Ditetradecyl selenide, (C14H29)2Se, a new chemical shift reference compound for77Se NMR

Abstract

Ditetradecyl selenide, (C14H29)2Se, is suggested as an alternative to Me2Se as a reference compound for 77Se NMR in organic solvents. This selenide, a crystalline, non‐odorous and stable compound, is readily prepared and purified and is sufficiently soluble in most of the usual organic solvents at room temperature to give a satisfactory 77Se signal; in methanol, acetonitrile and dimethyl sulfoxide temperatures above ∼310 K are required. The chemical shifts, +162.3 ppm in CDCl3 at 298 K relative to a 60% solution of Me2Se in CDCl3, defined as 0.0 ppm, and +167.2 ppm relative to a 0.25 M solution of Me2Se in CDCl3, is independent of the concentration in the 0.01–0.40 M range. The shift in CDCl3 increases fairly linearly with temperature in the 270–345 K range with a slope of ∼0.075 ppm K−1. The shift appears to be less dependent upon the solvent than the shift of Me2Se. Copyright © 2000 John Wiley & Sons, Ltd.

Solvent effect on the 77Se NMR chemical shifts of diphenyl diselenides

“…45–56 Additionally, some 77 Se NMR investigations are performed under different experimental conditions, which could make the assignment of different signals somewhat troublesome because of the effect of the solvent on the chemical shift value. 45–60…”

“…Furthermore, an accurate and practical referencing protocol must be used to properly assign each signal. [57][58][59] For the 77 Se NMR spectra, different organic compounds (secondary standards) have been employed, 60 because Me 2 Se 60% v/v (primary standard; d = 0.0 ppm) is volatile, toxic, and has a very bad smell.…”

“…[45][46][47][48][49][50][51][52][53][54][55][56] Additionally, some 77 Se NMR investigations are performed under different experimental conditions, which could make the assignment of different signals somewhat troublesome because of the effect of the solvent on the chemical shift value. [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] Based on the great applicability of diphenyl diselenide derivatives in organic synthesis 45 and in bioorganic chemistry, [45][46][47][48][49][50][51][52][53][54][55][56] and the possibility of employing different diphenyl diselenides as reference compounds, 65,66 here we describe the solvent effect on the most commonly used diphenyl diselenides to obtain precise chemical shift values in each solvent, which can be useful for referencing purposes, and for understanding the chemical shift variations with the solvent polarity. To gain a deeper insight into the latter e...…”