Linear free energy relationship (LFER) parameters are routinely used to parametrize physicochemical effects while investigating reaction mechanisms. In this Communication, we describe an alternate application for LFERs: training sets for model building in an analytical application. In this study, the sterics, quantified by Charton parameters (Δv), of nine secondary chiral alcohol analytes were correlated to the circular dichroism output from a chiral alcohol optical sensor. To test the validity of the model, the correlative linear model was applied to determine the enantiomeric excess of samples of two alcohols without a priori knowledge of a calibration curve. The error in this method was comparable to those of previous experimental methods (<5%).
An undergraduate chemistry experiment that draws from primary research is described. The experiment exploits chiral supramolecular assemblies for the determination of enantiomeric excess by 1 H NMR spectroscopy. This report describes the delivery of the experiment to a cohort of students, and as a result of feedback from those involved, an optimized protocol is presented. Particular care has been taken to facilitate ready adoption in other institutions by providing comprehensive teaching support materials as well as technical guidance for supporting the experiment.
The importance of developing method for thiocyanate becomes obvious, because thiocyanate can inhibit iodine uptake of thyroid gland leading to mumps disease. In this work, thiocyanate is oxidized by permanganate in the acid donor stream to cyanide, which is directly converted to hydrogen cyanide. Then, hydrogen cyanide diffuses through a Teflon membrane into acceptor stream containing nickel(II) in ammoniacal buffer to form tetracyanonickelate(II) which is detected spectrophotometrically at 267 nm. Analytical figures of merit were linear up to 50 mg L-1 for thiocyanate, with RSD of 1.34%, and detection limit of 0.07 mg L-1, respectively. Interfering anions were eliminated under stoichiometric amount of permanganate and sample throughput was 20 h-1. The method was validated for determining thiocyanate samples from synthetic and gold process waters with satisfactory results. Keywords: Thiocyanate, flow injection, permanganate, spectrophotometry
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