Physical properties of amines

Which of the amines listed next can be resolved into enantiomers In each case, explain why interconversion of the enantiomers would or would not take place. 

TABLE 19-1 Comparison of the Boiling Points of an Ether, an Alcohol, and Amines of Similar Molecular Weights  

TABLE 19-2 Melting Points, Boiling Points, and Water Solubilities of Some Simple Amines  

All amines, even tertiary ones, form hydrogen bonds with hydroxylic solvents such as water and alcohols. Therefore, amines tend to be soluble in alcohols, and the lower-molecular-weight amines (up to about six carbon atoms) are relatively soluble in water. Table 19-2 lists the melting points, boiling points, and water solubilities of some simple aliphatic and aromatic amines. 

Perhaps the most obvious property of amines is their characteristic odor of rotting fish. Some of the diamines are particularly pungent the following diamines have common names that describe their odors  

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The physical properties of amine oxides are attributed to the semipolar or coordinate bond between the oxygen and nitrogen atoms with high electron density residing on oxygen. 

Amines are polar compounds. Primary and secondary amines can form hydrogen bonds, but tertiary amines cannot. Table 1.8 lists some common physical properties of amines. 

The physical properties of amines depend in an important way on the extent of substitution at nitrogen. Thus primary amines, RNH2, and secondary amines, R2NH, are less volatile than hydrocarbons of similar size, weight, and shape, as the following examples show ... 

Q Describe the trends in the physical properties of amines, and contrast their physical properties with those of their salts. 

Amines exhibit dipole-dipole interactions because of the polar C-N and N—H bonds. Primary and secondary amines are also capable of intermolecular hydrogen bonding, because they contain N—H bonds. Because nitrogen is less electronegative than oxygen, however, intermolecular hydrogen bonds between N and H are weaker than those between O and H. How these factors affect the physical properties of amines is summarized in Table 25.1. 

Discuss the structure, classification, nomenclature and physical properties of amines. Give examples. 

Discuss how hydrogen bonding influences the physical properties of amines. (Section 6.3)... 

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