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A few more examples on the topic of couplings:
(You might also want to check page 85 for some additional explanations.)

molecule 1   The protons of the methyl group don't couple, since they are .
CH3-CO-CH2Br   The protons of the methyl and the methylen groups don't show any detectable coupling, since they are .
BrCH2-CC-H   The methyl protons couple with the C-H (JH,CH2 = 2.7 Hz), although they are connected through bonds, since due to the CC triple bond the coupling becomes .

Now try your luck with these two problems:

Determin for these two molecules which proton groups will couple with each other, and which ones won't.
(Give the reason for your answers!)
A)   B)
molecule A   molecule B

Continue on page 93!