The relationship between ignition quality and carbon type structure of fuels is summarized, and carbon groups that have dominant effect on ignition quality of the diesel fuels are identified. A scheme of characterizing the chemistry of hydrocarbon fuels in terms of these carbon groups using proton nuclear magnetic resonance spectroscopy has been proposed. Through the use of this analysis technique on 67 different diesel fuels, whose cetane numbers were determined on a number of standard cetane rating engines, an empirical expression that relates the cetane number to the carbon type structural composition of the fuels has been developed. The error in the predicted cetane numbers from the developed expression has been found to be smaller than the spread of the multiple standard cetane rating engine determinations.

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A steric effect of substituents in planar and tetrahedral NiX2L2 complexes has been attributed respectively to Ni-X16 and Ni-P17 bond lengthening.