Why is a tertiary amine less basic than a secondary and primary amine? Methyl groups are electron-donating so wouldn't the more substituted amine be more basic? according to BR, the relative basicity of methyl amines is : R2-NH > R-NH > R3-N > NH3
Why is a tertiary amine less basic than a secondary and primary amine? Methyl groups are electron-donating so wouldn't the more substituted amine be more basic? according to BR, the relative basicity of methyl amines is : R2-NH > R-NH > R3-N > NH3
Why is a tertiary amine less basic than a secondary and primary amine? Methyl groups are electron-donating so wouldn't the more substituted amine be more basic? according to BR, the relative basicity of methyl amines is : R2-NH > R-NH > R3-N > NH3
because it has a harder time finding the proton due to steric hinderance.
As usual, chiddler sums it up eloquently
Are amines really "weak bases" ?
because it has a harder time finding the proton due to steric hinderance.
I think there is more to it than sterics.
i don't. can you please explain what you mean?
This is from another forum discussing the topic:
The basicity trends of amines are most easily explained by looking at the acidity of ammonium-ions, which (in solution) follows the trend given below:
NH4+ > (CH3)3NH+ > CH3NH3+ > (CH3)2NH2+
That is NH4+-ions are the most acidic (least basic) ones, whereas (CH3)2NH2+-ions are the least acidic (most basic) ones.
This trend can be explained by two conflicting effects - polarizability and solvation.
If you look at gas phase acidities the trend is as follows:
NH4+ > CH3NH3+ > (CH3)2NH2+ > (CH3)3NH+
Which is what we would normally expect since more methyl-groups donates more electrons spreading out the positive charge and therefore stabilizing the ammonium-ion (making it less acidic, and the conjugate base more basic).
On the other hand solvation effects leads to the following trend:
(CH3)3NH+ > (CH3)2NH2+ > CH3NH3+ > NH4+
This trend can be explained by the size of the ammonium-ion - the larger, the least well solvated, therefore least stable and hence more acidic (less basic).
A combination of these two trends gives the acidity (and therefore basicity) trend of ammonium-ions (amines) in solution.