Because of its relevance for clathrate formation, the OH stretching spectrum of the THF monohydrate has been obtained in CCl 4 solution 78 at 268 K. A broad (about 80 cm -1 FWHM) hydrogen-bonded OH stretching fundamental was located near 3450 cm -1 at high dilution. Due to thermal and solvent effects, this absolute value is not suitable for the direct comparison to environment-free ground state calculations. In a theoretical study from 2005, it was concluded that the complex has never been observed in spectroscopic experiments . With respect to gas phase investigations, we found no evidence to revise this statement. In particular, there appears to be no rotational spectroscopy characterisation of the monohydrate, but one can expect one or two isomers, due to the complex pseudorotational dynamics of the monomer .