Proton magnetic resonance chemical shifts and coupling constants for a series of 2substituted-5-nitropyridines and 2-substituted-3-nitropyridines, both in the free base and protonated forms, are reported. The substituents were chloro, broino, iodo, and hydroxyl. The effect of the substituents on the chemical shifts are substantial but not unusual. The coupling constants are less sensitive to the nature of the substituent and are perturbed only slightly when the ring nitrogzn is protonated. This latter observation is consistent with the results of LCAO-MO calculations.

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Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

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