[furaniki18]

which of the following is most easily dehydrated using conc. sulfuric acid?

the mechanism is that first a proton attacks -OH group so that the leaving group is water. this results in formation of a carbocation...so i think stability of carbocation should be a major factor in deciding how easily will dehydration take place...but wont the presence of keto which would exert a -I effect decrease the stability of carbocation? so why in the 1st ques. compound (b) is most easily dehydrated?
and as -I effect gradually decreases on moving away from the functional group shouldn't in ques. 2 compound (b) form most stable carbocation and thus be most easily dehydrated?

[discodermolide]

which of the following is most easily dehydrated using conc. sulfuric acid?

the mechanism is that first a proton attacks -OH group so that the leaving group is water. this results in formation of a carbocation...so i think stability of carbocation should be a major factor in deciding how easily will dehydration take place...but wont the presence of keto which would exert a -I effect decrease the stability of carbocation? so why in the 1st ques. compound (b) is most easily dehydrated?
and as -I effect gradually decreases on moving away from the functional group shouldn't in ques. 2 compound (b) form most stable carbocation and thus be most easily dehydrated?

Just a point; the OH lone pair attacks the acid and gets protonated.

[orgopete]

Hint, you have assumed this is an E1 elimination. Since you know it is (b) that dehydrates most rapidly, what might that tell you about the rate determining step? Is it an E1 elimination?