Infrared Studies of Hydrogen Bonding of Methanol by the Matrix Isolation Technique

The O–H stretching mode of hydrogen bonded methanol has been studied by the matrix isolation technique using solid nitrogen at 20°K as a matrix. The bands are narrow and permit assignment of absorptions at 3660, 3490, 3445, 3290, and 3250 cm—1 to the species, respectively, monomer, dimer, trimer, tetramer, and higher polymers. The results correlate with the room temperature concentration dependence of the H bonded O–H stretching mode of methanol in solution. The dependence of frequency upon polymer size suggests that methanol dimers and trimers have cyclic structures and higher polymers have open (chain) structures. In the cyclic structures, the strain associated with the bent H bond is assumed to account for the low-frequency shift of dimers and trimers compared to higher polymers.