Question

On reduction of glycolic acid with $HI$, the product formed is :
A.Acetic acid
B.Iodo acetic acid
C.Formic acid
D.None of these

Answer 1

Hint: At first think about the chemical formula and the structure of glycolic acid. And also about the reaction between glycolic acid with hydrogen iodide. The chemical formula of glycolic acid is ${C_2}{H_4}{O_3}$.

Complete step by step answer:
The structure of glycolic acid is $COOH - C{H_2} - OH$. The hydrogen iodide is used to reduce alcohols, aldehydes and ketones to alkanes. So on reduction of glycolic acid with hydrogen iodide gives acetic acid. The overall reaction is given as,
$COOH - C{H_2} - OH\xrightarrow{{HI}}COOH - C{H_3}$
In the above reaction, hydrogen iodide reduced the alcohol part of the glycolic acid to alkane.

So the answer is A.

Additional Information:- Glycolic acid is the smallest $\alpha - $ hydroxyl acid. It is colorless, odorless and hygroscopic crystalline solid is highly soluble in water. It is used in various skin-care products. It is also found in some sugar crops. A glycolate is a salt or ester of glycolic acid. It can also be prepared using an enzymatic biochemical process that may require less energy. It is slightly stronger than acetic acid due to the electron withdrawing power of the terminal hydroxyl group. It is used in the textile industry as a dyeing and tanning agent. In food processing as a flavoring agent and as a preservative and in the pharmaceutical industry as a skin care agent.

Note:
Hydrogen iodide alone cannot reduce the carboxylic acid group. Hydrogen iodide and red phosphorus can combinely act as a strong reducing agent. The combination of hydrogen iodide and phosphorus can reduce the acid group in glycolic acid.