Sciencemadness Discussion Board

amide and nitrous acid?

iloveloli - 14-2-2016 at 08:10

just like the topic, adding nitrous acid to amide.
will they form acyl cation (acylium ion)??
i am thing that lf acylium ion can react with benzene-- likeFriedel–Crafts reaction

Metacelsus - 14-2-2016 at 19:49

Short answer: no, it won't.

Long answer: the reaction products depend on whether it's a a primary, secondary, or tertiary amide.

A tertiary amide won't react.
If it's a primary or secondary amide, a nitrosamide will be formed. If it's primary, it will decompose to a carboxylic acid with formation of nitrogen gas. If it's secondary, it may be stable. A secondary nitrosamide can be used to form a diazo compound.

DJF90 - 15-2-2016 at 04:14

Quote: Originally posted by Cheddite Cheese  
Short answer: no, it won't.

Long answer: the reaction products depend on whether it's a a primary, secondary, or tertiary amide.

A tertiary amide won't react.
If it's a primary or secondary amide, a nitrosamide will be formed. If it's primary, it will decompose to a carboxylic acid with formation of nitrogen gas. If it's secondary, it may be stable. A secondary nitrosamide can be used to form a diazo compound.


Whilst you're correct that the reaction pathway depends upon the degree of substitution of the amide nitrogen, I don't agree that the acylium ion is not involved in the case of primary amides. How do you think the hydrolysis of 1* amide to carboxylic acid works mechanistically if the acylium species is not an intermediate?

I'm not sure you could get it to participate in the Friedel-Crafts reaction though. You're generating (at least) one equivalent of water during the nitrosation reaction which will be a competitive nucleophile. Add to that the fact that any arene activated enough to compete with that water will also react with the nitrosating reagent, and you're probably not going to get very far.

[Edited on 15-2-2016 by DJF90]

Metacelsus - 15-2-2016 at 08:27

I was thinking that the primary nitrosamide would decompose by hydrolysis (after all, water will be present in the nitrosation, as you stated) directly to the carboxylic acid and nitrous amide (NH2NO); the nitrous amide would then immediately decompose to nitrogen gas and water.

I might be wrong about this, however.

Edit: Maybe you could get around hydrolysis by using N2O3.

[Edited on 2-15-2016 by Cheddite Cheese]

Nicodem - 15-2-2016 at 08:37

A related topic: Acid halides from amides