JEE Challenger
More from Aldehydes, Ketones and Carboxylic Acids
ChemMedAdv 2017 • Paper 1

Matching Reaction Steps Yielding Two Distinct Carboxylic Acids

Comprehension Passage

Answer questions Q.34, Q.35, and Q.36 by properly matching the information given in the three columns of the following table.

Columns 1, 2, and 3 list starting materials, reaction conditions, and type of reactions, respectively.

Column 1Column 2Column 3(I) Toluene(i) NaOH / Br2(P) Condensation(II) Acetophenone(ii) Br2/hν(Q) Carboxylation(III) Benzaldehyde(iii) (CH3CO)2O / CH3COOK(R) Substitution(IV) Phenol(iv) NaOH / CO2(S) Haloform\begin{array}{|l|l|l|} \hline \text{Column 1} & \text{Column 2} & \text{Column 3} \\ \hline (I)\ \text{Toluene} & (i)\ \text{NaOH / Br}_2 & (P)\ \text{Condensation} \\ \hline (II)\ \text{Acetophenone} & (ii)\ \text{Br}_2 / h\nu & (Q)\ \text{Carboxylation} \\ \hline (III)\ \text{Benzaldehyde} & (iii)\ (\text{CH}_3\text{CO})_2\text{O / CH}_3\text{COOK} & (R)\ \text{Substitution} \\ \hline (IV)\ \text{Phenol} & (iv)\ \text{NaOH / CO}_2 & (S)\ \text{Haloform} \\ \hline \end{array}

Identify the only CORRECT combination that yields two different carboxylic acids:

Options

A

(II) (iv) (R)

B

(IV) (iii) (Q)

C

(III) (iii) (P)

Correct
D

(I) (i) (S)

Topics & Concepts

Aldehydes, Ketones and Carboxylic AcidsCarboxylic Acids and DerivativesAldehydes and Ketones

Step-by-Step Solution

To find the correct combination that yields two different carboxylic acids, let us analyze the reaction corresponding to option C:

  1. Starting Material (III): Benzaldehyde (C6H5CHO\text{C}_6\text{H}_5\text{CHO})
  2. Reaction Conditions (iii): Acetic anhydride and Potassium acetate ((CH3CO)2O / CH3COOK)\left((\text{CH}_3\text{CO})_2\text{O} \ /\ \text{CH}_3\text{COOK}\right)
  3. Type of Reaction (P): Condensation (specifically, the Perkin Condensation)

Reaction Mechanism & Chemical Equation:

When an aromatic aldehyde lacking α\alpha-hydrogens (like benzaldehyde) is heated with an aliphatic acid anhydride containing at least two α\alpha-hydrogens in the presence of the sodium or potassium salt of the corresponding acid, a condensation reaction takes place.

C6H5CHO+(CH3CO)2O→ΔCH3COOKC6H5CH=CHCOOH+CH3COOH\text{C}_6\text{H}_5\text{CHO} + (\text{CH}_3\text{CO})_2\text{O} \xrightarrow[\Delta]{\text{CH}_3\text{COOK}} \text{C}_6\text{H}_5\text{CH}=\text{CHCOOH} + \text{CH}_3\text{COOH}

Products Formed:

  1. Cinnamic acid (C6H5CH=CHCOOH\text{C}_6\text{H}_5\text{CH}=\text{CHCOOH})
  2. Acetic acid (CH3COOH\text{CH}_3\text{COOH})

Since two distinct carboxylic acids (cinnamic acid and acetic acid) are produced in this condensation reaction, the correct combination is (III) (iii) (P).

Correct Option: C

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