Frozen structure

A stable lO-As-3 species (235) underwent a ready reaction with 144 to give adduct 236, which exhibited a single ferf-butyl and ring-proton resonance in the NMR at room temperature and showed a single resonance at 8 -54.0 in the NMR (85JA1089). Tire low temperature and NMR showed a split of the room temperature resonances suggestive of the frozen structure of 236. 

The complexes that can be starting points for addition of the next molecule of H2 are B3 (which we call Cl), B13(C4) and B21(C7). Because of atomic congestion, only Zr-P frozen structures were optimized for the expected TS s and products of these reactions. 

One can see such frozen structures that were formed due to an auto-catalytic reaction in tektites.12 There are several other geological processes that show such freezing of nonequilibrium structures.13... 

Figure 2.89 shows, how Tice measurements can be an indicator of the frozen structure of a 10% mannitol solution ... 

The n.m.r. spectrum of the trioxyphosphorane77 (86) Scheme 12 shows signals for two different benzylic protons at —75°, which corresponds to a frozen structure of the pair of enantiomers (86-(2 4) (3 5)) and (86-(l 4) (3 5)). The n.m.r. spectrum above +30° shows only one benzylic-protons signal. Note that the inversion of the enantiomers is accompanied by an exchange of the apical and equatorial benzylic protons. Fig. 17-IV and Scheme 12 show quite clearly that the (TR)3-proeess with the ring functioning as pair, is the only way of avoiding the placement of a carbon in an apical position. 

What John Walker determined was a frozen structure. Was it a complete proof ... 

No, not at all, but it made it much more probable. However, even though it was a frozen structure and had ADP at the tight site, it was still representative of the mechanism of the catalysis. The structure also made possible other experiments to probe the catalysis. 

Mixed signals arising by a fast and reversible transition between two mirror-image structures frozen structures would appear at 22 and 92 ppm for () (C) and 6 (C ), respectively Deuteration in the X position leads to splitting of the <5(C) signal to a 1 1 1 triplet (7 = 21-23 Hz). 

The most important information to be extracted from either experiment or theory is structural information. In first-principles methods this information is readily available. Experimentally, it may be extracted directly from diffraction techniques. While X-ray diffraction provides information on solids, which means on frozen structures, other techniques like neutron diffraction can provide statistical information like pair correlation functions that are also easily obtained from a molecular dynamics trajectory. 

The group which brings the C—H bond with its two electrons into the vicinity of the metal centre has been called agostic by Brookhart and Green. These complexes can be considered as frozen structures on the pathway for the insertion of a metal into a C—H bond, in the same way that molecular hydrogen complexes were treated on the oxidative addition pathway that leads to a dihydride ( 4.1.4). 

While the kinetics of plastic response in metallic glasses in the low-temperature realm exhibits a remarkable mechanistic universality, where the nucleation of STs occurs in a substantially frozen structure, the steep decrease in the temperature dependence of the yield stress and the stress exponent m of the plastic strain rate above 0.62rg signifies the onset of a fundamental change in the mechanism. Thus, the universal response at low temperature, with the slow decrease of plastic resistance with temperature, extrapolating to a vanishing level at a universal temperature of... 

Polymers with fixed liquid crystalline structure — if the polymerization temperature was below the glass ti ansition temperature ( ) of the polymer. These polymers exhibit a liquid crystalline structure in the solid glassy phase because the structure of the ordered monomer phase was "frozen in" by polymerization. By heating the polymer these frozen structures were irreversibly lost above the Tq An additional effect was observed starting from... 

Another consequence of the ion-dipole interaction is that it is often strong enough to bind polar solvent molecules to the ion and establish a local aligned or frozen structure composed of the ion and several associated polar molecules within the matrix of the solution (see Fig. 3.2). For the small monovalent cation Li+ in the presence of water molecules (as opposed to dissolved in water), for example, the following data may be used jji (water) = 1.85 D,... 

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