1. By: VEERESH HALEMANE M.sc. K-SLET (Ph.D)
Assistant Professor
Government First Grade College
Humnabad-585330.
R-OH
O
CH3 H
108.9
0
Ex:
96pm
142pm
1
2. What are Alchols?
When a hydrogen atom of an aliphatic or aromatic
hydrocarbon is replaced by – OH group we get alcohols or
phenols respectively.
When a hydrogen atom of a hydrocarbon is replaced by
alkoxy or aryoxy group 𝑅 − 0 𝐴 𝑟 − 0 we get ethers.
2
3. Classification of mono hydric alcohols
Alcohols and phenols are classified as mono, di, tri (or) poly
hydric compounds depending on whether they contain one, two,
three
(or) many Hydroxyl groups respectively in their structures
Monohydric alcohols may be further classified based on the
hybridisation of the carbon atom to which the hydroxyl group is
attached
1. - OH group attached to sp3 carbon
3
4. - OH group attached to sp3 carbon
Alcohols are classified in to primary, secondary and tertiary
alcohols based on the −OHgroup is attached to primary,
secondary and tertiary carbon atom.
CH2 OH
1
0
- alcohol
CH OH
2
0
- alcohol
C OH
3
0
- alcohol
Ex:
4
5. In these alcohols the - OH group is attached to a sp3
hybridised carbon next to the carbon – carbon double bond.
CH2
CH OH
CH2
1
0
- alcohol
C
CH OH
H
R
CH2
2
0
- alcohol
C
CH OH
R
R
CH2
3
0
- alcohol
Ex:
What are allylic alcohols?
5
6. In these alcohols the group and attached to a sp3 Hybridised
carbon atom next to an benzene ring.
CH2OH CH
R
OH C
R
OH
R
1
0
- alcohol 2
0
- alcohol 3
0
- alcohol
Ex:
What are benzylic alcohols?
6
7. These alcohols are of two types
(i) Vinyl alcohols: Ex :-
(ii) Phenols: Ex:-
CH2 CH OH
OH OH
CH3
- OH group attached to sp2 carbon
7
8. Nomenclature of alchols
The common name of an alcohol is obtained by adding
alcohol to the name of the Alkyl group
Ex:
CH3 OH
Methyl alcohol
CH3 CH2 OH
Ethyl alcohol
8
9. According to IUPAC system the name of the alcohol is
obtained by replacing the terminal ‘e’ of the primary suffix by
′𝑂𝑙′
Ex:
propan - 1 - ol
CH2
CH3 CH2 OH
CH3OH
Methanol
Nomenclature of alcohols
9
10. Cyclic alcohols are named using the prefix cycle and
considering the −OHgroup attached to C − 1
Ex:
Cycle Hexanol
OH OH
CH3
Br
4 - Bromo - 2 - methyl cyclo Hexan -1 - ol
Nomenclature of cyclic alcohols
10
11. Example-1
Classify the following as 10
, 20
and 30
alcohols, and Identify
allylic alcohols
C
H3 C CH2 OH
CH3
CH3
C
H2 CH CH OH
CH3
CH
OH
CH
CH3
CH3
CH3 C2H5
CH
C6H5
OH
CH
CH
H5C6 C
CH3
CH3
OH
(a)
(e)
(d)
(c)
(b)
11
12. 𝐀𝐧𝐬:
10 − alcohols d
20 − alcohols: a, c, e
30 − alcohols:b
Allylicalcohols: a, b, e
12
13. Name the following compounds according to IUPAC system
Cl
OH
(i)
OH
OH
H
O
1
2
3
4
5
6
7
(ii)
Example-2
13
16. General methods Preparation of
Alcohols
1. From alkenes – Hydration
2. From alkenes – Hydroboration and oxidation reaction
3. By Reduction of carbonyl compounds
4. By reduction of carboxylic acids and esters
5. By Grignard reaction
16
17. By acid catalysed hydration of
alkenes
Alkenes react with water in the presence of acid as a catalyst
to form alcohols.
In case of unsymmetrical Alkenes the addition reaction takes
place in according with Markovnikov’s rule.
C
H2 CH2
H3O+
+ H2O CH3 CH2 OH
CH3 CH CH2 + H2O
H3O+
CH3 CH CH3
OH
17
18. The mechanism of the reaction involves the following three
steps
Step 1: protonation of Alkene
C
H3 CH CH2 + H3O
+
+
C
H3 CH
+
CH3 H2O
Mechanism of acid catalysed
hydration of alkenes
18
19. Step 2: Nucleophilic attack of water on carbocation
H2O
C
H3 CH
+
CH3 + C
H3 CH CH3
OH2
+
Mechanism of acid catalysed
hydration of alkenes
19
20. Step 3: Deprotonation of form an alcohol
H3O
+
+
H2O
C
H3 CH CH3
OH2
+
+ C
H3 CH CH3
OH
Mechanism of acid catalysed
hydration of alkenes
20
21. This reaction Involves the addition of water across the double
bond according to anti markovnikov’s rule.
In this reaction carbocation intermediates are not formed so
rearrangement products are not formed
By hydroboration – oxidation
reaction
21
22. C
H3 CH CH2 + (BH3)2
C
H3 CH CH2
H BH2
C
H3 CH CH2
C
H3 CH2 CH2
B
H
CH2
CH2
C
H3
C
H3 CH CH2
C
H3 CH2 CH2
B
CH2
CH2
C
H3
CH2 CH2 CH3
H2O2/OH
-
CH2 CH2
C
H3 OH
By hydroboration – oxidation
reaction
22
23. Carbonyl compounds are reduced to alcohols by the following
reducing agents
(a) H2 P d, Pt, Ni (b) NaBH4 (c) LiAlH4
LialH4 is a strong reducing agent so It can also reduces the
carboxylic acids, Ester and Acid Chlorides
+
R CHO H2
Pd R CH2 OH 1
0
- alcohol
R C R
O
Na B Hy R CH R
OH
By Reduction of carbonyl compounds
23
24. Carboxylic acids are reduced to 10 alcohols by strong reducing
agent LiAlH4
LiAlH4is an Expensive reagent so commercially the following
method is used to reduce the acids to alcohols:
R COOH R CH2 OH
LiAlH4
H2O
R COOH
R1
OH
H3 O+
RCOOR
1 H2 /pd
R CH2 OH + R
1
OH
By Reduction of carboxylic acids
and esters
24
25. Grignard reagents react with carbonyl compound to form an
adduct which on hydrolysis gives respective alcohol.
C O + R Mg X C
R
O
-
MgX
+
H2O/H
+
C
R
OH
From Grignard reagents
25
26. The reaction of Grignard reagent with methanalproduces a
10 −alcohol, with other aldehydes, 20 −alcohols and with
ketones 30 −alcohols
HCHO + RMgX RCH 2 OMgX
H2 O
R CH2 OH + Mg(OH)X
R CHO + R
1
Mgx R CH OMgx
R
1
H2O
R CH OH
R
1
+
Mg(OH)X
R CH R
O
+ R
1
Mgx R C OMgx
R
1
R
H2O
R C OH
R
1
R
(OH)X
From Grignard reagents
26
