preparation and reactions of alcohols, identification test for alcohol,Classification of alcohol and uses of various alcohols

1. Alcohol
Mr. Mote G.D.
ADCBP, Ashta Dist: Sangli
Maharashtra

2. Alcohol
• Alcohols are compounds in which a hydroxyl(-OH group is attached
to saturated carbon atom.
• Classification depending upon number of hydroxyl Group.
• Alcohols containing one such —OH group are called Monohydric
alcohol.
• Those with two-OH groups are Dihydric alcohols,
• three-OH groups are trihydric alcohols
• Many-—OH groups are known as Polyhydric alcohols.
CH3CH2OH
ethanol
(Monohydric)
H2C
CH2 OH
OH
1,2 dihydroxy alkane
(Dihydric)
2HC
HC
OH
OH
CH2 OH
Glycerol
(Trihydric)

3. Classification of monohydric alcohol
Monohydric alcohol
Primary alcohol(1°)
e.g. Ethanol,
Secondary alcohol(2°)
e.g. Isobutanol
Tertiary alcohol(3°)
e.g. tert- butyl alcohol
CH3CH2OH
ethanol CH3 C
H
OH
CH3
isobutanol
CH3 C
OH
CH3
CH3
tert-butyl alcohol

4. Method of Preparation
1. Hydrolysis of alkyl halides.
2. Hydration of alkenes.
3. Catalytic hydrogenation
4. From Grignard reagents.
5. Reduction of carboxylic acid
6. Reduction of acid chlorides and esters.
7. Reduction of epoxides.
8. Oxymercuration- reduction of alkenes.
9. Hydroboration- oxidation of alkenes

5. 1. Hydrolysis of alkyl halides
• Alkyl halides react with aqueous potassium hydroxide to form
alcohol.
5Mr. Mote G.D
H3C
H2
C NaOH CH3 CH2 OH
Ethanol
Br
NaBr
ethyl bromide
H2O
NaOH Na+ + OH-
H3C
H2
C Br
 
CH3
H2
C Br
OH
CH3 CH2
OH
Mechanism
Na
-NaBr

6. 2. Hydration of alkenes
Water adds to alkene in presence of acid catalyst form alcohol
6Mr. Mote G.D
H OH- H+ + OH-
CH3 C
H
CH2 H++ CH3
H
C CH2
H
OH-
H3C
H
C CH2
OH H
prop-1-ene
2-Propanol
C
H
CH2
propene
C
H
OH
CH2
H
2- propanol
H2O
H+
H3C H3C

7. 3 . Catalytic hydrogenation of aldehydes and ketones
• Reduction of aldehyde and ketone to form alcohol.
7Mr. Mote G.D
Catalytic hydrogentation
CH3 C
O
H + H2
Pt
CH3CH2OH
ethanol
acetaldehyde
Reduction with lithium aluminium hydride or sodium borohydride
CH3 CH2 C
O
CH3
LiAlH4
NaBH4
H3C CH2 C
H
OH
CH3
H3C CH2 C
H
OH
CH3
butan-2-olbutan-2-ol

8. 4. From aldehyde and ketone using Grignard reagents
• Aldehydes and ketones react with Grignard reagents to give
an addition product which can be hydrolyzed to give alcohol.
8Mr. Mote G.D
CH3 C
O
H + CH3MgI
acetaldehyde
CH3 C
O
H
MgI
CH3
H2O
CH3 C
O
H
H
CH3
propan-2-oliodo(isopropoxy)magnesium

9. 5. Reduction with lithium aluminium hydride
R C
O
OH
LiAlH4, ether
H2O
R-CH2OH LiOH Al(OH)3
acid alcohol
3HC C
O
OH
LiAlH4, ether
H2O
CH3-CH2OH LiOH Al(OH)3
acetic acid ethanol

10. 6. Reduction of acid chlorides and esters
• Acid chlorides and esters undergo reduction with LiAlH4 to
form primary alcohol.
10Mr. Mote G.D
CH3 C
O
Cl
Acetyl chloride
LiAlH4
H2O
CH3 C
H
H
OH
ethanol
CH3 CH2 CH2 C
O
OCH3
LiAlH4
H2O
CH3 CH2 CH2 C
H
H
OH + CH3OH
methyl butyrate butan-1-ol

11. 7. Reduction of epoxides
• Epoxides contain polar C-O σ bonds that react with nucleophile are
reduced with metal hydride reagents, like lithium aluminium
hydride to form alcohol.
11Mr. Mote G.D
CH3
H
C CH2 CH3 C
H
CH2
H
LiAlH4
OH
H2O
O
2-methyloxirane
CH3
H
C CH2
O
Li+
H AlH3
CH3
H
C CH2
O-
H
H-OH
OH-
CH3
H
C CH2
OH H
propan-2-ol

12. 8. Oxymercuration-demercuration of alkenes
• Mercuric acetate and water add to alkenes called as
oxymercuration
• Reduction of oxymercuration product in presence of sodium
borohydride to form alcohol called as demercuration
12Mr. Mote G.D
CH3 C
H
CH2
CH3 C
H
CH2
Hg
NaBH4
H3C
H
C CH2
OH H
prop-1-ene
2-Propanol
Hg(OOCCH3)2
OH
O C
O
CH3
H2O

13. 8. Oxymercuration-demercuration of alkenes
13Mr. Mote G.D
CH3 C
H
CH2
CH3
H
C CH2
Hg
NaBH4
H3C C
H
CH2
HgOAc
prop-1-ene
OAc
Hg
AcO OAc
OH
HOAc-
-CH3COOH
OH
H3C C
H
CH2
H
OH
Mechanism

14. 9. Hydroboration- oxidation of alkenes
• Addition of borane to alkene, forming an alkylborane and
oxidation of alkylborane to form alcohol.
14Mr. Mote G.D
CH3 C
H
CH2
CH3 C
H
CH2
BH2
H3C C
H
CH2
OH
prop-1
-ene
BH3
H
Hydroboration
H
Propanol
H2O/OH-

15. Reactions of alcohols
1. Formation of salt with active metals.
2. Formation of alkyl halides.
3. Formation of esters.
4. Formation of carboxylic acid.
5. Formation of alkenes.
6. Formation of alkanes.
7. Formation of ketones.
8. Formation of aldehydes.
9. Formation of ethers.

16. 1. Reaction with Metals to form salt.
• Alcohols react with Li, Na, K to liberate hydrogen and metal
oxides.
16Mr. Mote G.D
H3C
H2
C NaOH
ethanol
22 CH3 CH2ONa H22
sodium ethoxide
+

17. 2. Formation of alkyl halides
• Alcohols react with HBr or HI to produce alkyl bromides or
alkyl halides.
17Mr. Mote G.D
H3C
H2
C HBr CH3 CH2 Br
ethyl bromide
OH
H2O
ethyl alcohol

18. 2.A. Action of halogen acids on alcohol
(Formation of alkyl halides)
• Alcohols react with HBr or HI to produce alkyl bromides or
alkyl halides.
18Mr. Mote G.D
H3C
H2
C HBr CH3 CH2 Br
ethyl bromide
OH
H2O
ethyl alcohol
Mechanism:
HBr H+ + Br-
H3C
H2
C OH
CH3 CH2 Br
ethyl bromide
H2O

19. 2. B. Action of Phosphorus halides on
alcohol(Formation of alkyl halides)
• Alcohols react with phosphorus halides to produce alkyl
halides.
19Mr. Mote G.D
H3C
H2
C PCl5
CH3 CH2 Cl
ethyl bromide
OH
HCl
ethyl alcohol
POCl3
P
Cl
Cl
Cl
Cl
Cl
H3C
H2
C OH
ethyl alcohol
+
-HCl
H3C
H2
C O-
P
Cl
Cl
Cl
Cl+
CH3 CH2 Cl
ethyl bromide
POCl3
Mechanism

20. 2.C Action of thionyl chloride on alcohol(Formation
of alkyl halides
• Alcohols react with thionyl chloride in the presence of
pyridine to produce alkyl halides.
20Mr. Mote G.D
H3C
H2
C SOCl2
CH3 CH2 Cl
ethyl chloride
OH
SO2
ethyl alcohol
HCl
pyridine
S OCl
Cl
H3C
H2
C OH
ethyl alcohol
-HCl
CH3 CH2 O- + S O
Cl
CH3 CH2 Cl
ethyl chloride
SO2+
Mechanism

21. 3. Formation of ester
Alcohol react with carboxylic acid in the presence of strong acid to form esters
H3C C
O
OH H H3C C
O
OCH3 H2O
acetic acid methyl acetate
OCH3
methanol
H OCH3
methanol
CH3O- + H+
H3C C
O
OH
 -H2O
H3C C
O
OCH3
methyl acetate
Mechanism

22. 4. Formation of carboxylic acid
Oxidation of primary alcohols and aldehydes: Primary alcohols
and aldehydes on oxidation with sodium or potassium
dichromate and sulphuric acid, or potassium permanganate,
give the corresponding carboxylic acids.
RRCH2OH
alcohol
C
O
H
aldehyde
R C
O
OH
acid
O
3HCCH3CH2OH C
O
H 3HC C
O
OH
K2Cr2O7
H2SO4
K2Cr2O7
H2SO4
ethyl alcohol acetaldehyde acetic acid
-H2O
O

23. 5. Dehydration of alcohol
• When alcohol is heated in the presence of sulphuric acid to
form alkene by elimination of water
R
H
C
H
CH2
OH
H2SO4

R
H
C CH2
alkene
H3C
H
C
H
CH2
OH
H2SO4

H3C
H
C CH2
Propene
alcohol
1-
propanol
H2O
H2O
23Mr. Mote G.D

24. 5.1 E1 dehydration of alcohol
• When alcohol is heated in the presence of sulphuric acid to
form alkene by elimination of water
24Mr. Mote G.D
CH3 C
CH3
OH
CH3 CH3 C
CH3
CH3
carbocation
H2O
H2C C
CH3
CH3
H
H2C C
CH3
CH3
Step-I
Step-II
fast
2-methyl butene
H-SO3H
slow
-SO3H
-H2SO4
Mechanism
H3C C
CH3
OH
CH3
H2SO4 H2C C
CH3
CH3
2-methyl butene
H2O+
ter-butyl alcohol

25. 5.2 E2 dehydration of alcohol
• When alcohol is heated in the presence of sulphuric acid to
form alkene by elimination of water
25Mr. Mote G.D
CH3 C
CH3
OH
CH3 CH3 C
CH3
CH3 H2C C
CH3
CH3
2-methyl butene
H-SO3H -SO3H
-H2SO4
Mechanism
H3C C
CH3
OH
CH3
H2SO4 H2C C
CH3
CH3
2-methyl butene
H2O+
ter-butyl alcohol
OH2

26. 6. Oxidation of alcohol
• Alkyl halide undergo reduction with nascent hydrogen in
presence of reducing agent like Zn/HCl to form alkanes.
26Mr. Mote G.D
CH3
H
C
H
OH
O
K2Cr2O7
CH3 C
H
O H2O
ethanol
acetaldehyde

27. 7. Catalytic dehydrogenation of alcohol
• Alkyl halide undergo reduction with nascent hydrogen in
presence of reducing agent like Zn/HCl to form alkanes.
27Mr. Mote G.D
CH3
H
C
H
OH
Cu
300°C
CH3 C
H
O H2
ethanol
acetaldehyde

28. 8. Reaction with Grignard reagents (Formation of
alkanes)
• Alcohols react with Grignard reagents(R-Mg-X) to form
alkanes.
28Mr. Mote G.D
H3C
H2
C CH3MgCl CH3 CH2 OMgClOH
CH4
ethanol
methane
Mechanism
CH3MgCl CH3 + MgCl
methyl radical
H3C
H2
C OH
CH3 CH2 O H+
CH3 + H CH4
CH3 CH2 O + MgCl CH3 CH2 OMgCl

29. 9. Reduction of alcohol to form alkane
• Alcohol undergo reduction with concentrated hydriodic acid
and phosphorus to form alkanes.
29Mr. Mote G.D
H3C
H2
C HIOH
ethanol
2 CH3 CH3
I2
ethane
+ H2O+
H3C
H2
C OH HI
-H2O
CH3 CH2 I
HI
I2
CH3 CH2 H
Mechanism

30. Identification test for alcohol
• Solution of alcohol and sodium metal gives hydrogen gas
indicate alcohol.
• Alcohol and phosphorus chloride evolves HCl confirms
alcohol.
• Alcohol and acetyl chloride produce separate layer of ester
and HCl gas evolves, indicates –OH group.
• Lucas test: alcohol, HCl and zinc chloride to form alkyl
halides or precipitate confirms sec and ter alcohol.
• Dichromate test: Alcohol is treated with sodium
dichromate in sulfuric acid, primary alcohol gives acid, sec
alcohol gives ketone means color of product is green color
but tertiary alcohol does not react under condition.

31. Uses of alcohol
Sr. No Name of comp. Uses
1 Ethyl alcohol Manufacturing of alcoholic beverages, industrial solvent, in manufacturing of drugs,
flavoring extract, perfumes, antiseptic in hospitals, freezing liquid , antifreeze in
automobile radiator, lacquers and vanishes, preservatives for biological specimens,
manufacturing of acetaldehyde, acetic acid, ethyl chloride, ethyl acetate, synthetic
rubber.
2 Chlorobutanol Antibacterial, Fungicidal, preservatives in injections, eye drops, mouth washes, salves,
creams, ointments.
3 Cetosteryl alcohol Emulsion stabilizers, opacifying agent, boosting surfectant, emolient, viscosity
increasing agent
4 Benzyl alcohol Benzyl alcohol forms esters which are used in perfumery, benzyl acetate, having
fragrance of jasmine, being as local anaesthetic and antiseptic, it is used in ointments
for reliving itching.
5 Glycerol Humectants, used in bakery product, hand lotion, vanishing creams, shaving soaps,
tooth paste, production of plastic , synthetic fibers, surface coating, in manufacturing
of explosives like Dynamite and cordite
6 Propylene glycol Drug stablizer in topical, oral and injectable medications, sanitizers, humactant,
solvent.
CH3 CH2 OH
C C OH
Cl
Cl
Cl
CH3
CH3
H2C C
H
CH2
HO OH OH
CH2 OH
H2C C
H
CH2
H OH OH
OH