Amide



   

In chemistry, an amide is one of three kinds of compounds:

  • (sometimes called acid amide) the nitrogen atom (N), or a compound that contains this functional group (pictured to the right); or
  • a particular kind of nitrogen anion.
  • any organic compound derived by the replacement of a hydroxyl group by an amino group.

Amides are the most stable of all the carbonyl functional groups.

Many chemists make a pronunciation distinction between the two, saying (nitrogen compound and /ˈæmɑɪd/ for the anion. Others substitute one of these pronunciations with /ˈæmɨd/, while still others pronounce both /ˈæmɨd/, making them homonyms.

In the first sense referred to above, an amide is an ammonia.
Compounds in which a metal cation are also known as amides or azanides.

The second sense of the word amide is the amide anion, which is a deprotonated form of analogues as Brønsted acids.

The remainder of this article is about the Lithium diisopropylamide.

Amide synthesis

  • Cyclic amides are synthesized in the oximes.
  • Amides also form ketones in the Schmidt reaction
  • Amides can be prepared from aryl alkyl ketones, sulfur and morpholine in the Willgerodt-Kindler reaction
  • Other amide-forming reactions are the Ugi reaction
  • In the Bodroux reaction an amide RNHCOR' is synthesized from a aniline derivative ArNHR' [1] [2]
  • In the Chapman rearrangement (first reported in 1925) an aryl imino ester is converted to a N,N-diaryl amide:
The nucleophilic aromatic substitution. [3]

Amide reactions

  • Amide breakdown is possible via amide hydrolysis. Such hydrolysis can occur under basic or acidic conditions. Acidic conditions yield the carboxylic acid and the ammonium ion while basic hydrolysis yield the carboxylate ion and ammonia.
  • In the imine.
  • amines.

Owing to their resonance stabilization, amides are relatively unreactive under physiological conditions, even less than similar compounds such as cyclol or, more specifically, a thiacyclol, an oxacyclol or an azacyclol, respectively.

The proton of an amide does not dissociate readily under normal conditions; its pKa is usually well above 15. However, under extremely acidic conditions, the carbonyl oxygen can become protonated with a pKa of roughly -1.

Amides will react with nitrous acid (HONO) forming the carboxylic acid and yielding nitrogen. Nitrous acid is formed by addition of a strong acid to a nitrate (III) salt in solution at temperatures of between 0 and 10 degrees.

Amides undergo the lithium aluminum hydride yields an amine with the same number of carbon atoms.

Amides are dehydrated with phosphorus (V) oxide forming the nitrile. Care should be taken when performing such a reaction since phosphorus (V) oxide smoulders when in contact with organic matter.

Amide linkage (peptide bond)

An amide linkage is kinetically stable to hydrogen bonding abilities of amides.

Amide properties

Compared to quinuclidone.

Solubility

Amides contain carbonyl (C=O) and ether (N-C) dipoles arising from covalent bonding between electronegative oxygen and nitrogen atoms and electro-neutral carbon atoms. Primary and secondary amides also contain two- and one N-H dipoles, respectively. Because of the pi-bonding arrangement of the carbonyl and the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N-C dipole. The presence of a C=O dipole and, to a lesser extent a N-C dipole, allows amides to act as H-bond acceptors. In primary and secondary amides, the presence of N-H dipoles allows amides to function as H-bond donors as well. Thus amides can participate in hydrogen bonding with water and other protic solvents; the oxygen and nitrogen atoms can accept hydrogen bonds from water and the N-H hydrogen atoms can donate H-bonds. As a result of interactions such as these, the water solubility of amides is greater than that of corresponding hydrocarbons

While hydrogen bonding may enhance the water solubility of amides relative to hydrocarbons (alkanes, alkenes, alkynes and aromatic compounds), amides typically are regarded as compounds with low water solubility. They are significantly less water soluble than comparable acids or alcohols due to: 1). their non-ionic character 2). the presence of nonpolar hydrocarbon functionality, and 3). the inability of tertiary amides to donate hydrogen bonds to water (they can only be H-bond acceptors). Thus amides have water solubilities roughly comparable to esters. Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds, and can ionize at appropriate pHs to further enhance solubility

Derivatives

carbon.

Cyclic amides are called lactams.

Naming conventions

References

  1. ^ Bodroux F., Bull. Soc. Chim. France, 1905, 33, 831;
  2. ^ Bodroux reaction at the Institute of Chemistry, Skopje, Macedonia Link
  3. ^ Advanced organic Chemistry, Reactions, mechanisms and structure 3ed. Jerry March ISBN 0-471-85472-7
  4. ^ "Amide Resonance" Correlates with a Breadth of C-N Rotation Barriers Carl R. Kemnitz and Mark J. Loewen J. Am. Chem. Soc.; 2007; 129(9) pp 2521 - 2528; (Article) doi:10.1021/ja0663024
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