The reaction of trichloromethyl radicals with hydrogen chlorid and a new estimation of the rate of combination of trichloromethyl radicals

The effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio k₈/(k₅)^1/2 to be determined. Since k_?8 is well established, k₅ can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined: The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.     

Oxygenation and chlorination of aromatic hydrocarbons with hydrochloric acid photosensitized by 9-mesityl-10-methylacridinium under visible light irradiation

Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr⁺–Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr⁺ moiety of Acr⁺–Mes, which affords the electron-transfer state, Acr^?–Mes^?+. The Mes^?+ moiety can oxidize chloride ion (Cl^?) by electron transfer to produce chlorine radical (Cl^?), whereas the Acr^? moiety can reduce O₂ to O ₂ ^?? . The Cl^? radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl^?. The benzyl radical reacts with O₂ rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr^?–Mes^?+. In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene.     

Synthesis of 3,4-dibromo-3,4,4-trichloro-1-phenylbutan-1-one and 1-aryl-2-bromo-3,4,4-trichlorobut-3-en-1-ones from 3,4,4-trichlorobut-3-enoic acid

Bromination of 3,4,4-trichlorobut-3-enoic acid in boiling carbon tetrachloride led to the formation of 2-bromo-3,4,4-trichlorobut-3-enoic acid as a result of replacement of hydrogen in the CH₂ group. The reaction at 40°C involved the double C=C bond to give 3,4-dibromo-3,4,4-trichlorobutanoic acid. The brominated acids were converted into the corresponding chlorides which were used to acylate benzene, toluene, and bromobenzene according to Friedel-Crafts. The acylation was not selective, and only the reaction of 3,4-dibromo-3,4,4-trichlorobutanoyl chloride with benzene gave 3,4-dibromo-3,4,4-trichloro-1-phenylbutan-1-one as the only product. 1-Aryl-2-bromo-3,4,4-trichlorobut-3-en-1-ones were synthesized by bromination of the corresponding 1-aryl-3,4,4-trichlorobut-3-en-1-ones which were prepared previously by Friedel-Crafts acylation of substituted benzenes with 3,4,4-trichlorobut-3-enoyl chloride.     

Rate constants for the termination of benzyl radicals in solution

The rate constant for the bimolecular combination of benzyl radicals in cyclohexane and toluene is determined as a function of temperature. Further, it is studied in cyclohexane–toluene mixtures of different compositions. In the entire range covered, 9.8 × 10⁸ ? 2k_t ? 9.0 × 10⁹M^?1·sec^?1, the data are very well described by the Smoluchowski equation for a diffusion-controlled reaction to ground-state products using a spin statistical factor of 1/4, a temperature- and solvent-independent reaction distance, and the known diffusion coefficient of toluene.     

Polymerization of vinyl chloride and copolymerization with carbon monoxide by a new initiator

The system comprising the ethoxydized product of triethylaluminum, cuprous chloride, and carbon tetrachloride was used as an initiator for polymerization of vinyl chloride, and the polymerization kinetics was studied. From plots of the molar number of number-average polymer chain Y/P? versus yield Y, the two parameters a ( = ∫ R_idt ? 1/2 ∫ R_tdt) and b ( = ∫ R_trdt/∫ R_pdt) were estimated to be 6 × 10^?3 mole/l. and 6.6 × 10^?4 respectively. Studies of the tacticity of the poly(vinyl chloride) showed isotactic = 49.3% and syndiotactic = 50.7%. The present initiator also permitted copolymerization of vinyl chloride with carbon monoxide; the monomer reactivity ratios were r₁ = 0.40 (vinyl chloride) and r₂ = 0.01 (carbon monoxide).     

Polymerization of aromatic nuclei. XIV. Polymerization of toluene with aluminum chloride–cupric chloride

The polymerization of toluene with aluminum chloride and cupric chloride was performed in carbon disulfide and in a neat system. The solvent reaction produced an insoluble, light-brown product which did not melt below 350°C. In the neat system, polymerization was much more vigorous, yielding a dark, purple-brown solid with mp ～250°C and molecular weight of 634. Infrared, NMR, and ultraviolet spectroscopy, along with elemental analysis and oxidative degradation, indicated that the backbone chain contains o-polyphenylene units with the methyl group situated in the 4-position. Some p-polyphenylene structures may also be present. Evidence for small amounts of benzyl and polynuclear moieties was obtained. The mechanistic aspects are discussed. Our principal conclusions concerning oligomer structure are in disagreement with those of Kuwata.     

Room temperature rate constants for the reaction of OH with selected chlorinated and oxygenated hydrocarbons

A study was conducted to measure the hydroxyl radical rate constants using a relative rate procedure in which the photolysis of methyl nitrite was the source of OH. During the course of this study, the OH rate constant was measured for a number of chlorinated solvents for which measurements have not previously been reported or for which there are few reliable measurements. Room temperature OH rate constants are presented for six chlorinated hydrocarbons (allyl chloride, benzyl chloride, chlorobenzene, epichlorohydrin, trichloroethylene, and vinylidene chloride) and four oxygenated hydrocarbons (acrolein, methacrolein, methyl ethyl ketone, and propylene oxide). Also included are OH rate constants for alkanes (ethane, propane, isobutane, and cyclohexane), alkenes (trans?2-butene and isoprene), and aromatic hydrocarbons (benzene, toluene, o^?, m^?, and p-xylene). Rate constants for compounds not previously reported include vinylidene chloride (1.49 ± 0.21 × 10^?11 cm³ molecule^?1 s^?1) and benzyl chloride (2.96 ± 0.15 × 10^?12 cm³ molecule^?1 s^?1). The analysis for chlorinated hydrocarbons included a correction for possible chlorine atom reactions.     

Kinetics and products of the gas-phase reactions of the OH radical and O3 with allyl chloride and benzyl chloride at room temperature

The kinetics of the gas-phase reactions of allyl chloride and benzyl chloride with the OH radical and O₃ were investigated at 298 ± 2 K and atmospheric pressure. Direct measurements of the rate constants for reactions with ozone yielded values of ??(O₃ + allyl chloride) = (1.60 ± 0.18) × 10^?18 cm³ molecule^?1 s^?1 and ??(O₃ + benzyl chloride) < 6 × 10^?20 cm³ molecule^?1 s^?1. With the use of a relative rate technique and ethane as a scavenger of chlorine atoms produced in the OH radical reactions, rate constants of ??(OH + allyl chloride) = (1.69 ± 0.07) × 10^?11 cm³ molecule^?1 s^?1 and ??(OH + benzyl chloride) = (2.80 ± 0.19) × 10^?12 cm³ molecule^?1 s^?1 were measured. A study of the OH radical reaction with allyl chloride by long pathlength FT-IR absorption spectroscopy indicated that the co-products ClCH₂CHO and HCHO account for ca. 44% of the reaction, and along with the other products HOCH₂CHO, (ClCH₂)₂CO, and CH₂ ? CHCHO account for 84 ± 16% of the allyl chloride reacting. The data indicate that in one atmosphere of air in the presence of NO the chloroalkoxy radical formed following OH radical addition to the terminal carbon atom of the double bond decomposes to yield HOCH₂CHO and the CH₂Cl radical, which becomes a significant source of the Cl atoms involved in secondary reactions. A product study of the OH radical reaction with benzyl chloride identified only benzaldehyde and peroxybenzoyl nitrate in low yields (ca. 8% and ?4%, respectively), with the remainder of the products being unidentified.     

Physical and chemical properties of hydroxyflavones. IV. Infrared absorption spectra of dihydroxyflavones containing the 5-hydroxyl group

Solid state infrared curves (O-H and C-H stretching region) are given for 5, n-dihydroxyflavones, where n is 2′, 3′, 4′, 6, 7 and 8. In chloroform solution spectra of 3,5-dihydroxyflavone and 3-hydroxy-5-methoxyflavone, the 3-OH stretching band appears at 3400 and 3334 cm^?1, respectively, indicative of a stronger hydrogen bond in the latter substance. Solid state and solution carbonyl bands are presented for twenty-six flavone derivatives which contain a hydroxyl, methoxyl or acetoxyl group at the 5-position. The solution spectra (dioxane or carbon tetrachloride) of fourteen flavone derivatives containing a free 5-hydroxyl group show carbonyl bands at 1655±2 cm^?1. Eleven flavones in which the 5-hydroxyl is blocked (carbon tetrachloride solution) give spectra with flavone carbonyl bands at 1653±3 cm^?1. The high resolution chloroform solution spectrum of 3, 5-dihydroxyflavone possesses a multi-peaked carbonyl band with midpoint at 1641 cm^?1. The chloroform solution spectrum of 3-hydroxy-5-methoxyflavone has a very strong band at 1616 cm^?1, with shoulder at 1646 cm^?1. Spectral data of this and a previous paper support the postulate that in 4′-hydroxyflavone the flavone carbonyl oxygen is the donor atom in an intermolecular hydrogen bond. Certain details of synthesis, and analytical data, are given for 3, 5-dihydroxyflavone.     

Kinetics of the oxidation of nitric oxide by chlorine and oxygen in nonaqueous media

The kinetics of the reaction between nitric oxide and chlorine have been investigated in both carbon tetrachloride and glacial acetic acid. The nitric oxide-oxygen reaction has been investigated in carbon tetrachloride. The appearance of product, NOCl or NO₂, was monitored spectrophotometrically at a wavelength of 475 nm for NOCl and 343 nm for NO₂. These measurements were performed using an Amino-Morrow stopped-flow apparatus equipped with a Beckman D U monochromator. The data for both the NO? Cl₂ and NO? O₂ systems could be fitted to the third-order integrated equation and the calculated rate constants were 2.75 × 10³ M^?2 s^?1 and 2.79 × 10⁶ M² s^?1, respectively, at 25.1°C. There was a noted increase in rate constants on changing the solvent from carbon tetrachloride to acetic acid. The likelihood of a termolecular encounter is inherent in the mechanism, however, no real evidence to substantiate either a direct termolecular or a series of two bimolecular steps has been obtained, although a ?7 kcal for ΔH⁰ would support the latter.     

Metal-containing initiator systems. VI. Polymerization of butadiene with metal–organic halide systems

The polymerization of butadiene with binary initiator systems consisting of some activated metals and organic halides was investigated at 60°C. From the results obtained, it was found that systems of reduced nickel and methyltrichlorosilane or dimethyldichlorosilane were most effective for the polymerization, and those of reduced nickel and carbon tetrachloride, benzyl chloride, benzyl bromide and benzoyl chloride, showed moderate activity. The polybutadienes obtained with these systems were observed to contain product of more than 80% cis-1,4 microstructure. From detailed studies on the reduced nickel–methyltrichlorosilane system, these polymerization mechanisms were explained by the hypothesis that the initiation occurred through the reaction of the dissociated transition state complex with the monomer or with a trace amount of water, and then the propagation proceeded via a coordinated cationic mechanism. These systems did not show a good activity for the cis-1,4 polymerization of isoprene.     

Base-catalyzed hydrogen isotope exchange and the aqueous acidity of toluene

Measurements of hydrogen isotope exchange of toluene-α-d and -α-t in aqueous sodium hydroxide are reported for temperatures of 150–200°C. The reaction shows essentially no primary isotope effect. The rate extrapolated to 24°C is combined with the rate constant for reaction of benzyl anion with water obtained earlier by Bockrath and Dorfman⁸ to derive the aqueous pk_a, of toluene as 39.6 (per hydrogen basis).     

Relative rates of nucleophilic reactions of benzyl carbocation formed in photolysis of benzyl chloride and benzyl acetate in aqueous solution

Benzyl chloride and benzyl acetate were photolyzed in 30% methanol–water mixtures (V/V) at 0°C. The photolysis produces benzyl carbocations that react with nucleophiles. The reaction products were analyzed by gas chromatography or liquid chromatography. From the amounts of products the relative values of rate constants of reactions of benzyl carbocation with nucleophiles N and water k(N)/k(H₂O) were calculated. Benzyl carbocation reacts with I^?, Br^?, Cl^?, and Ac^? ions with approximately diffusion-controlled rate. A value of 2.4 × 10⁷ dm³ mol^?1 s^?1 for the rate constant k(H₂O) and a lifetime of 0.7 ns were estimated for benzyl carbocation in the aqueous solution.     

Mechanism of Thermal Toluene Autoxidation

Aerobic oxidation of toluene (PhCH₃) is investigated by complementary experimental and theoretical methodologies. Whereas the reaction of the chain‐carrying benzylperoxyl radicals with the substrate produces predominantly benzyl hydroperoxide, benzyl alcohol and benzaldehyde originate mainly from subsequent propagation of the hydroperoxide product. Nevertheless, a significant fraction of benzaldehyde is also produced in primary PhCH₃ propagation, presumably via proton rather than hydrogen transfer. An equimolar amount of benzyl alcohol, together with benzoic acid, is additionally produced in the tertiary propagation of PhCHO with benzylperoxyl radicals. The “hot” oxy radicals generated in this step can also abstract aromatic hydrogen atoms from PhCH₃, and this results in production of cresols, known inhibitors of radical‐chain reactions. The very fast benzyl peroxyl‐initiated co‐oxidation of benzyl alcohol generates HO₂^. radicals, along with benzaldehyde. This reaction also causes a decrease in the overall oxidation rate, due to the fast chain‐terminating reaction of HO₂^. with the benzylperoxyl radicals, which causes a loss of chain carriers. Moreover, due to the fast equilibrium PhCH₂OOH+HO₂^.?PhCH₂OO^.+H₂O₂, and the much lower reactivity of H₂O₂ compared to PhCH₂OOH, the fast co‐oxidation of the alcohol means that HO₂^. gradually takes over the role of benzylperoxyl as principal chain carrier. This drastically changes the autoxidation mechanism and, among other things, causes a sharp decrease in the hydroperoxide yield.     

Polymerization of phenylacetylene by triethyl aluminum and titanium tetraethoxide

The polymerization of phenylacetylene to polyphenylacetylene was accomplished with the combined catalysts triethyl aluminum and titanium tetraethoxide. The progress of the reaction was monitored by gas chromatography. The parameters included temperature (?80, 25, 140°C), solvent (benzene, chlorobenzene, toluene, cyclohexane, and nitrobenzene), mole ratio of catalysts (Al/Ti; 1.5, 3.0, 4.5, 6.0, and 9.0), aging times of catalysts (2, 10, and 40 min), and order of addition of reagents. Derivatives of polyphenylacetylene were obtained by the acylation of polyphenylacetylene with p-nitrobenzoyl chloride, the sulfonation of polyphenylacetylene with benzenesulfonyl chloride, and the formation of polyphenylacetylene complexes with complexing agents such as bromine, iodine, iodine chloride, boron trifluoride, and ferric chloride. A new phenylacetylene-acetylene product mixture was produced by the polymerization of phenylacetylene and acetylene at 25 and ?80°C. The electrical conductivity of polyphenylacetylene and its derivatives is in the range of 10^?10?10^?3 Ω^?1 cm^?1.     

Determination of Phthalate Esters in Wine Using Dispersive Liquid–Liquid Microextraction and Gas Chromatography

A simple and rapid efficient method was developed for the determination of phthalate esters using dispersive liquid–liquid microextraction followed by gas chromatography with flame ionization detection. A mixture of isopropanol (0.75 mL, dispersant) and carbon tetrachloride (30 µL, extractant) with sodium chloride (1%, w/v) was used for extraction. Under optimum conditions, the method provided linear calibration curves between 0.5 and 200 µg L^?1 for dibutyl phthalate, and 1.0 and 200 µg L^?1 for butyl benzyl phthalate, diethyl phthalate, and diisooctyl phthalate. The relative standard deviations for intra-day and inter-day analyses were less than 5.8% and 6.9%, respectively, with enrichment factors between 229 and 424. Two wine samples were analyzed with recoveries between 70.1% and 119.3%.     

Sorption of organic vapors by polystyrene

Activity coefficients of benzene, toluene, cyclohexane, carbon tetrachloride, chloroform, and dichloromethane in binary solutions with polystyrene at 23.5°C have been determined using a piezo-electric sorption apparatus. The investigated solvent concentration ranges were 15 to 39 wt % for benzene, 14 to 29 wt % for toluene, 15 to 28 wt % for cyclohexane, 26 to 38 wt % for carbon tetrachloride, 24 to 46 wt % for chloroform, and 21 to 41 wt % for dichloromethane. The polystyrene (weight-averaged) molecular weights were 1.1 × 10⁵ and 6.0 × 10⁵ g/gmole. The weight-fraction activity coefficients (Ω₁ = a₁/w₁) of cyclohexane, toluene, and carbon tetrachloride in polystyrene solutions determined in this work agree within experimental error with previously published values determined by measurement of vapor pressure lowering and vapor absorption by thin films. We find disagreement, at low solvent concentrations, between our results for benzene and chloroform and previously published results. We have analyzed our results using Flory's version of corresponding-states polymer solution theory. The theory can account, qualitatively, for the cyclohexane and carbon tetrachloride results. It cannot account for the toluene, benzene, dichloromethane, or chloroform results.     

Kinetics and activation energy of the oxidation of para‐tolyl radical by cobalt(III) in acetic acid: Competition kinetics

The title reaction gives rise to a benzylic cation that is rapidly transformed to its bromide in competition with the reaction of the radical with carbon tetrachloride. Experiments were carried out over 17–69°C in acetic acid containing cobalt(II) acetate, para‐xylene, hydrobromic acid, carbon tetrachloride, and meta‐chloroperoxybenzoic acid. The product ratio, ArCH₂Cl/ArCH₂Br, in combination with other pertinent rate constants, was used to determine the rate constant for the step of interest: log k (L mol^?1 s^?1 = 19.9 – (75 ± 11 kJ mol^?1/2.303 RT). The large pre‐exponential factor, which gives ΔS? = 128 J K^?1 mol^?1, signals an unusual transition state, because a negative value of ΔS? would be expected for a simple bimolecular reaction. The production of the ion pair ArCH‖OAc^? in HOAc, which has the same dielectric constant as benzene, may be responsible, at least in part. Furthermore, inner sphere reorganization of cobalt may also contribute. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 599–604, 2005     

Excess volume of mixing of some polar and nonpolar liquids with propylene carbonate

The excess volume of mixing as a function of composition has been measured at 30°C and 40°C for mixtures of propylene carbonate with nitrobenzene, chlorobenzene, benzene, toluene, cyclohexane, dioxane, carbon tetrachloride, and chloroform. The highly polar nitrobenzene forms an ideal mixture with propylene carbonate. Chloroform, carbon tetrachloride, dioxane, chlorobenzene, benzene, and toluene give negative volume changes on mixing. In mixtures with cyclohexane,V _m ^E is positive at lower mole fractions of cyclohexane but becomes negative as the mole fraction of cyclohexane increases.     

The mechanism in the elimination kinetics of 2-chloropropionic acid in the gas phase

The elimination kinetics of 2-chloropropionic acid have been studied over the temperature range of 320–370.2°C and pressure range of 79–218.5 torr. The reaction in seasoned vessel and in the presence of the free radical suppressor cyclohexene, is homogeneous, unimolecular, and obeys a first-order rate law. The dehydrochlorination products are acetaldehyde and carbon monoxide. The rate coefficient is expressed by the following Arrhenius equation: log k₁(s^?1) = (12.53 ± 0.43) – (186.9 ± 5.1) kJ mol^?1 (2.303RT)^?1. The hydrogen atom of the carboxylic COOH appears to assist readily the leaving chloride ion in the transition state, suggesting an intimate ion pair mechanism operating in this reaction.