From the Raman and i.r. spectra of 2-mercaptoethanol in the liquid state and the temperature variation of the intensity of the Raman lines, it has been concluded that both the trans-and garrclleisomers are present in the liquid. A tentative analysis of the vibrational frequencies of the isomers has been presented. D'apres les spectres Raman et i.r. du mercapto-2 Cthanol a 1'Ctat liquide et aussi d'apres la variation en fonction de la temperature de I'intensite des raies du spectre Raman, on peut conclure que les isomtres cis et gauclle existent tous les deux dans le liquide. Une analyse provisoire des frequences de vibration des isomeres est prCsentCe.[Traduit par le journal]Can.

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The effects of intermolecular hydrogen-bond formation by protic solvents on the absorption and luminescence properties of acetophenone have been investigated. It has been concluded from analysis of the T←S0 absorption, phosphorescence excitation spectra and the emission characteristics that the lowest triplet state of acetophenone in its vapor phase and in nonpolar as well as in moderately polar solvents (e.g., ethanol, EPA etc.) is of n-π* character. In rigid polar media, acetophenone exhibits a very weak 1π-π*→S0 fluorescence and a weak 3π-π*→S0 phosphorescence superposed with the principal 3π-π*→S0 emission. A progressive enhancement of both of these emissions with increasing polarity of the solvent has been observed. It is shown that the fluorescence and the dual phosphorescence emissions from acetophenone in rigid polar media arise as a result of decreased efficiencies of the spin-orbit and vibronic coupling interactions due to intermolecular hydrogen-bond formation by the protic solvents.

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The Raman and infrared spectra of 1,2-propanedithiol in the liquid state and the Raman spectrum in the solid state at 93°K have been investigated and probable assignments of the observed vibrational frequencies have been made. The results indicate that the molecules exist as a mixture of three rotamers, one trails and two gauche, of which the trans form is more stable in the liquid state and is the only form in the solid state. The spectra further indicate that the fraction of the higher energy gauche form is very small and the energy difference between the trans and the more abundant gauche isomer is about 450 ± 100 cal/mol.