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![[Post New]](/templates/default/images/icon_minipost_new.gif) 14 Jul 2008 22:51:25 IST
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Rate of addition of Halogen acid(HX) is least in
(a)CH2=CHCl
(b)CH2=CH2
(c)CH3-CH=CH2
(d)(CH3)2C=CH2
Please explain with reason.
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14 Jul 2008 22:54:04 IST
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Is 'b' d ans?? - plz verify then i'd tell u d reason/xplaination
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You gotta do wat u gotta do |
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15 Jul 2008 01:09:21 IST
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no 'b' is not the ans but anyways tell me what concept did u use .
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15 Jul 2008 01:22:29 IST
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The answer is a)
looking at the question option c) and d) can be clearly ruled out.
now we are left with a) and b)
in option b) the Carbocation is not stabilized by any means...
but in a) the carbocation is stabilized by resonance of Cl, but not to forget the inductive effect of Cl, which is much more dominating/instability providing than the stability provided by resonance.
so the story is clear.
option a) carbocation but electron withdrawing effect(on the whole)
b) carbocation, with no effect on it...
so the answer is clearly a)
hope its clear now :)
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PROGRESS ISN'T MADE BY EARLY RISERS OR HARD WORKERS, BUT BY LAZY PEOPLE TRYING TO FIND EASIER WAY TO DO THE SAME.....SO BE LAZZZZYY!!!! |
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15 Jul 2008 12:10:18 IST
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can u plz explain why c & d are wrong
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15 Jul 2008 15:36:38 IST
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because the carbocation formed will be stabilized by hyperconjugation and inductive effect of the 2 Me groups
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PROGRESS ISN'T MADE BY EARLY RISERS OR HARD WORKERS, BUT BY LAZY PEOPLE TRYING TO FIND EASIER WAY TO DO THE SAME.....SO BE LAZZZZYY!!!! |
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15 Jul 2008 21:02:16 IST
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IT should be "b". The -I effect of Cl in a) disperses the negative charge on the carbanion.
@svj29: Why have you assumed that the carbocation is formed on the carbon attached the Cl?
What is the source of the problem?
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Let us learn to dream, gentlemen, and then perhaps we shall learn the truth.
- August Kekule |
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15 Jul 2008 22:02:49 IST
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@conjurer
a carbocation intermediate is formed and not a carbanion..
1st H+ will attack, and the reaction will proceed according to Markonikoff Addn.
and more stable the intermediate, more is the speed of the reaction.
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PROGRESS ISN'T MADE BY EARLY RISERS OR HARD WORKERS, BUT BY LAZY PEOPLE TRYING TO FIND EASIER WAY TO DO THE SAME.....SO BE LAZZZZYY!!!! |
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15 Jul 2008 22:07:44 IST
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rate of addition is the greatest in A n least in D.
apply the elctrophillic addition mechanism that r followed by the alkenes
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B.TECH MECH NIT ALLAHABAD |
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15 Jul 2008 22:11:16 IST
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It shud b D--- bcoz it has only 2 alpha H atoms... intermediate is least stable... all others hav 3 or 4 alpha H atoms...
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Electronics & Electrical Engineering
(1st yearite)
BITS-pilani campus
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15 Jul 2008 22:28:42 IST
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Whats going on...???
i'm explainin the whole thing agian
The answer is a)
looking at the question option c) and d) can be clearly ruled out.
WHAT HAPPENS: H-X bond dissaciates and H+ attacks.
Markowonikoff addition occurs and carbocation intermediate is formed
the carbocation formed will be stabilized by hyperconjugation and inductive effect of the Me group/s in c) and d)
now we are left with a) and b)
in option b) the Carbocation is not stabilized by any means...
but in a) the carbocation is stabilized by resonance of Cl, but not to forget the inductive effect of Cl, which is much more dominating/instability providing than the stability provided by resonance.
so the story is clear.
option a) carbocation but electron withdrawing effect(on the whole)
b) carbocation, with no effect on it...
AND MORE STABLE THE REACTION INTERMEDIATE, MORE IS THE RATE OF REACTION.
so the answer is clearly a)
hope its clear now :)
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PROGRESS ISN'T MADE BY EARLY RISERS OR HARD WORKERS, BUT BY LAZY PEOPLE TRYING TO FIND EASIER WAY TO DO THE SAME.....SO BE LAZZZZYY!!!! |
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16 Jul 2008 12:47:33 IST
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Yes ofc. What a stupid mistake. I have to revise :)
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Let us learn to dream, gentlemen, and then perhaps we shall learn the truth.
- August Kekule |
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