Syn addition

  • 0_1551370558790_IMG_20190228_214508399~2.jpg
    If it is written that syn addition occurs, how can trans isomer be formed? Please explain.

  • @anag

    C means cis
    T means trans
    A means anti
    S means syn
    M means meso
    R means racemic

    In dis case the addition is on Cis isomer and it is Syn addition so we will follow CSM which means meso product will be formed.
    This was for cis 2 butene

    Now for trans 2 butene, addition is Syn again so by following TSR we get racemic mixture

    Just remember dis order.

  • @harshal-patil thanks but in case of cyclopentene, how can there be cis or trans isomer? All atoms attached to the carbon are same.

    Here are they talking in general about any alkene?

    Cis or trans isomer can exist in cyclic compounds only when the ring has more than 8 Carbons. Isn't it? Please explain.

  • @anag when carbon is less than 8 then trans isomer does not exist. Loosely we can say that the cyclic chain is cis type. Note that there is no geometrical isomerism in cyclic alkenes bcoz trans type does not exist. So we will again follow CSM. Also we can observe dat the product formed is meso.

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