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Organic Chemistry

Blazing goIITian

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16 Apr 2009 11:03:34 IST

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Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid,
gives
(1) 2,4,6-trinitrobenzene (2) o-nitrophenol
(3) p-nitrophenol (4) nitrobenzene

fiitjee soln says it is o-nitrophenol ...but shouldn't it be choice (1) ??

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Comments (12)

prudhviraj

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16 Apr 2009 11:07:09 IST

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if it is nitration mixture that is h2so4,hno3 used at a time then it is 1

prudhviraj

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16 Apr 2009 11:13:37 IST

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is my explanation correct?

Siddhartha Gupta

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16 Apr 2009 11:14:56 IST

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but wat if they are not used at once ...ie one after the another ...?? then shouldn't the temp be mentioned coz at low temp , phenol forms ortho-sulphonic acid and at high it forms para ...

NugoRama

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16 Apr 2009 11:37:53 IST

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First reaction is of sulphonation, para product is obtain in major yield. The SO3H group at para position to OH

group on benzene ring blocks addition of nitro group at para position. Upon nitration nitro group adds

exclusively on ortho position to OH group. HSO3 group is removed by hydrolysis.

so ORTHO-NITRO PHENOL

BALGANESH

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16 Apr 2009 11:44:34 IST

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we get a mixture of o and p nitro phenol....i fee the answer must be 3 para nitro phenol

NugoRama

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16 Apr 2009 11:51:17 IST

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no....para product is impossibe in sulphonation is done first.blocking of para site ..(duh....)

prudhviraj

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16 Apr 2009 11:53:35 IST

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dam sure ans is 2

NugoRama

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16 Apr 2009 11:54:14 IST

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thats wat i m trying to say..

BALGANESH

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16 Apr 2009 11:56:27 IST

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AIEEE 2008 ques

BALGANESH

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16 Apr 2009 11:57:13 IST

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ok sorry ya it must be o- than -p bcos of inter hydroigen bondign which makes it comparatively more stablebut if it was chloro benzene instead of phenol it wud have been para

NugoRama

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16 Apr 2009 12:00:46 IST

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helloooooooo..

sulphonation is the cause for para blocking ...and ortho product..

not ne hydrogen bonding.

Siddhartha Gupta

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16 Apr 2009 19:19:44 IST

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Now i m totally confused!! what is this blocking?? nugorama , pls explain .... My notes mention that phenol at low temp give o-sulphonic temp & at high temp, they give para -sulphonic acid ...also, there is no hydrolysis being done here (not exclusively mentioned) , then where does -SO3H dissapear ??

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