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|Type:||Artigo de periódico|
|Title:||Conformational preferences and orbital interactions for methyl haloacetates|
|Abstract:||Conformational preferences and orbital interactions of methyl chloroacetate (1), methyl bromoacetate (2) and methyl iodo-acetate (3) were analyzed using experimental infra-red data, theoretical calculations and NBO analyses. The conformational equilibria of compounds 1-3 can be represented by their cis and gauche rotamers. The gauche form of 1 is stable in the vapour phase and in a non-polar solvent, but the cis is predominant in a polar solvent. For 2 the gauche form is more stable than the cis, in both the vapour and liquid phases, but for compound 3 only the gauche form was observed both in vapour phase as in solution. These conformational preferences were attributed to the orbital interaction between two antibonding orbitals pi(*)(C=O) -> sigma(*)(C-X). This unexpected interaction was possibly due to the high (0.2) electron density on pi(*)(C=O), which results from the interaction between ether oxygen lone pair and pi(*)(C=O). (c) 2005 Elsevier B.V. All rights reserved.|
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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