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

    1
    ReputationRep:
    A reason for the boiling point of phenylamine bieng higher than other compounds of similar Mr is hydrogen bonding
    what i dont get is how does the nitrogen in -NH2 form hydrogen bonds when its electrons are delocalised in the benzene ring its attached to?
    Offline

    0
    ReputationRep:
    (Original post by RRC)
    A reason for the boiling point of phenylamine bieng higher than other compounds of similar Mr is hydrogen bonding
    what i dont get is how does the nitrogen in -NH2 form hydrogen bonds when its electrons are delocalised in the benzene ring its attached to?
    It is true that the lone pair is partially delocalised into the benzene ring. However they are only PARTIALLY delocalised and hydrogen bonding can still occur. The strength of the hydrogen bonding is reduced as a result of the partial delocalisation.

    This affect is also true of phenol (C6H6OH).

    (Cited: http://www.nrcresearchpress.com/doi/abs/10.1139/v62-144)

    All the best,

    Mr Lawlor
    Offline

    0
    ReputationRep:
    Sorry if you get two replies my first is waiting to be checked by the moderation team.

    You are right the lone pair on the nitrogen is partially delocilised throughout the benzene ring. However it is only PARTIALLY delocalised and is still partially present on the nitrogen. This means that the hydrogen bonding is not as strong as it could have been but does still exist.

    This effect is also true in phenol (C6H6OH), where hydrogen bonding does occur but not as strongly as expected because the lone pairs on the oxygen are partially delocalised throughout the benzene ring.

    Hope this helps. All the best,

    Mr Lawlor
    • Thread Starter
    Offline

    1
    ReputationRep:
    i understand thanks for the help
    one more thing and this sounds stupid but how are the the electrons only partially delocalised?i mean do they keep on oscillating between the delocalised ring and the nitrogen atom or is it something else?i would appreciate if you could adress this part
    Offline

    10
    ReputationRep:
    (Original post by RRC)
    i understand thanks for the help
    one more thing and this sounds stupid but how are the the electrons only partially delocalised?i mean do they keep on oscillating between the delocalised ring and the nitrogen atom or is it something else?i would appreciate if you could adress this part
    No they're not oscillating. The real picture is that they are spread across between the two forms. Here the electrons act more like waves than particles (you know the whole wave-particle duality thing)
    Offline

    8
    ReputationRep:
    (Original post by RRC)
    i understand thanks for the help
    one more thing and this sounds stupid but how are the the electrons only partially delocalised?i mean do they keep on oscillating between the delocalised ring and the nitrogen atom or is it something else?i would appreciate if you could adress this part
    This is phenol, but it is pretty much the same.

    Name:  11(12).png
Views: 90
Size:  8.9 KB

    EDIT: If you haven't seen double headed arrows before, it isn't the same as an equilibrium. It shows the possible position of electrons and the real structure is a combination of all of them. The species below don't really exist.
    Attached Images
     
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 21, 2014
Poll
Are you going to a festival?

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.