Fourier transform infrared absorption spectra, between 1850 and 2700 cm(-)(1), were used to study the intermolecular interactions between methanol and water. Digitized spectra obtained from methanol-water mixtures, with methanol mole fraction varying from 0 to 1.00, were subjected to factor analysis. Principal factor analysis indicated that three chemical factors were responsible for the data. Window factor analysis, a model-free method, was used to extract the concentration profiles of three species, which were identified as water, methanol, and a methanol-water complex. The profiles were used to deduce the stoichiometry of the complex, which was found to consist of one molecule of methanol and two molecules of water. The dissociation constant of the complex was determined to be 306 ± 33 M(2). These results differ from those reported by other investigators.
The visible spectra of methylene blue (MB) in aqueous-methanol solutions were used to determine the extent of hydration of MB aggregates. The investigation was carried out at MB concentrations of 1.000 × 10−4 M and 1.000 × 10−3 M. Abstract factor analysis (AFA) was used to determine the number of chemical species responsible for the spectral data. The species were identified as aqueous MB monomer, dimer, and trimer, and a methanoic MB monomer. The absorptivity spectra of the aqueous MB species obtained from the previous studies were used to extract their concentration profiles in methanol–water mixtures. With the addition of methanol to the aqueous solvent, the concentration of water could be varied from 0% to 100%. This variation was used to determine the extent of hydration and solvation of each of the four MB species, as well as their mutual equilibria. The species were identified as (1) MB+CH3OH, MB monomer monomethanol; (2) MB+H2O, MB monomer monohydrate; (3) (MB)2++ 6H2O, MB dimer hexahydrate; and (4) (MB)3Cl++ (H2O)13, MB trimer monochloro tridecahydrate. The dissociation constants for the hydrated monomer, dimer, and trimer were determined to be 0.48, 1.29 × 103 M5 and 7.2 × 106 M13, respectively.
A robust analytical methodology is developed for the quantitative determination of all six insecticidal components of pyrethrum extract: jasmolin I, cinerin I, pyrethrin I, jasmolin II, cinerin II, and pyrethrin II. This method, based on the separation technique normal-phase high-performance liquid chromatography, offers selectivity, accuracy, precision, linearity, range, ruggedness, and robustness as well as efficiency and ease.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.