Kinetics of the reactions of O3 and OH radicals with a series of dialkenes and trialkenes at 294 ± 2 K

Rate constants for the gas phase reactions of O₃ and OH radicals with 1,3-cycloheptadiene, 1,3,5-cycloheptatriene, and cis- and trans-1,3,5-hexatriene and also of O₃ with cis-2,trans-4-hexadiene and trans -2,trans -4-hexadiene have been determined at 294 ± 2 K. The rate constants determined for reaction with O₃ were (in cm³ molecule^-1s^?1 units): 1,3-cycloheptadiene, (1.56 ± 0.21) × 10^-16; 1,3,5-cycloheptatriene, (5.39 ± 0.78) × 10^?17; 1,3,5-hexatriene, (2.62 ± 0.34) × 10^?17; cis?2,trans-4-hexadiene, (3.14 ± 0.34) × 10^?16; and trans ?2, trans -4-hexadiene, (3.74 ± 0.61) × 10^?16; with the cis- and trans-1,3,5-hexatriene isomers reacting with essentially identical rate constants. The rate constants determined for reaction with OH radicals were (in cm³ molecule^?1 s^?1 units): 1,3-cycloheptadiene, (1.31 ± 0.04) × 10^?10; 1,3,5-cycloheptatriene, (9.12 × 0.23) × 10^?11; cis-1,3,5-hexatriene, (1.04 ± 0.07) × 10^?10; and trans 1,3,5-hexatriene, (1.04 ± 0.17) × 10^?10. These data, which are the first reported values for these di- and tri-alkenes, are discussed in the context of previously determined O₃ and OH radical rate constants for alkenes and cycloalkenes.     

Relative rate constant measurements for the gas-phase reactions of hydroxyl radicals with 4-methyl-2-pentanone,trans-4-octene,and trans-2-heptene

The relative OH reaction rates from the simulated atmospheric oxidation of 4-methyl-2-pentanone, trans-4-octene, and trans-2-heptene have been measured. Reactions were carried out at 297 ± 2 K in 100-liter FEP Teflon®-film bags. The OH radicals were produced from the photolysis of methyl nitrite. The measured rate constants (×10¹¹ cm³ molecule^?1 s^?1) were as follows: 6.77 ± 0.50 for trans-4-octene, 1.40 ± 0.07 for 4-methyl-2-pentanone, and 6.70 ± 0.23 for trans-2-heptene using an absolute rate constant of 2.63 × 10¹¹ cm³ molecule^?1 s^?1 for the reaction of OH with propene; the principal reference organic. © John Wiley & Sons, Inc.     

Rate constants for the gas-phase reactions of cis-3-Hexen-1-ol,cis-3-Hexenylacetate,trans-2-Hexenal,and Linalool with OH and NO3 radicals and O3 at 296 ± 2 K,and OH radical formation yields from the O3 reactions

Rate constants for the gas-phase reactions of the four oxygenated biogenic organic compounds cis-3-hexen-1-ol, cis-3-hexenylacetate, trans-2-hexenal, and linalool with OH radicals, NO₃ radicals, and O₃ have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): cis-3-hexen-1-ol: (1.08 ± 0.22) × 10^?10 for reaction with the OH radical; (2.72 ± 0.83) × 10^?13 for reaction with the NO₃ radical; and (6.4 ± 1.7) × 10^?17 for reaction with O₃; cis-3-hexenylacetate: (7.84 ± 1.64) × 10^?11 for reaction with the OH radical; (2.46 ± 0.75) × 10^?13 for reaction with the NO₃ radical; and (5.4 ± 1.4) × 10^?17 for reaction with O₃; trans-2-hexenal: (4.41 ± 0.94) × 10^?11 for reaction with the OH radical; (1.21 ± 0.44) × 10^?14 for reaction with the NO₃ radical; and (2.0 ± 1.0) × 10^?18 for reaction with O₃; and linalool: (1.59 ± 0.40) × 10^?10 for reaction with the OH radical; (1.12 ± 0.40) × 10^?11 for reaction with the NO₃ radical; and (4.3 ± 1.6) × 10^?16 for reaction with O₃. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO₃ radicals, and O₃ results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc.     

Rate constants of the gas‐phase reactions of OH radicals with trans‐2‐hexenal,trans‐2‐octenal,and trans‐2‐nonenal

The rate constants of the gas‐phase reaction of OH radicals with trans‐2‐hexenal, trans‐2‐octenal, and trans‐2‐nonenal were determined at 298 ± 2 K and atmospheric pressure using the relative rate technique. Two reference compounds were selected for each rate constant determination. The relative rates of OH + trans‐2‐hexenal versus OH + 2‐methyl‐2‐butene and β‐pinene were 0.452 ± 0.054 and 0.530 ± 0.036, respectively. These results yielded an average rate constant for OH + trans‐2‐hexenal of (39.3 ± 1.7) × 10^?12 cm³ molecule^?1 s^?1. The relative rates of OH+trans‐2‐octenal versus the OH reaction with butanal and β‐pinene were 1.65 ± 0.08 and 0.527 ± 0.032, yielding an average rate constant for OH + trans‐2‐octenal of (40.5 ± 2.5) × 10^?12 cm³ molecule^?1 s^?1. The relative rates of OH+trans‐2‐nonenal versus OH+ butanal and OH + trans‐2‐hexenal were 1.77 ± 0.08 and 1.09 ± 0.06, resulting in an average rate constant for OH + trans‐2‐nonenal of (43.5 ± 3.0) × 10^?12 cm³ molecule^?1 s^?1. In all cases, the errors represent 2σ (95% confidential level) and the calculated rate constants do not include the error associated with the rate constant of the OH reaction with the reference compounds. The rate constants for the hydroxyl radical reactions of a series of trans‐2‐aldehydes were compared with the values estimated using the structure activity relationship. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 483–489, 2009     

Theoretical interpretation of the kinetics and mechanisms of the HNO + HNO and HNO + 2NO reactions with a unified model

Previously measured decay rates of HNO in the presence of NO have been kinetically modeled on the basis of thermochemical data calculated with the BAC-MP4 technique. The results of this modeling, aided by TST-RRKM calculations for the association of HNO and the isomerization, decomposition, and stabilization of the many dimers of HNO, reveal that the decay of HNO under NO-lean conditions occurs primarily by association forming cis- and trans-(HNO)₂ at temperatures below 420 K. N₂O, which is a relatively minor product, is believed to be formed by H₂O elimination from cis-HON ? NOH, a product of succesive isomerization reactions: trans-(HNO)₂^? → HN(OH)NO^? → HN(O)NOH^? → cis-HON NOH^?. The calculated rate constants, which fit experimental data quantitatively, can be represented by k = 10^16.2 × T^?2.40e^?590/T cm³/mol sec for the HNO recombination reaction and k = 10^?2.44T^3.98e^?600/T cm³/mol sec for N₂O formation in the temperature range 80–420 K, at a total pressure of 710 torr H₂ or He. Under NO-rich conditions, HNO reacts predominantly by the exothermic termolecular reaction, HNO + 2NO → HN(NO)ONO → HN NO + NO₂, with a rate contant of (6 ± 1) × 10⁹ cm⁶/mol² sec at room temperature, based on both HNO decay and NO₂ production. All existing thermal kinetic data on HNO + HNO and HNO + 2NO processes can be satisfactorily rationalized with a unified model based on the thermochemical data obtained by BAC-MP4 calculations.     

A relative rate study of the reaction of bromine atoms with a variety of organic compounds at 295 K

The relative rate technique has been used to determine rate constants for the reaction of bromine atoms with a variety of organic compounds. Decay rates of the organic species were measured relative to i-butane or acetaldehyde or both. Using rate constants of 1.74 × 10^?15 and 3.5 × 10^?12 cm³ molecule^?1 s^?1 for the reaction of Br with i?butane and acetaldehyde respectively, the following rate constants were derived, in units of cm³ molecule^?1 s^?1: 2, 3?dimethylbutane, (6.40 ± 0.77) × 10^?15; cyclopentane, (1.16 ± 0.18) × 10^?15, ethene, (≤2.3 × 10^?13); propene, (3.85 ± 0.41) × 10^?12; trans-2-butene, (9.50 ± 0.76) × 10^?12, acetylene, (5.15 ± 0.19) × 10^?15; and propionaldehyde, (9.73 ± 0.91) × 10^?12. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure of synthetic air or nitrogen. The results are discussed with respect to the mechanisms of these reactions and their utility in serving as a laboratory source of alkyl and alkyl peroxy radicals.     

Rate coefficients and mechanisms of the reaction of cl‐atoms with a series of unsaturated hydrocarbons under atmospheric conditions

Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10^?10cm³ molecule^?1 s^?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k( MACR ) = (2.4 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10^?10 cm³ molecule^?1 s^?1; k(1‐butene) = (3.0 ± 0.4) × 10^?10 cm³ molecule^?1 s^?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH₂O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO₂ (58 ± 5%), CH₂O (47 ± 7%), CH₃OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO₂ (23 ± 2%), CH₂O (18 ± 2%), and HCOCl (5%) from MACR ; CH₂O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH₃CHO (22 ± 3%), CO₂ (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH₂O (7.6 ± 1.1%), and CH₃OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH₂O (7 ± 1%), CO₂ (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O₂‐dependent. In the case of trans‐2‐butene, the observed O₂‐dependence is the result of a competition between unimolecular decomposition of the CH₃CH(Cl)? CH(O?)? CH₃ radical and its reaction with O₂, with k_decomp/k_O2 = (1.6 ± 0.4) × 10¹⁹ molecule cm^?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol^?1. The variation of the product yields with O₂ in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH₂CH(O?)CH₂CH₃ and ?OCH₂CHClCH₂CH₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003     

Hole transport of trans-1,2-biscarbazolylcyclobutane-doped poly(bisphenol A carbonate) film

The hole transport of trans-1,2-biscarbazolylcyclobutane (CB) doped poly(bisphenol A carbonate) (PC) film has been investigated in the CB concentration range of 3.8 × 10^?4 mol cm^?3 (12 wt%) to 1.6 × 10^?3 mol cm^?3 (51 wt%). The hole mobility increased drastically with increasing CB concentration. The hole mobility was analyzed by a random hopping model. The localization radius ρ₀ of the CB/PC system was 1.9 Å, which is larger than that obtained for the N-isopropyl-carbazole-doped PC system. This suggests that the larger localization radius of the CB/PC system is related to the larger spatial extent of the CB molecule. The highest hole mobility of 2.9 × 10^?6 cm² V^?1 s^?1 was obtained when the CB concentration was 1.6 × 10^?3 mol cm^?3 (51 wt%) at E = 1.6 × 10⁵ V cm^?1 and T = 298 K. This mobility is about 10 times higher than that of poly(N-vinylcarbazole) (PVCz). The activation energy of hole mobility for the CB/PC system decreased with increasing CB concentration and was 0.31 eV at 51 wt% of CB, which is lower than the 0.45 eV for PVCz. The low activation energy for the CB/PC system is ascribed to the absence of an excimer-forming site that works as a multiple-trapping site for hole carriers.     

The reactions of S(3PJ) atoms with thiiranes

The reactions of ground-state S(³P_J) atoms with thiirane, methylthiirane, and trans-2,3-dimethylthiirane have been studied by flash photolysis-VUV kinetic absorption spectroscopy. From the analysis of the S(³P_J) decay plots the following rate constants were determined: (1.4 ± 0.2) × 10¹³, (2.7 ± 0.3) × 10¹³ and (4.0 ± 0.2) × 10¹³ (in cm³ mol^?1 s^?1 units) for thiirane, methylthiirane and trans-2,3-dimethylthiirane, respectively, showing an upward trend with increasing methylation.     

Halide‐Anion Binding by Singly and Doubly N‐Confused Porphyrins

The halide‐binding properties of N‐confused porphyrin (NCP, 1 ) and doubly N‐confused porphyrins (trans‐N₂CP ( 2 ), cis‐N₂CP ( 3 )) were examined in CH₂Cl₂. In the free‐base forms, cis‐N₂CP ( 3 ) showed the highest affinity to each anion (Cl^?, Br^?, I^?) with association constants K_a=7.8×10³, 1.9×10³, and 5.8×10² M ^?1, respectively. As metal complexes, on the other hand, trans‐N₂CP 2–Cu exhibited the highest affinity to Cl^?, Br^?, and I^? with K_a=9.0×10⁴, 2.7×10⁴, and 1.9×10³ M ^?1, respectively. The corresponding K_a values for cis‐N₂CP 3–Cu and NCP 1–Cu were about 1/10 and 1/2, respectively, of those of 2–Cu . With the help of density functional theory (DFT) calculations and complementary affinity measurements of a series of trisubstituted N‐confused porphyrins, the efficient anion binding of NCPs was attributed to strong hydrogen bonding at the highly polarized NH moieties owing to the electron‐deficient C₆F₅ groups at meso positions as well as the ideally oriented dipole moments and large molecular polarizability. The orientation and magnitude of the dipole moments in NCPs were suggested to be important factors in the differentiation of the affinity for anions.     

HPLC method with on-line SPE preconcentration for quantification of permethric acid sorption to goethite

Pesticide metabolites are often found to be more mobile in soil than their parent compounds. Pyrethroids are bound strongly to soil and therefore sorption of the pyrethroid metabolite permethric acid (PA) to a typical soil sorbent, goethite, was investigated. An on-line solid-phase extraction (SPE)-HPLC-UV procedure was developed for quantification of trans- and cis-permethric acid in aqueous samples. Limits of detection (LOD) were 500 times lower than those obtained with conventional HPLC-UV, resulting in LODs of 1.4 and 0.3?nM for the trans- and cis-isomers, respectively. Sorption of nanomolar concentrations of PA to goethite was found to be specific up to less than 1% surface coverage. In this range the data was described by a Langmuir equation with K _ads = 7.1 × 10^?9?L/mol and Γ_max = 7.1 × 10^?9?mol/m² for total PA (trans + cis) at pH = 3. K _ads,?cis (1.4 × 10⁶?L/mol) was approximately twice K _ads,?trans (7.9 × 10⁵?L/mol). At higher PA concentrations the slope of the sorption isotherm increased, which is ascribed to hydrophobic interactions between adsorbed and dissolved PA molecules. Based on comparison with reported K _om values, metal oxides are expected to have a relatively greater significance to the retention of PA than soil organic matter.     

Quenching of biacetyl (3Au) molecules by near-resonant and off-resonant collisional partners

Laser-induced time-resolved phosphorescence has been used to evaluate the quenching of gaseous biacetyl (³A_u) molecules by various molecules at 25°C. The quenching of biacetyl (³A_u) molecules by biacetyl itself was not detectable under our experimental conditions, and a pressure-independent lifetime of 1.70 ± 0.08 msec was found. The bimolecular rate constants (units of l/mol·sec) for quenching of the ³A_u molecules by cis-2-pentene, trans-2-pentene, cis-1,3-pentadiene, trans-1,3-pentadiene, and oxygen were found to be (3.3 ± 1.9) × 10³, (4.0 ± 0.2) × 10⁴, (3.9 ± 0.1) × 10⁸, (1.3 ± 0.1) × 10⁸, and (5.2 ± 0.4) × 10⁸, respectively.     

Mechanisms and kinetics of the ozonolysis reaction of cis-3-hexenyl acetate and trans-2-hexenyl acetate in atmosphere: a theoretical study

Gas-phase reaction mechanisms of ozone with cis/trans-3-hexenyl acetate and cis/trans-2-hexenyl acetate are performed using density functional theory. The reactions are initiated by the formation of the primary ozonides which are followed by the reactions of biradicals with H₂O or NO. The formation of the secondary ozonide (SOZ) is also studied. On the basis of the above DFT calculations, the modified multichannel RRKM theory is used to evaluate the rate constants. At 298 K and 101 kPa, the calculated total rate constants are 9.84 × 10^?17, 1.39 × 10^?17, 2.50 × 10^?17, and 7.37 × 10^?17 cm³ mol^?1 s^?1 for cis-3-hexenyl acetate, trans-2-hexenyl acetate, cis-2-hexenyl acetate, and trans-3-hexenyl acetate, respectively. Our results are in good agreement with experimental values. The total rate coefficients are almost pressure-independent in the range of 0.01–10,000 Torr, but show temperature dependence over the whole study range (200–2,000 K). In addition, branching ratios of the favorable reaction channels are obtained.     

Rate constants for the reactions of OH radicals with alkyl substituted olefins

Relative rate constants for the reactions of hydroxyl radicals with a series of alkyl substituted olefins were measured by competitive reactions between pairs of olefins at 298 ± 2 K and 1 atmospheric pressure. Hydroxyl radicals were produced by the photolysis of H₂O₂ with 254-nm irradiation. The obtained rate constants were (× 10^?11 cm³ molecule^?1 s^?1): 2.53 ± 0.06, propylene; 5.49 ± 0.17, cis-2-butene; 5.47 ± 0.1, isobutene; 6.46 ± 0.13, 2-methyl-1-butene; 6.37 ± 0.16, cis-2-pentene; 6.23 ± 0.1, 2-methyl-1-pentene; 8.76 ± 0.14, 2-methyl-2-pentene; 6.24 ± 0.08, trans-4-methyl-2-pentene; 10.3 ± 0.1, 2,3-dimethyl-2-butene; 9.94 ± 0.1, 2,3-dimethyl-2-pentene; 5.59 ± 0.07, trans-4,4-dimethyl-2-pentene. A trend in alkyl substituent effect on the rate constant was found, which is useful to predict k_OH on the basis of the number of alkyl substituents on the double bond.     

Rate constants for the reactions of Br atoms with a series of alkanes,alkenes, and alkynes in the presence of O2

Rate constants of Br atom reactions have been determined using a relative kinetic method in a 20 l reaction chamber at total pressures between 25 and 760 torr in N₂ + O₂ diluent over the temperature range 293–355 K. The measured rate constants for the reactions with alkynes and alkenes showed dependence upon temperature, total pressure, and the concentration of O₂ present in the reaction system. Values of (6.8 ± 1.4) × 10^?15, (3.6 ± 0.7) × 10^?14, (1.5 ± 0.3) × 10^?12, (1.6 ± 0.3) × 10^?13, (2.7 ± 0.5) × 10^?12, (3.4 ± 0.7) × 10^?12, and (7.5 ± 1.5) × 10^?12 (units: cm³ s^?1) have been obtained as rate constants for the reactions of Br with 2,2,4-trimethylpentane, acetylene, propyne, ethene, propene, 1-butene, and trans-2-butene, respectively, in 760 torr of synthetic air at 298 K with respect to acetaldehyde as reference, k = 3.6 × 10^?12 cm³ s^?1. Formyl bromide and glyoxal were observed as primary products in the reaction of Br with acetylene in air which further react to form CO, HBr, HOBr, and H₂O₂. Bromoacetaldehyde was observed as an primary product in the reaction of Br with ethene. Other observed products included CO, CO₂, HBr, HOBr, BrCHO, bromoethanol, and probably bromoacetic acid.     

TETRAETHYLPHYROPHOSPHITE AS A BRIDGING LIGAND IN A BIMETALLIC RUTHENIUM(II) - RUTHENIUM(II) COMPLEX

Abstract

The complex μ-TEPP-trans-bis[P(OEt)₃Ru(NH₃)₄]₂(PF₆)₄ has been prepared and characterized by microanalysis, vibrational and electronic spectroscopy (λ_max=299 nm, ?=6.4 × 10² M^?1 cm^?1; λ_max=262 nm, ?=8.6 × 10² M^?1 cm^?1), and cyclic voltammetry (E°'=+0.64 V versus S.C.E., 25°, μ=0.10 M NaCf₃COO, C_H+=1 × 10^?3 M). In aqueous solutions, ([H⁺] > 1 × 10^?4 M), the binuclear species undergoes hydrolysis yielding the mononuclear species trans-(Ru(NH₃)₄P(OEt)₃(H₂O)]²⁺ with a specific rate constant of 2.4 × 10^?5 sec^?1 at 25° δH^#=84.5 kJ mol^?1; δS^#=?49.4 J mol^?1 K^?1.     

Kinetics of the gas-phase reactions of Cl atoms with chloroethenes at 298 ± 2 K and atmospheric pressure

Using a relative rate technique, rate constants have been determined for the gas-phase reactions of Cl atoms with the cholorethenes and ethane at 298 ± 2 K and 735 torr total pressure of air. Using a rate constant of 1.97 × 10^?10 cm³ molecule^?1 s^?1 for the reaction of Cl atoms with n-butane, the following rate constants (in units of 10^?11 cm³ molecule^?1 s^?1) were obtained: vinyl chloride, 12.7 ± 0.2; 1,1-dichloroethene, 14.0 ± 0.2; cis-1,2-dichloroethene, 9.65 ± 0.10; trans-1,2-dichloroethene, 9.58 ± 0.18; trichloroethene, 8.08 ± 0.10; tetrachloroethene, 4.13 ± 0.23; and ethane, 6.17 ± 0.08 (where the indicated error limits do not include the uncertainties in the rate constant for n-butane). A small amount of cis-trans isomerization was observed for the reactions involving the cis- and trans-1,2-dichloroethenes. These data are compared and discussed with the available literature data.     

Polarized Raman scattering of concentrated solutions of poly(dimethyl siloxane) in benzene

Raman depolarization (ρ) measurements have been made over the temperature range 20 > T > 60°C for solutions of poly(dimethyl siloxane) (mol wt 7.7 × 10⁴ and 2.0 × 10⁴) for several concentrations up to 100%. The band studied was the highly polarized methyl stretch at 2907 cm^?1. Computer calculations of the probability p_t of a rotational isomer being trans allow the ρ values to be related to ΔG, the free energy of mixing. ΔG is plotted as a function of concentration and minima are observed at 60 ± 3% (mol wt = 7.7 × 10⁴) and 70 ± 3% (mol wt = 2 × 10⁴).     

Amperometric Biosensor for the Determination of Phenols Using a Crude Extract of Sweet Potato (Ipomoea Batatas (L.) Lam.)

Abstract

An amperometric biosensor for the determination of phenols is proposed using a crude extract of sweet potato (Ipomoea batatas (L.) Lam.) as an enzymatic source of polyphenol oxidase (PPO; tyrosinase; catechol oxidase; EC 1.14.18.1). The biosensor is constructed by the immobilization of sweet potato crude extract with glutaraldehyde and bovine serum albumin onto an oxygen membrane. This biosensor provides a linear response for catechol, pyrogallol, phenol and p-cresol in the concentration ranges of 2.0×10^?5-4.3×10^?4mol L^?1, 2.0×10^?5-4.3×10^?4 mol L^?1, 2.0×10^?5-4.5×10^?4 mol L^?1 and 2.0×10^?5-4.5×10^?4mol L^?1, respectively. The response time was about 3–5 min for the useful response range, and the lifetime of this electrode was excellent for fifteen days (over 220 determinations for each enzymatic membrane). Application of this biosensor for the determination of phenols in industrial wastewaters is presented.     

Inhibition of Emulsin by D-Gluconhydroximo-1,5-lactone and Related Compounds

At pH 4.5 (citrate buffer), D -gluconhydroximo-lactone ( 2 ), the N-methylurethane 3 and the N-phenylurethane 4 inhibit competitively the hydrolysis of p-nitrophenyl β-D -glucopyranoside by emulsin. The IC₅₀ values of 2, 3 , and 4 were 1.6 × 10^?4, 1.0 × 10^?4, and 5.8 × 10^?6 M , respectively. The K_i values of 2 and 4 were 9.8 × 10^?5 and 2.3 × 10^?6 M , respectively, while D-glucono-1,5-lactone ( 1 ) showed IC₅₀ = 1.1 × 10^?4 M and K_i = 3.7 × 10^?5 M .