Sulfoxides models

The behavior of the ort/io-methyl resonances of diarylsulfoxides is also exceptional (48). For example, both methyls of o-tolyl-p-tolylsulfoxide show nonequivalence of the same sense as that expected for the p-methyl group on the basis of the general sulfoxide model. The senses observed for o-methyl groups in several other o-tolyl-sulfoxides are also inverted, whereas those of other resonances are normal. This behavior, which may result from an intramolecular shielding of these groups by either sulfinyl or aromatic moieties in rotamers whose populations are affected by the CSA, is not well understood. 

As)fmmetric oxidation of allylic selenides gives allylic alcohols via a [2,3]-sigmatropic selenoxide-selenate rearrangement (eq 5). In both oxidations, eqs 4 and 5, the configuration at the selenoxide is that predicted based on the sulfoxide model. 

Determining the effect of DMSO (a product sulfoxide model) on the rate of catalysis. Varying amounts of DMSO were added to the normal reaction components to assess the effect on induction period, rate of catalysis, and self-inhibition. 

Figure 3-17. Consecutive application of two reaction schemes to model the oxidation of thioethers to sulfoxides.

Clearly, for symmetry reasons, the reverse process should also be considered. In fact, early versions of our reaction prediction and synthesis design system EROS [21] contained the reaction schemes of Figures 3-13, 3-15, and 3-16 and the reverse of the scheme shown in Figure 3-16. These four reaction schemes and their combined application include the majority of reactions observed in organic chemistry. Figure 3-17 shows a consecutive application of the reaction schemes of Figures 3-16 and 3-13 to model the oxidation of thioethers to sulfoxides. 

Find the model of dimethyl sulfoxide [(CH3)2S=0] on Learning By Modeling and exam me Its electrostatic potential map To which atom (S or O) would you expect a proton to bond d... 

Verify, by making molecular models, that the bonds to sulfur are arranged in a trigonal pyramidal geometry in sulfoxides and in a tetrahedral geometry in sulfones. Is phenyl vinyl sulfoxide chiral What about phenyl vinyl sulfone ... 

DMF, see Dimethylformamide DM SO, see Dimethyl sulfoxide DMT (dimethoxytrilyl ether), DNA synthesis and, 1114 DNA, see Deoxyribonucleic acid DNA fingerprinting, 1118-1119 reliability of, 1119 STR loci and, 1118 Dopamine, molecular model of. 930 Double bond, electronic structure of, 16... 

Two qualitative models have been successful in accounting for many of the structural changes in sulfoxides and sulfones5. One is the Faience Shell Electron Pair Repulsion (VSEPR) theory8, while the other approach involves considerations of nonbonded ligand/ligand interactions9. 

FIGURE 2. The molecular model of dimethyl sulfoxide. The following C—H lengths (A), S—C—H bond angles (deg) and x(C—S—C—H) torsional angles (deg) were determined from microwave spectra by Typke17 ... 

FIGURE 4. The molecular model of diphenyl sulfoxide (Cs point group) the benzene rings are nearly perpendicular to the CSC plane. 

Oae and coworkers oxidized several diaryl, dialkyl and alkyl aryl sulfides to their corresponding sulfoxides using purified cytochrome P-450 obtained from rabbit liver microsomes138. In agreement with expectations, this enzyme did not exhibit much stereospecificity. Some examples including the observed e.e. values are shown by 121-125. A model was proposed to account for the absolute configurations of the sulfoxides produced (126). The sulfur atom is preferentially oxidized from the direction indicated. 

The three highest occupied orbitals of sulfoxides are the lone pairs ns and n0, as well as the 7iso bond210. The 1,3-dithietane 1-oxide adds a lone-pair ionization and destabilizes the n0 and nso radical-cation states compared with thietane oxide. According to a hyperconjugative MO model, the ns+ combination in 1,3-dithietane is destabilized by about leV relative to the basis orbital energy a(ns) due to the combination with the... 

And finally, we may mention that a statistical analysis of the sulfur d orbital problem has been carried out with dimethyl sulfoxide as a model compound36. The results provide a clear answer to the sulfur d orbital problem, since no simultaneous reproduction of experimental geometry and an adequate approximation to the variationally optimum total energy have been possible without including d polarization functions on sulfur . 

FIGURE 3. Qualitative energy model of a radical-anion pair in sulfoxides where A = CH3, C2H5 B = SOCH3, "SOC2H5 u is the potential energy R(AB) is the distance between A and B. Reproduced by permission of the authors from Reference 16. 

Biologically, the reduction of methionine sulfoxide to methionine with NADPH is catalyzed by an enzyme79. Recently, the mechanism of reduction of sulfoxides by treatment with an NADPH model has been studied80. 

ABSTRACT Zeolite Y modified with chiral sulfoxides has been foimd catal rtically to dehydrate racemic butan-2-ol enantioselectively depending on the chiral modifier used. Zeolite Y modified with R-l,3-dithiane-1-oxide shows a higher selectivity towards conversion of S-butan-2-ol and the zeolite modified with S-2-phenyl-3-dithiane-1-oxide reacts preferentially with R-butan-2-ol. Zeolite Y modified with dithiane oxide demonstrates a significantly higher catalsdic activity when compared to the unmodified zeolite. Computational simulations are described and a model for the catalytic site is discussed. 

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