Rate constants for the reaction of ground state atomic oxygen with methanol

1981 ◽  
Vol 75 (6) ◽  
pp. 2693-2704 ◽  
Author(s):  
David G. Keil ◽  
Tsuneo Tanzawa ◽  
Edward G. Skolni ◽  
R. Bruce Klemm ◽  
Joe V. Michael
Keyword(s):  
Ground State ◽  
Rate Constants ◽  
Atomic Oxygen

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

High-Efficiency and Ground-State Atomic Oxygen-Dominant Photodegradation of Carbamazepine by Coupling Chlorine and g-C3N4

2021 ◽  
Vol 60 (5) ◽  
pp. 2112-2122
Author(s):  
Zhu Ren ◽  
Shuo Chen ◽  
Shun-Feng Jiang ◽  
Wei-Fei Hu ◽  
Hong Jiang
Keyword(s):  
Ground State ◽  
Atomic Oxygen ◽  
High Efficiency

Effect of Medium on Reactivity for Alkaline Hydrolysis of p-Nitrophenyl Acetate and S-p-Nitrophenyl Thioacetate in DMSO-H2O Mixtures of Varying Compositions: Ground State and Transition State Contributions

2021 ◽  
Author(s):  
Ik-Hwan Um ◽  
Seungjae Kim
Keyword(s):  
Transition State ◽  
Alkaline Hydrolysis ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Data ◽  
Reaction Medium ◽  
Stepwise Mechanism ◽  
Rate Determining Step ◽  
Leaving Group ◽  
Hydrolysis Of

Second-order rate constants (kN) for reactions of p-nitrophenyl acetate (1) and S-p-nitrophenyl thioacetate (2) with OH‒ have been measured spectrophotometrically in DMSO-H2O mixtures of varying compositions at 25.0 ± 0.1 oC. The kN value increases from 11.6 to 32,800 M‒1s‒1 for the reactions of 1 and from 5.90 to 190,000 M‒1s‒1 for those of 2 as the reaction medium changes from H2O to 80 mol % DMSO, indicating that the effect of medium on reactivity is more remarkable for the reactions of 2 than for those of 1. Although 2 possesses a better leaving group than 1, the former is less reactive than the latter by a factor of 2 in H2O. This implies that expulsion of the leaving group is not advanced in the rate-determining transition state (TS), i.e., the reactions of 1 and 2 with OH‒ proceed through a stepwise mechanism, in which expulsion of the leaving group from the addition intermediate occurs after the rate-determining step (RDS). Addition of DMSO to H2O would destabilize OH‒ through electronic repulsion between the anion and the negative-dipole end in DMSO. However, destabilization of OH‒ in the ground state (GS) is not solely responsible for the remarkably enhanced reactivity upon addition of DMSO to the medium. The effect of medium on reactivity has been dissected into the GS and TS contributions through combination of the kinetic data with the transfer enthalpies (ΔΔHtr) from H2O to DMSO-H2O mixtures for OH‒ ion.

Plasma agriculture based on quantitative monitoring of reactions between fungal cells and atmospheric-pressure plasmas

2012 ◽  
Vol 1469 ◽  
Author(s):  
Masafumi Ito ◽  
Takayuki Ohta ◽  
Keigo Takeda
Keyword(s):  
Uv Radiation ◽  
Absorption Spectroscopy ◽  
Ground State ◽  
Atmospheric Pressure ◽  
Atomic Oxygen ◽  
Fungal Spores ◽  
Ultra Violet ◽  
High Density ◽  
Inactivation Rate ◽  
The Absolute

ABSTRACTA high-density non-equilibrium atmospheric pressure plasma (NEAPP) applied for inactivating fungal spores of P. digitatum is introduced as an environmentally safe and rapid-inactivation method. The contributions of ozone, ultra violet (UV) radiation and ground-state atomic oxygen in the NEAPP on the inactivation of the spores are evaluated using colony count method.The absolute densities of ozone were measured by using ultraviolet absorption spectroscopy. The ozone density increased from 2 to 8 ppm with an increase in the distance from the plasma source, while the inactivation rate decreased. The inactivation rate of plasma was evaluated to be thousand times higher than that of an ozone generator using the integrated number density of ozone. In addition, it was clarified that the contribution of UV radiation to inactivation was not dominant for P. digitatum inactivation by NEAPP by filtering the active species using quartz plate. From these results, we can speculate that the inactivation efficiency of reactive oxygen species (ROS) will be larger than those of others.In order to investigate the effect of ground-state atomic oxygen as one of ROS, the inactivation of P. digitatum spores using an oxygen radical source that employs a high-density atmospheric-pressure O2/Ar plasma. The absolute O density was measured to be 1.4×1014 and 1.5×1015 cm–3 using vacuum ultra violet absorption spectroscopy (VUVAS) using a microdischarge hollow cathode lamp. The behaviors of the O densities as a function of O2/(Ar+O2) mixture flow rate ratio correspond to that of the inactivation rate. This result indicates that ground-state atomic oxygen is concluded to be the dominant species that causes inactivation.

Die Lösungsmittelabhängigkeit der thermischen cis-trans-Isomerisierung von N-Benzylidenanilinen mit Donator/Akzeptor-Substituenten.

1976 ◽  
Vol 31 (7) ◽  
pp. 953-959 ◽  
Author(s):  
U. Berns ◽  
G. Heinrich ◽  
H. Gusten
Keyword(s):  
Ground State ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Solvent Polarity ◽  
Linear Functions ◽  
Aryl Group ◽  
Trans Isomerization ◽  
Solvatochromic Shifts ◽  
Z Value ◽  
Inversion Mechanism

Thermal cis →-trans isomerization of eight N-benzylideneanilines with donor and/or acceptor substituents in the para, para'-positions was studied in different solvents by observing the rapid relaxation to the thermodynamic stable trans isomer following flash photolysis. With the push-pull effect of the substituents in the direction of the N-aryl group the rate constant at 25°C is by three powers of 10 faster compared to the N–benzylideneaniline with opposite arrangement of substituents. The rate constants are independent of the nature of the substituents in the para-position of the benzylidene group. The rate constants of N-(4-nitrobenzylidene)-p-anisidine are linear functions of the solvent polarity scale based on solvatochromic shifts (Kosowers Z-value or Dimroths ET-value). With increasing push-pull effect of the substituents in the direction of the N-aryl group the rate constants do no longer depend on the polarity of the solvent. The observed solvent effects on the rates and the activation energies for thermal cis→ trans isomerization suggest that the transition state of the reaction is less polar than the ground state of the sterically hindered cis-N-benzylideneaniline, thus favouring an inversion mechanism to become operative with respect to the N-benzylideneanilines.

Evidence for diffusing atomic oxygen uncovered by separating reactants with a semi-permeable nanocapsule barrier

2019 ◽  
Vol 55 (12) ◽  
pp. 1706-1709 ◽  
Author(s):  
Sara M. Omlid ◽  
Sergey A. Dergunov ◽  
Ankita Isor ◽  
Kathryn L. Sulkowski ◽  
John T. Petroff ◽  
...  
Keyword(s):  
Ground State ◽  
Atomic Oxygen

Ground-state atomic oxygen [O(3P)] is an oxidant whose formation in solution was proposed but never proven.

Inactivation ofPenicillium digitatumSpores by a High-Density Ground-State Atomic Oxygen-Radical Source Employing an Atmospheric-Pressure Plasma

2011 ◽  
Vol 4 (11) ◽  
pp. 116201 ◽  
Author(s):  
Sachiko Iseki ◽  
Hiroshi Hashizume ◽  
Fengdong Jia ◽  
Keigo Takeda ◽  
Kenji Ishikawa ◽  
...  
Keyword(s):  
Ground State ◽  
Atmospheric Pressure ◽  
Atomic Oxygen ◽  
Atmospheric Pressure Plasma ◽  
Oxygen Radical ◽  
High Density ◽  
Pressure Plasma
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