Steady-state and transient photolysis of p-nitroaniline in acetonitrile
ABSTRACT Both transient photolysis and steady-state photo-degradation experiments were performed to gain insight into the kinetics and mechanisms of degradation of p-nitroaniline (p-NA) in acetonitrile (MeCN) solutions. Complete degradation of p-NA was observed at diverse irradiation conditions under 254 nm UV light. Once H2O2 was added into the experimental system, degradation of p-NA was enhanced remarkably. The removal rate increased rapidly with increment of the irradiation time and reached 90% at 30 min. p-NA could be totally removed after 90 min in UV/H2O2 process. In the presence of O2 and H2O2, removal rate increased linearly with increment of the irradiation time and reached 90% at 10 min. p-NA could be totally removed after 20 min in UV/(O2 + H2O2) process. For transient photolysis, excited states of p-NA were observed after 355 and 266 nm laser flash photolysis (LFP). The transient absorption spectra were recorded and bimolecular rate constant of 6.89 × 109 M−1 s−1 was calculated for the self-quenching of 3p-NA*. Production of 3p-NA* in MeCN and H2O mixed solution was also studied. LFP of p-NA with addition of H2O2 was investigated for the first time.
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ABSTRACT: Low-lying excited electronic states of an important class of molecules known as push-pull chromophores are central to understanding their potential nonlinear optical properties. Here we report that a combination of high-sensitivity nanosecond time-resolved dispersive IR spectroscopy and DFT calculations on p-nitroaniline (PNA), a prototypical push-pull molecule, reveals that PNA in the lowest excited triplet state has a partial quinoid structure. In this structure, the quinoid configuration is restricted to a part of the phenyl ring adjacent to the NO(2) group. The partial quinoid structure of PNA cannot be explained by a commonly used hybrid of a neutral form and a zwitterionic charge-transfer form. Our findings not only cast doubt on the general applicability of the classical way of looking at excited states, based exclusively on characteristic resonance structures, but also provide deeper insights into excited-state structure of highly polarizable molecular systems.Chemistry - A European Journal 02/2012; 18(9):2543-50. DOI:10.1002/chem.201103235 · 5.70 Impact Factor
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ABSTRACT: A hyper-cross-linked polymeric adsorbent with "-CH2-phenol-CH2-" as the cross-linked bridge (denoted GQ-05), and another hyper-cross-linked polymeric adsorbent with "-CH2-p-cresol-CH2-" as the cross-linked bridge (denoted GQ-03) were synthesized to reveal the effect of the steric hindrance of micropores in the hyper-cross-linked polymeric adsorbent on adsorption capacity and adsorption rate of p-nitroaniline (PNA) from aqueous solution. The results of adsorption kinetics indicated the order of the adsorption rate GQ-05 > GQ-03. The pseudo-first-order rate equation could describe the entire adsorption process of PNA onto GQ-05 while the equation characterized the adsorption process of GQ-03 in two stages. The order of the adsorption capacity GQ-05 > GQ-03 was demonstrated by thermodynamic analysis and dynamic adsorption. The steric hindrance of micropores in the hyper-cross-linked polymeric adsorbent was a crucial factor for the order of the adsorption capacity and adsorption rate.Journal of Hazardous Materials 09/2014; 280:97–103. DOI:10.1016/j.jhazmat.2014.07.057 · 4.33 Impact Factor