1-cycloprop-2-enecarboxylic acid methyl ester;cycloprop-2-ene-1-carboxylic acid methyl ester;2-cyclopropene-1-carboxylic acid, methyl ester;InChI=1/C5H6O2/c1-7-5(6)4-2-3-4/h2-4H,1H;methyl cycloprop-2-ene-1-carboxylate