Question

How will you bring about following conversions?
i.Acetic acid to acetyl chloride
II.Methyl cyanide to acetic acid
iii..Acetyl chloride to ethyl acetate
iv.Ethyl iodide to ethyl acetate

Answer 1

Hint: To answer this question, you must recall the reactions of various carbonyl compounds. Carbonyl compounds are reactive because of the presence of an electrophilic carbon atom and undergo a variety of reactions.

Complete step by step solution:
(i) Acetic acid to acetyl chloride
The following conversion involves the changing of a carboxylic acid into an acid chloride. It involves the substitution of the hydroxyl group of the carboxylic acid with a chlorine atom. So to carry out this conversion we need to react with acetic acid with a good chlorinating agent like phosphorous pentachloride, phosphorus trichloride and thionyl chloride (Sulphur dichloride oxide).
The reaction for the conversion can be given as
$C{H_3}COOH\xrightarrow{{SOC{l_2}{\text{ or }}PC{l_5}{\text{ or }}PC{l_3}}}C{H_3}COCl$
(ii) Methyl cyanide to acetic acid
The following conversion requires the breaking of a carbon nitrogen triple bond. The methyl cyanide is heated under reflux with a dilute acid. The hydrolysis of the cyanide group occurs resulting in the formation of a carboxylic acid.
$C{H_3}CN\xrightarrow[{hydrolysis}]{{{H^ + }/{H_2}O}}C{H_3}COOH$
(iii) Acetyl chloride to ethyl acetate
The following conversion involves the changing of an acid chloride into an ester. When reacted with alcohol, acid chlorides undergo a highly exothermic reaction producing an ester. The reaction follows a nucleophilic addition elimination mechanism.
The reaction for the conversion is given as:
$C{H_3}COCl\xrightarrow{{{C_2}{H_5}OH}}C{H_3}COO{C_2}{H_5}$
(iv) Ethyl iodide to ethyl acetate
This conversion of ethyl iodide to ethyl acetate is a comparatively longer process which involves initially the basic hydrolysis of the ethyl iodide to form ethyl alcohol. This alcohol can now be esterified with ethanoic acid to obtain the ethyl acetate ester.
$C{H_3}C{H_2}I\xrightarrow[{hydrolysis}]{{O{H^ - }}}C{H_3}C{H_2}OH\xrightarrow[{esterification}]{{C{H_3}COOH}}C{H_3}COO{C_2}{H_5}$

Note:
Acid halides are extremely reactive compounds. Each of their reactions involves the replacement of the halide group by another functional group, which might be the reacting nucleophile. All reactions of acyl halides are characterized by production of steamy acidic fumes of hydrogen halides in the first step.