2612-33-1Relevant academic research and scientific papers
Preparation of Di- and polynitrates by ring-opening nitration of epoxides by dinitrogen pentoxide (N2O5)
Golding, Peter,Millar, Ross W.,Paul, Norman C.,Richards, David H.
, p. 7037 - 7050 (2007/10/02)
Eighteen epoxides of various kinds were reacted with N2O5 in chlorinated hydrocarbon solvents (principally CH2Cl2) to give vicinal nitrate ester products by a novel ring-opening nitration reaction. The procedure offers easier temperature control and simpler isolation procedures compared with conventional mixed acid nitrations; it also enables selective nitration reactions to be carried out on polyfunctional substrates. The scope and limitations of the reaction, as well as those of an alternative route utilising N2O4 with in situ oxidation of an intermediate nitrite-nitrate, are discussed.
Chemistryl of Anthocyanin Pigments. 9. UV-Visible Spectrophotometric determination of the Acidity Constants of Apigeninidin and Three Related 3-Deoxyflavinium Salts
Brouillard, R.,Iacobucci, G. A.,Sweeny, J. G.
, p. 7585 - 7590 (2007/10/02)
The equilibrium constants for the structural transformations of some 3-deoxyanthocyanidins in water at 25 deg C have been measured by using the pH-jump method.This method have been described previously.According to their particular substitution patterns, hydroxylated flavinium salts can exist in slightly acidic media in several neutral forms: the quinoidal bases A, the carbinol pseudobase B, and the chalcone pseudobase C.Two of the conpounds investigated, namely 4',5,7-trihydroxyflavinium (apigeninidin) and 4'-methoxy-4-methyl-5,7-dihydroxyflavinium chlorides, exist essentially as a mixture of the three neutral forms A, B, and C, the colored species A being the most abundant.As expected, 4',7-dihydroxyflavinium chloride is stable in the open chalcone structiure C.This result is in a good agreement with the catalytic light effect generally observed for the ring-closure reaction of this species leading to the flavinium cation AH+.Only the monohydroxylated pigment 4'-methoxy-4-methyl-7-hydroxyflavinium chloride is the quinoidal base A perfectly stable, whatever the pH.In contrast to natural anthocyanins, the hydration of the pyrilium ring is less efficient and occurs, therefore, at much higher pH values (pH 5-6).Proton loss from the phenolic acidic hydroxyl groups of the flavinium cation takes place in the usual acidity range (pH 4-5), indicating that these groups are strongly hydrogen bonded to the surrounding water molecules.The chalcone content is much higher than for the anthocyanins, and for 4',7-dihydroxyflavinium chloride for instance, the value for the equilibrium ratio of the chalcone to the carbinol is as high as 20.6.
