basicity order

hello,
can someone please explain to me the order of the basicity of the following compounds:

ortho methyl aniline
meta methyl aniline
para methyl aniline

if we make the conjugate acids we'll find that ortho is the most stabilized by inductive effect of methyl (as it is closest to the anilium ion) and then meta and para, so, acc to this logic ortho should be the most basic but it is actually the other way round.
why is this logic wrong???

2 Answers

11
Gone.. ·

the order will be
para methyl aniline>meta methyl aniline>ortho methyl aniline.

see the all ortho substituted annilines are least basic.The steric effect destabilizes the cation making amine a weaker base.
(This is actually something called ortho effect ).

para - +I and hyperconjugation.
meta - only + I.
ortho - reason mentioned above.

1
aieeee ·

well,cipher the reason u hv mentioned affects the acidity of the three. thus the acidic order is what u hv given as the basic order. so,this logic is obviously wrong.
the basicity order will thus be just opposite than that of acidity one.

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