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Organic Chemistry

Blazing goIITian

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29 Jan 2009 13:39:10 IST

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2 tricky ones from ELECTROPHILIC SUBSTITUION

None

1.amng the folowin compounds 1),toluene 2),benzene 3),p-och3benzene and4) p-cf3 benzene the decreasing order of reactivity towars electrophilics substituiton is

2.how can n02+ electrophile be at meta position in ccl3-benzene (1st postion ccl3)

plzz xplain and solve im not able to arrive at a propr conclusion

rates assured

thanx

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Comments (7)

Atul Mohan

Cool goIITian

Joined: 24 Jan 2009

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29 Jan 2009 17:31:30 IST

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1.p-och3 benzene>toluene>p-ocf3 benzene>benzene............................ 2.ccl3-benzene is a meta director because of the presence of e- withdrawing cl s attached to carbon in ccl3 which deactivates benzene ring....

10904him

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29 Jan 2009 17:42:03 IST

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2---CCl3 group is deactivating as well as meta directing due to -H effect.You must have seen +H(Hyperconjugation) of Hydrogen similarly for chlorine here.1---pls explain what you mean by p-0ch3 benzene and p-ocf3 benzene etc.......single substituent cannot be named ortho- meta or para......clarify the names....

rafa in revival mode

Blazing goIITian

Joined: 25 Jan 2009

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29 Jan 2009 18:28:21 IST

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i am telling you an intersting concept for 2 ques-the way to judge if a substituent is a meta or a o/p directing is if the most electronegative atom of the group(among the subst like o in oh grp) or a atom having lone pairs is attached to the ring then it will be o/p directing otherwise it will be a meta directing.thats why ccl3 is meta directing bcoz less electronegative c is attached to the ring.

make your 1 ques little bit clear and iwill send ans to it soon.

plzzzz rate me.its the best way you can reward someones good work at goiit.

mohmmad amer sohail

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29 Jan 2009 21:06:08 IST

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for second question -ccl3 is an metadirecting group so the second substituent is at meta position

mohmmad amer sohail

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29 Jan 2009 21:11:10 IST

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2. -ccl3 is a strong deactivating group it is a electro withdrawing group and decreases the rate of ARSE reaction and please rate me

JPS

Blazing goIITian

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30 Jan 2009 00:30:24 IST

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1.p-och3benzene >toluene >benzene >p-cf3benzene . p-cf3benzene is least reactive towards electrophilic substitution bcoz it will deactivate the ring by withdrawing the electrons due to the presence of F atom. OCH3- group and CH3- groups activate the ring with OCH3 > CH3.

JPS

Blazing goIITian

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30 Jan 2009 00:32:40 IST

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2. Cl being a electronegative atom deactivates the ring by withdrawing electron from the ring. so in comparision to o- and p- groups the m- position will have more electron density and hence NO2+ will be attracted towatrds m- position.

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