Rates of reaction between the nitrate radical and some aliphatic ethers

Rate coefficients for the reaction of NO₃ with dimethyl ether, diethyl ether, di-n-propyl ether, and methyl t-butyl ether (MTBE) have been determined. Absolute rates were measured at temperatures between 258 and 373 K using the fast flow-discharge technique. Relative rate experiments were also made at 295 K in a reactor equipped with White optics and using FTIR spectroscopy to follow the reactions. The measured rate coefficients (in units of 10^?15 cm³ molecule^?1 s^?1) at 295 K are: 0.26 ± 0.11, 2.80 ± 0.23, 6.49 ± 0.65, and 0.64 ± 0.06 for dimethyl ether, diethyl ether, di-n-propyl ether, and methyl t-butyl ether, respectively. The corresponding activation energies are 21.0 ± 5.0, 17.2 ± 4.0, 15.5 ± 2.1, and 20.1 ± 1.7 kJ mole^?1. The error limits correspond to the 95%-confidence interval. © 1994 John Wiley & Sons, Inc.     

Electron Capture Gas Chromatography of Nitrazepam in Human Plasma as Methyl Derivative

Abstract

A method for quantitative determination of nitrazepam in human plasma in the range 5 - 100 ng/ml is presented.

Nitrazepam is extracted with benzene from plasma samples of 0.5 ml, methylated with methyl iodide and determined gas chromatographically with an electron capture detector of ⁶³Ni-type.

Acid dissociation constants of nitrazepam are determined and the partition properties studied with benzene, methylene chloride and diethyl ether as organic phases.

The selectivity of the method with respect to the metabolites has been thoroughly studied.     

New Camphor Derivatives Functionalized at C3 and C10

Base-catalyzed condensation of 10-methylenecamphor with diethyl oxalate gave the corresponding (Z)-3-ethoxycarbonyl(hydroxy)methylene derivative which was converted into methyl ether and acetate. The Z-methyl ether undergoes isomerization into the E-methyl ether on treatment with N-bromosuccinimide in the presence of radical initiator [azobis(isobutyrodinitrile)]. (Z)-3-Ethoxycarbonyl(hydroxy)methylene-10-methylenecamphor smoothly reacts with N-bromosuccinimide to afford stereoisomeric 3-bromo derivatives.     

Cationic Polymerization of Isobutyl Vinyl Ether in Solution by Radiation

The radiation-induced cationic polymerization of isobutyl vinyl ether in solutions of diethyl ether and methylene chloride was investigated under conditions where the monomer and solvents were dried with molecular sieves to high levels of dryness. The investigation covered the temperature range from -16 to 90° C, the dose-rate range from 10¹⁵ to 10²⁰ eV/ (g)(sec) (using both gamma rays and electrons), and the influence of diethyl ether and methylene chloride as solvents for the monomer.

For the solution of the monomer in diethyl ether, a very high overall activation energy of 29.7 kcal/mole was found, which decreased sharply to a value of 1.2 kcal/mole above 30° C. No such change was found for the monomer solution in methylene chloride.

The dose-rate dependence of the rate of polymerization for the monomer solution in methylene chloride was found to be close to unity over the entire dose-rate range investigated.     

Reformatsky Reaction with N-Substituted 6-Bromo-2-oxochromene-3-carboxamides

Reformatsky reactions of ethyl -bromopropionate, methyl -bromobutyrate, and methyl -bromo-isobutyrate with N-substituted 6-bromo-2-oxochromene-3-carboxamides in the system diethyl ether–benzene– HMPA give N-benzyl-6-bromo-4-(1-alkoxycarbonylalkyl)-2-oxochroman-3-carboxamides, while in the system diethyl ether–benzene–HMPA–THF, 3-R¹-1-R²-1-R³-9-bromo-2,3,4,4a,5,10b-hexahydro-1H-chromeno[3,4-c]-pyridine-2,4,5-triones are obtained.     

Rate constants for the gas‐phase reactions of Cl atoms with a series of ethers

The laser photolysis–resonance fluorescence technique has been used to determine the absolute rate coefficient for the Cl atom reaction with a series of ethers, at room temperature (298 ± 2) K and in the pressure range 15–60 Torr. The rate coefficients obtained (in units of cm³ molecule⁻¹ s⁻¹) are dimethyl ether (1.3 ± 0.2) × 10⁻¹⁰, diethyl ether (2.5 ± 0.3) × 10⁻¹⁰, di‐n‐propyl ether (3.6 ± 0.4) × 10⁻¹⁰, di‐n‐butyl ether (4.5 ± 0.5) × 10⁻¹⁰, di‐isopropyl ether (1.6 ± 0.2) × 10⁻¹⁰, methyl tert‐butyl ether (1.4 ± 0.2) × 10⁻¹⁰, and ethyl tert‐butyl ether (1.5 ± 0.2) × 10⁻¹⁰. The results are discussed in terms of structure–reactivity relationship. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 105–110, 2000     

Heterogeneous Parahydrogen-Induced Polarization of Diethyl Ether for Magnetic Resonance Imaging Applications

Magnetic resonance imaging (MRI) with the use of hyperpolarized gases as contrast agents provides valuable information on lungs structure and function. While the technology of ¹²⁹Xe hyperpolarization for clinical MRI research is well developed, it requires the expensive equipment for production and detection of hyperpolarized ¹²⁹Xe. Herein we present the ¹H hyperpolarization of diethyl ether vapor that can be imaged on any clinical MRI scanner. ¹H nuclear spin polarization of up to 1.3 % was achieved using heterogeneous hydrogenation of ethyl vinyl ether with parahydrogen over Rh/TiO₂ catalyst. Liquefaction of diethyl ether vapor proceeds with partial preservation of hyperpolarization and prolongs its lifetime by ≈10 times. The proof-of-principle 2D ¹H MRI of hyperpolarized diethyl ether was demonstrated with 0.1×1.1 mm² spatial and 120 ms temporal resolution. The long history of use of diethyl ether for anesthesia is expected to facilitate the clinical translation of the presented approach.     

A simplified synthesis of the hexamethylplatinate(IV) ion

Tetra-n-butylammonium hexachloroplatinate (IV) reacts with lithium methyl/lithium iodide in ether to give a solution containing lithium hexamethylplatinate (IV). With lithium methyl/lithium bromide in ether however, tetrabutylammonium hexamethylplatinate (IV) is precipitated together with lithium halides. Solid [Bu₄N)₂[Pt(Ch₃)₆] is stable under nitrogen at room temperature, but ether solutions of [Pt(Ch₃)₆]^2- decompose in a few minutes at room temperature in the absence of excess lithium methyl.     

Temperature dependence of the rate coefficients for the reactions of Br atoms with dimethyl ether and diethyl ether

The rate constants for the reactions of atomic bromine with dimethyl ether and diethyl ether were measured from approximately 300 to 350 K using the relative rate method. Both isooctane and isobutane were used as the reference reactants, and the rate constants for the reactions of these hydrocarbons were measured relative to each other over the same temperature range. The kinetic measurements were made by photolysis of dilute mixtures of bromine, the reference reactant, and the test reactant in mixtures of argon and oxygen at a total pressure of 1 atm. The resulting ratios of rate constants were combined with the absolute rate constant as a function of temperature for the reference reaction of Br with isobutane to calculate absolute rate constants for the reactions of Br with isooctane, dimethyl ether, and diethyl ether. The absolute rate constant, in the units cm3 molecule(-1) s(-1), for the reaction of Br with dimethyl ether was given by k = (3.8 +/- 2.4) x 10(-10) exp(-(3.54 +/- 0.21) x 10(3)/T) while for the reaction of Br with diethyl ether the rate constant is given by k = (2.8 +/- 2.7) x 10(-10) exp(-(2.44 +/- 0.32) x 10(3)/T). On the same basis, the rate constant for the reaction of Br with isooctane is given by k = (3.34 +/- 0.59) x 10(-12) exp(-(1.80 +/- 0.11) x 10(3)/T). In each case, the activation energy of the reaction is significantly smaller than the endothermicity of the reaction. This is discussed in terms of a complex mechanism for these reactions.     

A novel synthesis of 3′-deoxy-3′-nitrothymidine via nucleophilic substitution with nitrite anion

Nucleophilic substitution at C3′ of 1-(2-deoxy-5-O-trityl-β-D-erythr-pentofuranosyl)-2-methoxy-5-methyl-4(1H)-pyrimidinone (5) with methyl iodide/triphenylphosphine/diethyl azodicarboxylate gave the expected inverted iodide 6 and minor epimer 7 . Treatment of 6 with lithium nitrite/phloroglucinol yielded the desired nitro derivative 8 and subsequent acidic deprotection afforded the title compound 1 . This represents a novel method for the introduction of a nitro group into the furanosyl moiety of a nucleoside. The nmr spectroscopic techniques (COSY, NOESY, nOe, HMQC and HMBC) were used to determine the stereochemistry at C3′ of the nucleosides. Spectral analysis of H-D exchange at the 3′-position of 1 did not indicate the formation of its epimer 10 .     

Manganese(III)–Arsenic(III) Reaction Catalyzed by Some Antidotic Oxime Iodides

Manganese(III)–arsenic(III) reaction in the presence of sulfuric acid is proposed in this work as an indicator reaction for the kinetic determination of some antidotic oxime iodides. As 2-hydroxyiminomethyl-1-benzyl-3-methylimidazolium iodide, 2-hydroxyiminomethyl-3-benzyl-1-[3-(2-hydroxyiminomethyl-3-benzyl-1-imidazolio)-2-oxapropyl]-imidazolium diiodide, and 2-[(hydroxyimino)methyl]-1-methylpyridinium iodide catalyze the proposed reaction, a kinetic method for their determination in the range from 1.0 × 10⁻⁸to 8.0 × 10⁻⁸mol dm⁻³was developed. The effect of some other antidotic oximes on the accuracy of these determinations was investigated.     

Anionic synthesis of in-chain 3° amine-functionalized polybutadienes

Anionic copolymerizations of butadiene (M₁) with excess 1-(4-dimethylaminophenyl)-1-phenylethylene (M₂) were conducted in benzene at room temperature for 24–48h using sec-butyllithium as initiator. Anisole, triethylamine and t-butyl methyl ether were added in ratios of [B]/[RLi] = 60, 20, 30, respectively, to promote copolymerization. Narrow molecular weight distribution copolymers with M̄n = 14 × 10³ to 32 × 10³ g/mol (M̄_w/M̄n =1.02–1.03) and 8,12 and 30 amine groups per chain for anisole, triethylamine and t-butyl methyl ether, respectively, were obtained. The butadiene monomer reactivity ratios (r1) were 42, 33 and 14 for anisole, triethylamine and t-butyl methyl ether, respectively.     

1-Methyl-2(3,4)-(1-vinylpyrrol-2-yl)pyridinium iodides: some structural features revealed by 1H and 13C NMR spectroscopy

The reactions of 2-, 3-, and 4-(1-vinylpyrrol-2-yl)pyridines with methyl iodide afford the corresponding quaternary salts. Analysis of their ¹H and ¹³C NMR spectra showed that the quaternization of the nitrogen atom considerably enhances the -acceptor effect of the pyridine ring on the pyrrole ring and on the vinyl group. 1-Methyl-2-(1-vinylpyrrol-2-yl)pyridinium iodide contains no weak intramolecular C--H...N hydrogen bond present in the starting compound.     

Cationic Surfactant Ion-Selective PVC Membrane Electrode Containing Macrocyclic Diimine Crown Ether

ABSTRACT

DP⁺ ion-selective PVC membrane electrode based on 2,3,11,12-dibenzo-5,9-diaza-4,9(10)-cis-diimino-1,13-dioxacyclopentadecane as a novel macrocyclic diimine crown ether is proposed. o-Nitrophenyl octyl ether as plasticizer and potassium tetrakis(4-chlorophenyl)borate as lipophilic salt were used. The electrode exhibits a Nernstian response for 1.0 x 10^?2-1.0 x 10^?6 mol 1^?1 DPCl with a slope of 58 mVdecade^?1. The detection limit is 2.5 x 10^?7 mol 1^?1. The electrode response was stable over a wide pH range (3-11). The lifetime of the electrode was about 2 months. The electrode shows a high selectivity towards inorganic cations. Among the organic cations tested, only hexadecyltrimethylammonium ion interferes. The electrode was suitable for determining the critical micelle concentration and as an end-point detector in the potentiometric titration of the cationic surfactants.     

Determination of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea by reaction with 2,4-dinitro-β-henylethylamine

A method for the determination of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) in body fluids is described. After extraction from urine or plasma with diethyl ether, methyl is treated with 2,4-dinitro-β-phenylethylamine to. The urea is separated of the amine and treated with trifluacetic anhydride; the trifluoroacetyl derivative is quantified by gas chromatography. Calibration graphs were linear urine, plasma and aqueous standards of metal-CCNU over the range 0.4–2.0 μg ml. The limits of detection for methyl-CCNU are in urine and 0.08 μg ml^?1 in plasma.     

Preparation and Properties of a Chromatographic Adsorbent Based on γ-Alumina Modified with Octylphosphonic Acid Diethyl Ester

Aluminum oxide modified with octylphosphonic acid diethyl ether with the concentration of bound groups equal to 3.4 nm^–2 (6.6% C) was synthesized. The retention times and Kovats indices were determined for pentane, hexane, heptane, benzene, methyl ethyl ketone, nitromethane, pyridine, and ethanol.     

Determination of chloramphenicol at ultra-trace levels by high-performance differential pulse polarography: Application to Milk and Meat

High-performance differential pulse polarography (h.p.d.p.p.) is used to determine the antibiotic chloramphenicol. Optimum operating conditions are discussed. Calibration curves are linear from 10 ng ml^-1 to 1 μg ml^-1; the detection limit is about 3 ng ml^-1. Above 1 μg ml^-1, deviations from linearity occur, because of adsorption of chloramphenicol at the mercury electrode. A correction, based on variations in natural drop time, is suggested. Chloramphenicol is readily extracted from milk or minced meat with diethyl ether. The ether is evaporated, and the residue is taken up in acetate buffer pH 4.7 and filtered through a membrane filter. Recoveries from samples fortified at levels of 10–1000 ng ml^-1 are about 60% for milk and 50% for minced meat.     

Formation of Methyl Iodide in the Radiolysis of Aqueous Cesium Iodide and Acetic Acid Solutions

Volatile compounds of radioactive iodine, including methyl iodide, are released into the environment in the cases of serious accidents at nuclear power plants. The aim of this study was to find a conceivable mechanism of the radiation-chemical formation of methyl iodide in aerated aqueous solutions of cesium iodide and acetic acid. This provides the basis for subsequent investigations aimed at preventing the formation of methyl iodide. The radiation-chemical yield of methyl iodide formation in 10^–3M CsI solutions containing CH₃COOH (0.1 mol/l) decreased with increasing the pH. This fact is primarily explained by a decrease in the steady-state concentration of molecular iodine with increasing the pH. An increase in the pH of irradiated solutions up to pH 9 was found not only to prevent the formation of methyl iodide but also to enhance its radiation-chemical degradation.     

Reaction products of methyl tricyclo[4.1.0.02,7]heptane-1-carboxylate and tricyclo[4.1.0.02,7]hept-1-yl phenyl sulfone with dinitrogen tetraoxide

The reaction of methyl tricyclo[4.1.0.0^2,7]hepatne-1-carboxylate with dinitrogen tetraoxide in diethyl ether at ?10 to 0°C, followed by treatment of the reaction mixture with methanol, gave approximately equal amounts of methyl exo,syn-6,7-dinitro-and exo-6-hydroxy-syn-7-nitrobicyclo[3.1.1]heptane-endo-6-carboxylates. Tricyclo[4.1.0.0^2,7]hept-1-yl phenyl sulfone reacted with dinitrogen tetraoxide under analogous conditions to produce a mixture of diastereoisomeric exo,syn-and endo,syn-6,7-dinitro-6-phenylsulfonylbicyclo-[3.1.1]heptanes and 6,6-dimethoxy-endo-7-nitrobicyclo[3.1.1]heptane at a ratio of 4.5:2:1. Probable factors responsible for the different stereoselectivities in the addition of N₂O₄ at the central C¹-C⁷ bond of the initial tricycloheptane compounds were discussed. The structural parameters of the dinitro ester and related dinitro sulfone were compared on the basis of the X-ray diffraction data.     

Perfluoroalkylated eight- and nine-membered benzoheterocycles from F-2-methyl-2-pentene

The reactions of $\text{F}$-2-methyl-2-pentene (1) with several $\text{ortho}$- difunctional benzenes afforded eight- and nine-membered benzoheterocyclic compounds carrying perfluoroalkyl groups. Salicylic acid, salicylaldehyde, and their methyl or chloro derivatives reacted in triethylamine-acetonitrile system giving perfluoroalkylated 2H,6H-1,5-benzodioxocin-2,6-dione (8) and 4H,6H-1,5-benzodioxocin (9) compounds respectively, while phthalyl alcohol and o-hydroxyphenethyl alcohol in triethylamine-diethyl ether system gave perfluoroalkylated 1H,3H,7H-2,6- and 4H,6H,7H-1,5-benzodioxonin compounds, (10) and (11). o-Aminobenzyl alcohol and (1) in diethyl ether afforded a perfluoroalkylated benzoxazocinobenzoxazocinone compound (15).