Stephen reaction is also known as Stephen aldehyde synthesis as the end product of this reaction is aldehydes. It is another important named reaction of organic chemistry. It was discovered by Henry Stephen that’s why it is known as Stephen Reaction or Stephen Aldehyde Synthesis. Henry Stephen is an English chemist. Stephen reaction is an organic redox reaction. It is also called Stephen Reduction Reaction.
In Stephen reaction nitrile reacts with tin chloride and hydrochloric acid and forms iminium salt then quenching of iminium salt with water gives aldehyde. We get ammonium chloride or ammonia also as a byproduct. Reaction can be written as follows-
Following are the examples of Stephen reaction –
Conversion of acetonitrile into acetaldehyde.
Conversion of benzonitrile into benzaldehyde.
Tin(II) chloride reacts with hydrochloric acid and forms tin tetra chloride and two H+ ions. As Sn+2 changes into Sn+4 two electrons are released. Reaction is given below –
We are using methyl cyanide (as alkyl cyanide) to show the mechanism. In cyanide group nitrogen is more electronegative than carbon. So, its partially negative and carbon is partially positive. One pie bond breaks between carbon and nitrogen of cyanide and electrons move to nitrogen atom simultaneously two electrons released in the above reaction accepted by carbon atom of cyanide. Thus, both carbon and nitrogen atoms get negative charge on them. Reaction is given below –
Now it reacts with two H+ ions and form iminium. Then iminium reacts with water and gives desired product aldehyde. In the process ammonia is released as by product. Reaction is given below –
Stephen reaction is used for production of aldehydes by using alkyl cyanides.
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