“…18 Numerous theoretical studies of this reaction (mostly the reverse reaction, i.e. the formaldehyde hydration) [19][20][21][22][23][24][25][26] have shown that the inclusion of additional water molecules in the process of proton transfer significantly lowers the barrier and brings the theoretical value close to the experimental one. Although methanediol was not isolated experimentally either in the gas or in condensed phases, other geminal diols, such as 2,2-dihydroxyacetic acid, (HOCQO)CH(OH) 2 , 27 or 1,1-dihydroxypropan-2-one, (CH 3 CQO)CH(OH) 2 , 28 were characterized spectroscopically in the gas phase and some more compounds were detected in the solid state, such as chloral hydrate, CCl 3 CH(OH) 2 , [29][30][31][32] dichloroacetaldehyde hydrate, CHCl 2 CH(OH) 2 , 33 hexachloroacetone hydrate, (CCl 3 ) 2 C(OH) 2 , 34 and ninhydrin.…”