Question

Identify the products A and B in the reactions: \(R-X + AgCN \longrightarrow A + AgX\)  \(R-X + KCN \longrightarrow B+ KX\)

• A. A = RNC; B = RCN
• B. A = R - CN; B = RCN
• C. A - RNC; B = RNC
• D. A = RCN; B = RNC

Answer 1

The Correct Option is A

The products A and B in the reactions can be identified as follows:
\(\text{R-X} + \text{AgCN} \rightarrow \text{A} + \text{AgX}\)
In this reaction, the cyanide ion (\(\text{CN}^-\)) acts as a nucleophile and substitutes the leaving group X in \(R-X\).
The resulting product A is formed by the attachment of the cyano group\((-CN)\) to the R group, while the silver ion (Ag⁺) combines with the leaving group X to form AgX.
\(\text{R-X} + \text{KCN} \rightarrow \text{B} + \text{KX}\)
In this reaction, the cyanide ion \(\text{CN}^-\) from KCN also acts as a nucleophile and substitutes the leaving group X in R-X. The resulting product B is formed by the attachment of the cyano group (-CN) to the R group, while the potassium ion (K⁺) combines with the leaving group X to form KX.
Based on the above reactions, we can conclude that:
\(A = RCN\) (cyano group attached to R)
\(B = R - CN\) (cyano group attached to R)
Therefore, the correct identification of products A and B in the reactions is (A) \(A = \text{RNC}; \quad B = \text{RCN}\)

Answer 2

Correct Answer: A = RNC; B = RCN

Explanation: 

When alkyl halides (R–X) react with:

• AgCN (silver cyanide): The product is isocyanide (R–NC).
• KCN (potassium cyanide): The product is nitrile (R–CN).

This difference occurs due to the nature of the nucleophile:

• KCN is an ionic compound. The nucleophilic attack occurs through the carbon atom of the –CN group, forming a nitrile.
• AgCN is covalent in nature. The nucleophile behaves differently, and the attack happens via the nitrogen atom, forming an isocyanide.

Hence, A = RNC and B = RCN

Answer 3

The reactions involve the attack of cyanide ion (CN^-) on an alkyl halide (R-X). The nature of the product depends on whether the cyanide is covalently bonded (as in AgCN) or ionically bonded (as in KCN).

Reaction 1: R-X + AgCN ---> A + AgX

• AgCN is predominantly covalent. The carbon atom is not as free to attack the alkyl group as the nitrogen atom. Thus, the nitrogen of the cyanide group attacks the alkyl group forming an isocyanide.
• A = RNC (alkyl isocyanide)

Reaction 2: R-X + KCN ---> B + KX

• KCN is an ionic compound, so the cyanide ion (CN^-) is free to attack. Carbon is more electronegative, and therefore attacks the alkyl group.
• B = RCN (alkyl cyanide or nitrile)

Therefore, A = RNC and B = RCN.

Answer:

A = RNC; B = RCN