Just one sec...
Hey! Sign in to get help with your study questionsNew here? Join for free to post

Mass spectrum of pentan-3-one

Announcements Posted on
Win a year's supply of BIC stationery for the new academic year! 20-08-2016
    • Thread Starter
    Offline

    ReputationRep:


    In the above example, the molecular ion has fragmented into the cation [CH3CH2CO]+ (because the Mr of this is 57)..

    Would it be correct if you wrote [CH3CH2CO]+ as [C3H5O]+?

    Also could the molecular ion fragment into the below (instead of the above):

    [C4H9]+; since the Mr of this is also 57..

    Thanks
    Offline

    ReputationRep:
    (Original post by sabre2th1)
    x
    Yes, you can write it like that, but the structural formula is better as it's more detailed.

    No it couldn't, as [CH3CH2CH2CH2]+ cannot be formed from CH3CH2COCH2CH3 (in terms of fragmentation), as in pentan-3-one, the oxygen is on the 3rd carbon, but there's no oxygen in [CH3CH2CH2CH2]+.
    • Thread Starter
    Offline

    ReputationRep:
    (Original post by thegodofgod)
    Yes, you can write it like that, but the structural formula is better as it's more detailed.

    No it couldn't, as [CH3CH2CH2CH2]+ cannot be formed from CH3CH2COCH2CH3 (in terms of fragmentation), as in pentan-3-one, the oxygen is on the 3rd carbon, but there's no oxygen in [CH3CH2CH2CH2]+.
    So each element (from the molecular ion) has to be present in the cation? And the number of atoms of each element present doesn't matter (as long as there is at least 1 atom of each, and overall it adds up to the peak's M/Z value)?
    Offline

    ReputationRep:
    (Original post by sabre2th1)
    So each element (from the molecular ion) has to be present in the cation? And the number of atoms of each element present doesn't matter (as long as there is at least 1 atom of each, and overall it adds up to the peak's M/Z value)?
    No, sorry, what I wanted to express was that if you split [CH3CH2COCH2CH3]+ in any way, there is no way you can get [CH3CH2CH2CH2]+.

    What you've written above isn't correct :no:
    • Thread Starter
    Offline

    ReputationRep:
    (Original post by thegodofgod)
    No, sorry, what I wanted to express was that if you split [CH3CH2COCH2CH3]+ in any way, there is no way you can get [CH3CH2CH2CH2]+.

    What you've written above isn't correct :no:
    Oh I see. So in an exam question, if you were asked to write down the structural formula for a cation, how would you know if its right?

    Cheers
    Offline

    ReputationRep:
    (Original post by sabre2th1)
    Oh I see. So in an exam question, if you were asked to write down the structural formula for a cation, how would you know if its right?

    Cheers
    You can normally work the structural formula out
    • Thread Starter
    Offline

    ReputationRep:
    (Original post by thegodofgod)
    You can normally work the structural formula out
    Oh okay, thank you

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: May 14, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Poll
How do you sleep?

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

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