1200-11-9Relevant articles and documents
Autoxidation of hydrazones. Some new insights
Harej, Maja,Dolenc, Darko
, p. 7214 - 7221 (2008/02/11)
(Chemical Equation Presented) Autoxidation of hydrazones is a generally occurring reaction, leading mostly to the formation of α- azohydroperoxides. All structural kinds of hydrazones, having at least one hydrogen atom on nitrogen, are prone to autoxidation; however, there are marked differences in the rate of the reaction. Hydrazones of aliphatic ketones are 1-2 orders of magnitude more reactive than analogous derivatives of aromatic ketones. Even less reactive are the hydrazones of chalcones, which function also as efficient inhibitors of autoxidation of other hydrazones. These differences can be attributed to the reduction of the rate of the addition of oxygen to a hydrazonyl radical, which is a reversible reaction. In the case of conjugated ketones, it becomes endothermic, making this elementary step slow down and the chain termination reactions become important. Substituents influence the stability of hydrazonyl radicals and, consequently, the bond dissociation energies of the N-H bonds. In acetophenone phenylhydrazones, the substituents placed on the ring of hydrazine moiety exhibit a higher effect (Hammett ρ = -2.8) than those on the ketone moiety (ρ = -0.82), which denotes higher importance of the structure with spin density concentrated on nitrogen in delocalized hydrazonyl radical. Electronic effects of the substituents also affect the transition state for the abstraction of hydrogen atom by electrophilic peroxy radicals; NBO analysis display a negative charge transfer of about 0.4 eu from hydrazone to a peroxy radical in the transition state.
1,2,4-Triazolium salts from the reaction 1-aza-2-azoniaallene salts with nitriles
Wang,Jochims,Kohlbrandt,Dahlenburg,Al-Talib,Hamed,Ismail
, p. 710 - 718 (2007/10/02)
Aryl- and alkylhydrazones 1 of alkyl ketones and propanal are transformed to 1-chloroalkylazo compounds 2 with tert-butyl hypochlorite. Compounds 2 react with antimony(V) chloride or aluminum(III) chloride to give 1-aza-2-azoniaallene salts 3 as reactive
Geminal Azo- and Heteroelement-Functions, II: α-Substituted 2-(4-Chlorophenylazo)-propane Derivatives. Oxidation Products of Arylhydrazone Compounds, 14.
Schantl, Joachim G.,Gstach, Hubert
, p. 1329 - 1344 (2007/10/02)
The reaction of acetone-4-chlorophenylhydrazone (6) with bromine in the presence of acetamide yields 2-bromo-2-(4-chlorophenylazo)-propane (7) and 2,2-bis(4-chlorophenylazo)propane (8).The unstable heteroallylic bromide 7 was subjected without isolation t
Geminal Azo- and Heteroelement Functions, I: Reaction of Grignard Reagents with 1-(4-Chlorophenylazo)-1-methylethylisocyanate
Schantl, Joachim G.,Gstach, Hubert
, p. 1051 - 1064 (2007/10/02)
The Grignard reagents 3 attack the azo group of the α-arylazoalkylisocyanate 2 in the manner of a nucleophilic addition; by involving the geminally situated isocyanate function the heterocyclic anions 6 are formed and afford the 1-N-substituted triazolidi
