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Effect of ring strain on the thiolate-disulfide exchange. A computational study
Steven M Bachrach1, Joshua T Woody, Debbie C Mulhearn
1Department of Chemistry, Trinity University, 715 Stadium Drive, San Antonio, Texas 78212, USA.
The Journal of Organic Chemistry
|December 7, 2002
Summary
The reaction mechanism of hydrosulfide anion (HS-) with cyclic disulfides depends on ring size. Smaller, strained rings (three- and four-membered) undergo S(N)2 reactions, while larger rings (five- and six-membered) follow an addition-elimination pathway.
Area of Science:
- Computational Chemistry
- Organic Chemistry
- Reaction Mechanisms
Background:
- Cyclic disulfides are important structural motifs in various chemical and biological systems.
- Understanding their reactivity with nucleophiles is crucial for predicting chemical behavior.
Purpose of the Study:
- To elucidate the reaction mechanisms of hydrosulfide anion (HS-) with small cyclic disulfides.
- To investigate the influence of ring size on the reaction pathway.
Main Methods:
- The study employed computational chemistry methods, specifically B3LYP/aug-cc-pVDZ and MP2/6-31+G calculations.
- Theoretical calculations were used to model the interactions between HS- and cyclic disulfides.
Main Results:
- A distinct difference in reaction mechanisms was observed based on ring size.
- Five- and six-membered rings reacted via an addition-elimination pathway, similar to acyclic disulfides.
- Three- and four-membered rings, due to strain, reacted via an S(N)2 mechanism, involving direct nucleophilic attack and ring cleavage.
Conclusions:
- The reaction pathway of HS- with cyclic disulfides is highly dependent on the conformational flexibility and strain of the disulfide ring.
- Smaller, strained rings favor S(N)2 mechanisms, while larger, less strained rings adopt addition-elimination pathways.