Question

The mode of reduction of acid to alcohol can be affected only by:
$RCOOH \to RC{H_2}OH$
(A) $Zn/HCl$
(B) $Na - alcohol$
(C) Aluminium isopropoxide and isopropyl alcohol
(D) $LiAl{H_4}$

Answer 1

RCOOH is known as the carboxylic acid. It shows different chemical properties because of their hydrogen atom which is present in the carboxylic acid and hydroxyl group of the carboxylic acid. The carboxylic acids are polar in nature because of the presence of two electronegative oxygen atoms. When they are placed in the non polar solvent they have the tendency to form dimer through hydrogen bonding.

Complete step-by-step answer: The compounds which contain carboxylic functional groups, their solubility depends upon the size of the compound. In the carboxylic acid the alpha carbon can be easily halogenated through Hell Volhard Zelinsky reaction. It can be reduced to alcohol by treating it with hydrogen. The $LiAl{H_4}$is a strong reducing agent. It has the tendency to form hydride ions by the presence of polar metal hydrogen. The aluminium hydrogen bond is a polar bond by making it a strong reducing agent. The presence of hydride ions in $LiAl{H_4}$have the ability to react with the carboxylic acid and then attack the lone pair of oxygen and then at last remove the double bonded oxygen and add two hydrogen to give the alcohol.

So the correct answer is option (D).

Note: The other method to reduce carboxylic acid to alcohol we can use diborane in ether. In this the diborane acts as a reducing agent. The structure of diborane is made up of four hydrogen atoms and two boron atoms. It has a sweet smell and highly flammable colourless gas at room temperature.