proton nmr question - please help!

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shawn_o1
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#1
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#1
The proton NMR spectrum of a chloroalkyl ketone, A, C5H9ClO, is shown.

The measured integration trace gives the ratio 1.2 to 1.2 to 1.2 to 1.8 for the peaks at (delta) 3.8, 2.8, 2.4 and 1.1 respectively. Refer to the spectrum and the data in the table on page 1 to answer the following questions.

How many different types of proton are present in compound A?
What is the actual ratio of the numbers of each type of proton?
The peaks at (delta) 2.4 and 1.1 arise from the presence of an alkyl group. Identify the group and explain the splitting pattern.
What can be deduced from the splitting of the peaks at (delta) 3.8 and 2.8?
Suggest the structure of compound A.
What I don't understand is, there is a peak at (delta) 2.8 that doesn't correspond to what I'm given in the data sheet (AQA GCE Chemistry). The ranges that 2.8 lie are the proton types ROH (d 0.5-5.0) and RNH2 (d 1.0-4.5) but neither are part of a "chloroalkyl ketone".
I've already worked out the presence of RCH3 (d 1.1), RCOCH (d 2.4) and RCH2Cl (d 3.8).
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Bradshaw
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#2
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#2
Both the shifts at d=2.4 and d=2.8 correspond to CH2 groups. I can't see the splitting so I'm not sure the exact structure, but it is possible that both of these CH2 groups are next to the ketone.
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shawn_o1
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#3
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Oh, the question came from here:
http://www.chemsheets.co.uk/A2/CHEM4...EM4.11.001.doc
Task 9 Question 2
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charco
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#4
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(Original post by shawn_o1)
Oh, the question came from here:
http://www.chemsheets.co.uk/A2/CHEM4...EM4.11.001.doc
Task 9 Question 2
There are only four proton environments

You can see from the splitting (triplet, quartet) that the peaks at 1.1 and 2.4 arise from a CH3CH2

The shift at 2.4 suggests that this environment is next to the carbonyl

CH3CH2CO

Then the next triplet appears at 2.8 is coupled with the triplet at 3.8 (notice how the inner peak of each triplet 'grows' towards the other), which is shifted by the presence of the halogen.

CH3CH2COCH2CH2Cl
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shawn_o1
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#5
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(Original post by charco)

CH3CH2COCH2CHCl
That's eight hydrogens I counted. I think you meant CH3CH2COCH2CH2Cl (or is that wrong)?
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charco
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#6
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#6
(Original post by shawn_o1)
That's eight hydrogens I counted. I think you meant CH3CH2COCH2CH2Cl (or is that wrong)?
typo - sorry. Well spotted!

Now corrected...
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peachlet
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#7
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#7
(Original post by charco)
There are only four proton environments

You can see from the splitting (triplet, quartet) that the peaks at 1.1 and 2.4 arise from a CH3CH2

The shift at 2.4 suggests that this environment is next to the carbonyl

CH3CH2CO

Then the next triplet appears at 2.8 is coupled with the triplet at 3.8 (notice how the inner peak of each triplet 'grows' towards the other), which is shifted by the presence of the halogen.

CH3CH2COCH2CH2Cl
Tnx
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