Pictures of the Day CH320M328M

Above are various representations of the simplist alkyne, acetylene. The main point is that, like alkenes, the reactivity of alkynes is dictated by the pi bonds. Due to the pi bonds, alkynes react as weak nucleophiles with various electrophiles. Of course, alkynes react two times with most electrophiles, since there are two pi bonds. A key difference between alkynes and alkenes is that when water adds (H-O-H adds), alkynes initially give enols, that spontaneously tautomerize to the keto form (giving ketone or aldehyde final products).