A series of substituted methyl derivatives of the type Tp'Rh(CNneopentyl)(CH2X)H (CH2X = CH2C(=O)CH3, CH2C CCH3, CH2O-t-Bu, CH2CF3, CH2F, CHF2) was synthesized either by photolysis of Tp'Rh(CNneopentyl)(PhNCNneopentyl) in neat CH3X or by exchange with the labile hydrocarbon in Tp'Rh(CNneopentyl)(n-pentyl)H or Tp'Rh(CNneopentyl)(CH3)H. Only a single product was observed in each case. Clean reductive elimination was observed for all compounds in C6D6. Structures of these complexes and their corresponding chlorinated derivatives have been characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. Relative Rh-C bond energies are calculated using previously established kinetic techniques, and two separate linear correlations are observed versus known C-H bond strengths, one for the parent hydrocarbons, and one for the substituted hydrocarbons. Both correlations have slopes of 1.4, and are separated vertically by 7.5 kcal mol(-1) (-CH2X above -CxHy). In addition, it is now clear that preferences for linear vs branched olefin insertion products in substituted derivatives can be predicted on the basis of the strengths of the beta-C-H bonds. The DFT calculations of the metal-carbon bond strengths in these Rh-CH2X derivatives with alpha-substitution show a trend that is in good agreement with the experimental results.