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Isomeric alkyl cation/arene complexes in the gas phase
Antonello Filippi1, Graziella Roselli, Gabriele Renzi
1Facoltà di Farmacia, Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive (No. 64), University of Rome La Sapienza, Piazza le A. Moro 5, 00185 Rome, Italy. antonello.filippi@uniroma1.it
Chemistry (Weinheim an Der Bergstrasse, Germany)
|May 13, 2003
Summary
Investigating the isomerization of a specific butane molecule reveals a meta isomer forms with full racemization. Low-energy intermediate complexes are key to this reaction pathway.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Computational Chemistry
Background:
- Protonation-induced unimolecular isomerization is a key reaction in organic chemistry.
- Understanding reaction mechanisms and stereochemistry is crucial for predicting chemical behavior.
Purpose of the Study:
- To investigate the kinetics and stereochemistry of the protonation-induced unimolecular isomerization of (S)-(+)-1-D(1)-3-(p-tolyl)butane.
- To elucidate the role of intermediate species in the isomerization process.
Main Methods:
- Gas-phase kinetic and stereochemical analysis.
- Ab initio calculations at the MP2(full)/6-311++G**//HF/6-31+G** level of theory.
Main Results:
- The isomerization predominantly forms the meta isomer with complete racemization.
- A partial 1,2-H shift occurs within the migrating sec-butyl group.
- Evidence suggests the formation of low-energy, tightly bound isomeric sec-butyl cation/toluene complexes.
Conclusions:
- The observed results and activation parameters support the existence of stable intermediate complexes.
- Ab initio calculations confirm the eta(1)-type structure of these low-energy intermediates.
- These intermediates play a significant role in the isomerization energy surface and reaction outcomes.