Amines, amino acids and proteins
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From the Ka values, I have noticed that a tertiary amine is weaker than a secondary amine.
Won't three alkyl groups increase the electron density of nitrogen? Is there something to do with a tertiary amine being less soluble?
260308
Corrie writes....
Yes, you would expect the trend to continue as more alkyl groups are added, increasing the electron density on nitrogen. The usual explanation for tertiary amines being weaker bases than secondary is that as more and more alkyl groups are added, the less soluble the resultant ammonium ion becomes (as H-atoms are replaced, decreasing the possibility for hydrogen bonding with the solvent).
This factor means the equilibrium
R3N + H2O <=> R3NH+ + OH-
is less favoured in the direction of the R3NH+ species than one might have expected based on electron density grounds.
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updated: 28 March 2008
