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Alkyne NMR

1-pentyne

C≡C-H: 1.7 - 2.7 ppm. The presence of this proton confirms that the triple bond is at the end of a chain.

C≡C-C-H: 1.6 - 2.6 ppm.

H-C≡C-C-H coupling has J of 2-3Hz.

Allylic coupling isn't very strong, but it can be noticed. For example, C in the above spectra is actually a finely split triplet. Likewise, D would show a triplet of doublets, if it were expanded.

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