2986-54-1Relevant articles and documents
Synthesis and catalytic testing of Lewis acidic nano zeolite Beta for epoxide ring opening with alcohols
Parulkar, Aamena,Spanos, Alexander P.,Deshpande, Nitish,Brunelli, Nicholas A.
, p. 28 - 34 (2019)
Lewis acidic zeolites are robust catalytic materials that are capable of a range of important chemistry for fine chemical production, including the epoxide ring opening with alcohols. The crystalline structure imposes diffusion limitations for large molecules that are overcome through reducing the particle size to produce nano zeolite beta substituted with Lewis acidic tin (nSnBeta). nSnBeta is characterized using standard methods to demonstrate that tin is efficiently incorporated into the zeolite framework with open and closed sites similar to the micron-sized conventional Sn-Beta (cSnBeta). While nSnBeta exhibits comparable catalytic activity to cSnBeta for reactions involving small substrates such as epichlorohydrin and methanol, an improvement in catalytic performance is observed for nSnBeta relative to cSnBeta when using large substrates such as 1,2-epoxyoctane and ethanol. nSnBeta and cSnBeta convert a cyclic epoxide too large to enter the pores to similar extents, indicating that the improved performance is not associated with an increased number of catalytic sites on the external surface. Catalyst reuse experiments demonstrate that organic accumulation on the material reduces catalytic activity that can be partially restored through calcination. Overall, the results demonstrate that nano zeolite beta can be synthesized with small particle sizes (i.e., 150 nm) to help overcome diffusion limitations for bulky substrates for the alcohol ring opening of epoxides.
Odor-structure relationships using fluorine as a probe
Michel, Dominique,Schlosser, Manfred
, p. 4253 - 4260 (2007/10/03)
Eight ethers, nine esters and one ketone were submitted to a systematic structural variation by replacing a hydrogen atom in the vicinity of the oxofunction by fluorine and methyl. As long as steric factors dominate, a fluorine substituent alters the olfactory properties of the parent compound much less than a methyl substituent does. However, if it occupies a position adjacent to a carbonyl group, the halogen may more profoundly affect the odor perception, presumably as a consequence of conformational changes. (C) 2000 Elsevier Science Ltd.
Photochemistry of Alkenes. 9. Medium-sized cycloalkenes
Kropp, Paul J.,Mason, J. Derek,Smith, Gardiner F. H.
, p. 1845 - 1849 (2007/10/02)
The behavior of three medium-sized cycloalkenes cyclooctene (10), cyclodecene (17) and cyclododecene (21) on direct irradiation in pentane and methanol solution has been studied.The results are summarized in Tables 1-3.Irradiation of medium-sized cycloalkenes is a convenient procedure for the preparation of bicyclic products (cf. 13, 14, 19, 20 and 23) through transannular insertion reactions of carbene intermediates (cf. 11, 18, and 22) thought to arise from rearrangement of the 1 state via a 1,2-hydrogen shift.The formation of trans-decalin (20) is in contrast to the reported formation of the cis isomer on base-initiated decomposition of the corresponding tosylhydrazone.None of the three cycloalkenes 10, 17, or 21 underwent competing nucleophilic trapping of the 1 state in methanol, in contrast with other alkenes previously studied.However, cyclododecene (21) afforded the methyl ether 25, which apparently resulted from protonation of the 1(?,?*) state, and the epoxide 26, which is thought to arise from electron transfer to oxygen by the 1 state followed by protonation of the resulting superoxide ion and oxidation of unreacted cyclododecene (21).
