Amide
http://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Amide-general.png/180px-Amide-general.pngIn chemistry, an amide is usually an organic compound that contains the functional group consisting of an acyl group (R-C=O) linked to a nitrogen atom (N). The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia (NH3) or an amine, often represented as anions R2N-. The remainder of this article is about the carbonyl-nitrogen sense of amide.

 

Nomenclature
Amides (R-CO-NH2) take the suffix "-amide". There is no prefix form, and no location number is required since they always terminate a carbon chain, e.g. CH3CONH2 (acetamide) is named ethanamide.
Secondary and tertiary amides are treated similarly to the case of amines: alkane chains bonded to the nitrogen atom are treated as substituents with the location prefix N: HCON(CH3)2 is N,N-dimethylmethanamide.

  • Functional group is an amide therefore suffix = -amide
  • Hydrocarbon structure is an alkane therefore -an-
  • The longest continuous chain is C4 therefore root = but

Butanamide

simple amide

CH3CH2CH2C(=O)NH2
  • Functional group is an amide therefore suffix = -amide
  • Hydrocarbon structure is an alkane therefore -ane
  • The longest continuous chain is C4 therefore root = but
  • The nitrogen substituent is C1 i.e. an N-methyl group

 

N-methylbutanamide

N-subs amide
CH3CH2CH2C(=O)N(CH3)H
  • Functional group is an amide therefore suffix = -amide
  • Hydrocarbon structure is an alkane therefore -ane
  • The longest continuous chain is C2 therefore root = eth
  • The two nitrogen substituents are C1 i.e. an N-methyl group
  • There are two methyl groups, therefore multiplier = di-

N,N-dimethylethanamide

N,N-disubs amide
CH3C(=O)N(CH3)2

Properties

Basicity

Compared to amines, amides are very weak bases. amides don't have as clearly noticeable acid-base properties in water; however, amides are much stronger bases than carboxylic acids, esters, aldehydes, and ketones.
Because of 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.

Solubility

The solubilities of amides and esters are roughly comparable. Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds. Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water.

Amide synthesis

Amides are commonly formed via reactions of a carboxylic acid with an amine. Many methods are known for driving the unfavorable equilibrium to the right:
RCO2H + R'R"NH \overrightarrow{\leftarrow}RC(O)NR'R" + H2O
For the most part, these reactions involve "activating" the carboxylic acid and the best known method, the Schotten-Baumann reaction, which involves conversion of the acid to the acid chlorides:
Amide bond formation

Amide reactions

Amides undergo many chemical reactions, usually through an attack on the carbonyl breaking the carbonyl double bond and forming a tetrahedral intermediate. Thiols, hydroxyls and amines are all known to serve as nucleophiles. Owing to their resonance stabilization, amides are less reactive under physiological conditions than esters.