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    Hi, i have a real difficulty identifying chiral centres.

    For example,

    Glycine, Tyrosine, phenylalanine, Leucine all appear to have a chiral centre to me, but apparently one of them doesn't.

    Help?
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    chiral centres at carbon atoms must have 4 different groups attached, Glycine doesn't as it has two H's on the centre carbon
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    yep... its like this a chiral centre has 4 diffferent side groups/atoms...for example
    ...........F
    ...........l
    ......Br-C-Cl
    ...........l
    ..........H
    the C in this is a chiral centre...but if one of the halogens were replaced by a hydrogen then this will not be a chiral centre...also some compounds can have 2 chiral centres...but the organic compound will not be optically active if there is a plane of symmety between these 2 chiral centres...:rolleyes:
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    Logically: a molecule can't possibly have a non-superimposable mirror image if it has two or more same atoms joined to it. The molecule would have a mirror image, but it would just superimpose easily on it.
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    (Original post by vaporize)
    Logically: a molecule can't possibly have a non-superimposable mirror image if it has two or more same atoms joined to it. The molecule would have a mirror image, but it would just superimpose easily on it.
    Actually you can in certain situations, but you don't need to know it for A-level
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    all amides have chiral carbons
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    (Original post by zzzzzoe)
    all amides have chiral carbons
    I think you mean amino acids! :p: except for glycine anyway
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    (Original post by EierVonSatan)
    I think you mean amino acids! :p: except for glycine anyway
    oh oops! i think i do. the RC=ON-H cant be chiral can it? aghhh my mistake
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    No the RCONHR' is generally flat, so if anything it shows a type of 'cis-trans isomerism' called rotational isomerism leading to two 'rotamers' where the hydrogen is 'cis' or 'trans' to the C=O
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    The identfication of the chiral centre or asymmetric carbon is easy. the carbon must have 4 different groups attached to it, in a tetrahedron arrangement. even if the groups are ethyl, methyl, propyl and butyl, the molecule is still chiral. hope that helps...........
    by the way Chemguide is a really good website it certainly helped me understand chirality and about how enantiomers rotate the plane of polarized light ie clockwise positive or anticlockwise negaive
 
 
 
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