Turn on thread page Beta
    • Thread Starter
    Offline

    12
    ReputationRep:
    So is the product always a racemic mixture?
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (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!
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by charco)
    sn = nucleophilic substitution.

    This cannot apply to addition!
    Ohh lol. Description edited. So any idea?
    Offline

    18
    ReputationRep:
    Not if it's enzyme catalysed.
    Offline

    3
    ReputationRep:
    (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.
    Offline

    3
    ReputationRep:
    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!
    Offline

    18
    ReputationRep:
    (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.
    Offline

    3
    ReputationRep:
    (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.
    • Thread Starter
    Offline

    12
    ReputationRep:
    (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!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 20, 2016

3,207

students online now

800,000+

Exam discussions

Find your exam discussion here

Poll
Should predicted grades be removed from the uni application process

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.