It is estimated that for acetamide, structure A makes a 62% contribution to the structure, while structure B makes a 28% contribution. The structure of an amide can be described also as a resonance between two alternative structures: The inability to rotate distinguishes amide groups from ester groups which allow rotation and thus create more flexible bulk material. This planar restriction prevents rotations about the N linkage and thus has important consequences for the mechanical properties of bulk material of such molecules, and also for the configurational properties of macromolecules built by such bonds. Consequently, the three bonds of the nitrogen in amides is not pyramidal (as in the amines) but planar. In fact the O, C and N atoms have molecular orbitals occupied by delocalized electrons, forming a conjugated system. The lone pair of electrons on the nitrogen atom is delocalized into the carbonyl group, thus forming a partial double bond between nitrogen and carbon. Low-molecular-weight amides, such as dimethylformamide, are common solvents.īall-and-stick model of the formamide molecule, showing the π molecular orbitals (gray). Amides include many other important biological compounds, as well as many drugs like paracetamol, penicillin and LSD. Proteins and important plastics like Nylons, Aramid, Twaron, and Kevlar are polymers whose units are connected by amide groups ( polyamides) these linkages are easily formed, confer structural rigidity, and resist hydrolysis. The core −C(=O)N< of amides is called the amide group (specifically, carboxamide group).Īmides are pervasive in nature and technology. It can be viewed as a derivative of a carboxylic acid ( RC(=O)OH) with the hydroxyl group ( −OH) replaced by an amine group ( −NR′R″) or, equivalently, an acyl (alkanoyl) group ( R−C(=O)−) joined to an amine group.Ĭommon examples of amides are acetamide ( H 3C−CONH 2), benzamide ( C 6H 5−CONH 2), and dimethylformamide ( HCON(−CH 3) 2).Īmides are qualified as primary, secondary, and tertiary according to whether the amine subgroup has the form −NH 2, −NHR, or −NRR', where R and R' are groups other than hydrogen. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, such as in the amino acids asparagine and glutamine. In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula RC(=O)NR′R″, where R, R', and R″ represent organic groups or hydrogen atoms. Asparagine, an amino acid with a side chain (highlighted) containing an amide group
0 kommentar(er)
