(1) Action of HCN on acetaldehyde :
When acetaldehyde is treated with hydrogen cyanide, acetaldehyde cyanohydrin is formed.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=5234966372665564403)
(2) Action of HCN on acetone :
When acetone is treated with hydrogen cyanide, acetone cyanohydrin is formed.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=15957783823629170469)
(3) Action of HCN on benzaldehyde :
When benzaldehyde is treated with hydrogen cyanide, benzaldehyde cyanohydrin is formed.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=12521955149126816627)