# Reaction of Grignard reagent with primary amines

What does the reaction $\ce{CH3CH2NH2 + CH3MgBr ->}$ form? Does it form a secondary amine or a tertiary amine or an alcohol? I can't find what a Grignard reagent does to a primary amine.

• Deprotonates the NH2 group to form methane plus magnesium salt. May 13 '18 at 20:46

## 1 Answer

Here's the thing about Grignard reagents. Though we typically want them to do nucleophilic addition to something, these powerful bases tend to go for protons -- a faster reaction -- if there is just about anything that might make the proton vulnerable. Attaching the proton to an electronegative atom like nitrogen is enough, so primary and even secondary amines will react like that with Grignard reagents. You just deprotonate the amine, the hydrocarbon part of the Grignard reagent ends up an an alkane (or an arene if there are aromatic rings), then on acid workup you get just the amine (or ammonium ion) back. Yup, this is not a very productive synthesis.

Choose your substrate carefully with Grignard reagents to avoid this deprotonation and get the addition you want, or consider less strongly basic alternatives like an organocadmium compound (which itself can be made from a Grignard reagent plus a cadmium salt).