|Author||Shiner, V. J. ♦ Smith, Morris L.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Publisher||American Chemical Society (ACS)|
|Subject Keyword||CHEMISTRY ♦ ACIDITY ♦ ACTIVATION ENERGY ♦ ARRHENIUS EQUATION ♦ BARRIERS ♦ BROMINATED HYDROCARBONS ♦ CARBON ♦ CHEMICAL REACTIONS ♦ DEUTERIUM ♦ DEUTERIUM COMPOUNDS ♦ EQUATIONS ♦ ETHANOL ♦ ETHOXIDES ♦ FREQUENCY ♦ INFRARED RADIATION ♦ INSTRUMENTS ♦ IONS ♦ ISOTOPE EFFECTS ♦ LITHIUM FLUORIDES ♦ ORGANIC COMPOUNDS ♦ OSCILLATIONS ♦ OXIDES ♦ PHENYL RADICALS ♦ PROPANE ♦ PROTONS ♦ QUANTITATIVE ANALYSIS ♦ REACTION KINETICS ♦ SELF-DIFFUSION ♦ SODIUM OXIDES ♦ SPECTRA ♦ STYRENE ♦ TEMPERATURE ♦ THERMODYNAMICS|
|Abstract||ABS>The rates of reaction of 1-bromo-2-phenylpropane and the 2-deuterio analog with sodium ethoxide in ethanol were determined from 5 to 55 deg C. The reaction product was shown to be quantitatively alpha -methylstyrene with no competing substitution reaction. By reference to the infrared spectra taken with a lithium fluoride prism instrument, the tertiary carbon-hydrogen and carbon- deuterium vibrational stretching frequencies of these compounds were assigned as 2904 and 2160 cm/sup -1/, respectively. The approximately doubly degenerate bending frequencies of these bonds were tentatively assigned as 1299 and 934 cm/ sup -1/, respectively. The experimentally determined Arrhenius equations are: log k/sub H/ = 11.033 - (20,655/2.303RT); log k/sub D/ = 11.443 - (22,406/ 2.303RT); and log (k/sub H//k/sub D/) = -0.437 + (1,790/2.303RT). An upper limit for the isotope activation energy effect, neglecting tunneling, was estimated using the observed groundstate vibrational frequencies and found to be significantly less than that obtained experimentally. The frequency factors are abnormal in that the one for the deuterium compound is almost three times that for the hydrogen analog. These apparent discrepancies between the experimental and theoretical activation parameters are rationalized on the basis of nonclassical barrier penetration by the proton. The proton tunneling through the potential barrier effectively increases the activation energy difference for the two isotopes. The general utility of the deuterium isotope rate effect in mechanistic studies is not greatly altered by the occurrence of tunneling.|
|Learning Resource Type||Article|
|Publisher Department||Indiana Univ., Bloomington|
|Journal||Journal of the American Chemical Society|
|Organization||Indiana Univ., Bloomington|
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