2-Methylpropene in the presence of W-H/Ni 1%-Al 2O 3-(500) is transformed in high selectivity into a mixture of 2,3-dimethylbutenes (2,3-DMBs = DMB-1 and DMB-2) and neohexene. 2,3-DMBs arise from the unfavoured 2-methylpropene self-metathesis reaction whereas the neohexene originates from a cascade reaction: 2-methylpropene dimerisation followed by cross metathesis. © 2012 The Royal Society of Chemistry.
Schuquel, Ivânia T. A.; Ducati, Lucas C.; Custodio, Rogério; Rittner, Roberto; Klapstein, Dieter
The photoelectron (PE) spectra of some 3-monosubstituted 2-methylpropenes H 2C dbnd C(CH 3)CH 2X [X = Cl, Br, I, OH, OMe, OEt, SH, SMe, SEt, N(Me) 2 and N(Et) 2] have been recorded. A preliminary analysis is presented indicating some trends in the ionization potentials associated with application of OVGF method and NBO analysis from MP2/6-31G(d,p) and cc-pVDZ level of theory indicating that the more effective hyperconjugation effect leads to the most stable conformers. The sensitivity of the outermost ionization energies of selected molecules with respect to the level of theory was analyzed. Application of the CASPT2 method with ANO basis set and geometries from MP2 calculations provided results in excellent agreement with the experimental data.
was measured in the urine of male and female mice as an indicator of isobutene exposure at 6, 12t 6, 12,and 18 months. The amount of HIBA excreted increased with increasing exposure concentration. However, when HIBA concentration was normalized to isobutene exposure concentration, the relative amount of HIBA excreted decreased with increasing exposure concentration, implying nonlinear kinetics. Pathology Findings: The incidences of hyaline degeneration of the respiratory epithelium in all groups of exposed males and females were significantly greater than those in the chamber control groups. The incidences of hyaline degeneration of the olfactory epithelium in 2,000 and 8,000 ppm mice were greater than those in the chamber controls. GENETIC TOXICOLOGY: Isobutene was not mutagenic in any of four strains of S. typhimurium, with or without S9 metabolic activation, and no increase in the frequency of micronucleated erythrocytes was seen in peripheral blood of male or female mice treated with isobutene by inhalation for 14 weeks. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of isobutene in male F344/N rats based on an increased incidence of follicular cell carcinoma of the thyroid gland. There was no evidence of carcinogenic activity of isobutene in female F344/N rats or male or female B6C3F1 mice exposed to 500, 2,000, or 8,000 ppm. Exposure to isobutene by inhalation for 2 years resulted in increased incidences and/or severities of nasal lesions including hyaline degeneration of the olfactory epithelium in male and female rats and mice and hyaline degeneration of the respiratory epithelium in male and female mice. Synonyms: Isobutylene, 2-methylpropene, liquified petroleum gas, g-butylene.