Clark R. Landis, Daniel M. Root, and Thomas Cleveland

*Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706*

There is an error in the MM3 bond stretch term published on pages 82-83. The authors correctly reproduced the originally published expression [equation 1 of N. L. Allinger, Y. H. Yuh, and J.-H. Lii, *J. Am. Chem. Soc.,* **111,** 8551 (1989). Molecular Mechanics. The MM3 Force Field for Hydrocarbons. 1.]. However, the original publication is incorrect due to a misprint. To slow the unfortunate propagation of this error, the following clarification is presented.

Below are the original and corrected MM3 bond stretching terms. For some representative parameters, the bond stretching term is plotted as it appeared in the original publication and the author's chapter, and as it appears with the correct function. The change in the function is dramatic. A side-by-side comparison of the effect of the extra factor of 2.55 on the MM3 bond stretching curve is seen in the last plot.

MM3 - original

MM3 - corrected

Figure 4 - original

Figure 4 - corrected

Figure 4. A comparison of bond stretch functions (k*r *= 340 kcal/mol.Å, r*o *= 1.1 Å, and the Morse D*o *= 100 kcal/mol).

Bond stretching curves for the original (red) and correct (green) potential functions.