Raman spectra of liquid <i>n</i>-alkanes. III. Energy difference between <i>t</i> <i>r</i> <i>a</i> <i>n</i> <i>s</i> and <i>g</i> <i>a</i> <i>u</i> <i>c</i> <i>h</i> <i>e</i> <i>n</i>-butane

Abstract

The energy difference between the trans and gauche forms of liquid n-butane has been determined from the temperature dependence of Raman band intensities. A value of 557±13 cal/mole was derived from the summed integrated intensities of six bands of each rotamer measured at nine temperatures between 0 and −127 °C. This value is considerably lower than those determined earlier from Raman spectra of the liquid and is in line with ΔE values for longer n-alkanes in the liquid state. However, there is a large difference between the value reported here for liquid n-butane and that reported for the gas (∼966 cal/mole).