Acrylonitrile rate constants

Teruel, M.A., M.B. Blanco, and GR. Luque (2007), Atmospheric fate of acryhc acid and acrylonitrile Rate constants with Cl atoms and OH radicals in the gas phase, Atmos. Environ., 41, 5769-5777. 

Dir, whereas for small distances d < r), /r Did. The large effective obtainable enables fast heterogeneous reaction rates to be measured under steady-state conditions. Zhou and Bard measured a rate constant of 6 x 10 Ms for the electro-hydrodimerization of acrylonitrile (AN) and observed the short-lived intennediate AN for this process [65]. 

Giese and Kretzschmar7j found the rate of addition of hexenyl radicals to methyl acrylate increased 2-fold between aqueous tetrahydrofuran and aqueous ethanol, Salikhov and Fischer74 reported that the rate constant for /-butyl radical addition to acrylonitrile increased 3.6-fold between tetradecane and acetonitrile. Bednarek et al75 found that the relative reactivity of S vs MMA towards phenyl radicals was ca 20% greater in ketone solvents than it was in aromatic solvents. 

Absolute rate constants for addition reactions of cyanoalkyl radicals are significantly lower than for unsubstituted alkyl radicals falling in the range 103-104 M V1.341 The relative reactivity data demonstrate that they possess some electrophilic character. The more electron-rich VAc is very much less reactive than the electron-deficient AN or MA. The relative reactivity of styrene and acrylonitrile towards cyanoisopropyl radicals would seem to show a remarkable temperature dependence that must, from the data shown (Table 3.6), be attributed to a variation in the reactivity of acrylonitrile with temperature and/or other conditions. 

Waters61 have measured relative rates of p-toluenesulfonyl radical addition to substituted styrenes, deducing from the value of p + = — 0.50 in the Hammett plot that the sulfonyl radical has an electrophilic character (equation 21). Further indications that sulfonyl radicals are strongly electrophilic have been obtained by Takahara and coworkers62, who measured relative reactivities for the addition reactions of benzenesulfonyl radicals to various vinyl monomers and plotted rate constants versus Hammett s Alfrey-Price s e values these relative rates are spread over a wide range, for example, acrylonitrile (0.006), methyl methacrylate (0.08), styrene (1.00) and a-methylstyrene (3.21). The relative rates for the addition reaction of p-methylstyrene to styrene towards methane- and p-substituted benzenesulfonyl radicals are almost the same in accord with their type structure discussed earlier in this chapter. 

Other substituted olefins such as acrylonitrile, fumaronitrile, crotono-nitrile, cinnamonitrile, and diethylfumarate also formed adducts with Co (DMG)2 complexes containing py, H2O, or PBuj and, in one case, with [Co (DMG-BF2)2py]. Second-order rate constants were reported for the formation of several Tr-olefin-Co(I) complexes from organocobalt(III) complexes containing, for example, NCCH2CH2- with DMG, DPG, DMG-BF, py, H2O, and PBuj. 

On the other hand, the use of a-cyclodextrin decreased the rate of the reaction. This inhibition was explained by the fact that the relatively smaller cavity can only accommodate the binding of cyclopentadiene, leaving no room for the dienophile. Similar results were observed between the reaction of cyclopentadiene and acrylonitrile. The reaction between hydroxymethylanthracene and N-ethylmaleimide in water at 45°C has a second-order rate constant over 200 times larger than in acetonitrile (Eq. 12.2). In this case, the P-cyclodextrin became an inhibitor rather than an activator due to the even larger transition state, which cannot fit into its cavity. A slight deactivation was also observed with a salting-in salt solution (e.g., quanidinium chloride aqueous solution). 

The principal pathway leading to degradation of acrylonitrile in air is believed to be photooxidation, mainly by reaction with hydroxyl radicals (OH). The rate constant for acrylonitrile reaction with OH has been measured as 4.1 x 10" cm /molecule/second (Harris et al. 1981). This would correspond to an atmospheric half-life of about 5 to 50 hours. This is consistent with a value of 9 to 10 hours measured in a smog chamber (Suta 1979). 

Thereafter, the reaction between the coordinated dienoate ligand in 106 and acrylonitrile was examined (Scheme 12). Surprisingly, this reaction is complete within 56 h (pseudo-first-order rate constant k — 1.4 x 10-5 s-1, ti/2 ca. 0.5 day) and affords only two products 107a and 107b in a ratio of 57 43 (or the correepsonding acids 103a,b via acid hydrolysis). Thus, in... 

The formation of the hydrogen bond between hydroperoxide and polar monomer, for example, methyl acrylate or acrylonitrile, does not influence the rate constant of the reaction of hydroperoxide with the double bond of monomer [101]. The values of the rate constants of the reaction of hydroperoxide with olefins are given in Table 4.13. The effect of multidipole interaction was observed for reactions of hydroperoxide with polyfunctional monomers (see Table 4.14, Ais the Gibbs energy of multidipole interaction in the transition state). 

The dependence of relative rates in radical addition reactions on the nucleophilicity of the attacking radical has also been demonstrated by Minisci and coworkers (Table 7)17. The evaluation of relative rate constants was in this case based on the product analysis in reactions, in which substituted alkyl radicals were first generated by oxidative decomposition of diacyl peroxides, then added to a mixture of two alkenes, one of them the diene. The final products were obtained by oxidation of the intermediate allyl radicals to cations which were trapped with methanol. The data for the acrylonitrile-butadiene... 

On treatment with acrylonitrile in 2% aqueous sodium hydroxide at 0°, tetrahydropyran-2-yl /3-D-glucopyranoside gave the 2-, 3-, 4-, and 6-0-(2-cyanoethyl) ethers (together with some diethers) in yields that, on extrapolation to zero reaction, showed3 9 k2 k3 k4 k6 to be in the ratios of 3 1 2 8 these values represent equilibrium, not rate, constants. The tendency for substitution at 0-6 is a consequence of the greater stability of an ether derived from a primary (compared to a secondary) hydroxyl group, as a result of lower steric interactions in the former. 

TABLE 2. Rate constants for the Diels-Alder reaction of cyclopentadiene and acrylonitrile in different solvents... 

Photolytic. In an aqueous solution at 50 °C, UV light photooxidized acrylonitrile to carbon dioxide. After 24 h, the concentration of acrylonitrile was reduced 24.2% (Knoevenagel and Himmelreich, 1976). A rate constant of 4.06 x 10 cmVmolecule-sec at 26 °C was reported for the vapor-phase reaction of acrylonitrile and OH radicals in air (Harris et al., 1981). 

Chemical/Physical. Ozonolysis of acrylonitrile in the liquid phase yielded formaldehyde and the tentatively identified compound glyoxal, an epoxide of acrylonitrile and acetamide. The reported rate constant for the reaction of acrylonitrile and ozone in the gas phase is 1.38 x lO cm moFsec (Munshi et al., 1989). In the gas phase, cyanoethylene oxide was reported as an ozonolysis product... 

The hydrolysis rate constant for acrylonitrile at pH 2.87 and 68 °C was determined to be 6.4 x 10 Vh, resulting in a half-life of 4.5 d. At 68.0 °C and pH 7.19, no hydrolysis or disappearance was observed after 2 d. However, when the pH was raised to 10.76, the hydrolysis half-life was calculated to be 1.7 h (Ellington et al., 1986). Acrylonitrile hydrolyzes to acrylamide which undergoes additional hydrolysis forming acrylic acid and ammonia (Kollig, 1993). 

The reactions of 1,2,3-triazolium 1-imide (277) with a range of alkene and alkyne dipolarophiles give rise to a variety of new ring systems (Scheme 54). Compounds (276) and (278) are obtained from (277) by reaction with acrylonitrile and DMAD, respectively. These reactions are tandem 1,3-dipolar (endo) cycloadditions and sigmatropic rearrangements which are regio- and stereospecific <90JCS(Pl)2537>. Kinetic and mechanistic studies show that these reactions are dipole-HOMO controlled. The second-order rate constants are insensitive to solvent polarity, the reaction indicates... 

Confirmation was provided by the observation that the species produced by the photolysis of two different carbene sources (88 and 89) in acetonitrile and by photolysis of the azirine 92 all had the same strong absorption band at 390 nm and all reacted with acrylonitrile at the same rate (fc=4.6 x 10 Af s" ). Rate constants were also measured for its reaction with a range of substituted alkenes, methanol and ferf-butanol. Laser flash photolysis work on the photolysis of 9-diazothioxan-threne in acetonitrile also produced a new band attributed the nitrile ylide 87 (47). The first alkyl-substituted example, acetonitrilio methylide (95), was produced in a similar way by the photolysis of diazomethane or diazirine in acetonitrile (20,21). This species showed a strong absorption at 280 nm and was trapped with a variety of electron-deficient olefinic and acetylenic dipolarophiles to give the expected cycloadducts (e.g., 96 and 97) in high yields. When diazomethane was used as the precursor, the reaction was carried out at —40 °C to minimize the rate of its cycloaddition to the dipolarophile. In the reactions with unsymmetrical dipolarophiles such as acrylonitrile, methyl acrylate, or methyl propiolate, the ratio of regioisomers was found to be 1 1. 

Pulsed-laser photolysis of the azirines 158a-c in the presence of electron-dehcient alkenes (44,66) allowed the determination of the bimolecular quenching rate constants (feq) for reactions with acrylonitrile (1.0-5.4 x 10 and... 

Chain growth continues at a rate dependent on the concentrations of monomer [M] and of active sites [MJ. Monomer exponents in the range 1.3 to 1.5 or higher had been observed (110, 123, 127) especially at low [M], but first order dependence has now been established over a broad range of [M] (21). A stationary level of [M ] is reached rapidly and is typically of the order of 10-8 molar. Chains grow rapidly by successive monomer additions until the polymer chain is terminated by transfer or by reaction with another radical. The rate constant for propagation (ft2) at 60° in DMF is 1960 m-1 Is-1 (16), which is a comparatively high value [see Table 1 and ref. (76)]. On the other hand it is only about one-tenth of that found for acrylonitrile in aqueous systems (Table 6)... 

Rate constants have been measured for the capture of para-substituted phenylchloro-carbenes by chloride ions to form aryldichloromethide carbanions and for the additions of these carbanions to acrylonitrile.144 A conventional interpretation of the Hammett correlations has suggested that the reactions of carbenes with Cl- traverse early transition states. 

In designing multicomponent coupling reactions, the nature of the individual components is obviously a key factor. Generally speaking, carbon radical species, such as alkyl radicals, aryl radicals, vinyl radicals, and acyl radicals are all classified as nucleophilic radicals, which exhibit high reactivity toward electron-deficient alkenes [2]. To give readers some ideas about this, kinetic results on the addition of tert-butyl and pivaloyl radicals are shown in Scheme 6.2. These radicals add to acrylonitrile with rate constants of 2.4 x 106 M-1 s 1 and 5 x 105 M-1 s-1 at... 

Table I. Pseudo first-order rate constants for Michael addition of sulfur Nucleophiles (5 mM) to aciylic acid and acrylonitrile in seawater medium (salinity 35 and reaction pH 8.3 0.2)...

The addition of alkyl radicals to alkenes is important for C-C bond formation. A tert-butyl radical, a typical nucleophilic radical, reacts with acrylonitrile taking a rate constant of 2.4 X 106 M-1 s-1 (27 °C), through a SOMO-LUMO interaction. However, it reacts with 1-methylcyclohexene, an electron-rich alkene, taking a rate constant of 7.4 X 102M-1 s-1 (21 °C). On the other hand, the diethyl malonyl radical, a typical electrophilic radical, shows the opposite reactivity [66-71]. Similarly, the rate constant for the reaction of nucleophilic C2H5 and cyclohexene is2X 102 M 1 s 1, while that of electrophilic C3F7 with cyclohexene is 6.2 X 105 M-1 s 1. 

An acyl radical is also nucleophilic. For example, the rate constant of (CH3)3CC0 (te/T-butylcarbonyl radical, pivaloyl radical) with acrylonitrile is 4.8 X 105 M-1 s-1 (25 °C), and so its addition reaction proceeds effectively [72]. 

The preceding discussion has led us to the conclusion that the surface is the only locus of polymerization which needs to be considered in the heterogeneous polymerization of acrylonitrile. Radicals arrive at the surface at a rate determined by the decomposition of the initiator and efficiency of initiation. Propagation occurs on the surface at a rate determined by the activity of monomer at the surface. By analogy with emulsion polymerization, where monomer diffuses into the particles rapidly enough to maintain near equilibrium activity (14), we assume that the activity of the monomer adsorbed on the particle surface is approximately equal to the mole fraction in solution. The propagation rate constant is presumably influenced somewhat by the presence of the solid surface. 

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