[Messi]

I was looking at 1-heptyne on SDBS...

Why does the hydrogen attached to the triple bond only show up in the ~2 region in the NMR spectrum? This makes me confused!

Link:

http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/IMG.cgi?fname=HSP00932&imgdir=hspW

[discodermolide]

Imagine the pi electrons of the triple bond as a cylinder with the hydrogen sticking out of one end. The cylinder of the electron cloud influences the chemical shift of the alkyne proton. This proton sits in the so called shielding zone and therefore the shift appears upfield.

see http://en.wikipedia.org/wiki/Chemical_shift the section on "Factors affecting chemical shifts"