these
Q.17 Indicate the hydroxide which is acid
A. Si(OH)4 B. Al(OH)3
C. Mg(OH)2 D. Ca(OH)2
Q.18 Tetrachloride of which element doesn’t react with water
A. Carbon B. Silicon
C. Tin D. Lead
Q.19 Oxidation state of C2 in sodium carbide (Na2C2) is
A. -4 B. -3
C. -2 D. -1
Q.20 Which one react most violently with cold water
A. PbCl4 B. CCl4
C. SiCl4 D. GeCl4
Q.21 CO2 is gas while SiO2 is solid at room temperature. This is due to
A. Carbon is non-metal while silicon is semi-metal
B. CO2 is an independent molecule while SiO2 has network covalent structure
C. Carbon forms acidic oxide but silicon form basic oxide
D. CO2 and SiO2 have same hybridization.
Q.22 Which of the following is acidic oxide
A. BeO B. Al2O3
C. CO2 D. CaO
Q.23 Which is wrong statement about group IV-A tetrahalides
A. CCl4 does not react with water B. SiCl4 to PbCl4 react violently with water
C. All are ionic in nature D. All have same geometry
Q.24 Which of the following combination is acidic nature
A. Si (OH)4, NaOH, H3PO4 B. HClO4, H2SO4 , Ca (OH)2
C. Si(OH)4, HCl, H3PO4 D. Mg (OH)2, H3PO4, HClO4

1 D 11 D 21 B
2 C 12 D 22 C
3 D 13 B 23 B
4 D 14 A 24 C
5 A 15 A
6 B 16 D
7 D 17 A
8 B 18 A
9 B 19 D
10 D 20 A

Unit – 11 64
 Explain stereoisomerism and its types.
Stereoisomerism
“When isomerism is caused by different arrangement of atoms or groups in space, the
phenomenon is called steroisomerism”.
 The have same structural formula
 Differ in the arrangement of atoms or group in space. (Different configuration)
Stereoisomerism is of two types
(i) Optical isomerism.
(ii) Geometric or cis–trans isomerism.
Optical isomerism
“Optical isomerism is a type of isomerism in which the isomerism differ in their interaction
towards plane polarized light”.
 Optical isomerism is shown by compound which have chiral centre and may be optically active.
Chiral centres / chiral carbon
“A carbon atom which is bonded to four different groups is called a chiral carbon atom or
asymmetric carbon atom also called chiral centers”.
Optical activity
 Ordinary light consist of waves vibrating in many different planes. When these waves passed
through a monochromator and polarizer, the light is found to vibrate only in one plane is said to be
plane polarized light.

 Solution of some organic compounds have the ability to rotate the plane of polarized light. The
compounds are said to be optically active.
 Optical activity of a compound is measured by an instrument called polarimeter.
 An optically active compound which rotates the plane of polarized light the right (clockwise
direction) is said to be dextrorotatory isomer or (+) isomer
 An optically active compound which rotates the plane of polarized light the left (anti-clockwise
direction) is said to be levorotatory isomer or (–) isomer

Unit – 13 65
Example
 Lactic acid (2–hydroxy propanoic acid) shows optical isomerism. It contains one asymmetric
carbon atoms,

H
|
CH3  C*  COOH
|
OH

 The following three –dimensional structures are possible for lactic acid.

 A chiral atom is not necessary condition for

chirality.
 A molecule may not have a chiral atom but
still be a chiral
 A molecule may have more than one chiral
 Non- superimposable atom but still be achiral.
mirror image forms of optical isomers
are called enantiomers.
 Equimolar mixture of (+) and (-) forms of optical isomers which appear to be optically

inactive is called racemic mixture abbreviated as    .

 A single compound with (+) and (-) centers which appear to be optically inactive is called

mesomere abbreviated as    .

Unit – 13 66
 PRACTICE MCQs
Q.1 An optically active compound can exist in isomeric forms, which rotate the plane of
polarized light in opposite direction.
A. Four B. Three
C. Two D. Five
Q.2 Which type of isomerism required chiral center_________
A. Cis-trans B. Optical
C. Tautomerism D. Metamerism
Q.3 Which of following is correct for chiral carbon
A. Single bonded B. sp3 hybridized
C. Bonded with four different groups D. All of these
Q.4 The compound (1) and (2) can be regarded as

A. Enantiomers B. Diastereomers
C. Mesomers D. Geometrical isomers
Q.5 A racemic mixture contains
A. Equal amount of cis and trans isomers B. Equal amount of skeletal isomers
C. Equal amount of pair of enantiomers D. Equal amount of tautomers
Q.6 Which of the following amino acid is optically inactive
A. Alanine B. Glycine
C. Aspartic acid D. Glutamic acid
Q.7 A compound shows optical activity when it has
A. Plane of symmetry B. Plane of asymmetry
C. Achiral center D. All of these
Q.8 Racemic equal mixture of optically active compounds is
A. Optically inactive B. Optically active
C. Geometrical isomers D. Either A or B
Q.9 Which of the following compound has two chiral carbons
A. Lactic acid B. 1,2-Dichloroethane
C. Tartaric acid D. Aspartic acid
Q.10 A ℓevo rotatory compound rotates the light
A. Towards right B. Towards left
C. 1st left then right D. Unpredictable

1 C 6 B
2 B 7 B
3 D 8 A
4 B 9 C
5 C 10 B

Unit – 13 67
 Know about types and application of adhesive.
 Know about types of dyes and their uses.
 Known about condensation and addition polymers and their sub-types.
ADHESIVES
 Liquid or semi-liquid material that adhere or binds items together are called adhesives
 They can be originated either by the natural or synthetic sources
 These are especially useful for binding the thin materials
 Adhesives cure (harden) materials by two ways
(i) Evaporating a solvent
(ii) Chemical reactions that occur between two or more constituents
Importance of adhesives:
 Adhesives are used in every field of life for example
(i) Label on a beverage bottle
(ii) Protective coating on automobiles
(iii) Profile on window frames
(iv) Bonding formica to wooden counters
(v) Attaching out soles to uppers in foot wear
Types of adhesives
Type of adhesive Description Example
Natural  Octane from natural sources i.e. mineral or Starch (dextrin), natural
adhesives biological resins, casein glue
Synthetic Epoxies, silicones,
adhesive  They are man made; acrylics
Drying adhesive,
Pressure sensitive
1. Non-reactive
adhesives  These may be natural or synthetic origin adhesive, contact
adhesive,
hot adhesive
i) Solvent based adhesive:
 These are mixture of various polymers White glue,
contact adhesives,
dissolved in a solvent rubber cements
 Used for binding of wood and paper.
ii) Polymer dispersion adhesives:
 These are also called emulsion adhesives
Drying
adhesives  These are milky white dispersions that are
based on polyvinyl acetate (PVAc).
Uses: PVAc based adhesives
(i) Wood working and packing industries
(ii) Fabrics and fabric-based components
(iii) The engineered products such as
loudspeaker cones
 These form bond by the use of light pressure
to adhere the adhesive with the adherent
Pressure sensitive  Van der Waal’s forces bind adhesive with the Acrylate based polymers
adhesives (PSA) adherent
 Used in safety labels for power equipment
and automobile interior trim assembly

Unit – 20 68
  These form strong bonds with high “shear-
resistance” like laminates
Contact Uses: Natural rubber,
adhesives (i) Bonding formica to wooden counter polychloroprene (Neoprene)
(ii) Footwear
(iii) Attaching outsoles to uppers
 These are also called hot melt adhesives or
thermoplastics
 These are applied in molten form (65°C –
180°C) range which solidify on cooling and
form strong bonds
 These are common for craft due to their ease Ethylene vinyl acetate-
Hot adhesives
of use based polymers
 Glue-gun is a method of applying hot
adhesive
 In glue gun method, adhesive melts and allow
liquid to pass through its barrel and spread on
material
2. Reactive  These react chemically with material after
adhesives hardening
 These adhesives harden by chemical reaction
between two or more components
 Individual components of these adhesive are not
adhesive itself.
Multiparts
adhesives  Several combinations of multipart adhesives are
used in industry. Some of combination are;
(i) Polyester resin – polyurethane resin
(ii) Polyols-polyurethane resins
(iii) Acrylic polymers-polyurethane resins
 These adhesives harden by chemical reaction
with an external energy source
 Heat curing adhesive include epoxies, urethanes
and polyimides
 While moisture curing adhesive cure when they
react with moisture present on the substrate Heat curing adhesive
surface (i) Epoxies
 This type of adhesives include cyanoacrylates (ii) Urethanes
One part
and urethanes (iii) Polyimides
adhesives
 Light curing adhesives are acrylic based and due Moisture curing adhesive
to their rapid action, they are used in (i) Cyanoacrylates
(i) Electronics (ii) Urethanes.
(ii) Telecommunications
(iii) Medical
(iv) Aerospace
(v) Glass
(vi) optics
Unit – 20 69
 DYES
 A natural or synthetic substance used to add a colour or change the colour of something is
called dye
Characteristics of dye:
 A dye is a substance which adds value to products
 A dye must be coloured
 It must also be able to impart colour to something on permanent basis
Components of dye:
(i) Chromogen:
 A dye consists of a colour producing structure called “The chromogen” (electron acceptor)
 An aromatic body containing a colour giving group called “chromophore” is called chromogen
(ii) Chromophores:
 Groups which can cause colour by altering absorption bands in the visible spectrum is called
chromophores
Dye name Chromophore Structure
Nitroso dyes Nitroso group –NO or (= N – OH)
Nitro dyes Nitro group –NO2 or (NOOH)
Azo dyes Azo group –N= N–
Triarylmethane Aromatic ring in quinoid
–C=C–
dyes form
\
Indigo dyes Carbonyl group C O
/

Anthraquinone dyes Anthraquinone

(iii) Auxochrome:
 It is a part of dye used to regulate the solubility and dying properties is called auxochrome (electron
donor).
 The part of the dye which causes it to adhere to the material which it colours.
Types of auxochrome
 –NH2 and –NR2 groups cause solubility in acids
 –OH,–COOH and –SO3H groups cause solubility in basic solution.
Classification of dyes
Following is the classification of dyes on basis of their applications:

Unit – 20 70
 Type Description Examples
 Contain auxochrome in addition to azo group Para red
 Common auxo chromes are NH2, NR2, OH, SO3H. Congo red
Azo dyes Bismarck Brown
 Used for dying wool, cotton, leather(Bismarck Brown
for boot polishes)
 No auxo chrome Naphthol yellow S
Nitro and
and mordant green 4
Nitroso dyes
 In triarylmethane dyes, a central carbon is bonded to Malachite Green
three aromatic rings one of which is in the quinoid form
Triarylmethane (chromophore).
dyes  Contain auxochrome in addition to chromophore.
 Common auxo chromes are NH2, NR2, OH, SO3H.
 Used as a direct dye for wool and silk.
Anthraquinone  Contain para quinoid chromophore Alizarin
dyes  Used to dye wool and cotton
 Contain carbonyl group as chromophore Indigo
Indigo dyes
 Used for dying cotton by Vat process
 It is water soluble, contain acidic or basic auxo chrome. Martius Yellow
 Used to dye cotton and wool directly
Direct dyes  Used to dye union goods (mixed cotton and wool or silk)
Fiber  NH + HO  Dye   Fiber  NH3 +---O  Dye
 Applied as dispersed in a colloidal form in water Disperse red-77,
 Fabric is immersed in the colloidal dispersion of the dye Disperse blue 27 etc
Disperse dyes  Fine dye particles are absorbed in the crystal structure
of the fabric
 Used to dyes cellulose acetate, polyester, nylon, orlon
fibers
 Dyes which form insoluble coloured materials with Alizarion
metallic salt are called lakes (Lakes are used as pigment)
Mordant dyes  If clothes made up of cotton, wool or protein fiber is
(lakes) dipped in Al, Cr or Fe salt then metallic precipitate are
formed on the fiber and colours are fast to light and
washing
 These are water insoluble organic pigments but become Indigo
soluble on mixing with powerful reducing agents
(NaHS)
 Fabric in the solution of a reduced dye and then air
Vat–dyes
oxidized or treated with oxidants
 These are quite expensive dyes because require severe
conditions of washing and bleaching
 Used to dye cotton
 Water insoluble azo dye in produced in the fabric itself
 Cloth is first soaked in the solution of a coupling reagent
Azoic dyes usually phenol or naphthol
(ingrain dyes)  Then it immersed in the solution of an auxo chromes
 Used to dye cotton, other cellulosic fiber, and may also
be used for nylon
Unit – 20 71
 HAIR DYES
“Dyes used for hair colouration to make them fashionable or to restore the original hair colour are
called hair dyes”
Types of hair dyes
Types of hair dyes Description
 Its monomers are smaller and penetrate into hair cortex thus cause
lightening of hairs
 The ingredients includes
(i) Oxidizing agent (3 to 6% H2O2)
(ii) Coupling agents or couples (Meta-substituted derivative of Aniline)
Permanent hair dyes (iii) Primary intermediate (1,4-diaminobenzene , 4-aminophenol , 2,5-
diaminotoluene)
(iv) Basic medium (for which ammonia is used)
 Ammonia open the hair cuticle and H2O2 acts as developer
 Couplers define the colour of hair dye
 Primary intermediate and coupler give different shades of hair colours
 These dyes have smaller molecules and partially penetrate the hair shaft
 These survive washing with typically 4–5 shampoos
 These contain no or very low levels of developer, peroxide and ammonia
 These are suitable for damaged or fragile hair as they penetrate surface of
Semi- permanent
hair cuticle layer
hair dyes
 These contain toxic compound (p-phenylenediamine)
 These develop a large variation in shades across whole head
 These gives a more natural result than that of a solid permanent colour
 These dyes can lighten the hair
 These are in fact permanent hair dyes that contain alkaline agent other than
ammonia (ethanolamine, sodium carbonate)
 These contain lower concentration of hydrogen peroxide (1 to 2%),
Demi-permanent developers than that of permanent hair dyes
hair dyes  By using alkaline agent, colours of these dyes are less effective in removing
the natural pigment of hair than ammonia
 These provide no lightening to hairs
 These are less damaging to hair than that of permanent hair dyes
 These are used on special occasions such as weddings and costume parties
 These are available in various forms including resins, shampoos, gels,
sprays and foams
 These are more brighter and vibrant than semi-permanent and permanent
Temporary hair dyes
hair dyes
 These cannot penetrate the cuticle layer
 These remain absorbed to the hair shaft and are easily removed with a
single shampooing

Unit – 20 72
 TYPES OF POLYMERS

Polymer
A large molecule build up by the repetition of small and simple chemical units is called polymer.
Monomer
Small units or simple molecule from which macromolecules are formed are called
monomers.
STRUCTURE OF POLYMERS
Particular Description
Linear polymer Monomers are arranged in line.
Branched linear polymer Monomers are arranged in line and are branched.
Interconnected polymer Chains of polymers linked through branches.
Number of repeating unit in polymer is called degree of
Degree of polymerization
polymerization. (DP)
Molecular mass of polymer Molecular mass of repeat unit  DP

* * *
Linear polymer * *
* * *
*
* linear polymer*
Branched *
* * * *
* * * * *
*Cross-linked* linear polymer
* or Interconnected
*

Particular Homopolymer Copolymer Terpolymer

Two types of Three types of
Composition Single type of polymer.
monomer monomer
Butyl acrylate,
Vinyl acetate and butyl
Example Vinyl acetate methacrylate and
maleate
acrylic acid

Thermoplastic polymers Thermosetting polymers

The polymers that can softened repeatedly when The polymers that become hard on heating and
heated and hardened when cooled. cannot softened again.
Unit – 20 73
 POLYMERIZATION PROCESS
In 1929, W.H. Carothers suggested a classification of the polymerization process into two types depending
upon the way the polymers are formed.
 Addition polymerization
 Condensation polymerization
Addition polymerization Condensation polymerization
Empirical formula of monomer and polymer is Empirical formula of polymer and monomer is
same different
No by-product are produced. By-product are produced
Reaction takes place in main chain through free
Reaction takes place through functional groups
radical mechanism
Example: Polyethylene, PVC… Example: Bakelite, Nylon….
1. Addition Polymers:
In these polymers, the repeating unit (monomer) keeps on adding to itself or to the growing
polymer so that a long chain polymer is produced.
It is a free-radical addition reaction which involves
(i) Initiation (ii) Propagation (iii) Termination
There reactions are catalyzed by peroxides or acids.
The reactions require pressure of 1000 atmospheres at 2000 ¬C. Much lower temperatures and
pressures can be used with so called Ziegler catalysts which consist of a trialkyl aluminum
Al(R)3, and titanium tetrachloride TiCl4, in an inert solved.
(i) Initiation
Addition polymerization is catalyzed by thermal or photochemical decomposition of organic
peroxides to give free radicalsp. These peroxides are used as free radical initiator.

(i) Propagation
This alkyl free radical attacks on styrene molecule to initiate and propagate the reaction.

(ii) Termination
Alkyl free radical is required to terminate the reaction. Free radicals will combine to terminate the
reaction.

Unit – 20 74
2. Condensation Polymerization

“This type of polymerization results from the mutual reaction of two different functional groups. The
reaction usually involves the removal of a water molecule or a methanol molecule.”

It takes place at both ends of the growing chain.

A. Dicarboxylic acids or esters combine with diols to get polyester fibre.

B. Dicarboxylic acids or esters combine with diammine to get polyamide fibres.

Such polymerizations are generally ionic in nature.

BRIEF DESCRIPTION OF SYNTHETIC POLYMER

Name of Polymerization
Monomers present Uses
polymer Type
 Used in floor covering
Polyvinyl Vinyl chloride  Manufacturing in pipe
Addition
chloride (52C and 9atm)  Manufacturing in gramophone
recorders
Food containers, cosmetics,
Polystyrene Addition Styrene
bottles, toys etc.
Polyvinyl  Used in adhesive material
Addition Vinyl acetate
acetate  As binder in emulsion paint
 Used in plastic
Acrylic  Paints for cars
Condensation Methyl methacrylate
resins  Water based weather resistant
paint
Ethane-1,2-diol and
Polyester
Condensation benzene-1,4-dicarboxylic Clothing and water tanks.
resins
acid

Diamines(hexamethylenediamine)
Polyamide
Condensation and aliphatic dicarboxylic acid Textile fibre
resin
(Adipic acid)

2,2-Diphenylol propane and Used as coating material

Epoxy resins Condensation
epichloro hydrin adhesion and chemical resistant

Unit – 20 75
 PRACTICE MCQs
Q.1 Polyester resins are specially used in
A. Floor covering B. Emulsion
C. Clothing D. Paints
Q.2 Polymers described as large molecules built up from small repeating units called
A. Biopolymers B. Dimers
C. Monomers D. Metamers
Q.3 A polymer in which three different monomers combine called.
A. Copolymer B. Terpolymer
C. Homopolymer D. Biopolymer
Q.4 The important monomers of acryclic resins is
A. Vinyl chloride B. Styrene
C. Methylmethacrylate D. Hexamethylenediamine
Q.5 Polyester resins are the product of the reaction of
A. Dihydric alcohol and dicarboxylic aromatic acids
B. Polyamines with aliphatic dicarboxylic acids
C. Styrene in the presence of catalyst
D. Epichlorohydrin with diphenylolpropane
Q.6 Industrial materials and thermal power stations are coated with
A. Polyester resins B. Epoxy paints
C. Polyamide resins D. Polyvinyl chloride
Q.7 Nylon is obtained by heating
A. Acrylic acid B. Epichlorohydrin
C. Vinyl chloride D. Adipic acid with hexamethylene diamine
Q.8 Which of these polymers is a synthetic polymer?
A. Animal fat B. Starch
C. Protein D. Polyester
Q.9 From The following which is heterocyclic saturated compound
A. Epichlorohydrin B. Diphenylolpropane
C. Benzene D. Toluene
Q.10 The monomer of acrylic fibre is
A. Vinyl bromide B. Vinyl cyanide
C. Chloroprene D. Neoprene
Q.11 To which class given below is related to PVC pipes and plastic toys
A. Thermosetting polymers B. Thermoplastic polymers
C. Copolymer D. Terpolymer
Q.12 Which polymer is used in making water tanks
A. Polyvinyl chloride B. Polyester resin
C. Polyvinyl acetate D. Acrylic resins
Q.13 A colored aromatic body containing color giving group “chromophore” is called
A. Chromogen B. Auxochrome
C. Lake D. Pigment
Q.14 All are chromophoric groups except
A. Nitro group B. Azo group
C. Hydroxyl group D. Carbonyl group
Q.15 The correct combination of multiparts adhesives is
A. Polyester resin- Polyurethane resin B. Cyanoacrylates –non–reactive adhesive
C. PVAc – solvent adhesive D. PSAc – contact adhesive
Q.16 Adhesive which harden via chemical reaction with external energy source
A. One part adhesives B. Pressure sensitive adhesives
C. Contact adhesives D. Polymer dispersion adhesives
Unit – 20 76
Q.17 Dyes which form covalent bond with fibers
A. Mordant dyes B. Azo dyes
C. Fiber reactive dyes D. Direct dyes
Q.18 The type of non-reactive adhesives is
A. Contact adhesives B. Pressure sensitive adhesives (PSA)
C. Hot adhesives D. All of these
Q.19 The hair dyes which can survive washing with typically 4-5 shampoos is
A. Permanent hair dyes B. Semi-permanent hair dyes
C. Demi-permanent hair dyes D. Temporary hair dyes
Q.20 One of the following is reactive adhesive
A. Epoxies B. Poly vinyl acetate (PVAc)
C. Glue D. Rubber cements
Q.21 The external energy source for reaction of one part adhesives is / are
A. Light B. Moisture
C. Heat D. All of these
Q.22 Coupling agents used in permanent hair dyes are

A. B.

C. D. Both “a” and “b”

Q.23 All are heat curing reactive adhesives except
A. Epoxide B. Urethanes
C. Neoprene D. Polyimides
Q.24 The best known vat dye is ____.
A. Orange B. Indigo
C. White D. Red

1 C 11 B 21 D
2 C 12 B 22 D
3 B 13 A 23 B
4 C 14 C 24 B
5 A 15 A
6 A 16 A
7 D 17 D
8 D 18 D
9 A 19 B
10 B 20 A

Unit – 20 77