Question

Given below are two statements:
Statement I: The dipole moment of R–CN is greater than R–NC and R–NC can undergo hydrolysis under acidic medium to produce R–COOH.
Statement II: R–CN hydrolyses under acidic medium to produce a compound which on treatment with SOCl$_2$, followed by the addition of NH$_3$ gives another compound (X). This compound (X) on treatment with NaOCl/NaOH gives a product, that on treatment with CHCl$_3$/KOH/$\Delta$ produces R–NC.
In the light of the above statements, choose the correct answer from the options given below.

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Nitriles hydrolyse to carboxylic acids, while isocyanides are formed from primary amines via the carbylamine reaction.

Answer 1

The Correct Option is D

The question involves two chemical statements regarding the properties and reactions of certain organic molecules. Let us evaluate each statement individually to determine their correctness and arrive at the right conclusion.

Statement I: The statement asserts that the dipole moment of R–CN is greater than R–NC and that R–NC can undergo hydrolysis under acidic medium to produce R–COOH.

• The dipole moment of R–CN (nitriles) compared to R–NC (isonitriles or isocyanides) is known to be higher, primarily because in R–CN, the electronegative nitrogen atom is directly contributing to the dipole along the C–N bond. Thus, the first part of the statement is true.
• However, regarding hydrolysis of R–NC: Under acidic conditions, R–NC does not typically convert into the carboxylic acid (R–COOH) directly. Isonitriles (R–NC) are generally more stable to hydrolysis than nitriles (R–CN). Hence, the statement that R–NC hydrolyzes to produce R–COOH is inaccurate.

Thus, Statement I is false because although the part about dipole moments is correct, R–NC's conversion to R–COOH under acidic conditions is not generally feasible.

Statement II: The statement describes a sequence of reactions starting from R–CN:

• \(R–CN \rightarrow R–COOH\) upon acidic hydrolysis. This reaction is accurate; nitriles hydrolyze to carboxylic acids in acidic conditions.
• Treating the carboxylic acid with \(SOCl_2\) converts it to the acyl chloride, \(R–COCl\).
• Upon subsequent addition of ammonia \((NH_3)\), the acyl chloride forms an amide, \(R–CONH_2\) (denoted as compound X).
• The reaction of the amide with \(NaOCl/NaOH\) (Hofmann rearrangement) transforms it into an amine, \(R–NH_2\).
• Finally, the reaction described by \(CHCl_3/KOH/\Delta\) (Carbylamine reaction) converts primary amines to isocyanides: \(R–NH_2 \rightarrow R–NC\).

Each step in Statement II describes known reactions and is correctly sequenced. Therefore, Statement II is true.

Conclusion: Based on the analysis, the correct answer is: Statement I is false but Statement II is true.