6552-57-4Relevant articles and documents
Experimental investigation of the primary and secondary deuterium kinetic isotope effects for epoxidation of alkenes and ethylene with m- chloroperoxybenzoic acid
Koerner, Terry,Slebocka-Tilk,Brown
, p. 196 - 201 (2007/10/03)
The secondary deuterium kinetic isotope effect (DKIE) for the epoxidation of ethylene and d4-ethylene by m-chloroperoxybenzoic acid (MCPBA) is determined to be 0.83, or 0.95/α-H. The second-order rate constants for MCPBA and MCPBA-O-D epoxidation of a variety of alkenes that differ in the steric access to the double bond (anti-sesquinorbornene (2), tetramethylethylene (3), adamantylideneadamantane (4), 7-norbornylidene-7'- norbornane (5), bis(bicyclo[3.3.1.]non-9-ylidene) (6), bis(homoadamantane) (7), cyclohexene (8), 1-octene (9), trans-5-decene (10) and 2-methyl-1- pentene (11)) have been determined in dichloroethane at 25°C using UV kinetics, and the primary DKIE, k(OH)/k(OD), is 1.05 ± 0.05 in all eases. By comparison of the rates of epoxidation of sterically encumbered alkenes, it is suggested that the spiro epoxidation transition state is favored over a planar one. The products of the epoxidation of anti-sesquinorbornene are determined to be the epoxide and a cis-hydroxy ester, the latter most probably being formed by acid-catalyzed ring opening of the epoxide by in situ-produced m-chlorobenzoic acid produced in situ to form a β-hydroxy carbocation and carboxylate ion pair that collapses to product.
Infrared Photodissociation of Hydrogen-Bonded Complexes Trapped in Inert Matrices. The Ethylene Oxide-Hydrogen Iodide System
Bernadet, Philippe,Schriver, Louise,Schriver, Andre,Perchard, Jean-Pierre
, p. 7204 - 7210 (2007/10/02)
Matix isolation infrared spectroscopy applied to the ethylene oxide/H(D)I system trapped in solid Ar and N2 allows identification of several kinds of hydrogen-bonded complexes: a 1:1 species which exists under different structures and larger aggregates giving rise to proton transfer with formation of ionic species of the type + or (IHI)- characterized by quasi-symmetrical single-minimum potential functions for the proton (proton sharing).The interconversion between the hydrogen-bonded (C) and the non-hydrogen-bonded (U) form of the 1:1 complex is seen to depend on two parameters: temperature and infrared irradiation.Kinetic measurements of the disappearance (or appearance) of C have shown that the C->U conversion is mainly induced by IR radiations in the range 1500-2300 cm-1, corresponding to the excitation of νs (HI stretching mode), while the CU conversion rate with DI suggests a barrier greater than 1500 cm1- for this photoprocess.
The Mechanism of the Cationic Cyclooligomerization of Ethylene Oxide and the Concomitant Degradation of the Crown Ether Products Formed
Dale, Johannes,Daasvatn, Kari
, p. 327 - 342 (2007/10/02)
Cyclooligomerization of ethylene oxide-d4 with BF3 in CH2Cl2 in the presence of the higher cyclic oligomers, from 1,4-dioxan-h8 to 18-crown-6-h24, each separately, has been studied as a function of time, analyzing the product composition by gas chromatography, and the distribution of isotopically different species within each ring size by GLC-MS using chemical ionization.It is found that non-deuteriated units from any one of these rings become incorporated in both larger and smaller rings before they end up in dioxan, either alone or together with deuteriated units from ethylene oxide.The particular patterns observed for the degree of deuteriation permit quite far-reaching conclusions as to the detailed mechanism of these reactions, the most important of which is that the transition state for attack by oxygen on an oxonium ion has a strict linear SN2-like geometry.
