Most 5-nitrofuranyl derivatives, in particular, the frequently used 5-nitrofurfural building block in synthesis, are coloured compounds and their intrinsic colours can be a good indication of their purity by virtue of their specific extended π-delocalisation. To this end, the work herein reports a first-of-its-kind anhydrous synthesis of (E)-5- nitrofuran-2-yl methylene hydrazine, 5-nitrofuran-2-carbohydrazide, and its dimeric 5-nitro-N'-5-nitrofuran-2- carbonyl furan-2-carbohydrazide, alongside their intrinsic colours, and most importantly their reactivity towards several deuterated solvents together with their 1H and 13C NMR features in an attempt to unravel the basis of discrepancies in the appearance of purported (E)-5-nitrofuran-2-yl methylene hydrazine of high purity in the literature and that obtained herein.

中文翻译：

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5-硝基呋喃基衍生物对甲醇介质有反应性，如 1H、13C NMR 光谱及其颜色所示

大多数 5-硝基呋喃基衍生物，特别是合成中常用的 5-硝基糠醛结构单元，都是有色化合物，它们的固有颜色可以通过其特定的扩展 π 离域很好地指示其纯度。为此，本文报道了 (E)-5-硝基呋喃-2-基亚甲基肼、5-硝基呋喃-2-碳酰肼及其二聚体 5-硝基-N' 的首次无水合成。 -5-硝基呋喃-2-羰基呋喃-2-碳酰肼，除了它们的固有颜色之外，最重要的是它们对几种氘代溶剂的反应性以及它们的 1H 和 13C NMR 特征，试图揭示所声称的外观差异的基础文献中和本文中获得的高纯度(E)-5-硝基呋喃-2-基亚甲基肼。