Molecular Structure of Heterocycles: 6. Solvent Effects on the 17O Nmr Chemical Shifts of 5-Trichloromethylisoxazoles

Abstract

Com o objetivo de elucidar e quantificar os efeitos do solvente sobre os deslocamentos químicos de 17 O de três 5-triclorometilisoxazóis [(1a) não-, (1b) 3-metil-e (1c) 4-metil-substituído] foi realizada uma análise de regressão multilinear, utilizando os parâmetros solvatocrômicos de Kamlet-Abboud-Taft (KAT). Os deslocamentos químicos do átomo de oxigênio do anel, O1, dos compostos 1a-c mostraram dependências (em ppm) em função da polaridade-polarizabilidade do solvente de-4.8π*,-3.2π*,-8.9π*, em função da acidez do solvente (HBD) de 0.9α,-0.2α,-2.7α e em função da basicidade do solvente (HBA) de-0.4β, 1.9β, 0.9β, respectivamente. Os dados de carga líquida de O1 e de momento de dipolo, obtidos por cálculos de orbitais moleculares (AM1), são comparados com os parâmetros de efeitos do solvente determinados para os compostos 1a-c. A multilinear-regression analysis using the Kamlet-Abboud-Taft (KAT) solvatochromic parameters in order to elucidate and quantify the solvent effects on the 17 O chemical shifts of three 5-trichloromethylisoxazoles [(1a) non-, (1b) 3-methyl-and (1c) 4-methyl-substituted] is reported. The chemical shifts of ring oxygen atom, O1, of compounds 1a-c show dependencies (in ppm) on the solvent polarity-polarizability of-4.8π*,-3.2π*,-8.9π*, on the solvent hydrogenbond-donor (HBD) acidities 0.9α,-0.2α,-2.7α and the solvent hydrogen-bond-acceptor (HBA) basicities-0.4β, 1.9β, 0.9β, respectively. The data of net charges of O1 and dipole moment, obtained from MO calculations (AM1), are compared with the solvent effect parameters obtained for compounds 1a-c.

17O NMR studies of boronic acids and their derivatives

“…87 This method has been used in previously reported studies of the solvation 17 O NMR shifts. [88][89][90][91][92][93] Phenylboronic acid was used to avoid the effects caused by the interactions of the solvent with the substituent in the aryl ring. Moreover, phenylboronic acid 1,2-ethanediol ester was used for comparison as its molecule does not act as a hydrogen bond donor.…”

UJI AKTIVITAS ANALGETIKA EKSTRAK ETANOL DAUN SUKUN (Artocapus altilis) TERHADAP MENCIT PUTIH JANTAN YANG DIINDUKSI ASAM ASETAT

“…Menurut Hoa et al (2007) bahwa pelarut organik digunakan didasarkan pada sifat kepolaran, kelarutan dan transfer massa dari senyawa yang di ekstrak. Kelarutan senyawa sangat ditentukan oleh kepolaran, momen dipol, polarisabilitas dan ikatan hidrogen (Martins et al 2001).…”