E.p.r. searches of correlations between paramagnetic centre behaviour and chemical structure of reductively alkylated flame coal

Abstract

Electron paramagnetic resonance spectroscopy (X-band, 9.3 GHz) was used to characterize paramagnetic centres of reductively ethylated and butylated Polish flame coal (70.8 wt% C) in a potassium–liquid ammonia system. The processes of reduction and reductive alkylation decreased total concentration of paramagnetic centres in this coal. The decrease in the total amount of paramagnetic centres with the increase in H/C atomic ratio of the sample was observed for multistage reduced and butylated coal. Different correlations between total concentration of free radicals in 1–4 times reduced and reductively butylated coal and their yield of dichloromethane extract were demonstrated. Numerical analysis of the lineshape of the e.p.r. spectra proved existence of two groups of paramagnetic centres with narrow and broad lines in the studied coal samples. Paramagnetic centres responsible for the broad e.p.r. components were the most active during reductive alkylation of the coal.