Well, I tried reading my book and then a bunch of other sources, so I think I have just about completely confused myself. But I know acetylene is used in alkylation of terminal alkynes. Since acetylene has 2 terminal protons it can undergo alkylation twice, and that the acetylide ion is used with a primary alkyl halide, otherwise it undergoes elimination.
I haven't quite mastered mechanisms or choosing what halide to use in a reaction so I always second guess myself, and I think since the compounds have substituents it is really just throwing me off.