Solvent and temperature effects on the conformational equilibria of a dihydrobenzo[h]quinolinium fluoroborate

Abstract

Spectra of the N-phenyl-5,6-dihydro-2,4-diphenylbenzo[h]quinolinium tetrafluoroborate (1) and of the N-phenyl-5,6,8,9-tetrahydro-7-phenyldibenzo[c,h]acridinium tetrafluoroborate (2) were recorded in various solvents and temperatures. The analysis of the (1)H-NMR spectra of the tetrafluoroborate salt 1, recorded in acetone, acetonitrile, 1,1,2,2-tetrachloroethane and chloroform, revealed the existence of an equilibrium between two conformers in solution. Tight ion-pairing in chloroform led to a smaller barrier for interconversion between the two conformers. In more polar solvents, where the dihydrobenzoquinolinium exists as a free cation, theoretical calculations predicted larger barriers. The spectra of 1 in 1,1,2,2-tetrachloroethane also varied with temperature, resembling at higher temperatures the spectrum in CDCl(3) and at 300K spectra in more polar media. Spectra of 2 did not vary with the solvent or the temperature, in an indication of a much higher barrier to conformational interconversion, because of a greater steric hindrance between the N-phenyl substituent and the dihydrobenzo rings.

Horto Medicinal Em Um Centro De Atenção Psicossocial – Um Relato De Experiência

“…No Brasil, pesquisas demonstram que 91,9% da população fazem uso de alguma planta medicinal, sendo que 46% da mesma mantêm cultivo caseiro dessas plantas. Este uso tem persistido, entre outros motivos, pela dificuldade no acesso à assistência de saúde para parte da população, que não tem suas demandas e necessidades atendidas, sendo parcialmente supridas pelo uso das terapias alternativas e também por opção pessoal (REZENDE;COCCO, 2002;MOREIRA, 2013).…”