Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Aldehydes, Ketones and Carboxylic Acids

Question:

Read the passage carefully and answer the Questions.

Aldehydes, carboxylic acids and ketones are widespread in the animal and plant kingdoms. They play a pivotal role in various biochemical processes of life. Their presence in nature adds fragrance and flavor. These compounds are widely used in food products, pharmaceuticals, paints, resins and other important product industries. These compounds are prepared by various laboratory methods, which mainly include oxidation, formylation, acylation and reduction. Due to the polar nature of the carbonyl group in aldehydes and ketones, they can exhibit different reactions like nucleophilic addition. They do exhibit redox and various condensation reactions which lead to the formation of various important compounds. On the other hand, the carboxylic acids are mainly prepared by oxidation and hydrolysis of different compounds. The carboxylic acid consists of a carbonyl group and the hydroxy group (attached to the carbonyl carbon atom). This makes it possible for the carboxylic acid to participate in various chemical reactions which involve cleavage of the C-OH bond and the O-H bond along with the reactions involving the complete -COOH group.

The IUPAC name of following compound is

$OHC-C_6H_4-CHO-p$

Options:

Benzene-1,4-dial

1,4-Dioxobenzene

4-Formylbenzaldehyde

Benzene-1,4-dicarbaldehyde

Correct Answer:

Benzene-1,4-dicarbaldehyde

Explanation:

The correct answer is Option (4) → Benzene-1,4-dicarbaldehyde

The given compound OHC–C₆H₄–CHO (para) is a benzene ring with two aldehyde (–CHO) groups at the 1,4-positions.

For aldehyde groups directly attached to a ring, IUPAC prefers the suffix “carbaldehyde”.

Correct answer

Benzene-1,4-dicarbaldehyde

Why the others are incorrect:

  • Benzene-1,4-dial → Not the preferred IUPAC name
  • 1,4-Dioxobenzene → Would imply ketone (=O) groups, not aldehydes
  • 4-Formylbenzaldehyde → Used when one –CHO is principal and the other is a substituent, not when both are equivalent