Degradation and mineralization of ciprofloxacin by gas–liquid discharge non-thermal plasma

A typical quinolones antibiotic ciprofloxacin(CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive species(RS) generated in the gas phase were detected by the oscilloscope and the optical emission spectroscopy. The effects of various parameters on CIP degradation, i.e. input powers, initial concentrations addition of radical scavengers and p H values were investigated. With the increase of discharge power, the degradation efficiency increased but the energy efficiency significantly reduced. The degradation efficiency also reduced under high concentration of initial CIP conditions due to the competitive reactions between the plasma-induced RS with the degradation intermediates of CIP. Different radical scavengers(isopropanol and CCl_4) on ·OH and H· were added into the reaction system and the oxidation effects of ·OH radicals have been proved with high degradation capacity on CIP.Moreover, the long-term degradation effect on CIP in the plasma-treated aqueous solution proved that the long-lived RS(H_2O_2 and O_3, etc) might play key roles on the stay effect through multiple aqueous reactions leading to production of ·OH. The degradation intermediates were determined by the method of electrospray ionization(+)-mass spectroscopy, and the possible degradation mechanism were presented.

Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters

The amide C-N cleavage has drawn a broad interest in synthetic chemistry,biological process and pharmaceutical industry.Transition-metal,luxury ligand or excess base were always vital to the transformation.Here,we developed a transition-metalfree hydrogen-bond-assisted esterification of amides with only catalytic amount of base.The proposed crucial role of hydrogen bonding for assisting esterification was control experiments,density functional theory(DFT)calculations and kinetic studies.Besides broad substrate scopes and excellent functional groups tolerance,this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C–N bonds for organic synthesis and pharmaceutical industry.