The Quadrupole Coupling Constants of 1,2,5-Thiadiazole

Abstract

Abstract The nitrogen quadrupole coupling constants along the inertial axes o f 1,2,5-thiadiazole are determined as Xaa = 0.90 ± 0.01 MHz, Xbb = - 3.13 ± 0.06 MHz, Xcc = X (⟂) = 2.22 ± 0.06 MHz, and Dobyns and Pierce’s value for the dipole m om ent is confirmed as μ = μa = 1-58 ± 0.02D. (The uncertainties are three standard deviations.) Comparison o f these data with their counterparts in related compounds leads to speculation that the direction of the main field gradient in the molecular plane deviates from the SNC bisector towards the sulphur atom by Ɵ ~ 5° - 10°. From this assum ption the principal in-plane coupling constants are Xradial = Xzz ~ - 3.82 MHz and Xtangential = Xxx ~ 1.60 MHz, with uncertainties of ± 0.20 MHz due to a probable error of ± 2° in the assumed direction (Ɵ = 8°) of the z-axis o f the field gradient tensor.