I think the structure would be CH3-CHBRBR. You would say that the integration trace ( number of H above the peaks ) shows one carbon with 3 H and one carbon with 1 H, and the splitting patterns are a quartet and a doublet, and using the n+1 rule, you can see why from the structure.
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Yes it represents a CH3 and the CH. If we think logically, it makes sense with the formula at the top, it makes sense with the splitting pattern and it makes sense with the integration trace. 
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However, when looking at the data sheet, it would suggest a C=C bond... hmmm
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I would go with what we have discussed
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CH3CH(Br)2 sounds reasonable, as, the quartet is further up the TMS line due to bromine (being somewhat electronegative?) usually that's the case with electronegative atoms, plus, and the fact using n+1 rule, the protons are in different states and would show up as a doublet and quartet.
Not sure if you can get away with a c=c as there are too many hydrogen atoms to make up the numbers?
Not sure if you can get away with a c=c as there are too many hydrogen atoms to make up the numbers?
I realised that a C=C bond wouldn't make sense after I posted hahah.
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Original post by Jamo9809
Could any one help me on this question. I really don't understand how to work out the structure from the high res NMR spectra. Thank you. 
Using this data sheet for the chemical shifts: http://www.ocr.org.uk/Images/71984-datasheet.pdf
For reference the paper is June 2011 Question 4G : http://www.ocr.org.uk/Images/66938-question-paper-unit-f335-chemistry-by-design.pdf
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Using this data sheet for the chemical shifts: http://www.ocr.org.uk/Images/71984-datasheet.pdf
For reference the paper is June 2011 Question 4G : http://www.ocr.org.uk/Images/66938-question-paper-unit-f335-chemistry-by-design.pdf
what's confusing you? the triplet at 6ppm -> there's a -CH2 next to that. the doublet at 2.5ppm -> there's a -CH next to that. the ratio of the 2 peaks (which is also the ratio of H atoms) is 1:3 and we've got only 4 H atoms so... guess you can work it out from here.
I agree with the others, it's the only arrangement I can think of that would explain the doublet with an integration of 3, although the quartet looks like a triplet to me 
Peaks aren't very defined. It has to be a quartet though. Splitting tends to occur if the protons are within 3 bond lengths of another proton, so they're close enough to be affected by the spin. So you've got 3 protons that can 'see' one other proton, making it a doublet, and then another proton that's slightly more deshielded that can 'see' three others, hence the quartet.
I'm using this to procrastinate from pharmacokinetics. I hate pharmacokinetics. Plus convince myself it's useful because I have to do NMR in my exam.
Peaks aren't very defined. It has to be a quartet though. Splitting tends to occur if the protons are within 3 bond lengths of another proton, so they're close enough to be affected by the spin. So you've got 3 protons that can 'see' one other proton, making it a doublet, and then another proton that's slightly more deshielded that can 'see' three others, hence the quartet.I'm using this to procrastinate from pharmacokinetics. I hate pharmacokinetics. Plus convince myself it's useful because I have to do NMR in my exam.
(edited 10 years ago)
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