Silicon migration with inversion

This is generally true, but it should be noted that silicon-carbon double bonds with inverse electron demand behave differently. Silatriafulvene, for example, did not react with alcohol but underwent 1,2-silyl migration followed by ring expansion reaction to silacyclobutadiene63. Silacalicene also adds alcohol in a reverse fashion64. 

The 1,3-silyl migrations from C to C occurred with inversion of configuration at silicon and with a rather high activation enthalpy for the 1,3-silyl migration of a-methylallyltrimethylsilane studied by Kwart and Slutsky, AH =47.7 kcalmol-1 and AS = —6.2 calmol-1 K-1297. On the other hand, 1,3-silyl migrations in ketosilanes... 

Two transition structures with a retention (192, TSret) and an inversion (193, TSinv) configuration (Figure 2) were optimized for 1,3-silyl migration in allylsilane at HF/6-31G, MP2/6-31G and DFT/6-31G levels. The TSjnV 193 was found to be a distorted trigonal bipyramid (TBP) around the silicon with the two allylic carbons at the equatorial positions different from the TS illustrated by Kwart and Slutsky297,302, while 192 has a distorted square pyramid (SP) structure around silicon. Analysis of the orbital interaction in the transition states showed that the major stabilization of 193 was caused by the MO interaction as predicted by the Woodward-Hoffmann rules, while the major stabilization in 192 was ascribed to the subjacent orbital control. 192 was more stable than 193 at... 

In the previous methods, the use of a continuous membrane for measuring cell forces has the disadvantage that the traction forces are convoluted by the observed bead displacements. Because the calculation is not direct, constraints or assumptions are required to solve the inverse problem. A technique to transduce individual traction forces comes from the use of microfabricated cantilevers. The first demonstration of these sensors was a horizontal silicon cantilever that was made with microfabrication techniques (Figure 22.6a). As a cell migrates across the surface, it bends the cantilever under the load of the traction force. Because the sensor is mechanically decoupled from the substrate, the deflection of the cantilever directly reports only the local force. The simple spring equation relates the deflection of the cantilever beam 8 to the cellular traction force ... 

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