Chapter - X

HALOGENS AND HALOARENES

 Halo Alkanes - Compounds obtained from alkanes by the replacement of on or more hydro-
gen by corresponding number of halogen atoms (F, Cl, Br, I) are termed as Haloalkanes.
 Halo Benzene
When hydrogen atoms of Benzene nucleus is substituted by a halogen, it is known as
halobenzene adn has a general formula
-C6H5X
 When hydrogen aton of the side chain attached to benzene is substituted by a halogen, then it is
known as Aralkyl Halides
Eg: Benzyl Halide C6H5CH2Cl
 General formula and nomenclature of alkyl/aryl halides
- Monohalogen derivatives - CnH2n+1X(alkyl halides)
- Dihalogen derivatives CnH2n+1X2
- Chemical dihalides are formed when both halogens are on the same atom
Br
CH3CH (Ethylidene Bromide)
Br

- Vicinal dihalides are formed when both halogens are attached to adjacent carbon atom
Eg: CIH2C-CH2CL ( Ethylene Dichloride)

Nature of -X bond
 Since halogen atom are more electronegative than carbon, the C-X bond of an alkyl halide is
polarised; the carbon atom bears a partial positive charge whereas the halogen atom bears a
partial negative charge.
C X

 Since the size of halogen atom increases a we go down the group in the peridic table Fluoride
atom is the smallest and iodice aton, the largest consequently the carbon halogen bond length
increases from C-F to C-I
General methods of preparation of alkyl halides
RBr+HBr
i) From alkanes R - Br + BHr
Cl2
RH R - Cl + HCl
Sunlight
R - I + HI
I2, HIO3&HNO3
(oxidising agent)
45
ii) From alkenes X
R-CH=CH=R+HX  R-CH2 - CH - R
Symmetrical Alkene
X

R - CH =CH2 +HX  R - CH - CH3

(Unsymmetrical alkene)
 In the addition of halogen acids to unsymmetrical alkenes, generally Markownikoff’s rule is
followed by the addition occurs through an electrophilic attack. However, in case of reaction
with HBr in presence of peroxide,anti Markoffnikoff’s rule is followed known as peroxide effect
or Kharasch effect.
 The order of reactivity of halogen acids with alkene is HI>HBr>HCl>HI
iii) From Alcohols
SoCl2
R  OH   RCl  SO4  HCl (Pure alleyl halide is obtained because the other two
products are exapable gases) P Cl5
R-Cl
Red P + Br2
R-Br
PBr3
Red P + I2
R - OH R-I
PI3
SoCl2
R-Cl

Con HCl
R-Cl
Anhyd ZnCl2
iv) Swarts reaction

CH 3 Br  AgF  AgBr

v) Finkelstein reaction [Halide exchange]

Acetone
C2H5Br NaI Heat  C2H5I
 + NaBr
General methods of preparation of aryl halides
i) By direct halogenation of Benzene Cl2 /FeCl3
C6H5Cl

Br2 /FeBr3
C6H 6 C6H5Br

I2/HIO3
C6H5I
46
 It is an electrophilic substitution reaction
 Low temperature and the presence of a halogen carries favours nucleus substitution. The function
of the halogen carries is to generate the electrophile for the attack.
Electrophole

Cl2 + FeCl3  Cl+ +FeCl-4

ii) From Benzene diazonium salt

Cl
N+2+Cl-
CuCl/HCl
Sandmayer reaction
Cl
Cu/HCl
Gattermann reaction
+
N +Cl-
2

KI /  I

F Benzene diazonium fluoro

+ -
N BF4
2
Borate
 +N2+BF3 Balz Schiemann reaction
 

iii) By Raschig Process

CuCl2
2C6H6+2HCl+O2 
500k 2C6H5Cl+2H2O
iv) By Hundsdiecker reaction
Distillation
C6H5OOAg+Br2 
CCl4 +350K  C6H5Br+AgBr+WCO2

Physical Properties of alkyl halides

 Lower member [CH3Cl,CH3Br and C2H5Cl] are gases and the others are sweet smelling
liquids.
 Alkyl halides are polar in nature but are insoluble in water due to their inability to form H bond
with water
 They are solube in alcohol, ether Benzene etc
 Halo alkanes have higher molecular weight than coresponding alkanes because of which they
have considerably higher boiling points.
 Gradation in densities and boiling point of alkyl halides increases with the increase in the size of
the alkyl group.
 Alkyl halides usually darken on standing for sometime due to the decomposition by ligtht and
liberation of iodine.

h   R-R +I2
2RI 

47
Chemical Reaction of alkyl halides
SN1 Reaction
 Substitution nulcleophilic uni molecular reaction are abbreviated as SN1. Considet a general
reaction.
R-LG+ NO-  R-NO+LG-
Rate = K[R-LG]
 Reaction follows first order kinetics
 The rate of reaction is independent of the concentration of nucleophile.
 The SN1 mechanism is a two step process, first one thing being the slow and the rate determining
step.
Order of Reactivity
Benzyl > Ally1>3O>2O>1O>CH3 - X
SN2 Reaction
 SN1 mechanism is a single step process with no intermediate. Bond making and breaking take
place simultaneously with the reaction centre.
 Order of reactivity
CH3-X>1O>2O>3O> Allyl > Benzyl
Dehydrohalogenation
RCH2CHR-CH3 + KOH     RCH=CHCH3 + KX + H2O
alcohol
X P elimination
 Accordiong to Zaytzeff’s rul, H atom is eliminated preferentially from the adjacent C atom which
is joined to the least H atom.
 The reactivity of halo alkanes towards elimination reaction is 3o>2o>1o
Halobenzene is less reactive than halo alkanes.
 Delocalisation of electron by resonance
The C-X bond is halo benzene has a partial double bond character. Due to involvement of
halogen electrons in resonance with Benzene ring

X X X

X X

 Polarity of C-X bond

The C-X bond in aryl halogens is less polar compared to that in alkyl halides

48
Necleophile Substitution reaction of Chlorobenzene
Reaction with NaOH: Dows Process
360 C o
d il H C l
C6H5Cl+2NaOH 
320atm  C6H5ONa
 C H O 
H 6 5

The reaction proceeds through benzene intermediate.

For different halogen, the order is I>Br>Cl

Common Reaction

KOH(aq) R - OH + K x (hydrolysis)

AgOH R - OH + AgX
moist Ago(H2O)
A  C.NH3 R - NH2 + HX (Ammonolysis)

A  C.KCN R-C  N (Nitrile)

-KX

A  .C. AgCN 
R-X R - N  C (Isonitrile)

mg ether (reflux) R MgX

I-catalyst
Na(ether)
heat R - R + Na X (Wurtz reaction)

x+Na R + Na x (Wurtz - Fittig reaction)

ether/heat

anhy AlCl3 + H x (Friedal crafts reaction)

RlO Na/alcohol R
heat R - O - Rl + Na x (Williamson’s synthesis)

(H) (Zn+di/HCl)
R - H + H X (reduction)
(Zn-Co+EtoH)

49
Chemical properties Aryl Halides
 The aryl halides are relatively less reactive towards necleophile substitution reaction as com-
pared to alkyl halides, This low reactivity can attributed to the following factors.
 Due to resonance, the electron density increases more at ortho and para position than at meta
positions. Further the halogen atom, because of its - I effect has some tendency to with draw
electrons from the benzene ring. As a result the ring get some what deactivated as compared
to benzene and hence, the electrophilic substituition reaction in halo arenes occurs slowly and
requires more drastic conditions as compared to those in benzene.
Common reaction NH2

NH3/515
Cu2O
CH3
CH3-Cl/Na
Ether (Wurtz - fittig reaction)
Cl

2 Na (Fittig reaction)
Ether
Diphenyl (biphenyl)
Ni Al/NaOH

mgcl

Mg/dry
THF

Electrophile Substitution reaction

 Halo arenes undergo the usual electrophile reaction of the benzene ring such as halogenation
Nitration, Sulphonation and Fiedel Crafts reaction.
 Halogen atom besides being slightly de activating is O, P directing, there fore further substitution
occurs at ortho and para position with respect to halogen atom.
 It is used in carbylamine test for primary amines.
 It is used in organic solvent
 It is used in the preparationof important compounds like Chloropicrin
 Upon action of air and light, it forms a poisonous gas phosgene
2CHCl3+O2  light
 2COCl2 + 2 HCl
Phosgene
 So it is kept in a dark coloured bottle

50
Poly halogen compounds
1) Di-Chloromethane [CH2Cl2]
 It is used as a solvent, paint remove, propellant in aerosols and as a process solvent in the
manufacture of drugs.
 It is used as a metal cleaning and finishing solvent.
 Methylene Chloride harms the human central nervous system. Exposure to lower level of
methylene chloride in air can lead to slightly impaired hearing and vision.
 High level of methylene chloride in air cause dizziness, nausea, tingling and numbness in the
fingers and toes.
 Direct contact with cornea can burn it
2) Chloroform(CHCl3)
 Previously, it was used as an anaesthetic but has been replaced now due to its ill effects. Since in
this reaction. first elimination of HCl occurs and then addition of NH3 takes place it is called
elimination- addition reaction.
 If both the o position with respect to Cl atom is blocked, then benzyne intermediate is not
obtained

3) Iodoform [CHI3]
 Order of reactivity of trihaligen derivatives is iodoform > bromoform>chloroform
 Iodoform gives yellow precipitate of AgI with silver
 On heating with a primary amine and alkali foul smell of isocyanide is produced.

4) Freons
 Poly chloro fluro alkanes are known as freons. They are colourless, odourless, non toxic, non
inflammable liquids with very less chemical reactivity and high stability.
 Chlorofluoro carbons (CFC’s) known as freons commercially used for refrigeration purpose are
highly volatile and stable in nature.
 They react with ozone and deplete it and clears the path for the uv rays to get in to earth.

5) DDT (PPl dichlorodiphynyl trichloro ethane)

 It is a powerful insecticide and is effective against mosquito that spreads malaria
 Prepared by heating chlorobenzene and chlorine in presence of conc H2SO4

Cl

CCl3CH + H2O

Cl

***

51
 Chapter - XI

ALCOHOLS, PHENOLS AND ETHERS

 The compound obtaineds by replacing one hydrogen atom from aliphatic hydrocarbons by -OH
group are called alcohols where as those obtained by replacing hydrogen of aromatic
hydrocarbons are known as phenols.
 Compounds conataining an oxygen atom bonded to two ( same / different) alkyl/aryl groups are
knwon as ethers)

General Formula
 Alcohol : [R-OH]
 Phenol : [Ar-OH]
 Ethers : [R-O-R/R-OR’] n>1

Alcohols and Phenols

 Monohydric alcohols can be classified as primary, secondary and tertiary depending upon whether
the OH group is attached to 1o, 2o or 3o C- atom.

H R R
R C OH R C OH R C OH

H H R
Primary Alcohol Secondary Alcohol Tertiary Alcohol
10 20 30

 Phenols may be classified as mono, di or trihydric according to the no of -OH group attached to
Benzene group.

OH OH OH
OH
OH

OH

(Monohydric) (Dihydric) (Trihydric)

52
Ethers may be classified as
 Alphatic ethers
CH3-O-CH3 Dimethylether
CH3-O-CH2CH3 Ethylmethyl ether

 Aromatic ethers
Eg: C6H5O-CH3 Methyl Phenyl Ethers
C6H5O-C6H5 Diphenylether

Structure of functional group

 In alcohol, the oxygen of the -OH group is attached to carbon by a sigma bond formed by the
overlape of the sp3 hybrid orbitals of carbon with a sp3 hybrid orbital of oxygen.
 The bond angle in alcohols is slightly less than the tetrahedral angle [109o28’]
It is due to the repulsion between the unshared electron pair oxygen.
 In phenols OH group is attached to sp2 hybridised carbon of an aromatic ring.

General Methods of Preparation of Alcohols

NaOH
R-X

H+or OH-
R’COOR
H 2O
ROH
Dil H2SO4
R-O-R
H 2O
HNO2
RNH2
 Hydration of alkenes
Step I H2O + H+  H3O+
Step II nuclephilic attack of water on carbocation
Step III De protonation to form an alcohol. i) BH3/ THF
R-CH2-CH2OH
ii) H2O2,OH-
R-CH=CH2

Hg(OAC)2
R - CH - CH3
THF - H2O
OH
53
 From Carbonyl compounds
LiA lH 4
RCHO+2H  0
(Aldehyde)  RCH2OH (1 alcohole)
Pd
RCHO+ H2  RCH2OH
NaBH4
R-CO-Rl  l
 R - CH - R
(Ketone)
OH
 Addition of grignard reagent to carbonyl compounds
O
OH
H
C = O + RMg X +  H 2O  C + Mg
R X
Eg:-(1)
H OMgBr
H
C 0 + CH3MgBr C Hydrolysin
H
H CH3
Methanol
CH3-CH2-OH+MgBr(OH)
Ethanol

(2)
CH3 CH3 OMgBr
C 0 + CH3MgBr C CH3 CH CH3
Hydrolysin
H
H CH3 OH
Ethanol
Propan - 2-01

CH3
(3) CH OMgBr
3
CH3
C 0 + CH3MgBr C Hydrolysin CH3 C OH
CH3
CH3 CH3 CH3
Propanone
2-Methyl Propan - 2-01

1o Alcohol is obtained from HCHO

2o Alcohol is obtained from RCHO
3o Alcohol is obtained from RCOR, R may or may not be equal to R’

54
Preparation of phenol
H2S2O7, NaOH

H+/H2O
N2+Cl-
H 2O

OH

NaOH, 

Cl

(i) NaOH 623K, 300 At

(ii) Hcl

CH3 - CH - CH3
(i) O2
or (ii)H+, H2O

OH
Cumene O + CH3CO CH3
Acelone
 Hydrolysis of Aryl halides [Dows process]
Cl ONa Cl

0
N aOH ,300 C HCl

320 atm  
 N aCl 

Sodium Phenoxide Phenol

Physical Properties of Alcohols

 Physical State : Alcohols are colourless, volatile liquids having characteristic colour and bruning
taste.
 Smell and taste of alcohols become less pronounced with increase in molecular weight.

55
 Boiling point - Due to the presence of -OH group alcohols undergo intermolecular hydrogen
bonding and exist as associated molecule. Hence the boiling point of alcohols are much higher
thanthe corresponding hydrocarbons of comparable molecular weight,
 Amongst isomeric alcohols boiling point follow the order 1o>2o>3o which can be explained by
the decrease in surface are a with branching.
 Solubilty -Lower alcohols are soluble in water due to hydrogen bonding. But the solubility de-
creases with increase of molecular mass since hydrocarbon part increase which interrupts the
hydrogen bond formation.
 Among the isomeric alcohols solubility increases with branching since surface area of hydrocar-
bon part decreases with increase of branching.

Physical Properties of Phenols

 Physical State : Phenols are colourless liquids or low melting solids. But they turn reddish brown
due to auto oxidation on exposure to air and light.
 Boiling point :Phenols have much higher boiling points than the corresponding hydrocarbons due
to intermolecular hydrogen bonding.
 Solubility - Phenols form H Bonds with water molecules and hence are soluble in water. But their
solubility is lower than that of alcohols because of large hydrocarbon part.

Chemical Properties of Alcohol

Acidic Nature
i) Reaction with metals : Alcohols react with active metals (Sodium, K, Al) to yield corresponding
Alkoxides / Phenoxides and hydrogen
2R-O-H+2 Na  2R-O-Na +H2
Sodium Alroxide

 Alcohols are Bronsted acids, ic they can donate a proton to a stronger base

iii) Acidic character of alcohols is due to the polar nature of O-H bond. An electron density on
oxygen tendency to decreases. The Polarity of O-H bonds. This decreases the acid strength
 Acids strength of alcohols decreases as per the order

R
R
R  CH2OH > CHOH >> R - C OH
R
(10) R
(20) (30)
 Alcohols are weaker acids than water
 Water is a better proton donor (ie stronger acid)
 Alcohols act as Bronsted bases due to the presence of unshared electron pairs
 Common reactions of alcohols
56
 PCl3
RCl + H3PO3
PCl5
RCl + POCl3 + HCl
P/Br2
RBr
HNO3
ROH RONO2+H2O
R’COCl
R - O - COR1 + HCl
Na
RONa + H2
(RCO)2O
R - O - COR1 + R1 COOH
SOCl2 RCl+SO2 + HCl

 Dehydration
Con H 2SO 4
CH3CH2OH  
120 o C
 CH2= CH2+H2O
 Esterification
CH3COOH+CH3CH2OH H2SO4 CH3COOCH2CH3

Reactively of alcoholes
CH3OH>Primary>Secondary>Tertiary
Reactively of acides
HCOOH>CH3COOH>CH3CH2COOH

 Oxidation
[O]
CH3CH2OH  [O]
CH3CHO  CH3COOH
10 Alcohol

H3C H3C
[O]
OH  [O] CH COOH + H - COOH
C = 0  3
H3C H3C

20 Alcohol
 Iodoform test
CH3CH2OH I 2/ N aO H
    CHI3 + HCOONa+NaI+H2O
 Lucas test : When alcohols are treated with Lucas reagent (con Hcl&2ncl2) turbidity (Alkyl
chlorids) is produced. In case of 30 alcohols, turbidity is produced immediately. 10 alcohols do
not produce turbidity at room temperature.

57
Chemical Properties of Phenol
Audic Nature
Phenol is acidic in nature due ti greater resonence stabilization of phenoxides ion than phenol
itself.
 It turns blue litmas to red and reacts with alkali metal to form salt.
 Reaction of Phenols
NaOH
C6H5ONa+H2O

C6H5OH
Zndust
C6H6 + ZnO

OH
(i) NaOH COOH
(ii) CO2, H+ (Kolbe’s reaction)

dil HNO3 NO 2
+
OH
OH
NO 2

Conc.HNO3
2, 4, 6 - Trinitrophenol (Picric acid)

i) CHCl3. NaOH OH
CHO (Reimer - Tiemann reaction)
ii) H2O/Hcl

i) CCl4:NaOH OH
COOH (Reimer - Tiemann reaction)
ii) H2O/HCl
O
Na2Cr2O 7
H2SO4

O
Benzoquinone

Some Commercially important alcohols

 Wood Spirit
 Methanol is also known as wood spirit sence it was originally obtained by destrictive distillation
of wood.
58
 ZnO Cr2O3
CO+2H2     
200 300 atm500
 CH 3OH

 It is highly poisonous. That is why it is used for denaturing ethyl alcohol ie, to make it unfit for
drinking purpose.
Denatured spirit is also called methylated spirit.
 It is used as an Antificez for automobiles radeator and a substitute for petrol.

Rectified Spirit
 95% ethanol solution is known a reactified spirit and it is prepared by fementation of carbohy-
drate,
$59278092 C H O + C H O
C12 H22 O11 + H2O    6 12 6 6 12 6

(glucose) (fructose)
C6 H12 O6  5<6092 2C H OH + 2CO
2 5 2

 It is mainly used for manufacturing alcoholic beverages ie, Whisky, brandy, beer, rum etc.
 It is also used as antifieeze in automobile radiators and as a substitute for petrol.
 It is also used as an important solvent for plaints, varneshes, dyes, cosmetics, perfumes etc.
 Absolute alcohol
100% alcohol is known as absolute alcohole and it is prepared from rectified spirit.

Ethers - alkoxy alkanes

Classification
Ethers are classified into the following two categories.
 Allphatic ethers: Here two alkyl groups are linked to oxygen atom.
Eg: CH3-O-CH3 - Methoxymethane
H3C-CH2-O-CH2-CH3 - Ethoxy ethane
 Aromatic ethers - Here either one or two a aryl groups are linked to oxygen atom.
Eg: C6H5-O-CH3 (anisole)
C6H5-O-CH2CH 3

General Methods of Preparation

 William son’s synthesis
CH3-CH2-Br+CH3-O Na+  CH3CH2-O-CH3
 For better yields the alkyl halide should be 10 and Alkoxide should be 20 or 30

59
 Dehydiation of alcohols
CH3CH2OH+CH3CH2OH  !7516)7
5
 CH2 CH2 OCH2 CH3
6

 Action of diasomethane on alcohols

R-CH2OH + CH2 N2  35³ RCH - OCH + N
 2 3 2

 We can get aromatic ether from phenol as

OH O Na OR

90'6
  1$


Structure of ether
 In ether ‘O’ atom is in sp3 hybridised state ie, it has four sp3 hybrid orbitals. Two of these sp3
hybrid orbitals contain lone pair of electrons and rest of the two sp3 hybrid orbetals contain
unpaired electron which overlap with sp3 hybrid orbetal of carbon of two alkyl groups having
unpaired electrons and form a bond.
 ....C-O-C... bond angle in ether is about 1100 which is slightly greater than that of H2O molecular
(having 104.50)
 In ether the bond angle is slightly greater than the tetra hedral angle due to the repulsive
interaction between the two bulky (-R) groups. The C-O bond length (141p.m.) is almost the
same as in alcohols. This ether has a bent structure and are polar in nature.

Physical Properties of ether

 Dimethyl/ether, ethyl/methyl/ether are gases
 All other ethers are colourless liquids with good odour.
 Low polarity and water solubility.
 Boiling point increase gradually with increase in molecular mass.

60
Chemical Properties of ethers
 Reaction of aromatic ethers
OCH3 OCH3
Br
Br2
+
CH3COOH
Br
CH3 OCH3
H2SO4
OCH3 NO 2
HNO3
+
NO 2
CH3COCl/B
OCH3 OCH3
Anhy. AlCl3
CO-CH3
+
COCH3

 Cleavage of unsymmetrical ether

During the cleavage of unsymmetrical ether. Smaller alkyl group produce alkyl halides.
Eg:- CH3 - O - CH3 CH3 + HBr  CH3 Br + CH3CH2OH
ethy / methy / ether methyl promide ethanol

 If ether consists of one methyl group and one 10 or 20 alkyl group, then SN2 mechanism takes
place. In such a case methyl halide is obtained with alcohol of bulky alkyl group.
CH3 CH3

CH3 - CH - O - CH3 - HI  CH3I + CH3 - CH - OH

Mehylso-propyl ether methyl iodide Iso propyl alcohol
If ether consists of one methyl group and one 30 alkyl group, then reaction is completed by SN1
mechanism.

* * *

61
 Chapter XII
ALDEHYDES, KETONES AND CARBOXYLIC ACIDS
Aldehydes and Ketones
 Aldehydes and Ketones contains carbonyl > C=0 groups
 These are funcional isomers having general molecular formula CnH2nO

Nomenclature
 In IUPAC system, aliphatic aldehydes are named as alkanals. In the aromatic aldehydes the
parent member is called Benzaldehyde.
 In IUPAC aliphatic and Aromatic retones are names as alkanones.

Structure
 Carbonyl carbon of both aldehydes and ketones is Sp2 hybridised.
 One of the three sp2 hybridised orbital gets involved in a bond formation with half filled
p - orbital of oxygen aton whereas rest fo the two are consumed in bond formation with hydorgen
and carbon depending upon the structure of aldehydes or ketone.

aldehydes ketones

General methods of preparation

 By oxidation of alcohols:
K 2 CR 2 O 7/ H 2 SO 4
RCH2-OH + [O]      RCHO + H2O aldehyde
1o alcohol
K 2 CR 2 O 7/ H 2 SO 4
R- CH - R' + [O]     R- C - R' + H2O
OH O
 By dehydration of alcoholds

R - CH2 - OH Cu
 R - CHO+H2
3000 C

1o alcohol aldehyde
62
 R - CH - R' Cu
 R - C - R' +H2
3000 C

OH O
2o alcohol ketones

 By oxidation of alkenes
O 3/ H 2 O
R - CH = CH - R Zn 
2(R-(CHO)+ Zn O
alkene aldehyde
O 3/ H 2 O
R - C - = C - R' Zn 
R - C - R + R' - C - R' + ZnO
R R' O O
alkenes
 By reduction of acid chloride [Rosemund reaction]
R - COCl + H2  P
d - Ba SO 4
 0
140 C 
R - CHO + HCl
Formaldehyde can not be prepared by this method.
2R - COCl + CdR2'  2RCOR' + CdCl2
RCOCl + R'CdCl  RCOR' +CdCl2
acid chloride ketones

 By hydrolysis of gem dihalides

Cl OH
R CH H2O/OH R CH H 2O R CHO
Cl OH
gem dichloride unstable aldehyde

Cl OH
R C R H2O /OH- R C R -H2O R C R

Cl OH O
unstable Ketone

 By heatiing calcium salt of fatty acid

(R-COO)2Ca + (H-COO)2Ca  
 2(R-CHO) + 2CaCO3
Calcium salt Calcium formate aldehyde
(R-COO)2Ca 
 + R - CO - R + CaCO3
Calcium salt Ketone

63
 By stephen’s reduction reaction
SnCl 2 - HCl
R - CN + 2H  
 R - CH = NH
Alkyl Cyanide Aldimine
H 2O


 R-CHO + NH3
aldehyde

 By hydrolysis of aceto acetic ester

R
2KOH
CH3CO CH - COO - C2H5 


Alkyl acetoaciti acid

CH3COCH2R + K2CO3 + C2H5OH
Ketone

 From Grignard reagent

CH3 - CN + CH3 - Mg Br  CH3 - C = N Mg Br
CH3
2H 2 O CH3 - C- CH3 + Mg (OH) Br + NH3

H+

O Eacetone
 Field Carfts Acylation

O O
R C Cl Anhyd. AlCl3 C R + HCl
+

Benzene Aromatic Ketone

O O
+ Cl C Anhyd. AlCl3 C

Benzyl chloride Benzophenone

 Reemer Tiemen Reaction
OH HO

CHO
N aOH
+ CHCl3 
60-700 C


Salicyladehyde
64
Physical Properties
Only formaldehyde is a gas, where as higher members are liquids or solids.
 Boiling point of aldehydes and ketones are less than that of corresponding alohols because of
the lack of H-bonding in them. But more than corresponding alkanes because of the presence of
dipole - dipole interaction between them

Solubility
 Lower member of aldehydes and ketones are soluble in water due to the H - Bonding between
polar carbonyl group and water.
 Solubility decreases with increase in molecular weight.
 Aromatic aldehydes and ketones are much less soluble than corresponding aliphatic aldehydes
and ketones due to large benzene ring.

Chemical Property
 Carbonyl compunbd have C = O group which as polar due to presence of more electrone-
gative oxygen atom. The result in polarisation of electron as

 
C = O C - O

 The rate determining step is attack of necleophile over carbonyl carbon atom.
 The only difference between >C=O group reaction and >C=C<group reaction is that the former
one undergo nuclephile addition and latter one undergoes electrophilic addition reaction.
 The nucleophile addition depend on the positive charge.

Nucleophile Addition reaction

Addition of NaHSO3

R R OH
C = O +
+ Na HSO3 -
C Na+
R' R SO3-

65
 Ketones containing bulky alkyl group such as diethyl ketone, methyl felt butyl ketone etc do not
react with NaHSO3
 Only benzaldehyde forms sodium bisulphite
Addition of HCN
OH
C = O + HCN C
CN
Cyanohydrin
 Addition of Gridnard reagent
 Formaldehyde form primary alcohols
H
i) CH3MgBr
HCHO H3C OH
ii) H+ / H2O
H

CH3
i) CH3MgBr
CH3CHO H3C OH
ii) H+ / H2O
H
CH3

CH3COCH3 i) CH3MgBr
H3C OH
ii) H+ / H2O
CH3
Addition of Alcohols
Aldehydes react with alcohols in presence of dry HCl to form dialkoxy alkanes called acetals
 Ketones form cyclic Ketals
H

Dry HCl
CH3CHO + CH3OH  H3C OH


OCH3
Hemi acetal

CH3
CH3OH/HCl
H C OCH3
-H2O
OCH3
Acetal

66
 Nucleophile addition followed by loss of water
 Reaction with ammonia derivatives (NH2-2)

H +
C = O+ H2N - z 
PH  3.5
 C = N - Z + H2O

where z=OH, NH2, - NHC6H5M - NHCONH2 etc

 Oxidation of aldehyde and ketones

 Oxydation of aldehydes
 Aldehydes can be oxidised to carboxylic acids having same number of carbon atoms.
RCHO + 2[Ag(NH3)2]+ 3OH-  RCOO- + 4NH3 +2H20 + 2Ag (Silver mirror)
(Tollen’s reagent)
RCHO + 2Cu2+ + 3OH-  RCOO- + Cu+ + 2H2O
From fehling or
Benedict’s soln.

 Oxidation of Ketones
 Yields acids with lesser number of carbon atoms.

CH3COCH2CH2CH3  CH3COOH + CH3CH2COOH

 Oxidation with sodium hypohalite
CH3CHO + 3I2 NaOH Cl3-CHO NaOH CHI3 + HCOONa
   
Iodoform Sodium Formate

Reduction
 Reduction to alocohols
 Catalytic reduction with complex metal hydrides

R R OH
H2/Ni or PtaPd
C O C
H
LiAlH4 or NaBH4 H H
Aldehydes  1o alcohol
Ketones 2 o  alcohol

67
Reduction to hydrocarbons
Clemmensen Reduction
RCHO + 4[H] Zn -Hg/HCl R - CH3 + H2O

 Wolf - Kishner reduction

R - CH = O NH2 NH2 R - CH = NNH2
-H2O Hydrazone
KOH glycol R - CH3 + NH2
Acidity of  - hydrogen
 The  hydrogen of aldehyde and ketones are weakly audic due to
I effect of the C=O which reduces the electron density in the C - H bond
 The carbanion on the enolate ion left after the removal of the proton is stabilized by resonance.
Other reactions
 Aldol condensation - given by only those aldehydes and ketones which contain  - H atoms
H H
2CH3 - C = O dilNaOH CH3 - C - CH2 - CHO
OH
(Aldol)
H+
-H2O CH3CH = CHCHO

Cross Aldol Condensation

CH 3CHO
 NaOH
 

CH 3  CH 2  CHO


1) CH 3CHOH  CH 2 CHO   CH 3  CH  CH  CHO
But  2  enal

2) CH 3  CH 2  CHOH  CH  CHO   CH 3  CH 2  CH  C  CHO
CH3 CH3

2  Methylpent  2  enal


3) CH 3  CHOH  CH  CHO   CH 3  CH  C  CHO
CH3 CH3

2  Methylbet  2  enal

4) CH3  CH2  CH OH CH 2CHO   CH3  CH2  CH  CH  CHO
Pent  2  enal

68
 H3C Ba(OH)2 H3C
C = O C = CHCOCH3
H3C -H2O H3C
4 methylpent 3en zone
 Cannozzaro reaction : Given by those aldehyde whih do not conatain  H atoms
O
2H - C = H + NaOH CH3OH + HCOO-Na+
(50%)

Disfinction between aldehyde and ketones

 Tollen reagent - Both aliphatic and aromatic aldehydes give silver mirror but ketones do not.
 Fehling’s solution - Aliphatic aldehydes reduce Fehling’s solution to give red ppt of Cu2O
while aromatic aldehydes and ketones do not.
 Schiff’s reagent test: Aldehydes restore the pink colour of schiff’s reagent (magnenta or resontine
hydrochloride dissolved in water and its pink colour decolourins by passing SO2 or H2SO3)
 Iodoform test : Methyl Ketones (CH3COCH3, CH3COCH2CH3, C6H5COCH3 etc) on treat-
ment with I2 / NaOH give yellow ppt of iodoform.

Carboxylic Acids
 Organic compound containing COOH group are known as carboxylic acids.
 Formula CnH2nO2

Nomenclature
 Carbon chain is numbered from the carboxylic acid group.
 The longest chain containing the carboxylic group -COOH is selected
 While writing IUPAC name of carboxylic acid ‘e’ of alkane is replaced by oic acid.
Eg CH3CH2CHCOOHBr - 2 Bromo Butanoic Acid

Structure
 Carbon atom of carboxyl group is sp2 hybridised and form one one  bond with each oxygen
atom and one  bond with hydregen or carbon atom depending upon the structure of carboxy-
lic acid.
 Half filled p orbital of each oxygen atom and unhybridised p orbital of carbon atom lies in the
same plane and overlap to form a bond which is localised between three atoms one carbon and
two oxygen atom.

69
General method of preparation
 From 1o alcohol and aldehydes : Oxidation of primary alcohols and aldehydes with neutral
acid or alkaline KMnO4 or acidic K2Cr2O7 gives corresponding carboxylic acid.

RCH2OH [O] RCHO [O] R-COOH

 Oxidation of methyl Ketones

O O
R - C - CH3 3I2 4NaOH R - C - ONa + CHI3 + 3NaI + 3H2O

 Hydrolysis of nitriles
O

R-C N H2O R - C - NH2 H+/H2O RCOOH + NH4+

 KOH reaction [Carboxylation of olefins]

H2C = CH2 + CO+H2O H3PO4 CH3CH2 - COOH
300-400oC
Carbonation of Grignard Reagent O O
R - MgX + O = C = O Dryethane R
C OMgX Mg(OH) X + R - C - OH
H+/H2O
190

 Oxidation of alkyl benzene

COOH
CH3

+ 3[O] KMnO4/OH- + H20

Physical Properties
 Lower acids up to C10 are colour less liquids while higher ones are colourless waxy solids
 Solubility decreases as the molecular mass increases.
 Boiling point of aliphatic mono carboxylic acids are much higher than those of hydrocarbon and
some what higher than those of alohols of comparable molecular mass due to stronger H bond
 Melting point of an acid with even number of C atom is higher

Acidic Stength
 Carboxylic acid ionize in acqueous solution and exist in equilibrium with carboxylate ion.
 Carboxylate ion is stabilised by resonance.

70
Effect of Substituent on acidic strength

 If an electron with drawing group is present then there will be dispersion of negative charge on
the carboxylate ion as a result it will be more stable than those acids which do not have electron
withdrawing groups.
 More the effect of electron withdrawing group the compount will be more acdic. Thus fluoroacitic
acid is more acidic than chloroacetic and finally acetic acid.
 More the number of halogen atom, greater would be the dispersion of the negative charge and
hence more will be stabilization of anion and the compound will be more acidic. Thus
CCl3COOH>Cl2CHCOOH>ClCH2COOH>BrCH2COOH>ICH2COOH
Number of substituents

Cl3CCOOH>Cl2-CH-COOH>ClCH2COOH
Position of substituents
CHCl-COOH>CHCl-CH2COOH>CHCl-CH2CH2COOH

relative acidic strenght of substitued aromatic acids

 Electron donatong substituens(+I effect) decreases the acidic strength where as electron with
drawing groups (-I effect) increases the acidic strenght of substituted benzoic acids.
 Benzoic acid is less acidic than formic acid because of +I effect of Phenyl Group.
 The +I effect of Phenyl is less than that of methyl group hence
H-COOH >C6H5-COOH >CH3COOH
 Ortho substituted benzoic aicd are more acidic among the three isomers.

 This is called ortho effect and it arises due to combined effect of steric and electronic factors.

COOH COOH COOH COOH

CH3 > >

CH3
O-tolune acid Benzoic Acid m-toluic acid CH3
p-toluic acid

71
Chemical Properties
 Hell Volhard Zelnsky reaction
Cl
CH3CH2COOH + Cl2 + RedP
-
CH3CHC - COOH
HCl
 Chloropropanoic acid
Cl Cl2 + RedP - HCl
CH3 C COOH
Cl
  Diehlropropanoic acid

 Electrophilic aromatic substitution reaction

Na
RCOO Na + ½ H2

NaOH
RCOONa + H2O
NaHCO3
RCOONa +CO2+H2O
PCl5
RCOCl + PoCl3 + HCl
PCl3
RCOCl + H3 PO3
R-COOH
SOCl2
RCOCl + SO2 + HCl
LiAlH4
R - CH2 - OH

NH3
RCONH2

***

72
 Chapter XIII
AMINES
 Amines are the derivatives of NH3 in which one or more H atom have been replaced by alkyl or
aryl group.
 These are classified as primary (1o), secondary (2o) and tertiary (3o) depending on whether one,
two or all the three H atoms have been replace by alkyl or aryl group.
Nomenclature
 In the common system, amenes are called alkyl amInes or amino alkanes but in the IUPAC
systems, these are called alkanamines.
Eg: CH3CH2NH2, CH3CH2-NH-CH3
Ethanamine (1o) N- methylethanaamine(2o)

Structure of amino group

 Nitrogen atom of amino group is sp3 hybridised. Three of these orbitals get involved in sigma
bond formation with other atoms where as fourth orbital contain lone pair of electrons. Thus
amines are pyramidal in shape.

General method of Preparation

 from alcohols
primary
NH 3 CH 3 CH 2 OH/ 
CH3CH2OH 
H 2O CH3CH2NH2 H 2O  [CH3CH2]2NH((2oamine)
CH 3CH 2OH/ 

-H 2O
 (CH3CH3)3N

(Tertiary amine)
 Gabriel Phthalimide synthesis
O O
O

NH KOH NK+ CH3CH2Br NH2CH3

-KBr

O O O
COOH

H+/H2O CH3CH2NH2 +
Pthalimid (Ethylamice)
COOH
Pthalic acid
73
 Hofman bromamide reaction
 For converting amide to primary amines having one carbon atom less.
O
Br2
CH3 - C - NH2 CH3NH2 + K2CO3 + KBr + H2
KOH O

 Reduction of N containing compound

CH3CH2NO2 Sn/HCl or H2/Pt CH3CH2CH2NH2
Primary amine
CH3CH2CN LiAlH4 or Na / Alcohol CH3CH2CH2NH2
(Ethylcyanide) Primary amine
CH3CONH2 LiAlH4 CH3CH2NH2
(Ethanamide) Primary amine

 By hydorlysis of N containing compounds

CH3CH2NC H+/H2O CH3CH2NH2 + HCOOH
Ethyl isocyanide Ethanamine
CH3CH2N = C = O KOH CH3CH2NH2 + HCOOH
Ethyl isocyanate Ethanamine
 Schmidt Reaction
 To convert carboxylic acid to amines having one carbon atom less
CH3COOH N3H 
CH3NH2+ CO2+N2
H2SO4
COOH N3H  NH2
H2SO4
+ CO2+N2

Benzoic Acid Anilene

 Ritter Reaction
CH3
CH3
CH3C C O H (i) HCN H2SO4
H3C C NH2
CH3 (ii) H+/H2O
CH3
Ammonolysis of alkyl halides
NH3+ R - X R - N+H3X- (Substituted ammonium salt)
(Nucleophile)

74
Physical Properties
 Lower amines are gases and liquid but higher amines are solids
 Primary and secondary amines have higher boiling points than other organic compounds due to
hydrogen bonding.
 Primary and secondary amines are soluble in water due to hydrogen bonding between and H2O.

Basic Character
CH3NH2 + HCl  CH3NH+3Cl-
 Due to the presence of lone pair of electron on nitrogen atom, amines are basic in nature.
 Basic character of amines can be compared on the basic of inductive effect of alkyl groups, steric
effect and resonance involvements of lone pair of electrons.

Aliphatic Amines
 Among aliphatic amine +I effect of alkyl groups pushes the electron towards nitrogen atom an so
increase the basic character.

 In a acqeous solution , the following order is observed.

2oAmine >1oAmine > 3oAmine > Ammonia (aq. soln)
 This can be explained on the basis of solvation effect
In tertiary amines after accepting a proton there is no hydrogen to stabilize the positive ion by
hydrogen bonding.

Aromatic Amines
 Aromatic amines are less basic than aliphatic amines, because of the involvement of lone pair of
electron in resonance with the aromatic ring which now becomes less available for donation.
 Also sp2 hybridised carbon of the aromatic ring is more electron withdrawing than sp3 hybridisid
carbon of aliphatic amines and exerts a stronger withdrawing effect resulting in less tendency to
donate lone pairs.

Substituted atomatic amines

 In substituted aromatic amines, generally electron withdrawing groups, decrease the basic char-
acter and electron releasing group increases the basic character of amines.

75
 A group present at ortho position to amino group always decreases the basic character whether
it is electron releasing or electron withdrawing and this phenomonon is known as the ortho effect.

Chemical Properties
 Carbylamine reaction
RNH2 +CHCl3+ 3KOH(alc)  R-N = C + 4KCl + 3H2O
Only by 10 amines
 Reaction with grignard reagent
Br
RNH2 +R'Mg Br  R'H +Mg
NHR
 Oxidation of amines
 Oxidation with potassium permanganate
KMnO 4
R - CH2 - NH2   R - CH=NH
 R - CH=O + NH3

Oxidation of aniline
K 2 Cr2 O 7 / H 2 SO 4
Aniline   A black dye
( aniline black)
 Acylation of amines
R - NH2 
CH 3 COCl
 RNHCOCH3 + HCl
 Hoffmann mustard oil reaction
S SH

R - NH2 + C  R-NH - C 
HgCl2 HgS + 2 HCl + R - N = C = S
S S
 Ring substitution on aniline

NH2+ NH2+ NH2+

NH2 +NH2

(-) (-)

(-)
76
 Bromination
NH2
NH2
Br Br
Br2/H2O + 3H Br
+ 3 Br2

Br
2, 4, 6 - Hibromo ancline

 Nitration
NH2 NH2 NH2 NH2
HNO3 NO 2
H2SO4
+ +

NO 2
NO2

NH2 NHCOCH3 NHCOCH3 NH2

(CH3CO)2O HNO3, H2SO4 OH- or OH+

NO 2 NO 2
p - nitroacetanilide p - nitro aniline

 Sulphonation

NH2 N+H3HSO4- NH2 +NH3

H2SO4 453-473k

SO3H SO 3-
Aniline hydrogensulphide Zwitter ion

77
 Reaction with nitrous acid
NaNO2 + HCl  NaCl + HNO2
R-NH2 + HNO2  R- OH + N2 +H2O
R3N+HONO  [R3NH]+NO2-  R-OH + R2N-N=O (Nitrosamine)
 Diazonium Salts (ArN2X)
The diasonium salt have the general formula (ArN2X) where X may be an anion like Cl-Br-
HSO4- etc and the group N2+ is called diazonium ion group.
C6H5N2Cl is called benzene diazonium chloride.
273 278k
C6 H 5 NH 2  NaNO 2  HCl   C 6 H 5Cl  NaCl  H 2 O
The conversion of primary aromatic amines into diazonium salts is known as diazotisation.

Reaction of benzenediazonium chloride

 Sandmeyers reaction
CuCl/HCl C H Cl + N
6 5 2

CuBr/HBr C6H5Br + N2
C6H5N2Cl
CuCN, KCN
C6H5CN + N2
 Gatterman reaction
Cu/Hcl C6H5 - Cl + N2 + CuCl
C6H5N2Cl
Cu/HB C6H5 - Br + N2 + CuCl
 Other reactions
1) C6H5N2Cl + KI  C6H5I + KCl + N2
2) C6H5N2Cl + H3PO2 + H2O  C6H6 + N2 + H3PO3 + HCl
3) C6H5N2Cl + H2O  C6H5-OH + N2+HCl
1) HBF4
4) C6H5N2Cl 
2) NaNO ,Cu
2
 C4H5NO2 + N2 + NaBFu

Coupling Reaction
1) -
N2Cl + OH OH N=N- OH + Cl- + H2O

2)
N2Cl + NH2 N=N- NH2 + Cl- + H2O
(yellow dye)

***
78
 Chapter XIV
BIOMOLECULES
Biochemistry
The brach of Chemistry which deals with study of chemical composition and structure of living
organisation and chemical changes taking place in them.
Biomolecules
The complex organic molecules which build up organisam and form the basis of life.
Carbohydrates
These are polyhydroxy aldehydes or ketones or the compounds wich can provide them
on hydrolysis.

Classification of Carbohydrates
a) Monosacharides : Simple carbohydrates which can not be hydrolysed further.
eg: Glucose & Fructose
b) Oligo Scacharides : Carbohydrates which on hydrolysis give two to nine mono sacharides.
eg: Sucrose, Maltose and Lactose
c) Polysaccharides : Carbohydrates which on hydrolysis give large number of monosacharides.
eg : Starch, Cellulose and glycogen
Glucose  CH3-CH2 -CH2 -CH2 -CH2 -CH3
HI n-hexane

CHO NH4OH CH=N-OH

(CHOH)4 (CHOH)4
CH2OH
CH2OH Oxime
HCN CN
CH
OH
(CHOH)4
CH2OH
Cyenohydrum
Br2 Water
COOH
(CHOH)4
CH2OH]
Gluconic acid
Acetic anhychide CHO

(CHCOOH3 ) 4
CH2 COOCH3
Glucose pentaccetate

COOH
HNO3 (CHOH)4
Oxidation
COOH
Saccharic acid
79
Starch : It is a polymer of glucose and consists of 15-20% water souble Amylose and 80-85%
water insoluble Amylopectin.
* Sucros is a non reducing sugar
* Maltose and Lactose are reducing sugars.

Functions of carbohydrates
1) They act as biofuels to provide energy for functioning of living organism
2) They act as constituents of cell membrane.
Anomer : A Stereo isomer which differ in configuration about a carbon atom
amino acids : The organic compound containing - COOH and an NH2(Amino) group at the
same carbon atom (  - carbon)
eg: H2N-CH2-COOH Glycine H2N-CH2-CH3 COOH Alamine
Zwitter ion CH3
It is a neutral species carries both positive and negative charges. In the formation of a zwitter ion
a proton form -COOH part of the molecule is released and attaches itself to -NH2 part to form
a dipole ion.
O O

H2N - CH - C - OH H3N+ - C - C - O-

R R
Proteins : These are polymers of amino acids which are essential for the growth and maintenance of
life.

Structure of Protein
1) Primary Structure : The sequence in which amino acids are arranged in proteins.
2) Secondary Structure : The manner in which the polypeptile chains are folded.
3) Tertiary Structure : This gives the overall shape of proteins
4) Quarternary Structure : The special arrangement of two or more peptile chains.

Denaturation of Protein
The proces that brings about changes in physical and biological properties of the proteins. Dena-
turation does not change the primary structure but changes the secondary and tertiary structure
of proteins.
eg : When the egg is boiled hard, the soluble globular proteins present in it denatures resulting in
the formation of soluble fibrous proten.

80
Nucleic Acids
Bio molecules present in the living cell which play significant role in synthesis of proteins in living
organism

Difference between DNA X RNA

DNA RNA
1) DNA has 2 deoxy ribose as sugar unit 1) RNA has ribose as as sugar unit
2) The bases in DNA are Adenine(A), Thymine(T), 2) The bases in RNA areadrenine (A),
Guanine(G), Cytosine(C) Guanine(G), Uracil & Cystome (C)
3) DNA has double standard structure 3) RNA has single standard structure

Functions of Nucleic Acids

1) For Protein synthesis
2) for Replication
Vitamins
The organic compounds, other than carbohydrates, proteins and fats that are necessary to
maintain normal health and growth
a) Water soluble vitamins: B group vitamis and Vitamins C
b) Fat soluble vitamins : Vitamins which are soluble in fat and oils but insoluble in water
eg:- Vitamins A, D, E and K

Name and Vitamin Sources Deficiency Deseases

Vitamin A Carrots, Butter and Milk Night Blindness
Vitamin B1 Milk, Green Vegetables Beri Beri
Virtamin C Citrus Fruits
Green leafy vegetables Scurvy
Vitamin D exposure to sunlight Rickets
Vitamin K Green Leafy vegetables Increased blood clottiong time

***

81