Experimental determination of the t r a n s–g a u c h e energy difference of gaseous n-pentane and diethyl ether

The difference in enthalpy between the all-trans conformer and the conformer containing one gauche bond has been measured by Raman spectroscopy for n-pentane and for diethyl ether. For n-pentane, ΔH=465±30 cal/mol and for diethyl ether, ΔH=1150±110 cal/mol. The pentane value is close to the value for ΔH found in the neat liquid, and the ether value is close to or a bit below that found in the liquid. These numbers suggest that the effect of intermolecular interaction on the trans–gauche equilibrium in the liquid is small.