Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    17
    ReputationRep:
    Could someone please check this:

    Starting with methane, u.v. + Cl2, then OH-, H+/Cr2O72-/distil, H+/KCN, H+/reflux, NaBH4, H+/KCN, H+/reflux, LiAlH4.

    Ends up with glycerol?
    • Community Assistant
    • Study Helper
    Offline

    14
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Pigster)
    Could someone please check this:

    Starting with methane, u.v. + Cl2, then OH-, H+/Cr2O72-/distil, H+/KCN, H+/reflux, NaBH4, H+/KCN, H+/reflux, LiAlH4.

    Ends up with glycerol?
    chloromethane

    methanol

    methanal

    CH2(OH)CN (hydroxyethanonitrile ??)

    CH2(OH)COOH

    CH2(OH)CH2(OH)

    why should H+/KCN react with the above?
    • Thread Starter
    Offline

    17
    ReputationRep:
    Ooops (and oops to you too?), I meant H+/Cr2O72-/distil to go to CHOCOOH. As far as I can tell, this should react with H+/KCN, etc.

    NaBH4 doesn't reduce acids, only carbonyls.
    • Community Assistant
    • Study Helper
    Offline

    14
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Pigster)
    Ooops (and oops to you too?), I meant H+/Cr2O72-/distil to go to CHOCOOH. As far as I can tell, this should react with H+/KCN, etc.

    NaBH4 doesn't reduce acids, only carbonyls.
    fair point

    H+/Cr2O72-/distil of CH2(OH)CN ??

    Why would the alcohol group go to -CHO ?

    Maybe I'm getting the scheme wrong?

    (can't you just buy some from the chemist?)

    Name:  glycerol.jpg
Views: 80
Size:  5.4 KB
    • Thread Starter
    Offline

    17
    ReputationRep:
    CH4 + Cl2 + u.v. -> CH3Cl
    + OH- -> CH3OH
    + [O]/distil -> CH2O
    + HCN -> CH2(OH)CN
    + H+/H2O -> CH2(OH)COOH
    + [O]/distil -> CHOCOOH
    + HCN -> CNCH(OH)COOH
    + H+/H2O -> COOHCH(OH)COOH
    + LiAlH4 -> glycerol

    I'm just not 100% certain of step 7. I can't imagine it wouldn't work, but thought I'd check here to see if someone knew it would/n't.

    I teach a lot of very able students and I'm preparing some work for the new A-level spec.
    • Community Assistant
    • Study Helper
    Offline

    14
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Pigster)
    CH4 + Cl2 + u.v. -> CH3Cl
    + OH- -> CH3OH
    + [O]/distil -> CH2O
    + HCN -> CH2(OH)CN
    + H+/H2O -> CH2(OH)COOH
    + [O]/distil -> CHOCOOH
    + HCN -> CNCH(OH)COOH
    + H+/H2O -> COOHCH(OH)COOH
    + LiAlH4 -> glycerol

    I'm just not 100% certain of step 7. I can't imagine it wouldn't work, but thought I'd check here to see if someone knew it would/n't.

    I teach a lot of very able students and I'm preparing some work for the new A-level spec.
    Step 7?

    CHOCOOH + HCN -> CNCH(OH)COOH

    can't see why not.

    Incidentally (useless piece of info) CHOCOOH is a family name in Guatemala, eg Francisco Chocooh

    EDIT: A little research reveals that glyoxylic acid has an activated aldehyde group that undergoes all of the usual aldehyde reactions. So it seems perfectly feasible.

    p.s. Can I swap some of my students for some of yours?
    • Thread Starter
    Offline

    17
    ReputationRep:
    Ta muchly.

    We probably should have done it via pm, but hey.
    Offline

    0
    ReputationRep:
    Theoretically is more or less good... But those H+ steps might cause carboxylic acid to decarboxylate, and I'd perform last step using BH3.
    Also, for the oxidation you may like to try PDC or PCC, or even better, DMP. Those are enough to get you to de aldehyde. If you use H+ Cr2O7 you will get it to the carboxylic acid.
 
 
 
  • 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
    Has a teacher ever helped you cheat?
  • 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

    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.