Basicity of amides

It has been expected that reactivity of metalated pnictides is strongly dependent on the degree of association. One consequence is that the basicity of amides has been correlated with the grade of association by means of extensive 7Li and 16N NMR investigations (16, 17). In contrast, knowledge of structure-reactivity relationships for... 

TABLE 8. Hydrogen-bond basicity of amidates RCON N+Me3 and, for comparison, some carboxyamides in CCI4... 

The degree of basicity of amides is very much less than that of aliphatic amines. For ethanamide, Kh is about 10 13 (Ka of the conjugate acid is 10) ... 

The discus.sjon.s of basicity of amides on pages 334 and 342 are based upon the carbonyl oxygen being the basic site. It is akso possible that the amide nitrogen atom could act as a base. What experimental work could you suggest to determine which atom is the most basic site ... 

The lower basicity of amides when compared to amines can be understood in terms of resonance and inductive effects. An amide is stabilized by resonance involving the nonbonding pair of electrons on the nitrogen atom. However, an amide protonated on its nitrogen atom lacks this type of resonance stabilization. This is shown in the following resonance structures ... 

Amides are weaker bases than corresponding amines. For example, most water-insoluble amines (RNH2) will dissolve in dilute aqueous acids (aqueous HCI, H2SO4, etc.) by forming water-soluble alkylaminium salts (RNHs X"). Corresponding amides (RCONH2) do not dissolve in dilute aqueous acids, however. Propose an explanation for the much lower basicity of amides when compared to amines. 

Similarly, the relative basicity of amide enolates was estimated from the results of the proton-transfer reactions ... 

The kinetic basicity of amides, reported in Table 7.19, is related to their thermodynamic basicity by means of Equation 7.52 ... 

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