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Amides are organic compounds with a nitrogen atom attached to an acyl group, derived from carboxylic acids or amines. Peptide bonds in proteins are amides. The reaction to form an amide from a carboxylic acid and an amine is a two-step process. Amides are stable due to their configuration and are used in industry as surfactants, stabilizers, and release agents. Urea is a biological amide used in commercial fertilizers, while acetaminophen is a synthetic amide.
An amide is a class of organic compounds containing a nitrogen atom attached to an acyl group. Amides are considered a derivative of carboxylic acids and can also be prepared from amines, anhydrides, esters and nitriles. All peptide bonds in proteins are amides.
A carboxylic acid and an amine react to form amide. Organic acids are characterized by a terminal carbon bonded to a carbonyl group (-C=O) and a hydroxyl group (-OH), collectively written as -COOH. Amines have organic groups bonded to a nitrogen atom. The nitrogen atom can have one, two or three side groups called primary, secondary and tertiary amines. Only primary and secondary amines can react with carboxylic acid to form an amide.
The reaction to form an amide from the acid and amine is a two-step process at high temperature. Other synthesis routes will form the amide more easily. In order from most to least reactive raw material, the reactants are acyl halide, acid anhydride, ester, and carboxylic acid. With respect to the carboxylic acid formula (-COOH), an acyl halide replaces the hydroxyl group with a halide, such as chlorine (-C=OCl), whereas in an ester the substitute is another hydrocarbon (-COOC-). An acid anhydride is the result of the reaction of two carboxylic acids, removing a water molecule and bonding to form a central structure (-COOOC-) in which the two central carbon atoms each have a double bond with an oxygen atom and a single bond to a shared central oxygen atom.
An amide is a stable compound due to its configuration. The CO and CN bonds are all in the same plane. The CN bond acts as a partial double bond due to resonance, the sharing of electrons between multiple bonds. This resonance shortens the length of the CN bond, creating a higher energy barrier for the reaction. Peptide bonds in proteins are very stable.
Urea is another biological amide. It is the end product of the metabolic degradation of proteins by mammals. During this process, the amino group is removed from the hydrocarbon and converted into toxic ammonia. The liver converts ammonia to urea (NH2-CO-NH2) and the kidney filters the urea from the blood and excretes it in the urine. Commercial fertilizers use urea to promote plant growth due to its high nitrogen content.
Acetaminophen is an example of a synthetic amide. Amides are widely used in industry as surfactants, stabilizers and release agents for plastics and welding fluxes. Many amides are carcinogenic and their use is limited to non-human contact.
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