Trans-2,3-Dimethyloxirane

A similar convergence study has been reported for the B-spline calculation for trans-2,3 dimethyloxirane molecule, et al. [53] The authors in fact comment that the parameter is no more demanding on basis set size than the p parameter, but their data ([53] Fig. 1) show that when the asymptotic is increased from 10 to 15 there is a significantly greater improvement in the former angular parameter. A value of. (max = 15 was chosen for all subsequent B-spfine calculations for oxiranes, and the same limit tends to be applied in the other reported B-spline calculations of chiral molecule PECD [60, 61]. 

The metals are also different in the transformation of the cis- and trans-2,3-dimethyloxiranes. The cis-2,3-dimethyloxirane is transformed at a much higher rate than the trans isomer on Pt and Pd catalysts, whereas on Ni the two isomers are converted at almost the same rate.7... 

Figure 11.3 The acid-catalyzed hydrolysis of one trans-2,3-dimethyloxirane enantiomer produces the meso (21 ,3 S)-2,3-butanediol by path (a) or path (b). Hydrolysis of the other enantiomer (or the racemic modification) would yield the same product.

Figure 4. Symmetry breaking of the ethanol torsion potential (top, two gauche and one trans conformation) by interaction with a chiral acceptor molecule (dimethyl oxirane, bottom), in this case RR trans 2,3 dimethyloxirane [128]. Note that trans ethanol is less stable in the complex and that the two gauche (g) forms differ in energy.

N. Borho and Y. Xu, Molecular recognition in 1 1 hydrogen bonded complexes of oxirane and trans 2,3 dimethyloxirane with ethanol A rotational spectroscopic and ab initio study. Phys. Chem. Chem. Phys. 9, 4514 4520 (2007). 

Reaction of alkynyllithium reagents with epoxides. This reaction, particularly in the case of substituted epoxides, can be sluggish when conducted in THF alone. Doolittle1 has examined the effect of various cosolvents. Use of THF-HMPT (1 1) results in high yields and reasonable reaction rates at 0°. Of other additives examined, TMEDA is equivalent to HMPT and is more effective than DABCO or ethylenediamine. Note that use of HMPT does not permit reaction of 1-dodecynyllithium with either cis- or trans-2,3-dimethyloxirane even at 50° for 2 hours. 

Raman spectra for cis and trans-2,3-dimethyloxirane have been recorded in the vapour, liquid and polycrystalline solid phases111. Using infra-red data from the vapour and solid phases torsional analyses for these epoxides... 

For example, trflns-2-butene yields racemic trans-2,3-dimethyloxirane, because addition of oxygen to each face of the alkene generates an enantiomer. cw-2-Butene, on the other hand, yields only c -2,3-dimethyloxirane, no matter which face of the alkene accepts the oxygen atom, due to the plane of symmetry in both the reactant and the product. If additional chirality centers are present in a substrate, then diastereomers would result. 

When either of the tran -2,3-dimethyloxirane enantiomers undergoes acid-catalyzed hydrolysis, the only product that is obtained is the meso compound, (2/ ,35)-2,3-butanediol. The hydrolysis of one enantiomer is shown in... 

Analogously, from trans-2,3-dimethyloxirane the ( )-erythro-diastereomer is formed. 

Methyl torsion Raman optical activity of trans-2,3-dimethyloxirane has been compared with that of rraws-2,3-dimethylthiirane [5]. Torsion of the two methyl groups in these molecules can occur as in-phase and out-of-phase combinations. The former can be observed as a very weak and broad Raman band at -200 cm" in the dimethyloxirane with positive ROA of medium size, whereas it is observed as a shoulder at -220 cm i in the spectrum of the dimethylthiirane with large positive ROA. Contrary to the dimethyloxirane spectra, the dimethylthiirane spectra also contain the out-of-phase torsion it shows up as a medium size Raman band at -245 cm i with zero or small negative ROA. This is in good agreement with ab initio calculations and even with the old inertial model for methyl torsions. 

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