Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter
    Offline

    5
    ReputationRep:
    So when an alcohol and a carboxylic acid react together, we form an ester and water is produced.
    In order for this to happen, OH from the carboxylic acid and H from the alcohol are removed.

    But why isn't this the case in triglycerides. Glycerol contributes the OH and the fatty acid (i.e the carboxylic acid) only contributes a H. Why is this? Or shall I just accept it?


    Posted from TSR Mobile
    Offline

    13
    ReputationRep:
    (Original post by ps1265A)
    So when an alcohol and a carboxylic acid react together, we form an ester and water is produced.
    In order for this to happen, OH from the carboxylic acid and H from the alcohol are removed.

    But why isn't this the case in triglycerides. Glycerol contributes the OH and the fatty acid (i.e the carboxylic acid) only contributes a H. Why is this? Or shall I just accept it?


    Posted from TSR Mobile
    I'm not entirely sure of what you're asking but remember that glycerol has three -OH groups, not just one
    • Welcome Squad
    Offline

    13
    ReputationRep:
    Welcome Squad
    (Original post by ps1265A)
    So when an alcohol and a carboxylic acid react together, we form an ester and water is produced.
    In order for this to happen, OH from the carboxylic acid and H from the alcohol are removed.

    But why isn't this the case in triglycerides. Glycerol contributes the OH and the fatty acid (i.e the carboxylic acid) only contributes a H. Why is this? Or shall I just accept it?


    Posted from TSR Mobile
    Glycerol has the functional group -OH and is an organic compound correct?

    Therefore Glycerol is a type of alcohol

    Now, in regards to your question, it doesn't really matter what contributes what in this scenario since either way an ester bond forms

    H contributed from Glycerol and OH contributed from the fatty acid will be the same as saying that OH is contributed from the glycerol molecule and the H is contributed from the fatty acid

    Either way, you form the same bond (i.e. an ester bond) and the same product (i.e an ester - in this case, the ester is a triglyceride)
    Offline

    3
    ReputationRep:
    (Original post by ps1265A)
    So when an alcohol and a carboxylic acid react together, we form an ester and water is produced.
    In order for this to happen, OH from the carboxylic acid and H from the alcohol are removed.

    But why isn't this the case in triglycerides. Glycerol contributes the OH and the fatty acid (i.e the carboxylic acid) only contributes a H. Why is this? Or shall I just accept it?


    Posted from TSR Mobile
    Accept it x


    Posted from TSR Mobile
    Offline

    4
    ReputationRep:
    (Original post by ps1265A)
    So when an alcohol and a carboxylic acid react together, we form an ester and water is produced.
    In order for this to happen, OH from the carboxylic acid and H from the alcohol are removed.

    But why isn't this the case in triglycerides. Glycerol contributes the OH and the fatty acid (i.e the carboxylic acid) only contributes a H. Why is this? Or shall I just accept it?


    Posted from TSR Mobile
    Have you done anything on acid strength/delocalisation of negative charges and the actual mechanism of ester bond formation?

    In order to form the bond, you need to deprotonate (remove H+) from an OH group. This would leave O-, which then attacks an electropositive carbon atom. O- is unstable on glycerol, because the negative charge only exists on one oxygen. In carboxylic acids, the two oxygens attached to the terminal carbon are essentially the same once you remove the proton, so the negative charge can be "shared" between two oxygens.

    TL;DR - there is a reason why it's like that, but unless you've covered certain aspects of the course, what I've typed won't make much sense (in which case just accept it).
    Offline

    17
    ReputationRep:
    (Original post by kanra)
    In order to form the bond, you need to deprotonate (remove H+) from an OH group.
    But, the first step of an esterification mechanism is to protonate the carboxylic acid, not to de-protonate it.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 15, 2015
Poll
Do you like carrot cake?

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.