Draw a tree diagram for H* of CFBrCHOCHJCFE, The co pling constants are as follo

Question

Draw a tree diagram for H* of CFBrCHOCHJCFE, The co pling constants are as follow. I-,-40_ 4 e-k the bro 10Note the relative intensities of the peaks at the end ofyour tree. (10 marks)[Spin ofFl do NOT couple with H nes r All we need to do is follow the guideline of Section 13. 9. Draw the strueture of the molecule and identify the nuclides that split H. r H Br Br CH,Br Observations H* is split by 2 equivalent fluorines and the 3 hydrogens of the methyl group. This means we have a 5-generation tree. The maximum number of peaks (remember the spin of F-%)-(2 + 1X3 + 1)-12 peaks. Solution The tree diagram is drawn below. We start by using the splittings of the fluorines because they have largest coupling constant. Then we introduce the 3 hydrogens H* 40 Hz I0 Hz

Explanation / Answer

Step 1: The proton under investigation is first coupled with one fluorine (since H-F coupling is high, it will first couple with fluorine instead of methyl protons) atom to give a doublet (with 1:1 intensity).

Step 2:This doublet will couple with another fluorine atom present to give a triplet with 1: 2: 1 intensity (since the two fluorine present are in same chemical environment and with same coupling constant the peak will come as triplet instead of doublet of doublet).

Step 3: The triplet peak in step 2 is further spiltted by CH3protons as quartet. Here also all the three protons have the same coupling constant 10 Hz and they are in same chemical environment. Hence they will be split the each peak of triplet of step 2 into a quartet peak with intensity 1:3:3:1 to give total 12 peaks.

the middle peaks ratio can be simplified from 2:6:6:2 to 1:3:3:1.

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