The journal of chemical education has many little gems providing inspiration for laboratory experiments. Jonathan Piard reports one based on the reaction below[cite]10.1021/ed4005003[/cite]; here I investigate the mechanism of this transformation. There are two things going on here;

Nucleophilic addition of cyanide to a ketone or aldehyde is a standard reaction for introductory organic chemistry. But is all as it seems? The reaction is often represented as below, and this seems simple enough. Cyanohydrin formation. But attention to detail suggests that, HCN being a weak acid, there will be only a very small concentration of cyanide anion in the presence of HCl.