Alkynes have a very interesting structure as they consist of a sigma bond and two separate pibonds to make up the overall triple bond characteristic of the alkyne functionality. 1. Consider the structures below and discuss the reason for the different pKa values being indicated for the C-H bond of a terminal alkyne vs. Vinyl C-H (alkene) vs. Alkyl C-H bond. From these values it is clear that the terminal alkyne is most acidic (lower pKa). Your discussion needs to address the reason why rather than simply say "because the pKa is lower". Why is the pKa lower?