Brouwers

J. J. H. Brouwers, On the Motion of a Compressible Fluid in a Rotating Cylinder., Doctoral Dissertation, The Technische Hogeschool, Twente, the Nethedands, June, 1976. 

E. R. Brouwer, H. Lingeman and U. A. Th Brinkman, Use of membrane extr action disks for on-line trace enrichment of organic compounds from aqueous samples , Chromatographia 29 415-418 (1990). 

H. Bagheri, E. R. Brouwer, R. T. Ghijsen and U. A. Th Brinkman, Low-level multiresidue determination of polar pesticides in aqueous samples by column liquid chr O-matography-thermospray mass specrtometry , J. Chromatogr. 657 121-129 (1993). 

E. R. Brouwer, A. N. J. Elermans, El. Lingeman and U. A. Th Briknman, Determination of polycyclic aromatic hydrocarbons in surface water by column liquid cliromatogr a-phy with fluorescence detection, using on-line micelle-mediated sample preparation , J. Chromatogr. 669 45-57 (1994). 

H.J. Brouwer, V.V. Krasnikov, A. Hilbercr, G. Hadziioannou, Blue superradiancc from neat semiconducting alternating copolymer films, Adv. Mater. 1996, 8, 935. 

H.J. Brouwer, Semiconducting Polymers for Light-emitting Diodes and Losers a Structural. Photophysical and Electrical Study of PPV-type Alternating Copolymers and Oligomers, Ph.D. Thesis, Groningen, 1998. 

The type of disorder may be determined by conductivity measurements of electronic and ionic defects as a function of the activity of the neutral mobile component [3]. The data are commonly plotted as Brouwer diagrams of the logarithm of the concentration of all species as a function of the logarithm of the activity of the neutral mobile component. The slope is fitted to the assumption of a specific defect-type model. 

The equilibrium constant K is the same for R =t-C4HJ and t-CsHi. As also the rate constants of carbonylation and decarbonylation are about equal for these two ions, it is concluded that both the thermodynamics and the kinetics of the carbonylation reaction are independent of the structure of R+, if R+ is an acyclic tertiary alkyl cation. This agrees with former findings (Brouwer, 1968) on the relative stabilities of such ions. 

In discussing the elFect of structure on the stabilization of alkyl cations on the basis of the carbonylation-decarbonylation equilibrium constants, it is assumed that—to a first approximation—the stabilization of the alkyloxocarbonium ions does not depend on the structure of the alkyl group. The stabilization of the positive charge in the alkyloxocarbonium ion is mainly due to the resonance RC = 0 <-> RC = 0+, and the elFect of R on this stabilization is only of minor importance. It has been shown by Brouwer (1968a) that even in the case of (tertiary) alkylcarbonium ions, which would be much more sensitive to variation of R attached to the electron-deficient centre, the stabilization is practically independent of the structure of the alkyl groups. Another argument is found in the fact that the equilibrium concentrations of isomeric alkyloxocarbonium ions differ by at most a factor of 2-3 from each other (Section III). Therefore, the value of K provides a quantitative measure of the stabilization of an alkyl cation. In the case of R = t-adamantyl this equilibrium constant is 30 times larger than when R = t-butyl or t-pentyl, which means that the non-planar t-adamantyl ion is RT In 30= 2-1 kcal... 

The tertiary-secondary 1,2-H shift O itlO is not rate-determining in the interconversion of 5 and 6, but may become so in a conformationally fixed system. It has been found for the interconversion of tertiary and secondary adamantyloxocarbonium ions that <10" sec at 70°C (Hogeveen and Roobeek, 1971a) as compared with k= 1-5 x 10 sec at 20°C for the reaction 5 6. The absence of interconversion between tertiary and secondary adamantyloxocarbonium ions is due to the circumstance that 1,2-H shifts do not occur in the tertiary adamantyl ion as a result of the effect of orbital orientation (Brouwer and Hogeveen, 1970 Schleyer etal., 1970). That the secondary adamantyloxocarbonium ion can lose CO is demonstrated by the reaction with isopropyl cation in SbFs—SO2CIF solution at 0°C with formation... 

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