DDQ Oxidant Research Papers - Academia.edu (original) (raw)

Spectrophotometric method for determination of bambuterol hydrochloride after its conversion to bambuterol base by formation of charge transfer complexes as n-donor with π-acceptors, dichlorodicyanobenzoquinone (DDQ) and... more

Spectrophotometric method for determination of bambuterol hydrochloride after its conversion to bambuterol base by formation of charge transfer complexes as n-donor with π-acceptors, dichlorodicyanobenzoquinone (DDQ) and tetracyanobenzoquinodimethane (TCNQ) which were prepared in acetonitrile. They yield radical anions measured at 461 and 842 nm within concentration ranges of 36.7–183.7, 4.59–36.7 μg ml−1 with a good correlation coefficients (r2 = 0.9999–0.9998) respectively. The nature of the formed complexes was studied via determination of the association constant and the molar absorptivity using Bensi–Hildebrand equation. The free energy change (ΔG) and the enthalpy of formation (ΔH) as well as the entropy (ΔS) were determined for the reaction product with TCNQ. The method was successfully applied for the analysis of bambuterol hydrochloride in its pharmaceutical preparation where no interference could be observed from the additives commonly present as proven by good mean recoveries of 99.74% and 100.014%. There was no significant difference observed when the method was statistically compared with the pharmacopeial official method used for determination.

Tetraarylethylenes can be sequentially transformed into 9,10-diarylphenanthrenes and dibenzo[g,p]chrysenes using 1 and 2 equiv of DDQ, respectively, in CH2Cl2 containing methanesulfonic acid, in excellent yields. Efficient access to... more

Tetraarylethylenes can be sequentially transformed into 9,10-diarylphenanthrenes and dibenzo[g,p]chrysenes using 1 and 2 equiv of DDQ, respectively, in CH2Cl2 containing methanesulfonic acid, in excellent yields. Efficient access to substituted dibenzochrysenes from tetraarylethylenes establishes the versatility of this procedure over the existing multistep syntheses of dibenzochrysenes. Moreover, the ready regeneration of DDQ from easily recovered reduced DDQ−H2 continues to advance the use of DDQ/H+ for the oxidative C−C bond forming reactions.