Difference Between Imide and Amide

Key Difference – Imide vs Amide
 

Imides and amides are organic compounds containing C, H, N and O atoms. Both these compounds contain acyl groups attached to a nitrogen atom. The key difference between imide and amide is that imide is an organic compound composed of two acyl groups bonded to the same nitrogen atom whereas amide is an organic compound composed of an acyl group bonded to a nitrogen atom.

CONTENTS

1. Overview and Key Difference
2. What is Imide
3. What is Amide 
4. Side by Side Comparison – Imide vs Amide in Tabular Form
5. Summary

What is Imide?

An imide is an organic compound that consists of two acyl groups bonded to the same nitrogen atom. The structure of an imide resembles acid anhydrides. These compounds are highly polar and are well-dissolved in polar solvents.

Figure 1: General Structure of an Imide

The preparation of imides is done by heating dicarboxylic acids with ammonia (or primary amines). The type of chemical reaction involved in this preparation is a condensation reaction between the dicarboxylic acid and the amine that yields an imide.

Imides formed from ammonia contains an N-H bond between two acyl groups. This N-H bond gives the ability to form hydrogen bonds. This N-H center is acidic. This leads to the formation of alkali metal salts of imides; for example, Potassium phthalimide. The nitrogen atoms in imides are not that much basic. This allows the imides to form N-halo derivatives through the reaction between an imide and a halogen in the presence of a base.

What is Amide?

An amide is an organic compound that consists of one acyl group bonded to a nitrogen atom. It is also called an acid amide. Sometimes this term is used to name the conjugate base of ammonia (the NH₂^– anion). The simplest amides are derived from ammonia where one hydrogen atom of the ammonia is replaced by an acyl group. The complex amides are formed from primary and secondary amines. Primary amides are formed from ammonia while secondary amides are formed from primary amines, and tertiary amides are formed from secondary amines. Tertiary amines cannot participate in the formation of amides.

When considering the actual structure of an amide, there is a partial double bond between nitrogen and carbon atom of the acyl group due to the delocalization of the lone pair on the nitrogen atom. This means amides have resonance structures that determine the actual structure of the amide.

Figure 2: Resonance Structures of an Amide

There are several methods for the synthesis of an amide. The most basic method is the reaction between carboxylic acid and an amine. This reaction requires a high heat energy since the activation energy of the reaction is very high.

What is the Difference Between Imide and Amide?

Summary – Imide vs Amide

Both imides and amides are nitrogen-containing organic compounds. The key difference between imide and amide is that imide is an organic compound composed of two acyl groups bonded to the same nitrogen atom whereas amide is an organic compound composed of an acyl group bonded to a nitrogen atom.

Reference:

1. “Imide.” Wikipedia, Wikimedia Foundation, 3 Apr. 2018, Available here.
2. “Amides.” Chemistry LibreTexts, 11 Mar. 2017, Available here.

Image Courtesy:

1. “AmideResonance” By V8rik at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Imide functional group” By Cjp24 – Own work (Public Domain) via Commons Wikimedia

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