using a dynamical model based on the De Launay method we evaluate the phonon dispersion curves and the density of states of a family of compounds including MC(6) compounds (M=Li, Ba, Ca, Sr, Sm, Eu, Yb) and MC(8) compounds (M=K, Rb, Cs). Using a power law to fit the specific heat of each compound we evaluate the 2 dimensionnal character of these compounds.