1. SANTOSH CHEMISTRY DEPT
ALCOHOLS
SANTOSH
CHEMISTRY DEPT

2. Introduction
Alcohols constitute a class of compounds which are regarded as hydroxy derivatives of hydrocarbons.
Based on the no. of hydroxyl groups the alcohols are classified as mono-, di- and trihydric accordingly, if the molecules contain 1, 2 or 3 –OH groups respectively. The alcohols which contain four or more no. of –OH groups are called polyhydric alcohols.

3. Primary: carbon with –OH is bonded to one other carbon.
Classification CH3, 1o, 2o, 3o
Primary: carbon with –OH is bonded to one other carbon.
Secondary: carbon with –OH is bonded to two other carbons.
Tertiary: carbon with –OH is bonded to three other carbons.
Aromatic (phenol): -OH is bonded to a benzene ring.

4. IUPAC Nomenclature
Find the longest carbon chain containing the carbon with the -OH group.
Drop the -e from the alkane name, add -ol.
Number the chain, starting from the end closest to the -OH group.
Number and name all substituents.

5. Examples: 2-methyl-1-propanol 2-butanol 2-methyl-2-propanol
3-bromo-3-methylcyclohexanol

6. Unsaturated Alcohols
Hydroxyl group takes precedence. Assign that carbon the lowest number.
Use alkene or alkyne name.
pent-4-ene-2-ol

7. Hydroxy Substituent
When -OH is part of a higher priority class of compound, it is named as hydroxy.
Example:
4-hydroxybutanoic acid

8. Common Names Alcohol can be named as alkyl alcohol.
Useful only for small alkyl groups.
Examples:
isobutyl alcohol
sec-butyl alcohol

9. Naming Diols Two numbers are needed to locate the two -OH groups.
Use -diol as suffix instead of -ol.
1,6-hexanediol

10. Glycols 1, 2 diols (vicinal diols) are called glycols.
Common names for glycols use the name of the alkene from which they were made.
1,2-ethanediol
1,2-propanediol
ethylene glycol
propylene glycol

11. Preparation Reactions
Reduction of carbonyl compounds
Hydration of Alkenes
Grignard reactions

12. Reduction of Carbonyl Compounds
Reduction of Aldehydes/ketones
Reduction of Carboxylic acids/Esters

13. Reduction of Aldehydes/Ketones
Hydrogenation

14. Reduction of Aldehydes/Ketones
Hydride Reductions

15. Mechanism

16. Reduction of Carboxylic Acids and Esters
Lithium Aluminum Hydride Reduction

17. Hydration of Alkenes Acid catalyzed Hydration
Oxymercuration-Demercuration
Hydroboration-Oxidation

18. Acid-Catalyzed Hydration of Alkenes
Markovnikov addition
Formation of most stable carbocation
Shifts/rearrangements possible

19. Hydration of Alkenes via Oxymercuration/Demercuration
Markovnikov addition
Typically no shifts/rearrangements
Mercurinium ion involvement

20. Hydroboration-Oxidation of Alkenes
Anti-Markovnikov addition
No shifts/rearrangements
Syn addition

21. Grignard Addition Reactions
Addition to Aldehydes/Ketones
Addition to Esters
Addition to Epoxides

22. Grignard Additions to Aldehydes/Ketones
Formation of primary, secondary, and tertiary alcohols

23. Grignard Additions to Esters
Formation of secondary and tertiary alcohols

24. Grignard Addition to Epoxides

25. Physical Properties
Unusually high boiling points due to hydrogen bonding between molecules.
Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases.

26. Boiling Points

27. Solubility in Water
Solubility decreases as the size of the alkyl group increases.

28. CHEMICAL PROPERTIES
The hydroxy gp present in alcohols is a very reactive gp and the characterstic rxns of alcohols are the rxns of –OH gp. In general, these are divided into 3 categories:-
Rxns involving the cleavage of O-H bond
Rxns involving the cleavage of C-OH bond
Rxns involving both alkyl and hydroxyl gps of the acohol molecules.

29. Typical Alcohol Reactions
Salt formation
Dehydration
Oxidation
Alkyl halide formation
Ester formation
Ether synthesis
Periodic acid cleavage of glycols
Haloform reaction of methyl carbinols
THP acetal formation

30. Conversion of Alcohols to Salts
Reaction with Active Metals

31. Dehydration of Alcohols

32. Oxidation of Alcohols

33. Alcohol Conversion to Alkyl Halides
Reaction with Hydrogen halides
Reaction with Thionyl chloride
Reaction with Phosphorus trihalides or pentahalides

34. Hydrogen Halide Conversion of Alcohols to Alkyl Halides

35. Mechanisms

36. Ester Formation from Alcohols

37. Distinction b/w 1o, 2o & 3o alcohols
LUCAS TEST
Lucas reagent : equimolar mixture of c.HCl and anhyd. ZnCl2
Appearance of cloudiness in the rxn mixture indicates the conversion of alcohol into alkyl halide.
Observation-
30 alcohol:- reacts immediately & cloudiness appears immediately.
20 alcohol:- reacts within about 5 minutes when the cloudiness appears.
10 alcohol:- does not react appreciably at room temp. & therefore no cloudiness appears.
An older method known as Victor Meyer’s test is seldom used these days.

38. Dihydric Alcohols
Glycols

39. Periodic Acid Cleavage of Glycols