Reference

Thermal hydrocracking of hydrocarbons

Thermal hydrocracking of hydrocarbons. Hedden, Kurt; Weitkamp, Jens (Engler-Bunte-Inst., Karlsruhe 7500/1, Fed. Rep. Ger.Chemicals with cas numbers 2189-60-8 and 112-40-3 also play role.). Chem.-Ing.-Tech., 55(12), 907-14 (German) 1983. CODEN: CITEAH. ISSN: 0009-286X. DOCUMENT TYPE: Journal CA Section: 21 (General Organic Chemistry) Section cross-reference(s): 51 The thermal hydrocracking of dodecane, octane isomers, cyclohexanes, hexahydroindan, alkylbenzenes, naphthalene, and 2,3-dimethylnaphthalene was examd. At high conversions alkanes and naphthenes are transformed predominantly into C1-3 alkanes. Ethane is the main product. In alkylaroms. the side chain is cracked exclusively up to high conversions. Therefore, dealkylated aroms. can be obtained in high yields as intermediate products. .

A method for the calculation of normal-mode vibrational frequencies using symmetry coordinates

A method for the calculation of normal-mode vibrational frequencies using symmetry coordinates. Application to the calculation of secondary deuterium isotope effects on carbocations. Hout, Robert F., Jr.; Levi, Beverly A.; Hehre, Warren J. (Dep. Chem., Univ. California, Irvine, CA 92717, USA). J. Comput. Chem., 4(4), 499-505 (English) 1983. CODEN: JCCHDD. ISSN: 0192-8651. DOCUMENT TYPE: Journal CA Section: 22 (Physical Organic Chemistry) A method is introduced for the calcn. of normal-mode vibrational frequencies of polyat. mols. based on numerical differencing of anal. gradients in symmetry coordinates. This procedure requires a no. of gradient evaluations equal to the largest no. of symmetry coordinates belonging to any single irreducible representation of the mol. point group (plus a single gradient evaluation at the equil. configuration), which is fewer than the 3N-6 (N atoms) gradient evaluations needed for schemes based on Cartesian or internal coordinates. 74-84-0 and 19252-53-0 are also in the experiment. While the proposed method will not generally be as efficient as procedures which involve the direct calcn. of energy second derivs. anal. (as are now available for single-determinant wavefunctions) it appears to be equally accurate, and it should be the method of choice for frequency calcns. involving multideterminant wavefunctions for which anal. second-deriv. algorithms have yet to be developed. The method is illustrated by the calcn. of equil. secondary deuterium-isotope effects on a no. of reactions involving simple carbocations. .