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

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).