1its just a case of 2 kinds of prodts..
1)kinetically controled pdt...
2)theromdynamically controled pdt..
for ever reaction there is an energy barrier.., 2 reactants can react using 2 different paths..., normally, the one path dat results in the 'more thermodynamically stable product', has a higher activation energy..., and the one that results in the 'thermodynamically less stable product', has a lower activation energy...
at low temperatures, u donot have a large activation energy provided, so the reaction will go for the path where u have a lower activation energy, ie. according to our discussion, lead to the 'thermodynamically lesser stable product'...
at higher temperatures,
there is thermodynamic control,
or the high activation energy needed is achieved thru' a high temperature,
so the reaction goes thru' the path involving higher activation energy, but leading to the 'thermodynamically more stable product'
in this case as we can see, o-phenolsulphonic acid, is less thermodynamically stable, and
p-phenolsulphonic acid
is more thermodynamically stable...,
hence the result..
cheers!!
