PROPERTIES OF AMIDES

Amides have hydrogen bonds between their molecules and so their boiling points are relatively high. For example, formamide is a liquid with boiling point 190°C while all other amides are white-crystalline solids. Since they are polar, they are water soluble. They do not react with acids and bases, though when heated slowly with water they are hydrolyzed. 

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To name an amide, follow the steps on the next page. The Sample Problem that follows illustrates how to use these steps. Later, Table 1.14 describes some physical properties of amides. 

Polarity of functional group Because the nitrogen atom attracts electrons more strongly than carbon or hydrogen atoms, the C-N and N-H bonds are polar. As a result, the physical properties of amides are similar to the physical properties of carboxylic acids. 

L. Leiserowitz, F. Nader, The molecular packing modes and the hydrogen-bonding properties of amide dicarboxylic acid complexes, Acta Cryst. B33 (1977) 2719-2733. 

Kataky, R., Matthes, K. E., Nicholson, P. E., Parker, D., Buschmann, H. J., Synthesis and binding-properties of amide-functionalized polyaza macrocycles. J. Chem. Soc., Perkin Trans. 21990, 1425-1432. 

Table 20 Preparations and Properties of Amide and Peptide Complexes of Cobalt(ffl)...

Hydrogen Storage Properties of Amide and Imide Systems... 

D) Acid and Basic Properties of Amides. (1) Determine the pH of a sample of pure acetamide in water. Which amide is most likely to show definite acidic properties Devise a test to show that acetamide forms salts with metallic ions. 

Racape, E., Thibault, J.F., Reitsma, J.C.E. and Pilnik, W. 1989. Properties of amidated pectins II. Polyelectrolyte behaviour and calcium binding of amidated pectins and amidated pectic acids, Biopolymers, 28 f435-f448. 

Carbon-nitrogen single bonds are freely rotating however, amide carbon-nitrogen bonds are much more rigid. Why is this true What effect does this property of amide bonds have on the shapes that proteins can assume ... 

Atomic charges have been used to analyze the nature of the interaction between the nitrogen and carbon groups in amides. In VB language this interaction is described in terms of resonance. These resonance structures account for the most characteristic properties of amides. They are quite polar and react with protons and Lewis acids at oxygen, but not at nitrogen. The partial C=N double bond character also accounts for the observed rotational barrier of about 18kcal/mol. 

The general properties of amides can best be illustrated by a description of a typical member of the series. 

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