Molecular Modeling of an Electrophilic Addition Reaction with 'Unexpected' Regiochemistry
| Autor: | Diana Li, Katherine T. Best, Eric D. Helms |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
chemistry.chemical_classification
Addition reaction Alkene Electrophilic addition 05 social sciences Markovnikov's rule 050301 education Regioselectivity General Chemistry Carbocation Conjugated system 010402 general chemistry 01 natural sciences 0104 chemical sciences Education chemistry Computational chemistry Halogen Organic chemistry 0503 education |
| Zdroj: | Journal of Chemical Education. 94:936-940 |
| ISSN: | 1938-1328 0021-9584 |
| DOI: | 10.1021/acs.jchemed.6b00488 |
| Popis: | The electrophilic addition of a hydrohalic acid (HX) to an alkene is often one of the first reactions learned in second-year undergraduate organic chemistry classes. During the ensuing discussion of the mechanism, it is shown that this reaction follows Markovnikov’s rule, which states that the hydrogen atom will attach to the carbon with fewer substituents while the halogen atom will attach to the carbon with more substituents. However, in the preparation of tropic acid, the reaction of HCl with atropic acid (2-phenylpropenoic acid) does not follow this rule because it is a conjugated system. Molecular modeling of the possible carbocation intermediates suggests that the reaction follows a conjugate addition mechanism involving a 1,4-addition of HCl across the conjugated alkene and carboxyl group rather than addition across the alkene as students often first propose. PM3 semiempirical calculations are used to determine the energies of three possible carbocation intermediates. The energies obtained from the... |
| Databáze: | OpenAIRE |
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