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    Ok I'm trying to get to grips with drawing my resonance forms, and I've got this in my notes... but I want to know, is the top way of drawing the keto-enol tautomerism techincally correct. I refer to the simplication of the whole resonance process, at the top of the attachment.

    I refer to the arrow in the middle, where electrons seem to be going from a bond straight into another bond. I see where they've got that idea from but I thought that you always had to draw curly arrows from bond to atom... is it correct to represent electron movement from bond to bond that way?

    Also should there be a +ve charge on the protonated oxygen on the right?

    Thanks.

    P.s. sorry for the rubbish drawings
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    (Original post by SummitOfReason)
    Ok I'm trying to get to grips with drawing my resonance forms, and I've got this in my notes... but I want to know, is the top way of drawing the keto-enol tautomerism techincally correct. I refer to the simplication of the whole resonance process, at the top of the attachment.

    I refer to the arrow in the middle, where electrons seem to be going from a bond straight into another bond. I see where they've got that idea from but I thought that you always had to draw curly arrows from bond to atom... is it correct to represent electron movement from bond to bond that way?

    Also should there be a +ve charge on the protonated oxygen on the right?

    Thanks.

    P.s. sorry for the rubbish drawings
    very often, keto-enol tautomerism is either acid or base catalysed. depending on which is used, that will affect how your mechanism should proceed. i.e. a base catalysed one will have deprotonation initially to form your enolate that can protonate off a water molecule. an acid catalysed one will most likely protonate the ketone and having water acting as the base to form the enol then.
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    (Original post by SummitOfReason)
    Ok I'm trying to get to grips with drawing my resonance forms, and I've got this in my notes... but I want to know, is the top way of drawing the keto-enol tautomerism techincally correct. I refer to the simplication of the whole resonance process, at the top of the attachment.

    I refer to the arrow in the middle, where electrons seem to be going from a bond straight into another bond. I see where they've got that idea from but I thought that you always had to draw curly arrows from bond to atom... is it correct to represent electron movement from bond to bond that way?

    Also should there be a +ve charge on the protonated oxygen on the right?

    Thanks.

    P.s. sorry for the rubbish drawings
    All looks good apart from the 5 valent carbon on the right hand side of the top line!!!! Just change the bond from a double bond between the C and OH to a single bond.
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    (Original post by shengoc)
    very often, keto-enol tautomerism is either acid or base catalysed. depending on which is used, that will affect how your mechanism should proceed. i.e. a base catalysed one will have deprotonation initially to form your enolate that can protonate off a water molecule. an acid catalysed one will most likely protonate the ketone and having water acting as the base to form the enol then.
    interesting, thanks
    (Original post by JMaydom)
    All looks good apart from the 5 valent carbon on the right hand side of the top line!!!! Just change the bond from a double bond between the C and OH to a single bond.
    oh yeah, woops! haha. thanks
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    (Original post by SummitOfReason)
    interesting, thanks
    I should point out that while enolisation of a lone carbonyl requires acid or base, a 1,3-diketone (or aldehyde or the like), in a chain with free rotation, will enolise one carbonyl in any solvent which can act as a base (such as water), as keto-enol form with an intramolecular hydrogen bond in a 6 membered ring is of lower energy than the diketo form.

 
 
 
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