At least two hydrates of glyoxal are sold commercially:*glyoxal dimer, dihydrate: [(CHO)2]2[H2O]2, 1,4-dioxane-trans-2,3-diol (CAS# 4845-50-5, m.p.
* глиоксаль димер, дигидрат: [(CHO)2]2(H2O)2, 1,4-диоксан-транс-2,3-diol (CAS# 4845-50-5, т.пл.