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This heading covers amide derivatives of carboxylic acids and of carbonic acid (but not amide derivatives of other inorganic acids - heading 29.29).
Amides are compounds which contain the following characteristic groups :
(-CONH2) Primary amide
((-CO)2NH) Secondary amide
((-CO)3N) Tertiary amide
The hydrogen of the (-NH2) or (NH) groups may be substituted by alkyl or aryl radicals, in which case the products are N- substituted amides.
Some amides of this heading also contain a diazotisable amine group. These amides and their salts, diluted to standard strengths for the production of azo dyes, are also included here.
Ureines are derived from urea by replacing one or more hydrogen atoms of the -NH2 groups by alicyclic or aryl radicals.
Ureides are obtained from urea by replacing one or more of the hydrogen atoms of the -NH2 group by acid radicals.
This heading excludes, however, urea (H2NCONH2), the diamide of carbonic acid, which is principally used as a fertiliser and, even if pure, falls in heading 31.02 or 31.05.(A) ACYCLIC AMIDES (1) Acetamide. (2) Asparagine, the mono-amide of aspartic acid. Extracted from certain vegetables. Crystalline. (3) Open chain ureides (bromodiethylacetylurea, bromoisovalerylurea). (4) Ethyl carbamate (urethan). (5) Glutamine.
This heading excludes 1-cyanoguanidine (dicyandiamide) (heading 29.26). (B) CYCLIC AMIDES (1) Ureines and ureides.
The main ureines include : (ⅰ) p-Ethoxyphenylurea (dulcin). (ⅱ) Diethyldiphenylurea (centralite). (2) Acetanilide, methyl- and ethylacetanilide, acet-p-phenetidide (phenacetin), p‑acetamidophenol and p-acetamidosalol, used in medicine. (3) Phenylacetamide. (4) N-Acetoacetyl derivatives of cyclic amines, e.g., acetoacetanilide; amides of hydroxynaphthoic acid, e.g., 3-hydroxy-2-naphthanilide; diatrizoic acid and its salts, used as opacifiers in radiography. Some of these compounds are known in trade as "arylides". (5) 2-Acetamidobenzoic acid. Colourless to yellowish crystals in the form of needles, plates or rhomboids. Used as a precursor in the production of methaqualone (INN) (see the list of precursors at the end of Chapter 29).
This heading excludes, however, heterocyclic ureides, e.g., malonylurea (barbituric acid) and hydantoin (heading 29.33). Certain substances of this heading, which are regarded as narcotic drugs or as psychotropic substances under international instruments, are indicated in the List appearing at the end of Chapter 29.
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