Factors Affecting Alkalinity
While all organic bases are considered to be weak, many factors can affect the alkalinity of the compounds. One such factor is the inductive effect. A simple explanation of the term would state that electropositive atoms (such as carbon groups) attached in close proximity to the potential proton acceptor have an "electron-releasing" effect, such that the positive charge acquired by the proton acceptor is distributed over other adjacent atoms in the chain. The converse is also possible as alleviation of alkalinity: electronegative atoms or species (such as fluorine or the nitro group) will have an "electron-withdrawal" effect and thereby reduce the basicity. To this end, trimethylamine is a more potent base than merely ammonia, due to the inductive effect of the methyl groups allowing the nitrogen atom to more readily accept a proton and become a cation being much greater than that of the hydrogen atoms. In guanidines, the protonated form (guanidinium) has three resonance structures, giving it increased stability and making guanadines stronger bases.
Phosphazene bases also contain phosphorus and are, in general, more alkaline than standard amines and nitrogen-based heterocyclics. Protonation takes place at the nitrogen atom, not the phosphorus atom to which the nitrogen is double-bonded.
Read more about this topic: Organic Base
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