Prereactive complexes

The interaction of dihalogen molecules XY with different acceptors B quite often leads to vicious chemical reactions. In most cases, the 1 1 complexes are extremely short-lived. To investigate these prereactive complexes experimentally in a collision-free environment, pulsed-nozzle, Fourier-transform microwave spectroscopy has turned out to be the ideal technique. Legon and coworkers prepared a large number of these complexes and performed detailed rotational spectroscopic analyses. Several series of simple molecules... 

Legon AC (2007) Prereactive Complexes of Dihalogens with Lewis Bases in the Gas Phase (Chapter 2, this volume). Springer, Heidelberg... 

The initial prereaction complex (MIN-5) between GS HO-ONO (cw-conformer) and CH4 is stabilized by only 0.4 kcalmol (Figure 11). 

FIGURE 37. Prereaction complex (R-a) and transition stmcture (TS-b) with the natural (enzymatic) orientation of the p-OHB substrate with respect to the FlHO—OH 14... 

The authors proposed a working mechanism to explain the diastereoselectivities (Scheme 8.174). Thus, the prereaction complex 537 reacts with the Chloramine-T to yield an intermediate chlorosulfonium ion 538. Further reaction of 538 with toluenesulfonamide anion effected a configurational inversion to give the observed product. 

In order to more reliably predict the BChE mutants with a possibly higher catalytic efficiency against (-)-cocaine, MD simulations were also performed on the structures of (-)-cocaine binding with a number of hypothetical BChE mutants in their non-prereactive and prereactive complexes [101]. Table 4 summarizes the average values of some important geometric parameters in the simulated complexes. 

To make sure that this remarkable difference between the structures simulated for these two hydrolysis processes was not an artifact of the possibly different computational strategies used for the two different reaction processes, the prereactive complex between ACh and mouse AChE (using X-ray crystal structure IMAH in the Protein Data Bank [123]) was also simulated by using the same MD approach as used for the BChE-cocaine system. As... 

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