Comparison of the molecular abundances of the primary alcohols methanol, ethanol, n-propanol, and n-butanol measured towards the giant molecular cloud G+0.693 (red squares) with the values predicted by the models of Charnley et al. (1995, blue triangles) for the case with initial solid abundances of 10⁻⁶, 10⁻⁷ , and 10⁻⁸ for C₂H₅OH, propanol, and butanol, respectively. Error bars are also shown in red for the measured abundances, and the downward red arrow indicates an upper limit.