Kinetics of the reactions of 1,2,3-triphenyl-2-propanol (1), 1,2-diphenyl-2-propanol (2) and 3,3,3-trideuterio-1,2-diphenyl-2-propanol (3) with triphenylphosphine-carbon tetrachloride in the temperature range of 25-78 o C in several solvents are investigated. In a non-polar solvent (CCl 4 ), the reaction of (2) proceeds via intermolecular anti E2 elimination and/or intermolecular S N 2 nucleophilic substitution (28% substitution, ratio of 2-alkene/1-alkene=1.06, E/Z=<49). In a polar solvent (CH 3 CN) reaction proceeds via E1 and/or S N 1 (24% substitution, 2-alkene/1-alkene=1.9, E/Z=<6. At equilibrium, the ratio of 2-alkene/1-alkene is equal to 99 with E/Z=<4.21. The primary kinetic isotope effect (k H /k D ) for the elimination pathway in the non-polar solvent is equal to 4.90 and 3.90 at temperatures of 25 and 60 o C, respectively. A small secondary β-isotope effect of 1.10 was observed for substitution reaction at both temperatures. Direction of substitution (S N 2 vs. E2) depends on temperature and polarity of the solvent. The energetics (ΔS , ΔG , ΔH ), the rate orders, and optimization of molecular geometry of intermediates by semiempirical methods (AM1 and CNDO) all agree with intermolecular E2 and S N 2 mechanisms. New rules for stereoselectivity and Hofmann-Saytzeff eliminations are considered.