Pentacosane C25H52 exhibits two different rotator to rotator phase transitions. A phenomenological theory of the elastic properties of the rotator phases is developed on the basis of a free energy expansion. The temperature dependence of the elastic constants is calculated for the various rotator phases. We discuss the temperature variation of the heat capacity in the rotator phases in terms of the elastic constants. The theoretical predictions are found to be in good qualitative agreement with available experimental results.