Texts for educational purposes Synthesized and natural compounds of nitrogen

Amides are organic compounds containing the group -CO.NH₂ (the amide group). Compounds containing this group are primary amides. Secondary and tertiary amides can also exist, in which the hydrogen atoms on the nitrogen are replaced by one or two other organic groups respectively. Simple examples of primary amides are ethanamide, CH₃CONH₂, and propanamide, C₂H₅CONH₂. They are made by heating the ammonium salt of the corresponding carboxylic acid. Amides can also be made by reaction of ammonia (or an amine) with an acyl halide. Amides can also be defined as inorganic compounds containing the ion NH₂^-, e.g. KNH₂ and Cd(NH₂)₂. They are formed by the reaction of ammonia with electropositive metals.

Amination is a chemical reaction in which an amino group (-NH₂) is introduced into a molecule. Examples of amination reaction include the reaction of halogenated hydrocarbons with ammonia (high pressure and temperature) and the reduction of nitro- compounds and nitriles.

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Amines are organic compounds derived by replacing one or more of the hydrogen atoms in ammonia by organic groups. Primary amines have one hydrogen replaced, e.g. methylamine, CH₃NH₂. They contain the functional group -NH₂ (the amino group). Secondary amines have two hydrogens replaced, e.g. methylethylamine, CH₃(C₂H₅)NH. Tertiary amines have all three hydrogens replaced, e.g. trimethylamine, (CH₃)₃N. Amines are produced by the decomposition of organic matter. They can be made by reducing nitro compounds or amides.

Amine salts are salts similar to ammonium salts in which the hydrogen atoms attached to the nitrogen are replaced by one or more organic groups. Amines readily form salts by reaction with acids, gaining a proton to form a positive ammonium ion. They are named as if they were substituted derivatives of ammonium compounds; for example, dimethylamine ((CH₃)₂NH) will react with hydrogen chloride to give dimethylammonium chloride, which is an ionic compound [(CH₃)₂NH₂]⁺ Cl^-. When the amine has a common nonsystematic name the suffix -ium can be used; for example, phenylamine (aniline) would give [C₆H₅NH₃]⁺ Cl^-, known as anilinium chloride. Formerly, such compounds were sometimes called hydrochlorides, e.g. aniline hydrochloride with the formula C₆H₅NH₂.HC1.

Salts formed by amines are crystalline substances that are readily soluble in water. Many insoluble alkaloids (e.g. quinine and atropine) are used medicinally in the form of soluble salts (hydrochlorides). If alkali (sodium hydroxide) is added to solutions of such salts the free amine is liberated. If all four hydrogen atoms of an ammonium salt are replaced by organic groups a quaternary ammonium compound is formed. Such compounds are made by reacting tertiary amines with halogen compounds; for example, trimethylamine ((CH₃)₃N) with chloromethane (CH₃C1) gives tetramethylammonium chloride, (CH₃)₄N⁺ Cl^-. Salts of this type do not liberate the free amine when alkali is added, and quaternary hydroxides (such as (CH₃)₄N⁺ OH^-) can be isolated. Such compounds are strong alkalis, comparable to sodium hydroxide.

Amino acid is any of a group of water-soluble organic compounds that possess both a carboxyl (-COOH) and an amino (-NH₂) group attached to the same carbon atom, called the -carbon atom. Amino acids can be represented by the general formula R-CH(NH₂)COOH. R may be hydrogen or an organic group and determines the properties of any particular amino acid. Through the formation of peptide bonds, amino acids join together to form short chains (peptides) or much longer chains (polypeptides). Proteins are composed of various proportions of about 20 commonly occurring amino acids. The sequence of these amino acids in the protein polypeptides determines the shape, properties and hence biological role of the protein. Some amino acids that never occur in proteins are nevertheless important, e.g. ornithine and citrulline, which are intermediates in the urea cycle.

Plants and many microorganisms can synthesize amino acids from simple inorganic compounds, but animals rely on adequate supplies in their diet. The essential amino acids must be present in the diet whereas others can be manufactured from them.