Chemistry MCQs for NEET — Practice Questions with Answers

The NCERT explicitly states: 'Aldehydes are easily oxidised to carboxylic acids by mild oxidising reagents such as Tollens’ reagent and Fehling’s reagent.' Butanal is an aldehyde, and butanoic acid is its corresponding carboxylic acid. $NaBH_4$ and $LiAlH_4$ are reducing agents, not oxidizing agents. Concentrated $H_2SO_4$ is an acid catalyst but not an oxidizing agent for this conversion.

The context highlights: 'The above methods (Grignard reagents and nitriles from alkyl halides) are useful for converting alkyl halides into corresponding carboxylic acids having one carbon atom more than that present in alkyl halides (ascending the series).'

The NCERT states: 'Aromatic carboxylic acids can be prepared by vigorous oxidation of alkyl benzenes with chromic acid... The entire side chain is oxidised to the carboxyl group irrespective of length of the side chain.' To get benzene-1,4-dicarboxylic acid, the starting material must have two methyl groups at positions 1 and 4 on the benzene ring, which is p-xylene.

The NCERT specifies: 'Nitriles are hydrolysed to amides and then to acids in the presence of $H^+$ or $OH^-$ as catalyst.'

The NCERT text states: 'Anhydrides on the other hand are hydrolysed to corresponding acid(s) with water.'

The NCERT mentions: 'Primary alcohols are readily oxidised to carboxylic acids with common oxidising agents such as potassium permanganate ($KMnO_4$) in neutral, acidic or alkaline media or by potassium dichromate ($K_2Cr_2O_7$) and chromium trioxide ($CrO_3$) in acidic media (Jones reagent).'

The NCERT states: 'Acid chlorides when hydrolysed with water give carboxylic acids or more readily hydrolysed with aqueous base to give carboxylate ions which on acidification provide corresponding carboxylic acids.'

The NCERT mentions: 'Suitably substituted alkenes are also oxidised to carboxylic acids with these oxidising reagents,' specifically referring to chromic acid or acidic/alkaline potassium permanganate for vigorous oxidation. Cyclohexene is a cyclic alkene, and vigorous oxidation would break the ring and oxidize the carbons to carboxyl groups, forming a dicarboxylic acid like hexane-1,6-dioic acid.

The NCERT states: 'Nitriles are hydrolysed to amides and then to acids in the presence of $H^+$ or $OH^-$ as catalyst. Mild reaction conditions are used to stop the reaction at the amide stage.'

According to the IUPAC nomenclature, the names of open-chain aliphatic aldehydes are derived from the names of the corresponding alkanes by replacing the ending –e with –al. (NCERT, p. 229)