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To monitor whether all of the sample of propan-2-ol has been oxidized, you can look Watch

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    Hi,

    Can someone please explain the answer to this question.

    7 Infrared (IR) spectra can be used to follow the progress of reactions involving propan-1-ol and propan-2-ol. Some absorption ranges by chemical bonds in the IR spectrum are given below.


    1 O H stretching in alcohols at 3750−3200 cm–1
    2 C=O stretching in aldehydes at 1740−1720 cm–1
    3 C=O stretching in ketones at 1700−1680 cm–1
    4 C=O stretching in carboxylic acids at 1725−1700 cm–1




    To monitor whether all of the sample of propan-2-ol has been oxidized, you can look for:

    A a lack of absorptions in the IR spectrum at 1.
    B a lack of absorptions in the IR spectrum at 2.
    C absorptions in the IR spectrum at 3.
    D absorptions in the IR spectrum at 4.

    The answer is A but why wouldn't it be C. Since secondary alcohols are oxidized to ketones.

    Any help will be appreciated.
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    The oxidation product of propan-1-ol is either an aldehyde or carboxylic acid, both of which also have C=O peaks. IR is not precise enough to distinguish between these peaks when they are only 20cm-1 apart (or rather, while IR can tell the difference between 1720 and 1700, variation for individual molecules mean that positively identifying a compound by this method is not an accurate method.
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    (Original post by Linked)
    Hi,

    Can someone please explain the answer to this question.

    7 Infrared (IR) spectra can be used to follow the progress of reactions involving propan-1-ol and propan-2-ol. Some absorption ranges by chemical bonds in the IR spectrum are given below.


    1 O H stretching in alcohols at 3750−3200 cm–1
    2 C=O stretching in aldehydes at 1740−1720 cm–1
    3 C=O stretching in ketones at 1700−1680 cm–1
    4 C=O stretching in carboxylic acids at 1725−1700 cm–1




    To monitor whether all of the sample of propan-2-ol has been oxidized, you can look for:

    A a lack of absorptions in the IR spectrum at 1.
    B a lack of absorptions in the IR spectrum at 2.
    C absorptions in the IR spectrum at 3.
    D absorptions in the IR spectrum at 4.

    The answer is A but why wouldn't it be C. Since secondary alcohols are oxidized to ketones.

    Any help will be appreciated.
    The question asks you to monitor whether ALL of the alcohol has reacted. Looking at a product absorption tells you nothing about any remaining reactant ...
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    (Original post by charco)
    The question asks you to monitor whether ALL of the alcohol has reacted. Looking at a product absorption tells you nothing about any remaining reactant ...
    Yeh, this too
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    (Original post by PythianLegume)
    The oxidation product of propan-1-ol is either an aldehyde or carboxylic acid, both of which also have C=O peaks. IR is not precise enough to distinguish between these peaks when they are only 20cm-1 apart (or rather, while IR can tell the difference between 1720 and 1700, variation for individual molecules mean that positively identifying a compound by this method is not an accurate method.
    thank you for your help.

    Much appreciated.
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    (Original post by Linked)
    thank you for your help.

    Much appreciated.
    Well Mr Linked, it seems that you neg repped me for giving you the correct answer ...

    .... hmmmmmm

    That was hardly very sporting now, was it?
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    (Original post by charco)
    Well Mr Linked, it seems that you neg repped me for giving you the correct answer ...

    .... hmmmmmm

    That was hardly very sporting now, was it?
    Apologies. I did not mean to neg rep you. Do you know how I can reverse it?
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    (Original post by charco)
    Well Mr Linked, it seems that you neg repped me for giving you the correct answer ...

    .... hmmmmmm

    That was hardly very sporting now, was it?
    Don't worry, my points count for more
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    (Original post by PythianLegume)
    Don't worry, my points count for more
    Once again I am extremely sorry.

    I feel really bad that I neg repped you when you were trying to help.
 
 
 
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