Question

Compound (A) \( \left( \text{C}_6\text{H}_{12}\text{O}_2 \right) \) on reduction with LiAlH4 gives two compounds (B) and (C). The compound (B) on oxidation with PCC gives compound (D) which upon treatment with dilute NaOH and subsequent heating gives compound (E). Compound (E) on catalytic hydrogenation gives compound (C). The compound (D) is oxidized further to give compound (F) which is found to be a monobasic acid (Molecular weight = 60). Identify the compounds (A), (B), (C), (D), (E) and (F).}

Hint:

- Reduction with LiAlH4} reduces ester and carboxyl groups to alcohols. - Oxidation with PCC selectively oxidizes alcohols to aldehydes. - Hydrogenation reduces aldehydes to alcohols.

Answer 1

Identifying Compound (A) The molecular formula of compound (A) is \( \text{C}_6\text{H}_{12}\text{O}_2 \), which could be either a carboxylic acid or an ester. Upon reduction with LiAlH4}, it gives two compounds, indicating the presence of both a carboxyl group and an ester group in compound (A). The most likely structure of compound (A) is ethyl acetate (CH3}COOCH2}CH3}). \[ \, \text{CH}_3\text{CH}_2\text{COOCH}_3 \, \text{or} \, \text{CH}_3\text{COOCH}_2\text{CH}_3 \] Identifying Compound (B) Upon reduction with LiAlH4}, compound (A) gives compound (B), which is likely ethanol (CH3}CH2}OH). \[ \, \text{CH}_3\text{CH}_2\text{OH} \] Identifying Compound (C) Upon reduction with LiAlH4}, compound (B) (acetaldehyde) gets reduced to propyl alcohol (CH3}CH2}CH2}OH). LiAlH4} is a strong reducing agent, typically used to reduce aldehydes to primary alcohols. \[ \, \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} \] Identifying Compound (D) Compound (B) is ethanol (CH3}CH2}OH). When ethanol is oxidized using PCC (Pyridinium chlorochromate), it is converted to acetaldehyde (CH3}CHO). This reaction is typical for primary alcohols, where mild oxidants like PCC prevent further oxidation to carboxylic acids. \[ \text{D:} \, \text{CH}_3\text{CHO} \] Identifying Compound (E) Upon catalytic hydrogenation of acetaldehyde (CH3}CHO), acrolein (CH3}CH=CHCHO) is formed. This reaction involves the reduction of the carbonyl group in acetaldehyde into an alkene group while keeping the aldehyde functional group intact. \[ \, \text{CH}_3\text{CH} = \text{CH} - \text{CHO} \] Identifying Compound (F) Upon further oxidation of acrolein (CH3}CH=CHCHO), acetic acid (CH3}COOH) is produced. This is a common reaction where aldehydes undergo oxidation to form carboxylic acids. \[ \, \text{CH}_3\text{COOH} \]