Question

Reagent used for converting acetylene to oxalic acid

Answer 1

Oxalic acid can be produced from acetylene by reacting acetylene with alkaline KMnO4 (ref_3).

H−C≡C−H−→−−−−−−−KMnO4/OH− HOOC−COOH

EDIT: Response to OPs comment Here is a rough idea of what is going on mechanistically:

1) the permanganate forms a cyclic intermediate

2) that produces a diol

3) since a double bond is still present the reaction can be repeated to yield 2 gem-diols that can equilibrate to an alpha-diketone

4) now the standard alkaline permanganate oxidation of a carbonyl occurs

5) hydroxide can add to a carbonyl and

6) the manganese ion complexes with the carbonyl oxygen

7) the alpha-proton donates its electrons to reform the carbonyl which is now part of a carboxylic acid

8) repeat steps 5-7 on the other carbonyl and you have oxalic acid