Imine Hydrolysis

What are Imines?

Imines are one of several reactive groups found in a chemical known as functional groups. The features of the functional group are assigned to the method through which the molecule reacts. An imine is a chemical molecule with a double bond of C=N.

They are made up of amine (NH2) and either an aldehyde (CHO) or ketone (C=O) reacting with one another. A carbon atom is doubly bonded to hydrogen. It’s also known as a Schiff base.

Table of Contents

• Imines – An Overview
• Imine Synthesis Mechanism
• Imine Hydrolysis Mechanism
• Imine Reduction Mechanism
• Frequently Asked Questions – FAQs

Imines – An Overview

Imines are often substances with the connection R₂C=NR, as mentioned further below. Imine refers to the aza counterpart of an epoxide in ancient literature. Ethyleneimine is a three-membered ring species with the formula C₂H₄NH. As in acetamide vs succinimide, the link between imines and amines with double and single bonds continues over to imides and amides.

By replacing the oxygen with an NR group, imines are connected to ketones and aldehydes.

A primary aldimine is a primary imine in which C is linked to both a hydrocarbyl and hydrogen; a secondary aldimine is a secondary imine with similar groups. A primary ketimine is a primary imine in which C is linked to two hydrocarbyls; a secondary ketimine is a secondary imine containing similar groups.

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What is Imine?

Imine Synthesis Mechanism

Imines, which feature a C=N bond instead of a C=O connection, are the nitrogen equivalents of aldehydes and ketones. When an aldehyde or ketone combines with an amine to dehydrate it, they produce them. Imines made from aldehydes and ketones are referred to as aldimines and ketimines, respectively. Enamines are nitrogen counterparts of enols.

Because the reactions of aldehydes and ketones with alcohols and amines are all reversible, their derivatives – acetals, imines, and enamines – can be transformed back to carbonyl compounds if a substantial amount of water is utilised.

From a chemical standpoint, the production of an imine is a two-step process. The amine nitrogen attacks the carbonyl carbon in a nucleophilic addition reaction similar to hemiacetal and hemiketal synthesise.

We might predict that the following phase would be an attack by a second amine, resulting in a molecule with a carbon bound to two amine groups, the nitrogen equivalent of a ketal or acetal, based on our understanding of the acetal and ketal production mechanisms. Instead, the nitrogen lone pair electrons ‘push’ the oxygen away from the carbon, resulting in a C=N double bond (an iminium) and a water molecule that is displaced.

Imine Hydrolysis Mechanism

Imine hydrolysis reverses imine production, releasing the matching amine and carbonyl-containing molecule (aldehyde or ketone).

The intermediates are the same as in the synthesis of imines, but the stages are reversed. It begins with nitrogen protonation, which converts the imine into the iminium ion, which is highly electrophilic and attacked by water in the next step:

The ammonium ion is released as a neutral amine after a proton transfer from oxygen to nitrogen (likely an intermolecular event). This produces an oxonium ion, which is deprotonated to produce the required ketone.

The Shortcut to Imine Hydrolysis

There are a lot of steps in these reactions, but we don’t need to remember them all to anticipate the structure of the aldehyde and ketone that forms after hydrolysis.

Draw a line between the nitrogen and carbon atoms for a simple solution.

During the hydrolysis process, these bonds are cleaved. The amine contains nitrogen, and the carbon atom attached to it is the C=O carbon atom:

Imine Reduction Mechanism

Imines are reduced through reductive amination. An imine can be transformed to an amine by hydrogenation in creating m-tolyl benzyl amine, for example.

Lithium aluminium hydride and sodium borohydride are two other reducing agents.