Hey there! Sign in to join this conversationNew here? Join for free

Nomenclature help Watch

Announcements
    • Thread Starter
    Offline

    15
    ReputationRep:
    When naming compounds when do you add the prefix oxo for ketones and hydroxy for alcohols
    Offline

    3
    ReputationRep:
    hydroxy is used when there is also a carboxyl group, e.g. 2-hydroxypropanoic acid.

    for ketones you hardly ever use the oxo prefix, in fact in A level chem im pretty sure its never used.
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by The Diplomat.)
    hydroxy is used when there is also a carboxyl group, e.g. 2-hydroxypropanoic acid.

    for ketones you hardly ever use the oxo prefix, in fact in A level chem im pretty sure its never used.
    Right, thanks. What if if you had, butane for example and you had ethyl on the 2nd carbon and methyl on 3rd carbon. Would you label ethyl with the lowest number or methyl?
    Offline

    3
    ReputationRep:
    (Original post by kiiten)
    Right, thanks. What if if you had, butane for example and you had ethyl on the 2nd carbon and methyl on 3rd carbon. Would you label ethyl with the lowest number or methyl?
    the longest carbon chain in that compound is 5, so it would be 2,3-dimethylpentane
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by The Diplomat.)
    the longest carbon chain in that compound is 5, so it would be 2,3-dimethylpentane
    Ohhh, ok maybe that was a bad example. What about something like nonane or decane with the 2 branches in the middle e.g. If you label from either end one will have a lower no. then the other
    Offline

    2
    ReputationRep:
    (Original post by kiiten)
    Ohhh, ok maybe that was a bad example. What about something like nonane or decane with the 2 branches in the middle e.g. If you label from either end one will have a lower no. then the other
    I think you would do the ethyl with the smallest number because isn't it alphabetical order for the prefixes? I may be wrong thoigh


    Posted from TSR Mobile
    Offline

    3
    ReputationRep:
    (Original post by kiiten)
    Ohhh, ok maybe that was a bad example. What about something like nonane or decane with the 2 branches in the middle e.g. If you label from either end one will have a lower no. then the other
    You put the smaller number with ethyl because aplhabetical order
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by isabellacappio)
    I think you would do the ethyl with the smallest number because isn't it alphabetical order for the prefixes? I may be wrong thoigh


    Posted from TSR Mobile
    Wait - that does apply when naming the compound. But i mean which one would be attached to the lowest carbon
    Offline

    16
    ReputationRep:
    Whichever gives you the lowest number at the start.

    e.g. 4-ethyl-2-methylhexane rather than 3-ethyl-5-methylhexane.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Should Spain allow Catalonia to declare independence?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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.