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in addition reactions of carbonyl compounds, is the chiral product always racemic? Watch

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    So is the product always a racemic mixture?
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    (Original post by thebrahmabull)
    So whether it's via sn1 or sn2 mechanism is the product always a racemic mixture?
    sn = nucleophilic substitution.

    This cannot apply to addition!
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    (Original post by charco)
    sn = nucleophilic substitution.

    This cannot apply to addition!
    Ohh lol. Description edited. So any idea?
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    Not if it's enzyme catalysed.
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    (Original post by thebrahmabull)
    So is the product always a racemic mixture?
    Yeah.

    If you add a group onto the compound, such as in the case of nucleophilic addition, the attacking species can attack from above or below the carbonyl group. This is because it is planar so attack is not favoured either way.

    Thus there is a 50/50 chance of each enantiomer forming so you get a racemate.
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    In any reaction you'll come across at A-level, yeah its a racemate.

    You need something to be chiral to have the possibility of anything other than a racemic mixture. As SmashConcepts suggests, this could be an enzyme (the chiral pocket transfers its chirality) or some other chiral molecule that makes one enantiomer preferred over another. If the carbonyl compound itself is chiral (at another carbon next to the carbonyl), the chiral bit can interfere so attack at one face is preferred over another. See this if you're really interested: https://en.wikipedia.org/wiki/Asymmetric_induction but again at A-level you'd be safe assuming its a racemate!
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    (Original post by KombatWombat)
    In any reaction you'll come across at A-level, yeah its a racemate.

    You need something to be chiral to have the possibility of anything other than a racemic mixture. As SmashConcepts suggests, this could be an enzyme (the chiral pocket transfers its chirality) or some other chiral molecule that makes one enantiomer preferred over another. If the carbonyl compound itself is chiral (at another carbon next to the carbonyl), the chiral bit can interfere so attack at one face is preferred over another. See this if you're really interested: https://en.wikipedia.org/wiki/Asymmetric_induction but again at A-level you'd be safe assuming its a racemate!
    I thought that the A level syllabus mentioned the enzyme thing, might have been wrong.
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    (Original post by SmashConcept)
    I thought that the A level syllabus mentioned the enzyme thing, might have been wrong.
    No you're right, it is mentioned.

    I think though it's more mentioned in passing though rather than in the context of any specific enzyme/reaction, so any addition reaction that comes up can safely be assumed to be racemic.
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    (Original post by SmashConcept)
    Not if it's enzyme catalysed.
    (Original post by RMNDK)
    Yeah.

    If you add a group onto the compound, such as in the case of nucleophilic addition, the attacking species can attack from above or below the carbonyl group. This is because it is planar so attack is not favoured either way.

    Thus there is a 50/50 chance of each enantiomer forming so you get a racemate.
    (Original post by KombatWombat)
    In any reaction you'll come across at A-level, yeah its a racemate.

    You need something to be chiral to have the possibility of anything other than a racemic mixture. As SmashConcepts suggests, this could be an enzyme (the chiral pocket transfers its chirality) or some other chiral molecule that makes one enantiomer preferred over another. If the carbonyl compound itself is chiral (at another carbon next to the carbonyl), the chiral bit can interfere so attack at one face is preferred over another. See this if you're really interested: https://en.wikipedia.org/wiki/Asymmetric_induction but again at A-level you'd be safe assuming its a racemate!
    Thanks a lot!
 
 
 
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