A second generation Class II force field is derived for the alkyl group and alkane molecules. The Class II functional form is presented and force constants are given. The criteria that define this second generation force field are the following : (1) it accounts for the properties of both isolated small molecules, condensed phases, and macromolecular systems and (2) the functional form is characterized by being anharmonic, with quartic stretching and quartic angle bending, and includes a variety of important intramolecular coupling interactions. It is also characterized by a soft repulsion, either 9th power or exponential, rather than the more usual 12th power repulsion. The force field is derived by scaling an analytical representation derived from a fit to a quantum mechanical energy surface. Only seven parameters were needed in this scaling to reproduce 150 experimental observables. The resulting Class II force field is shown to fit the structural, energetic, and dynamic properties of the alkane molecules comprising the training set well. These molecules include small acyclic alkanes, strained molecules such as isobutane, and small rings including cyclopropane and cyclobutane. Thus the properties of highly strained molecules including small rings are accounted for with one set of transferable parameters. The results are compared with those obtained from Class I diagonal quadratic force fields commonly used in simulations of biological systems and the Class II functional form is shown to reproduce trends unattainable by the simpler forms where an harmonicity and coupling interactions are not accounted for. Most dramatic is its ability to fit the small ring compounds, cyclopropane and cyclobutane, with the same transferable energy functions that account for larger rings and acyclic molecules. This is the first energy surface able to achieve this range of applicability, a degree of transferability hypothesized in the literature to be unachievable. Finally, and perhaps most importantly it is pointed out that the methodology presented here provides a paradigm for the straightforward derivation of force fields for arbitrary molecules of interest even where experimental data is sparse or missing. The force field can be derived based on the techniques described here as long as the quantum mechanical calculation can be carried out. The resulting quantum force field, at that point, could either be used on its own or scaled to provide a pragmatic and reasonably accurate force field.