Controlling reagent approach geometry

For a symmetric-top molecule in the state JKM) where Jis the total rotational angular momentum quantum number of the molecule, K is the projection of J on the top axis, and M is the projection of J on the electric field direction, the JKM) state experiences a radial force witiiin a hexapole electric field that is proportional to the product KM/[J J -F 1)]. Molecules in states for which the 

K on the much larger I-end of ICl to form KCl has an apex half-angle of about 

2 Preparing aligned molecules with polarized radiation 

It is also possible to apply the same idea of using radiation to control the electron charge distribution in open-shell molecules. For example, the lithium dimer (Li2) has a closed-shell electronic structure in its X E+ ground state in which both valence electrons are spin paired in tire same a molecular orbital. Witii visible radiation, Li2 is readily excited to its A H state in which one electron 

An experiment that similarly shows the differential reactivity of an aligned electronic orbital is the photodissociation of the T-shaped van der Waals dimer Hg -H2. The Hg 6 So 6 Pi transition, where a single valence electron promoted to a orbital, is split by the close presence of H2 because now the 

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As the reagent and the substrate approach each other, attractive and repulsive interactions occur. The discrimination between the various possible transition states depends upon the relative magnitudes of these interactions, which in turn depend upon the transition-state geometries. Unlike enzymatic reactions, which are usually controlled by attractive interactions due to site recognition, chemically induced discrimination is usually dependent upon differences in repulsive interactions. 

Factors controlling regioselectivity in the reduction of polynitroaromatics in aqueous solution were examined with the use of SM2/AM1 model. The analysis supported the reliability of aqueous geometries predicted by SM2/AM1. Moreover, successful predictions for the regioselectivity of reduction further supported the validity of the modeling approach. The authors stated that "the ability of the SMk series of solvation models to predict the electronic structure of reagents in solution should open the door for the study of many environmentally important reactions taking place in aqueous or other liquid media" [123]. 

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