Aminolysis
Encyclopedia
Aminolysis is any chemical reaction in which a molecule is split into two parts by reacting with a molecule of ammonia
or an amine
.
An example of an aminolysis reaction is the replacement of a halogen
in an alkyl group (R-X) by an amine (R'-NH2) and the elimination of hydrogen halide (HX).
Another common example is the reaction of a primary amine or secondary amine with a carboxylic acid
or with a carboxylic acid derivative to form an amide
. This reaction is widely used, especially in the synthesis of peptide
s. On the simple addition of an amine to a carboxylic acid, a salt of the organic acid and base is obtained. To overcome this, the carboxylic acid first needs to be "activated". This is usually done by converting the acid into a more reactive derivative (i.e. anhydride, acid halide) or by using a coupling agent. In some cases, high temperatures (>200 °C) can overcome salt formation by driving off water, without the need for "activation" of the carboxyl group. The downside to this simple reation is that the compounds may decompose at these elevated temperatures.
The carboxylic acid derivatives can be ester
s, anhydrides, acid halides or any other activated species.
The choice of activated carboxyl group or coupling agent can be very important in peptide synthesis, as using the wrong one can lead to racemization
.
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
or an amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
.
An example of an aminolysis reaction is the replacement of a halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
in an alkyl group (R-X) by an amine (R'-NH2) and the elimination of hydrogen halide (HX).
- R-X + R'-NH2 → R-NH-R' + HX
Another common example is the reaction of a primary amine or secondary amine with a carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
or with a carboxylic acid derivative to form an amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...
. This reaction is widely used, especially in the synthesis of peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
s. On the simple addition of an amine to a carboxylic acid, a salt of the organic acid and base is obtained. To overcome this, the carboxylic acid first needs to be "activated". This is usually done by converting the acid into a more reactive derivative (i.e. anhydride, acid halide) or by using a coupling agent. In some cases, high temperatures (>200 °C) can overcome salt formation by driving off water, without the need for "activation" of the carboxyl group. The downside to this simple reation is that the compounds may decompose at these elevated temperatures.
The carboxylic acid derivatives can be ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s, anhydrides, acid halides or any other activated species.
The choice of activated carboxyl group or coupling agent can be very important in peptide synthesis, as using the wrong one can lead to racemization
Racemization
In chemistry, racemization refers to the converting of an enantiomerically pure mixture into a mixture where more than one of the enantiomers are present...
.