1. Explain methods of various alcohol preparation methods by using chemical reactions 2. Identify Fermentation

1. PREPARATION OF ALCOHOLS
D.M S.J K.M

2. Contents
Introduction: Learning Objectives
General Methods of Preparation of Alcohols:
Hydrolysis of Alkylhalides
Hydration of Alkenes
Reduction of acids to alcohols
Fermentation Process
2
Examples and Questions

3. Introduction: Learning Objectives
2. Define and explain fermentation
process
1. Explain methods of various alcohol
preparation methods by using chemical
reactions

4. 1. Hydrolysis of Alkylhalides in an aqueous solution of Alkalines (bases).
This general procedure produces primary and secondary alcohols.
R-X + KOH(aq) → R-OH + KX
Example:
General Methods of Preparation of Alcohols:
Hydrolysis of Alkylhalides

5. Ethene Ethanol
According to Markovnikov’s Rule the hydrogen adds to the double bonded
carbon of the alkene that has the greater number of hydrogen substituents,
and the hydroxyl group to the double bonded carbon of the alkene with the
fewer number of hydrogen substituents.
300°C / 60-65 atm
Hydration of Alkenes

6. Let’s practice: Complete the reactions:
H2O

7. Lithium aluminum hydride, LiAlH4, is one of the few reagents that can reduce an acid to
an alcohol.
4 RCOOH + 3 LiAlH4 → 4 RCH2OH (1o alcohol)
CO + 2 H2 ↔ CH3OH
Methanol
Reduction of acids to alcohols
Preparation of Methanol

8. Alcohols can be formed using fermentation.
Fermentation is usually done by using yeast to act on
carbohydrates to produce ethanol and carbon dioxide.
Rice, malt, fruits etc., which are sources of carbohydrates, are
used to react with yeast.
Ethanol being
formed in a bottle,
effervescence of
carbon dioxide
Fermentation is the slow decomposition of complex organic
compounds into simpler organic compounds by the activity of
enzymes. Enzymes are complex, nitrogenous (proteins), non-living
macromolecules of high molecular weight. We usually get these
enzymes from living organisms.
Fermentation Process

9. The first step is to break complex carbohydrates into simpler ones,
and then convert these in turn into ethanol and carbon dioxide.
C12H22O11 + H2O → 2 C6H12O6
C6H12O6 → 2 CH3CH2OH + 2 CO2
Ethanol
Note that: Yeast is killed by ethanol concentrations in excess of about 15%, and that limits
the purity of the ethanol that can be produced. The ethanol is separated from the mixture by
fractional distillation to give 96% pure ethanol.

10. Let’s practice: Among the alkenes which one produces tertiary butyl alcohol on acid
hydration?
a) (CH3)2C=CH2
b) CH3-CH=CH-CH3
c) CH3CH2CH=CH2
d) CH3CH=CH2