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    Hi guys, can someone please help with this question? The answer is C
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    So, with ketones what does the 43 ion signify (think in terms of position, 2-ketone, 3-ketone etc.)?
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    (Original post by Stiff Little Fingers)
    So, with ketones what does the 43 ion signify (think in terms of position, 2-ketone, 3-ketone etc.)?
    So CH3CO represents 43 but I am still confused how this is related to the question.. There are lots of fragments in one of the ketones that is not present in the other ketone like CH3CH2CO is present in the second ketone but not in the first.
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    (Original post by sienna2266)
    So CH3CO represents 43 but I am still confused how this is related to the question.. There are lots of fragments in one of the ketones that is not present in the other ketone like CH3CH2CO is present in the second ketone but not in the first.
    So you've got 2-pentanone and 3-pentanone.

    71 is loss of Methyl (-15), giving the equivalent of the M-1 for butanal/2-butanone for 2-pentanone or 2-butanone for 3-pentanone
    57 is loss of ethyl (-29), giving the equivalent the M-1 for Acetone (2-pentanone) or propanal (3-pentanone) - and the ethyl group gives your 29.
    43 is equivalent to the M-1 for acetaldehyde and is only possible with the 2-ketone, not the 3-ketone.

    It's not about the exact same structure of fragments but different fragments of the same mass
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    (Original post by Stiff Little Fingers)
    So you've got 2-pentanone and 3-pentanone.

    71 is loss of Methyl (-15), giving the equivalent of the M-1 for butanal/2-butanone for 2-pentanone or 2-butanone for 3-pentanone
    57 is loss of ethyl (-29), giving the equivalent the M-1 for Acetone (2-pentanone) or propanal (3-pentanone) - and the ethyl group gives your 29.
    43 is equivalent to the M-1 for acetaldehyde and is only possible with the 2-ketone, not the 3-ketone.

    It's not about the exact same structure of fragments but different fragments of the same mass
    Thank you very much! This is starting to make sense. But can you do this question without referring to the options given for the answer or is it not possible? It's just that I am finding it hard to do it by not looking at the options given.
    Also, for your last point, can't 43 be equivalent to the M-1 peak for CH3CH2CH3?
    Many thanks
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    (Original post by sienna2266)
    Thank you very much! This is starting to make sense. But can you do this question without referring to the options given for the answer or is it not possible? It's just that I am finding it hard to do it by not looking at the options given.
    I'm not sure what you mean, it's asking you which of the suggested fragments would be in one but not the other, of course you have to consider the options given

    Also, for your last point, can't 43 be equivalent to the M-1 peak for CH3CH2CH3?
    Many thanks
    It could, but that's also only possible in one of the two compounds in question
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    (Original post by Stiff Little Fingers)
    I'm not sure what you mean, it's asking you which of the suggested fragments would be in one but not the other, of course you have to consider the options given



    It could, but that's also only possible in one of the two compounds in question
    Thank you so much!!!!I get it now!
 
 
 
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