Posts Tagged ‘substitution products’

Dynamic effects in nucleophilic substitution at trigonal carbon (with Na+) revisited.

Monday, August 13th, 2012
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This reaction looks simple but is deceptively complex. To recapitulate: tolyl thiolate (X=Na) reacts with the dichlorobutenone to give two substitution products in a 81:19 ratio, a result that Singleton and Bogle argue arises from a statistical distribution of dynamic trajectories bifurcating out of a single transition state favouring 2 over 3. On the grounds (presumably) that the presence of both the cation X (=Na+) and H-bonded solvent (ethanol) are uninfluential, neither species was explicitly included in the transition state model used to derive the dynamics. I speculated whether in fact the spatial distribution of counterions and solvent (set up by explicit hydrogen bonds and O…Na+ interactions) might in fact be perturbed from un-influential randomness by co-ordination to the carbonyl group present in the system. I also raised the issue of what the origin of the electronic effects leading to the major product might be. 

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Dynamic effects in nucleophilic substitution at trigonal carbon.

Monday, July 16th, 2012
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Singleton and co-workers have produced some wonderful work showing how dynamic effects and not just transition states can control the outcome of reactions. Steve Bachrach’s blog contains many examples, including this recent one.

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