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

    1
    ReputationRep:
    My synthesis went CH4->CH3Cl->CH3CN->CH3CH2CN

    http://puu.sh/1I6HL

    http://puu.sh/1I6I8

    I used HCN - it says HCN is not allowed and KCN must be used, can someone explain why?

    I also used Sn/HCl is incorrect as it forms a Ketone, I was never taught how these two work, I was just told to use them. Could someone please explain?
    Offline

    16
    ReputationRep:
    (Original post by Hormonal)
    My synthesis went CH4->CH3Cl->CH3CN->CH3CH2CN

    http://puu.sh/1I6HL

    http://puu.sh/1I6I8

    I used HCN - it says HCN is not allowed and KCN must be used, can someone explain why?

    I also used Sn/HCl is incorrect as it forms a Ketone, I was never taught how these two work, I was just told to use them. Could someone please explain?
    HCN is an incredibly toxic gas. KCN is as toxic but due to the fact it is a solid it is much, much easier to handle. You also need the cyanide anion, which is easily present in KCN, whereas HCN is only weakly acidic so you don't get as much CN-.

    The Sn/HCl reduction is university level. The Sn donates one electon at a time (initially forming a radical), reducing the CN to an imine (C=N), which is then hydrolysed by the acid to form the carbonyl.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by illusionz)
    HCN is an incredibly toxic gas. KCN is as toxic but due to the fact it is a solid it is much, much easier to handle. You also need the cyanide anion, which is easily present in KCN, whereas HCN is only weakly acidic so you don't get as much CN-.

    The Sn/HCl reduction is university level. The Sn donates one electon at a time (initially forming a radical), reducing the CN to an imine (C=N), which is then hydrolysed by the acid to form the carbonyl.
    The thing is, normally we've been allowed HCN :/

    If asked the same question, shall I always say Ni/H2 and KCN?
    Offline

    16
    ReputationRep:
    (Original post by Hormonal)
    The thing is, normally we've been allowed HCN :/

    If asked the same question, shall I always say Ni/H2 and KCN?
    I'm surprised you've been allowed HCN, but I'd always say KCN in future.

    As for reduction of nitriles to amines, either catalytic hydrogenation (Ni/H2), or reduction with LiAlH4 will be fine. I prefer LiAlH4 as when it comes to catalytic hydrogenations, different metals are used for different reagents, so I find it easier to just remember LiAlH4.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by illusionz)
    I'm surprised you've been allowed HCN, but I'd always say KCN in future.

    As for reduction of nitriles to amines, either catalytic hydrogenation (Ni/H2), or reduction with LiAlH4 will be fine. I prefer LiAlH4 as when it comes to catalytic hydrogenations, different metals are used for different reagents, so I find it easier to just remember LiAlH4.
    Thank you very much, KCN it is!

    I'll only use HCN to form hydroxynitriles now >.>
 
 
 
  • 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
    What newspaper do you read/prefer?
  • 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.