Question

Acetic acid on reduction with excess lithium aluminum hydride, results is-
(A) ethanal
(B) ethanol
(C) methanal
(D) both(A) and (B)

Answer 1

Hint: Lithium aluminum hydride being reduced in nature , when treated with the carboxylic acids reduces them to the compounds which contain the -OH functional group. Now identify the compound.

Complete step by step solution:
-Organic compounds containing the -COOH as the functional group are called the carboxylic acids. The -COOH group which itself is made up of a carbonyl group (C=O) and a hydroxyl group (-OH) is called as the carboxyl group carboxylic acids are said to be aliphatic if the carboxyl group is attached to the alkyl group and it is said to be the aromatic if the carboxyl group is attached to the aryl group.
-Carboxylic acids can be further classified as monocarboxylic acid ( if it contains one carbonyl group), dicarboxylic (if contains two carbonyl groups),tricarboxylic(if it contains three carbonyl groups) and so on.
-Acetic acid is the acid containing the one carboxylic acid and its IUPAC name is ethanoic acid.
-Lithium aluminum hydride is a strong reducing agent i.e. it reduces the other and itself gets oxidized. When carboxylic acids are treated with this reducing agent i.e. the lithium aluminum
-Hydride, it reduces the carboxylic acids to the corresponding alcohols. So, thus, acetic acid on reaction with the lithium aluminum hydride is reduced to the alcohol i.e. the ethanol. The reaction occurs as;
\[\begin{matrix}
C{{H}_{3}}COOH \\
Acetic\text{ }Acid \\
\end{matrix}\xrightarrow[{{H}_{3}}{{O}^{+}}]{LiAl{{H}_{3}}}\begin{matrix}
C{{H}_{3}}C{{H}_{2}}OH \\
Ethanol \\
\end{matrix}\]
Thus, Acetic acid on reduction with excess lithium aluminum hydride, results in ethanol.

Hence, option (B) is correct.

Note: Acetic acid is used in many industries like in the production of plastics, cellulose acetate etc. and is mostly used as a chemical reagent in the production of esters, anhydrides etc. and in the homes, mostly used in the form of vinegar.