Inversion s. a. under

Wagner-Meerwein rearrangement, prevention of -19, 620s31 o-Wallach - 30, 96 Walden inversion (s. a. under Configuration)... 

Thionyl chloride (s.a, under h a2CO, CgH N, and (CH )2NCHO) Replacement of hydroxyl by halogen also with Walden inversion s. 11, 625... 

Table S.16 presents data on some representative nucleophilic substitution processes. The first entry illustrates the use of 1-butyl-l-r/p-bromobenzenesulfonate to dononstrate at primary systems react with inversion, even under solvolysis conditkms in formic acid. The observation of inversion indicates a concerted mechanism in fids weakly nucleophilic solvent.

Figure 18.17 shows that the characteristics of the stress-strain curve depend mainly on the value of n the smaller the n value, the more rapid the upturn. Anyway, this non-Gaussian treatment indicates that if the rubber has the idealized molecular network strucmre in the system, the stress-strain relation will show the inverse S shape. However, the real mbber vulcanizate (SBR) that does not crystallize under extension at room temperature and other mbbers (NR, IR, and BR at high temperature) do not show the stress upturn at all, and as a result, their tensile strength and strain at break are all 2-3 MPa and 400%-500%. It means that the stress-strain relation of the real (noncrystallizing) rubber vulcanizate obeys the Gaussian rather than the non-Gaussian theory. 

Alkylation of x-(.S )-A/-(2-phcnyl-l -propylidene)- -(methoxymethyl)benzeneethanamine with 4-chloromethyl-3,5-dimethylisoxazole proceeded with 12% ee by addition of the imine to the LDA solution at 0°C, whereas under inverse conditions (addition of LDA to imine) an enantiomeric excess of 70% was achieved (see Tabic 5)26. 

The HOMO of -3 TMEDA, showing a pyramidalized carbanionic unit, was visualized (Fig. 5) and compared with the HOMO of the benzyllithium compound (I ,S)-8, which displays a planar carbanionic unit. Whereas the planar system (R,S)-S reacts under inversion, in the case of the pyramidal system m-3-TMEDA retention of configuration should be expected. 

The inversion method for obtaining velocity structure has been fully described by (VanDecar 1991). By this method, P- and S-wave delay times are inverted independently for structure beneath the array. The model is parameterized identically for the P- and the S-wave inversion with splines under tension constrained by a series of regular knots (Fig. 4). Within the interior portion of the model, the knots are spaced 50 km apart in depth and 5 degree apart in latitude and longitude. Corrections for station elevation and crustal thickness from Nguuri (2002) are applied to the data before inversion. The data are inverted simultaneously for the slowness perturbation field, earth-... 

Inversion in cyclo-octane has been investigated by Harris and Sheppard (1961) down to — 160°K. At this temperature there is considerable exchange broadening ( 5-8 c.p.s.). A low enthalpy of activation of 2-6 + 0-9 kcal mole-1 was suggested with an abnormally large negative entropy — 30 e.u. The conformational inversion process under study is not easy to define. The conformations set out below would indicate that each separate form should contain four non-equivalent protons, which are designated by numbers. 

If these are configurationally stable, the situation is similar to that one encountered previously (Sect. 2) the enantiomeric ratio 243/ewr-243 (inversion in the substitution step assumed) reflects the diastereomeric ratio 242/cpi-242 after complete reaction. Configurational instability of the intermediates under the reaction conditions causes new problems, but also offers new possibilities [130] (s. a. Baek et al, in this volume). Two borderline cases and all situations between them are possible If kj pj and k2ep are very small compared to the rates of substitution kj and k4, after complete equilibration, the product ratio 243lent-243 equals the ratio epi-242/242 and reflects the difference of thermodynamic stabilities. On the other hand, if kj pi and k2e are very large in comparison to the rates k3 and k4, the product ratio equals the quotient k4/k3. This is the typical situation of a dynamic kinetic resolution [148]. Since equilibration can be enforced by higher temperature and the substitution step carried out at low temperature interesting possibilities for the enhancement of selectivities arise. These have been explored predominantly by Beak for aryl- and amino-substituted benzyl anions (s. a. Baek et al, in this volume). 

Inversion s. Carboxy-inversion and under Configuration lodacetone as hydrogen iodide scavenger 21, 966 Iodides (s. a. Halides, Replacement)... 

---