Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    i was wondering if anybody knew the mechanism of the hydrolysis of sucrose into glcose and fructose, using hydrochloric acid - is the hydrochloric acid a catalyst?

    if thats the case, is it present at the end f the reaction?
    Offline

    2
    ReputationRep:
    (Original post by Holly4679)
    i was wondering if anybody knew the mechanism of the hydrolysis of sucrose into glcose and fructose, using hydrochloric acid - is the hydrochloric acid a catalyst?

    if thats the case, is it present at the end f the reaction?
    The acid is a catalyst, and is present at the end of the reaction.

    In general, splitting up a disaccharide by (brute force) acid hydrolysis is a form of acetal hydrolysis into a hemiacetal (the -OH at same carbon as the -O- bit of the ring) of one monosaccharide and a random alcohol (-OH) of the other monosaccharide.

    But sucrose is an acetal which comes from two hemiacetal groups rather than one hemiacetal and one (normal) alcohol end (a 1,1-glycosidic bond, rather than a 1 with any other number but 1).

    But you could search up how to hydrolyse a general disaccharide, hydrolysing an acetal into its hemiacetal and alcohol.

    Spoiler:
    Show

    For the general disaccharide made from hemiacetal + (normal) alcohol: first the acetal -O- of the glycosidic bond can be protonated by the H+ ion. That consumes 1 mol of H+ ion.

    Then that whole second saccharide, which is joined via an alcohol -OH not near the -O- part of the ring, separates. The glycosidic -O- of the former acetal has been taken with that second saccharide.

    The -O- which is left in the ring becomes -O+=, while the acetal carbon is left with a hydrogen while still attached to that O in that ring.

    But then water attacks it, giving that carbon an extra -O+H2, and reforming a normal -O- in the ring.

    The -O+H2 finally loses a proton, which forms a neutral monosaccharide, and yields the catalyst again.


    I don't know if the mechanism is any different with sucrose.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: July 27, 2009
Poll
Cats or dogs?

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.