amide


amide
amidic /euh mid"ik/, adj.
/am"uyd, -id/, n. Chem.
1. a metallic derivative of ammonia in which the -NH2 group is retained, as potassium amide, KNH2.
2. an organic compound obtained by replacing the -OH group in acids by the -NH2 group.
3. an organic compound formed from ammonia by replacing a hydrogen atom by an acyl group.
[1840-50; AM(MONIA) + -IDE]

* * *

Any member of either of two classes of nitrogen-containing organic compounds related to ammonia and amines and containing a carbonyl group (―C=O; see functional group).

The first class, covalent amides are formed by replacing the hydroxyl group (―OH) of an acid with an amino group (―NR2, in which R may represent a hydrogen atom or an organic combining group, such as methyl). Amides formed from carboxylic acids, called carboxamides, are solids except for the simplest, formamide, a liquid. They do not conduct electricity, have high boiling points, and (when liquid) are good solvents. There are no practical natural sources of simple covalent amides, but the peptides and proteins in living systems are long chains (polymers) with peptide bonds (see covalent bond), which are amide linkages. Urea is an amide with two amino groups. Commercially important covalent amides include several used as solvents; others are the sulfa drugs and nylon. The second class, ionic (salt-like) amides (see ionic bond), are made by treating a covalent amide, an amine, or ammonia with a reactive metal (e.g., sodium) and are strongly alkaline.

* * *

      any member of either of two classes of nitrogen-containing compounds related to ammonia and amines. The covalent amides are neutral or very weakly acidic substances formed by replacement of the hydroxyl group (OH) of an acid by an amino group (NR2, in which R may represent a hydrogen atom or an organic combining group such as methyl, CH3). The carboxamides (R′CONR2), which are derived from carboxylic acids (R′COOH), are the most important group. Sulfonamides (RSO2NR2) are similarly related to the sulfonic acids (RSO3H).

      Ionic, or saltlike, amides are strongly alkaline compounds ordinarily made by treating ammonia, an amine, or a covalent amide with a reactive metal such as sodium.

      Covalent amides derived from ammonia are solids, except formamide, which is liquid; those containing fewer than five carbon atoms are soluble in water. They are nonconductors of electricity and solvents for both organic and inorganic substances. Covalent amides, even those of low molecular weight, have high boiling points.

      There are no practical natural sources of simple covalent amides, although polyamides (amides linked together to form large molecules called polymers) occur in great abundance as the protein of living systems. Simple amides ordinarily are prepared by reaction of acids or acid halides with ammonia or amines. They can also be produced by the reaction of water with nitriles.

      The characteristic reaction of covalent amides is hydrolysis (a chemical reaction with water), by which they are converted to acids and amines; this reaction ordinarily is slow unless it is catalyzed by a strong acid, an alkali, or an enzyme. Amides also can be dehydrated to nitriles. Amides are not readily oxidized nor reduced, although hydrogenation (addition of hydrogen at high temperatures and pressures) in the presence of a catalyst will convert most amides of carboxylic acids to amines. The powerful reducing agent lithium aluminum hydride transforms amides into amines. Reaction of amides with acid chlorides or anhydrides produces imides, which are compounds with two carbonyl (CO) groups attached to the same nitrogen atom.

      Among the amides of commercial importance are acetamide, also called ethanamide (CH3CONH2) and dimethylformamide HCON(CH3)2, which are used as solvents, the sulfa drugs, and the nylons. urea or carbamide [CO(NH2)2] is a crystalline compound that is formed as the end product of the metabolism of protein and excreted in the urine of mammals. It is synthesized in large quantities from ammonia and carbon dioxide for use in fertilizers, in animal feed, and in manufacturing a class of polymers known as urea-formaldehyde resins, used in making plastics.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Amide — functional group Amides possess a conjugated system …   Wikipedia

  • amide — [ amid ] n. m. • 1833; de oxamide, de oxalique et ammoniaque ♦ Tout composé organique dérivant de l ammoniac ou d une amine par substitution de radicaux acides à l hydrogène. ● amide nom masculin (de ammoniac) Nom générique des composés se… …   Encyclopédie Universelle

  • Amide — Amide, Säureamide, Verbindungen, die als Säuren aufzufassen, deren Säurehydroxyde sämtlich durch die einwertige Amidgruppe NH2 ersetzt oder als ein oder zwei Moleküle Ammoniak, worin ein bezw. zwei Wasserstoffatome durch ein Säureradikal (s.… …   Lexikon der gesamten Technik

  • Amide —   [Kurzwort], Singular Amid das, s, Sammelbezeichnung für Säure und Metallamide. Die Säureamide sind organische Verbindungen, die sich aus organischen oder anorganischen Säuren ableiten, und zwar dadurch, dass die Hydroxylgruppe OH durch eine …   Universal-Lexikon

  • -amide — also amide, in chemical use, 1850, denoting a compound obtained by replacing one hydrogen atom in ammonia with an element or radical, from Fr. amide, from AMMONIA (Cf. ammonia) + IDE (Cf. ide) …   Etymology dictionary

  • Amide — Am ide (?; 277), n. [Ammonia + ide.] (Chem.) A compound formed by the union of amidogen with an acid element or radical. It may also be regarded as ammonia in which one or more hydrogen atoms have been replaced by an acid atom or radical. [1913… …   The Collaborative International Dictionary of English

  • Amīde — (Säureamide), chem. Verbindungen, die man als Ammoniak NH3 betrachten kann, in dem Wasserstoffatome durch Säureradikale ersetzt sind. Acetamid leitet sich ab von der Essigsäure C2H3O.OH, in der die Hydroxylgruppe OH durch Amid NH2 ersetzt ist. A …   Meyers Großes Konversations-Lexikon

  • amide — [am′īd΄, am′id] n. [ AM(MONIA) + IDE] 1. any of a group of organic compounds containing the CO·NH2 radical (e.g., acetamide) or an acid radical in place of one hydrogen atom of an ammonia molecule (e.g., sulfanilamide) 2. any of the ammono bases… …   English World dictionary

  • Amide — Amīde, chem. Verbindungen, die sich vom Ammoniak durch Austausch eines oder mehrerer Wasserstoffatome gegen Säureradikale ableiten …   Kleines Konversations-Lexikon

  • Amide — Structure générale des amides Un amide est un composé organique dérivé d un acide carboxylique. Un amide possède un atome d azote lié à son groupement carbonyle. Les amides sont un groupe important dans la biochimie, parce qu ils sont… …   Wikipédia en Français

  • Amide — Allgemeine Struktur von Carbonsäureamiden. R1, R2 und R3 stehen für ein Wasserstoffatom oder einen Organyl Rest. Blau markiert ist oben die Carbamoyl Gruppe und unten die durch die Reste R2 und R3 substituierte Carbamoyl Gruppe …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.