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13. CARBOXYLIC ACIDS eLearn.Punjab

13.7.1 Laboratory Methods
1. By the Oxidation of Ethyl Alcohol or Acetaldehyde

When ethyl alcohol is oxidised with K2Cr2O7 and dilute H2SO4, acetic acid
is produced.

[ ]CH3  →K 2Cr2O7 [O]→
CH2OH + O H2SO4 CH3CHO CH3COOH

2. By the Hydrolysis of Methyl Cyanide

Ethanenitrile on hydrolysis with dilute HCI, gives acetic acid through acetamide.

13.7.2 Manufacture of Acetic Acid
1 . From Acetylene
Acetylene is treated with 20% H2SO4 and 1.0% HgSO4 at 80°C to give ethanal
(acetaldehyde) which is then oxidised using V2O5 to give acetic acid.

2. Acetic acid is also prepared commercially by the oxidation of ethyl
alcohol.Ethyl alcohol can be commercially prepared from molasses by
a process called fermentation.It is oxidized by potassium dichromate
in the presence of conc. sulphuric acid to give acetaldehyde which
is further oxidized under the same conditions to give acetic acid.

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