TOWARD A BETTER UNDERSTANDING OF COVALENT BONDS - THE MOLECULAR MECHANICS CALCULATION OF C-H BOND LENGTHS AND STRETCHING FREQUENCIES

Several items which affect the lengths of covalent bonds are enumerated and discussed. A quantitative formulation is derived for C-H bonds so as to permit calculation of the vibrational frequency, stretching force constant, and bond length with the MM3 program if any one of these is known. Illustrations are given for several classes of compounds including alkyl fluorides, ethers, amines, ketones, and sulfones, wherein the C-H stretching frequencies vary over a range of more than 300 cm(-1) and the calculated values (278 total frequencies) are reproduced with a root mean square error of 24 cm(-1).