4529 ratios (condition 2 described earlier).It is interesting to note that the CA/EA ratio for the enthalpy of base adduct formation with phenol is 0.102 while the CA*/EA* ratio for the phenol adduct frequency shift is 0.149. Note that the CA*/EA* ratio is not a fundamental acceptor property of the acid but includes in it the response of the acid property being measured. It is possible to have two different properties of an acid obey the E and C equation but not give a straight line when plotted against each other if their CA*/EA* ratios are different. Since the CA/EA and CA*/EA* ratios are closer to each other than those for CA*/EA* and fi (0.0287), a more general straight line plot of AYOH vs. -AH is obtained which will be valid as long as bases with a C B / E B ratio of 1.5 to 6 are employed. Thus this analysis extends our earlier proposal that this correlation is of more general applicability than r e p~r t e d~~~~~ and that the high polarizability of sulfur donors cause them to deviate from the -AH vs. AYOH relation. We now clearly understand what the limitations of the -AH vs. AuOH relation are, and when it can be used with confidence to predict enthalpies.With this work we have provided a set of parameters to be used in conjunction with the equation:Since in a new system, one does not know if the CA/EA ratio will be 0.0287, we feel it is first appropriate to determine if the observation, AX, is related to coordinate bond strengths and a relatively simple solvation model (eq 9). If the E, C, and D* analysis indicates a C / E ratio close to 0.0287, the very extensive compilation of p parameters can be used with confidence for solvents for which EB and CB values are not determined. In interpreting deviations from an attempted fit of a data set to eq 9, one must remember that the parameters have been derived for (19) Arnett, E. M.; Mitchell, E. J.; Murty, T. S. S. R. J. Am. Chem. SOC. (20) Ehrenson, S. J . Am. Chem. SOC. 1981, 103, 6036. 1974, 96, 3875.dilute solutes undergoing specific and nonspecific interactions with varying solvents. As the observation that one is attempting to correlate, AX, becomes more complex and has more independent factors contributing to it, the chance diminishes for a successful correlation. Lack of a correlation does not mean that the model is incorrect but suggests that factors other than coordinate bond strength and this simple solvation model dominate the chemistry. Bulk solvation effects are a complex phenomenon coupled to the structure of the liquid state. Though a theoretical rationalization of the SD* type of analysis has been provided,20 a wider range of systems must be studied to determine the limitations of the treatment of this effect by the SD* term.Abstract: Ab initio calculations using pseudopotentials have been carried out on the two singlet isomers of Ge2H, a t both SCF (double { + d basis set) and CI levels. Digermene (H,Ge=GeH,) is 5 kcal/mol more stable than germylgermylene (HGe-GeH,). Its trans-bent geometry does not depend strongly on correlation effects; the ...
