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61.
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The gas-phase kinetics of thermal decomposition of ethyl difluoroacetate, pentafluoropropionate, and hepatfluorobutyrate have been studied. The normal ester decomposition route to ethylene plus carboxylic acid is taken in each case, but the fluorinated acids decompose rapidly at the temperatures used. The primary decompositions are homogeneous and unimolecular, and the three Arrhenius equations are The postulate of a slightly electron-rich γ carbon in six-center ester transition states is supported by the higher rates and lowered activation energies observed when increasingly electron-withdrawing fluorinated groups are linked to this center. The stabilization is reflected in a ρ constant of +0.30. The results are compared with previous work on α substitution in fluorinated esters. 相似文献
64.
Louis H. Blake 《Stochastic Processes and their Applications》1976,4(2):149-155
A classical theorem of Meyer Jerison which shows that the convergence in the pointwise ergodic theorem is equivalent to the convergence of an associated martingale is expanded to a conditional setting. An equiconvergence theorem of the type established for martingales by N.F.G. Martin and E. Boylan is established in the ergodic case for an ergodic, non-invertible, measure-preserving transformation. 相似文献
65.
[reaction: see text] The synthesis of the carbasugar analogue of 1,4-anhydro-beta-d-galactopyranose, a proposed intermediate in the reaction catalyzed by uridine diphosphate-alpha-d-Galp mutase, in racemic form via Diels-Alder and Barton decarboxylation chemistry is reported. This compound was found not to inhibit the mutase from Mycobacterium tuberculosis, indicating that the enzyme does not possess a 1,4-anhydro-beta-d-galactopyranose binding pocket. 相似文献
66.
Parity-violating electron deuteron scattering and the proton's neutral weak axial vector form factor
Ito TM Averett T Barkhuff D Batigne G Beck DH Beise EJ Blake A Breuer H Carr R Clasie B Covrig S Danagoulian A Dodson G Dow K Dutta D Farkhondeh M Filippone BW Franklin W Furget C Gao H Gao J Gustafsson K Hannelius L Hasty R Hawthorne-Allen AM Herda MC Jones CE King P Korsch W Kowalski S Kox S Kramer K Lee P Liu J Martin JW McKeown RD Mueller B Pitt ML Plaster B Quéméner G Réal JS Ritter J Roche J Savu V Schiavilla R Seely J Spayde D Suleiman R Taylor S Tieulent R Tipton B Tsentalovich E 《Physical review letters》2004,92(10):102003
We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at Q2=0.038 (GeV/c)2. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A=-3.51+/-0.57 (stat)+/-0.58 (syst) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also consistent with theoretical predictions. 相似文献
67.
68.
Nickel A Maruyama T Tang H Murphy PD Greene B Yusuff N Wood JL 《Journal of the American Chemical Society》2004,126(50):16300-16301
A total synthesis of the biologically important diterpene ingenol has been completed. Ring-closing olefin metathesis was used to construct the strained "inside-outside" tetracyclic skeleton, and a series of diastereoselective reactions were employed to complete the synthesis. Another naturally occurring ingenane, 20-deoxyingenol, has also been prepared. 相似文献
69.
Givaja G Blake AJ Wilson C Schröder M Love JB 《Chemical communications (Cambridge, England)》2003,(19):2508-2509
The complexation of palladium(II) by a unique family of [2+2] diiminodipyrromethane macrocycles yields compounds that adopt structures reminiscent of Pac-Man porphyrins. 相似文献
70.
Minimal Length Elements of Thompson's Group F 总被引:1,自引:1,他引:0
S. Blake Fordham 《Geometriae Dedicata》2003,99(1):179-220
Elements of the group are represented by pairs of binary trees and the structure of the trees gives insight into the properties of the elements of the group. The review section presents this representation and reviews the known relationship between elements of F and binary trees. In the main section we give a method of determining the minimal lengths of elements of Thompson's group F in the two generator presentation
This method is an effective algorithm in that its order is linear in the size of the trees representing an element of F. We also give a method for constructing all minimal length representatives of an element in F. 相似文献