Hydrazide resonance

It remains to be clarified why the 1,2-diacylated hydrazine B and not the 1,1-diacylated hydrazine D is formed in the hydrazinolysis of Figure 6.20. In the intermediate C the only nucleophilic electron pair resides in the NH2 group and not in the NH group because the electron pair of the NH group is involved in the hydrazide resonance C —> C and is therefore not... 

The IR spectra of carbohydrazide 9 showed absorption bands at 3317 cm (OH,Hydrazide NH2), 3269 cm (aromatic CH), 1711 cm (CO stretching), and 1621-1640 cm (CO-NH-NH2 groups). The H NMR spectra exhibited a singlet due to the CONHNH2, NH proton at 9.32 ppm. Methylene protons resonated as a singlet at 4.23 ppm. The structures of the products lOa-1 were inferred from their analytical and spectral data. Thus, their IR spectra showed characteristic absorption bands at 3400-3240 cm (NH,OH), 1710-1700 cm (lactone CO), and NHCO at 1650-1600 cm . ... 

Because the Hydrazides are soluble in solvents which may contain significant amounts of water, it is often difficult to characterize the exchangeable proton resonances with confidence. In gen-eral, it appears that the NH2 group resonates at intermediate field and is often in exchange with any water which may be present in the solution producing an erroneous 3-hydrogen integration value. In addition, the C(=0)-NH proton may resonate at much lower field (7-9 ppm) as a very broad band which may be difficult to locate. 

C resonances of maleic hydrazide. A good range of data has been tabulated for 3,6-dis-ubstituted pyridazine derivatives <9IC.IC972>. 

Fig, 2. Variable temperature proton nuclear magnetic resonance spectra of lithium tris(trimethylsilyl)hydrazide (6) in hexane reveals the temperature-dependent intramolecular trimethylsilyl migration. Temperatures are recorded in degrees centigrade. 

Equilibria, Exchange Rates and Activation Energies for Organosilyl Hydrazide Rearrangements from Nuclear Magnetic Resonance... 

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