Structure hydrazine

The use of substituted hydrazines, phenylhydrazine, and 2,4-dinitrophenylhydra-zine (68T4285 74JOC843) can give both 5- and 3-acetylenylpyrazole (Table VT). In this case, the direction of cyclization depends both on the hydrazine structure and the experimental conditions. 

Reactions of cyclic and acyclic 1,2,3-triones with phenylhydrazine give rise to mono- and bis-(phenylhydrazones). The central carbonyl group of a vicinal tricarbonyl system is electron-deficient and highly electrophilic,255 which is why treatment with an aryldiazonium ion affords 2-phenylhydrazones. The structure of such bis(phenylhydrazones) as cyclopentane-1,2,3-trione 1,3-bis(phenylhydrazone), dehydroascorbic acid 2,3-bis(phenylhydrazone), and cy-clobutanetetraone l,3-bis(phenylhydrazone) has been studied by UV, IR,1H-, 13C-, and 15N-NMR spectroscopy.265-268 Quantum-mechanical calculations to predict the most stable tautomeric forms of some 1,2- and l,3-bis(phenylhydrazones) revealed that the chelated bis(hydrazone) structure was usually more stable than the azoene-hydrazine structure.269-271 This does not mean that such structures do not exist, for example cyclobutanetetraone l,2,3-tris(phenylhydrazone) exists in a stable phenylazoene-hydrazine structure (see 49 Scheme 8).257-263... 

Hydrazine, like hydroxylamine, may be considered as a derivative of ammonia, one hydrogen atom being replaced by an —NHj group. The structure is shown below (Figure 9.5). 

Nucleophilic addition of 2-aminothiazole to the double bond of di-maleic acid hydrazine has been reported (206). No spectroscopic proof, however, is given to establish the proposed structure (60) for the resulting product (Scheme 41). 

The principal reactions of this class of compounds are summarized in Scheme 172. In most of these reactions the reactive nucleophilic center is the terminal NHj group, although the other exocyclic nitrogen may also be involved, as shown by acetylation, which yields 284 and 285. However, the structure of compound 281 is not the one proposed in a recent report (1582) that attributes the attack to the other exocyclic nitrogen. The formation of osazones (287) from sugars, 2-hydrazinothiazoles, and hydrazine has been reported (525, 531). 

Structural data of a diaziridine come from gas phase electron diffraction measurements (74CC397). The N—N bond of 3-methyldiaziridine (24) is longer than in hydrazine (1.449 A) the C—N bond distances in (24) and in diazirine are nearly equal (1.479 versus 1.482 A),... 

Nitrogen forms more than 20 binaiy compounds with hydrogen of which ammonia (NH3, p. 420), hydrazine (N2H4, p. 427) and hydrogen azide (N3H, p. 432) are by far the most important. Hydroxylamine, NH2(OH), is closely related in structure and properties to both ammonia, NH2(H), and hydrazine, NH2(NH2) and it will be convenient to discuss this compound in the present section also (p. 431). Several protonated cationic species such as NH4+, N2H5+, etc, and deprotonated anionic species such as NH2 , N2H3 , etc. also exist but ammonium hydride, NH5, is unknown. Among... 

Structural data are in the diagram these data were obtained from the microwave spectrum of the gas at low temperatures. The long (weak) N-N bond is notable (cf. 145 pm in hydrazine, p. 428). In this N2O3 resembles N2O4 (p. 455). 

Is the second step of the overall reaction for R=Me (N-methylphthalimide + hydrazine —> phthalimide hydrazide + methylamine) exothermic or endothermic Will higher temperatures accelerate or inhibit the reaction Is the structure drawn above for phthalimide hydrazide its lowest-energy form or are either the imine or diimine tautomers preferred Compare energies for the hydrazide and imine and diimine tautomers. Examine the geometry of phthalimide hydrazide and any low energy tautomer, and draw the Lewis structure(s) that best describes it. Can your Lewis structures account for the energy differences Examine electrostatic potential maps for all three molecules. Which molecule(s) are stablized by favorable electrostatic interactions Which are destabilized Can this help explain the energy differences Elaborate. 

Factor b above is discussed in Sections II, B, 1 II, B, 4 and II, C. A hydrogen-bonded structure such as 221 can account for the facile reaction of 5-bromouracil or for the unique, so-called hydrolyzability of carboxymethylthio-azines (237). The latter may also react via the intramolecular mechanism indicated in 136. The hydrogen-bonded transition state 238 seems a reasonable explanation of the fact that 3,4,6- and 3,4,5-trichloropyridazines react with glacial acetic acid selectively to give 3-pyridazinones while other nucleophiles (alkoxides, hydrazine, ammonia, or sulfanilamide anion) react at the 4- and 5-positions. In this connection, 4-amino-3,5-dichloro-pyridazine in liquid hydrazine gives (95°, 3hr, 60%yield)the isomer-... 

Evidence in favor of the amino-thionic tautomeric form of 2-amino-l,3,4-thiazoline-5-thione 239 (A = X = S R = H) was obtained from X-ray structural determinations [72AX(B)1584]. A NMR-spectroscopic study (77JOC3725) of compounds 239 (A = Se X = S R = Me) demonstrated their amino-thionic structure. A similar tautomeric form 240 is also dominant for the hydrazine derivative (R = NHNHCOPh) [73JCS(P2)4]. 

The cyclization of l-alkoxybut-l-en-3-ynes with hydrazine was first achieved by Franke and Kraft (55AG395). By heating 1-methoxybut- l-en-3-yne with hydrazine sulfate in an aqueous alcohol medium they obtained 3(5)-methylpyrazole (13) in high yield. Winter (63HCA1754) used the cyclization of 1-methoxybut-l-en-3-yne with hydrazine hydrate and phenylhydrazine to establish the structure of the initial enyne ether [in this case a mixture of l-phenyl-3(5)-propylpyrazoles was obtained]. The reaction with hydrazine sulfate gives only one product, 3(5)-propyl-pyr azole. 

In a recent review of heterocyclic compounds no further mention is made of the three-membered ring structures for the condensation products from hydrazine and carbonyl compounds. However, the products obtained from azodicarbonyl derivatives with aliphatic diazo compounds were formulated as diaziridines [Eq. (1)]. Recent investi-... 

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