Reactions of Oriented Molecules

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Science  02 Jul 1976:
Vol. 193, Issue 4247, pp. 11-16
DOI: 10.1126/science.193.4247.11


Beams of oriented molecules have been used to directly study geometrical requirements in chemical reactions. These studies have shown that reactivity is much greater in some orientations than others and demonstrated the existence of steric effects. For some reactions portions of the orientation results are in good accord with traditional views of steric hindrance, but for others it is clear that our chemical intuition needs recalibrating. Indeed, the information gained from simultaneously orienting the reactants and observing the scattering angle of the products may lead to new insights about the detailed mechanism of certain reactions.

Further work must be done to extend the scope and detail of the studies described here. More detailed information is needed on the CH3I reaction and the CF3I reaction. The effects of alkyl groups of various sizes and alkali metals of various sizes are of interest. In addition, reactions where a long-lived complex is formed should be studied to see if orientation is important. Finally, it would be of interest to apply the technique to the sort of reactions that led to our interest in the first place: the SN2 displacements in alkyl halides where the fascinating Walden inversion occurs.

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