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Organic Chemistry

Scorching goIITian

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4 Jul 2008 09:25:14 IST

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279

Alkynes reaction with alkyl halide

None

We have to synthesize 4,4-Dimethyl pent-2-ene using any of the following reagents :

CH3CC, (CH3)3CBr, (CH3)3CCCH, CH3I

Sodium amide & liquid ammonia are available. Give the best synthesis.

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Comments (3)

Neeraj Phadnis

Scorching goIITian

Joined: 29 Dec 2007

Posts: 207

5 Jul 2008 21:26:06 IST

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hello..

Neeraj Phadnis

Scorching goIITian

Joined: 29 Dec 2007

Posts: 207

5 Jul 2008 21:40:20 IST

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I got 2 mechanisms:

1] (CH3)3CBr + Na+ (CH3)3+

CH3CCH + NH2- CH3CC-

(CH3)3+ + CH3CC-CH3CCC(CH3)3

2] (CH3)3CCCH + Na+ (CH3)3CCCNa

(CH3)3CCCNa + CH3I CH3CCC(CH3)3 + NaI

Which one is better? In arihant, the 2nd mechanism is given as answer

aNdRoMeDa

Blazing goIITian

Joined: 10 Sep 2007

Posts: 1319

6 Jul 2008 00:00:07 IST

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yeah..d second is rite ,........... i guess that's rite coz c in d first one itz a tertiary carbocation thus d xtend or d positive charge is less coz of inductiev effct weras on d alkyne wid a sp hybridised anion d negatiev charge density is high thus hw can they react ..........

this also happns c wen we use a LiAlH4 wer d charge density on H is high(negative) and we use a tertiary carbocation .in this case instead of formin an alkane it forms an alkene ..remember???

thus then we use TPH ......

correct em if i m wrng

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