Efeito da substituição por átomos de flúor no equilíbrio conformacional de chalcona

Química Nova

Dari Cesarin-sobrinho²  José Carlos Netto-ferreira²  Raimundo Braz-filho¹ 

[1] ,Universidade Federal Rural do Rio de Janeiro Departamento de Química Seropédica RJ

关键词: chalcone;    conformational equilibrium;    spectral data;   

DOI  :  10.1590/S0100-40422001000500006

来源: SciELO

【 摘 要 】

Chalcone (1) and its fluorinated derivatives 2-4, as well as their cyclic analogues 5-10, were synthesized through an aldol condensation reaction between the corresponding ketone and aldehyde. These compounds were characterized by IR, EIMS and ¹H and 13C NMR spectral data. Modern NMR techniques allowed us to conclude that the compounds obtained show E configuration. These techniques were also employed to investigate the equilibrium involving the s-cis and s-trans conformations of 1-4, with this equilibrium being dependent on the fluorine substitution on both aromatic rings, A or B. IR studies indicated that the yield of the s-cis conformation in the fluorinated derivatives is 57.4±1.4; 88.1±0.4 and 66.4±0.7%, for 2, 3 and 4, respectively, based on previous ¹H NMR calculations for chalcone. Theoretical calculations, using the MMX method, were employed to justify the variation of chemical shifts for the fluorinated derivatives and cyclic analogues. These chemical shifts are consequence of the anisotropic effect showed by the carbonyl group on these compounds.

【 授权许可】

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