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![[Post New]](/templates/default/images/icon_minipost_new.gif) 29 Mar 2008 22:13:45 IST
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THE FREE RADICAL MECHANISM HAS BEEN SUGGESTED FOR WURTZ REACTION . FOR FORMATION OF FREE RADICALS THE ALKYL HALLIDE BOND CLEAVES HOMOLYTICALLY TO PRODUCE ALKYL FREE RADICAL AND HALOGEN FREE RADICAL . THE REACTION TAKES PLACE IN DRY ETHER MEDIUM . MY QUESTION : SHOULDNT THE ALKYL HALLIDE BOND CLEAVE HETEROLYTICALLY DUE TO THE ELECTRONAGATIVITY DIFFERENCE . I THOUGHT OF THIS -- FIRST THE ALKYL HALLIDE BOND CLEAVES HETEROLYTICALLY TO PROCDUCE A CARBOCATION AND HALLIDE ION . ENERGY RELEASED IN THIS PROCESS IS EQUAL TO OR GREATER THAN IONISATION ENERGY OF NA SO U GET NA+ AND e- . NA+ AND X- GIVE U NAX AND CARBOCATION + e GIVES U ALKYL FREE RADICAL N THEN PROCEED AS SAME . WHY IS THIS NOT RIGHT ????
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29 Mar 2008 22:36:49 IST
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i have found no fault in ur question
but there would have been some reason (would not ,ight in our syllabuls) behind this
for exmaple if the energy liberated during hetero division might not be sufficient to ionise sodium
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30 Mar 2008 11:04:43 IST
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Actually there are two mechanisms proposed for Wurtz rn, ionic and free radical :)
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30 Mar 2008 11:09:11 IST
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sandeep ramesh is wrong
all remember that all bonds will undergo homolytic fission in the presence of light
high temp
or peroxide
this can be explained as the photon which strikes the electron cloud disturbs it and the bonf=d is cleaved homolitycally
hope it helps
plz rate
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30 Mar 2008 11:09:18 IST
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but how can free radical mechanism the way it is proposed be true ?
how can a polar bond cleave homolytically ?
i agree that hbr cleaves homolytically in presence of peroxide but here no such thing can happen .
@ridhima it is not necessary that the sample must be irradiated u can also give other forms of energy but it must serve as the activation energy . sandeep is prerfectly correct in terms of fact . i want 2 question it please not here that a non polar bond usually cleaves homolytically whereas a polar bond due to e.n difference cleaves heterolytically . photon a chargeless species can disturb electron cloud density with its mere size ? it can provide activation energy but it itself never disturbs electron cloud density . the activation energy transmitted from the photons to the electron cloud increases their degrees of freedom and hence it cleaves due to increased internal energy .
@evryone please comment..............
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COPYRIGHT :
The copyright for the facts written above is held by x4
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30 Mar 2008 11:12:48 IST
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excuse me, there are in reality two mechanisms proposed for the Wurtz rn and im not expressing my sole opinion on this issue!  Want me to post those proposed mechanisms? or find a link?
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30 Mar 2008 11:26:18 IST
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yes there are two mechanisms proposed......see the goiit material
Wurtz Reaction
Two following mechanism have been suggested for wurtz reaction:
If we take one alkyl and one aryl group, this is known as wurtz fittig reaction (practically possible)
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30 Mar 2008 17:02:35 IST
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alright
alright
i am sorry
i accept my mistake
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30 Mar 2008 18:35:40 IST
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Hmm, again a very gud doubt x4.
Well, first of all, if U R thinking that R-X-------> R. + X. (means both radicals), than it is wrong.
It is R. + X-
Now how to get R.???
SO, U hav Na. A very electropostive element, can easily donate its electron. Now in R-X, the C-X bond is polar, means C is delta + and X is delta -.
Now when Na gives an electron, it goes to C as it is delta +.
So now as an electron has come there, it pushes out X-.
If it was simple heterolytic fission(without any external electron), then it wud hav given R+ but as we hav provided an electron to it, so we cant get R+.
So we get R.
Hope U get it.
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30 Mar 2008 22:55:46 IST
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yes tarin is right... because of heterolytic cleavage, R+ and X- are formed. Na being higly electropositive, easily donates its valence electron to R+ and itself becomes Na+ and since R+ gains one electron, it becomes R. That is, a radical is formed and not an anion. R+ + Na -------------> R. + Na+ After that, Na+ + X- --------> NaX Then, sodium again donates an electron to R radical and the radical gets converted to an anion. R. + Na -------> R- + Na+ which is nothing but RNa Finally, R-Na+ + RX -----> R-R + Na+X-
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30 Mar 2008 22:56:58 IST
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Some of the above replies are also correct.
It is given in Peter Sykes also that Wurtz reaction follows 2 mechanisms.
''It is actually a reaction involving carbanions but under some conditions radicals may be involved''
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The quality of a person's life is in direct proportion to their commitment to excellence, regardless of their chosen field of endeavor.
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Check out my blog at:
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30 Mar 2008 22:58:36 IST
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yes that is because both radical and carbanion are formed. i hope it is clear from the mechanism.
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