[satya reddy]

why tertiory amines are more basic than primary amines?

[Archer]

What are your thoughts? Do you think this is counter intuitive?

[spirochete]

There are two factors controlling the basicity of amines in solution. One is electron donation from alkyl groups, via hyperconjugation and polarizable induction. The other is charge solvation. In the gas phase things are much simpler because electron donation from alkyl groups is the only factor.

Archer was probably hinting at this but I figured I'd get things rolling a little bit. There is an excellent thread on this forum about this issue. What it boils down to is that relative pKas for ammonium species are hard to predict because there are competing factors that contribute in opposite ways.

[cbn]

The resaon may be alkyl groups ?

[magician4]

actually, if memory serves, in general secondary amines are sporting the smallest pKb , and hence are considered to be the most basic
(for example , pKb values: CH₃NH₂ 3.4 ; (CH₃)₂NH 3.29 ; (CH₃)₃N 4,11 )

usually, this anti - intuitive feature is taken as an example for "steric effects at times overcompensate electronic effects"

regards

Ingo