Nitrofurans stability

Such nucleophilic displacements are likely to be addition-elimination reactions, whether or not radical anions are also interposed as intermediates. The addition of methoxide ion to 2-nitrofuran in methanol or dimethyl sulfoxide affords a deep red salt of the anion 69 PMR shows the 5-proton has the greatest upfield shift, the 3- and 4-protons remaining vinylic in type.18 7 The similar additions in the thiophene series are less complete, presumably because oxygen is relatively electronegative and the furan aromaticity relatively low. Additional electronegative substituents increase the rate of addition and a second nitro group makes it necessary to use stopped flow techniques of rate measurement.141 In contrast, one acyl group (benzoyl or carboxy) does not stabilize an addition product and seldom promotes nucleophilic substitution by weaker nucleophiles such as ammonia. Whereas... 

The instability of nitrofurans in meat or liver has been well documented (36-38). Hence, a major concern from a regulatory point of view has arisen regarding the stability of nitrofuran residues during transport of the samples from the collection place to the testing facility. 

ESR study of the electrochemical dehalogenation of 2-halo-5-nitrofurans showed that the first step involves the formation of radical anions the dehalogenation of which proceeds via a dianion intermediate for chloro compounds, for the iodo compounds. Both routes were involved for the bromo compounds. The stability of the intermediate anion radicals of 2-halo-5-nitrofurans increased in the order I < Br < Cl208. 

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