Shweta Thakur posted an Question
June 27, 2020 • 14:52 pm 30 points
  • IIT JAM
  • Chemistry (CY)

Plz check this explanation for why hoffman product dominated in hoffman elimination....... and plz tell why there is + ve charge on nitrogen ... he m

He mann CPinari» itDa A-U A O1, C1 - 9nthis hol!mannoductdomime induned Caubon Page min& -1= ma due Gulky Astbaat absixa c Hiden leai

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  • Shweta thakur

    this sir

    cropped1327164934994059272.jpg
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    see when the base is bulky and leaving group is poor...the transition state resembles more like carabanionic charcater not carbocationic character

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    so the concerted mechanism proceeds and hoffman products dominates

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    see the two images i have send...you got it from there

  • comment-profile-img>
    Priyanshu kumar

    yess when base is bulky...hoffman products dominates..

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    why on nitrogen there is positive cagrge

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    but the pic u have sent me .there it is written that nr3is bad leaving group

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    why

  • comment-profile-img>
    Priyanshu kumar

    see this you understand how base affects which products dominants....

    cropped8300385742593569913.jpg
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    my explanation is correct ?

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    plz tell one thing more that n(ch3)3 is good leaving group or bad

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    if bad then how in Hoffman elimination it elimanate

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    although there is carbonation character oncarbon

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    N+(Ch3)3 is poor leaving group

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    why

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    nitrogen is highly electronegative....and you know that electronegative elements can't bear positive charge effectively

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    it is weak base

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    you know in the group the electronegativity increases and basicity decreases

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    and best leaving group are weak bases

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    see the images i have attached and read the 2nd line

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    but sir

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    I m sending u one more pic. plz see that

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    okk send

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    I sent the pic

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    in this post only

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    this pic u which u have sent me there it is written that nr3 is bad leaving group

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    yess so hoffman product dominates and see the transition state images which send

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    sir

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    initially u are saying than nr3is bad leaving group

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    there is confusion among book also...in some book it is written bad levaing group and somewhere good

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    always keep in mind...neutal compound is stable so quaternary ammonium salts leaves to give neutral form

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    nr3 is bulky leaving group therefore i Hoffmanbproduct dominates.

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    right

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    yess see in newman projection you see...to avoid repulsion

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    hoffmann dominates

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    okok

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    and why there is positive charge on nitrogen

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    when ammonia takes H+ the ammonium salts is formed in which nitrogen carry positive charge

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