# Why is acetyl cyanide not obtained from acetyl chloride?

Why doesn't acetyl chloride or any other aliphatic acyl chloride react with cyanide ions and undergo nucleophilic addition elimination to form aliphatic acyl cyanide, even though this reaction occurs for aromatic acyl chloride?

This was the related question in my workbook:

Which of the following compounds will react with ethanolic $\ce{KCN}$?
A) ethyl chloride B) acetyl chloride C) chlorobenzene D) benzaldehyde

My answer is A, B, D undergoing SN2, nucleophilic addition-elimination, and benzoin condensation respectively. Answer is given as only A,D.

Searching the internet led me to this article, but I am not able to understand why.

• Are you sure about Chlorobenzene reacting with cyanide under these conditions? – Waylander Feb 23 '18 at 10:31
• Acetyl chloride in ethanolic KCN will give ethyl acetate – Waylander Feb 23 '18 at 10:35
• @Waylander Oh I wanted to type B. Thanks for pointing out. – Govind Balaji S Feb 23 '18 at 11:22
• @Waylander But isn't CN- a stronger nucleophile than ethanol? – Govind Balaji S Feb 23 '18 at 11:25
• It is - but if acetyl cyanide is formed at all under the reaction conditions that just makes it more reactive than acetyl chloride (better leaving group) so it forms ethyl acetate even more readily. – Waylander Feb 23 '18 at 11:54

Acetyl chloride on reacting with $\ce{KCN}$ in ethanol will give ethyl acetate. If acetyl cyanide forms at all, it will immediately react with the ethanol solvent as it is a more reactive species than acetyl chloride.