Trimethylamine-acetone interaction

The trimethylamine may be generated by the action of alkali on trimethylamine hydrochloride and dissolved in acetone. The submitter prepared trimethylamine by the method of Som-melet and Ferrand and obtained a 65% yield by the interaction of ammonia, formaldehyde, and formic acid. The checkers found that a commercial 25% solution of trimethylamine in methanol (210 ml.) gave the same yields as the acetone solution. 

Of these, probably the most decisive are type 2 and the combination of types 1 and 3. It is difficult to rationalize the weak H bonds formed by acetonitrile as a base (molecular dipole moment of 3.44 d) and the strong H bonds formed by trimethylamine (molecular dipole moment of 0.7 d) together with the interpretation that an acid A—H forms H bonds with these bases because of the electrostatic interaction of the A—H dipole with point charges on the nitrogen atoms. Another interesting comparison is afforded by the approximately equal H bond properties of acetone, diethyl ether, and dioxane, with dipole moments of 2.85 D, 1.15 D, and 0.4 d, respectively. These qualitative discrepancies can be backed by a substantial body of quantitative data. Table 8-1 collects some of these data, and verifies the absence of any systematic dependence of enthalpy of H bond formation upon the molecular dipole moment. Compilations of At, (814) and of AFshow that these properties are similarly unrelated to /i- Certainly these data show that the strength and behavior of a H bond are not determined in a direct way by the dipole moment. This lack of dependence is not easily reconciled with... 

Formaldehyde and ammonia are not exactly a typical case for a carbonyl-amine interaction, but this result certainly suggests that whatever Lewis bonding occurs in more typical cases wiU likely be pretty small. The more typical case is shown in Figure 9.9, which is for the interaction of acetone with trimethylamine. 

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