Kinetics of reaction of methyl α-eleostearate with phenol

The kinetics of addition reactions between methyl α-eleostearate which forms the main chain of tung oil and phenol when catalyzed by an acid, p-toluene sulfonic acid, have been studied. The addition reactions, carried out with phenol was shown to be second order with regard to methyl α-eleostearate concentration and first order with regard to phenol concentration. The reactions were additions of two phenol molecules to one methyl α-eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step is rate determining: ((1)) ((2)) The apparent reaction rate constant (l/mol min) was found to be 0.036 and its value was nearly equal to that in the case of m-cresol. The apparent activation energie (kcal/mol) was found to be 4.76 and its value was larger than that in the case of m-cresol.     

Rearrangements in the mass spectra of α-phenylcinnamic acid and its derivatives

The electron impact ionization and collisional activation mass spectra of α-phenylcinnamic acid and its derivatives have been studied. The loss of a phenylic hydrogen is not an important process in these molecules, unlike the unsubstituted cinnamic acids. However, in o-chloro-α-phenylcinnamic acid and its methyl and trimethylsilyl derivatives loss of Cl resulting in the formation of 2-substituted-3-phenylbenzopyrilium ion is an important fragmentation pathway. The rearrangement ions observed at m/z 118 and 107 in the Spectrum of α-phenylcinnamic acid have been found to have the structures of the M⁺˙ of benzofuran and PhCH?$ \mathop {\rm O}\limits^{\rm +} $H, respectively. The ion at m/z 121 in the spectrum of the methyl ester of α-phenylcinnamic acid has been found to have the structure PhCH?$ \mathop {\rm O}\limits^{\rm +} $Me.     

Thermal stability of alcohols

3,3-Dimethylbutanol-2 (3,3-DMB-ol-2) and 2,3-dimethylbutanol-2 (2,3-DMB-ol-2) have been decomposed in comparative-rate single-pulse shock-tube experiments. The mechanisms of the decompositions are The rate expressions are They lead to D(iC₃H₇? H) – D((CH₃)₂(OH) C? H) = 8.3 kJ and D(C₂H₅? H) – D(CH₃(OH) CH? H) = 24.2 kJ. These data, in conjunction with reasonable assumptions, give and The rate expressions for the decomposition of 2,3-DMB-1 and 3,3-DMB-1 are and      

Hydrolysis of 2-aminoethanethiolsulfate ions

The kinetics of the acid catalyzed hydrolysis of 2-aminoethanethiolsulfate (AETS) ions were investigated. The dependence of the hydrolysis rate constant on acidity and temperature was determined. The hydrolysis rate equation can be expressed as where H_o is the Hammett acidity function. The rate constant, k, can be expressed as The pK_a's for the compound were measured and literature value of pK_a was found to be in error. The values determined in this study are pK_a1 < ?0.5 and pK_a2 = 9.1 ± 0.1. General acid catalysis of the hydrolysis reaction was found not to proceed to a significant degree. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Kinetics and mechanism of the reaction between N-and N,N′-methyl ethylenediamines and palladium(II) chloro complexes in aqueous acid medium

The substitution of N-alkyl substituted ethylenediamines for chloride ions in the rapidly equilibrating system has been investigated in aqueous acid medium. The kinetic data can be accommodated by the general rate law where n = 0, 1, or 2 and m = 0, 1, or 2, depending on whether none, one, or two methyl groups are attached to the two nitrogen atoms of ethylenediamine. Reaction with the most heavily substituted ethylenediamine, namely, N₂N₂en discloses a change of the mentioned rate law to on going from a lower to a higher chloride ion concentration range. This change in the mathematical form of the rate law can be explained in terms of an ion-pair association of N₂N₂enH⁺ and free chloride ions.     

The kinetics of thermal dimerization of hexatriene

The thermal isomerization of cis-hexatriene (cHT) to cyclohexadiene (CHD) and the dimerization of CHD and trans-hexatriene (tHT) in the liquid phase in the temperature range 380 K-473 K are reported. The rate coefficients are: for the cHT to CHD isomerization for tHT dimerizationlog and for CHD dimerization; endo form exo form © 1993 John Wiley & Sons, Inc.     

The self-inhibited pyrolysis of isobutane

The pyrolysis of isobutane was investigated in the ranges of 770° to 855°K and 20 to 150 Torr at up to 4% decomposition. The reaction is homogeneous and strongly self-inhibited. A simple Rice-Herzfeld chain terminated by the recombination of methyl radicals is proposed for the initial, uninhibited reaction. Self-inhibition is due to abstraction of hydrogen atoms from product isobutene giving resonance-stabilized 2-methylallyl radicals which participate in termination reactions. The reaction chains are shown to be long. It is suggested that a previously published rate constant for the initiation reaction (1) is incorrect and the value k₁ = 10^16.8 exp (?81700 cal mol^?1/RT)s^?1 is recommended. The values of the rate constants for the reactions (4i) (4t) (8) are estimated to be and From a recalculation of previously published data on the pyrolysis of isobutane at lower temperatures and higher pressures, the value k_11c, = 10^9.6 cm³ mol^?1 s^?1 is obtained for the rate constant of recombination of t-butyl. A calculation which is independent of any assumed rate constants or thermochemistry shows that the predominant chain termination reaction is the recombination of two methyl radicals in the conditions of the present work and the recombination of two t-butyl radicals in those of our previous study at lower temperatures and higher pressures.     

Pyrolysis of 2,4-dimethylhexene-l and the stability of isobutenyl radicals

2,4-Dimethylhexene-l has been decomposed in single-pulse shock tube experiments. Rate expressions for the initial reactions are and sec^?1 at 1.5–5 atm and 1050°K. This leads to ΔH^°_f300 (CH₂ = C(CH₃)CH₂) = 124 kJ/mol, or an allylic resonance energy of 50 kJ/mol. Rate expressions for the decomposition of the appropriate olefins which yield isobutenyl radicals and methyl, ethyl, isopropyl, n-propyl, t-butyl, and t-amyl radicals, respectively, are presented. The rate expression for the decomposition of isobutenyl radical is (at the beginning of the fall-off region). For the combination of isobutenyl and methyl radicals, the rate constant at 1020°K is Combination of this number and the calculated rate expression for 2-methylbutene-1 decomposition gives S. (1100) = 470 J/mol °K. This yields It is demonstrated that an upper limit for the rate of hydrogen abstraction by isobutenyl from toluene is      

Pyrolysis of Propyne/2-Methylbut-1-ene-3-yne mixtures between 350 and 450°C

2-Methylbut-1-ene-3-yne and Propyne mixtures were pyrolyzed at 350–450°C in the absence and presence of O₂ and NO. The major product of the reaction is a polymer, but m-xylene and p-xylene are also produced and were studied as the species of interest. The C₈H₁₀ formation rate is first-order in C₃H₄ and C₅H₆. The rate coefficient is best fitted by though it is not inconsistent with where R is the ideal gas constant in kJ/mol-K. Experiments in the presence of NO show that m-xylene and p-xylene formation occur by two processes: a concerted molecular mechanism (? 41%) and a singlet diradical mechanism (? 59%).     

The addition of methyl radicals to hexafluoroacetone

The reaction of methyl radicals (Me) with hexafluoroacetone (HFA), generated from ditertiary butyl peroxide (dtBP), was studied over the temperature range of 402–433 K and the pressure range of 38–111 torr. The reaction resulted in the following displacement process taking place: where TFA refers to trifluoroacetone. The trifluoromethyl radicals that were generated abstract a hydrogen atom from the peroxide: such that k_6a is given by: where θ = 2.303RT kcal/mol. The interaction of methyl and trifluoromethyl radicals results in the following steps: Product analysis shows that k₁₇/kk = 2.0 ± 0.2 such that k₁₇ = 10^10.4±0.5M^?1 · s^?1. The rate constant k₅ is given by: It is concluded that the preexponential factor for the addition of methyl radicals to ketones is lower than that for the addition of methyl radicals to olefins.     

Phase equilibria in systems containing o-cresol,p-cresol,carbon dioxide,and ethanol at 323.15–473.15 K and 10–35 MPa

Phase equilibria in binary and ternary systems containing o-cresol, p-cresol, carbon dioxide, and ethanol have been investigated experimentally at temperatures between 323.15 K and 473.15 K and pressures ranging from 10 MPa to 35 MPa. The experimental results provide a systematic basis of phase equilibrium data, yielding the effect of temperature on the influence of the position of the methyl groups of cresols that are in phase equilibria with carbon dioxide. Based on the different solubilities of the cresol isomers in carbon dioxide, the separation of o-cresol and p-cresol was investigated. The dependence of the separation factor between both cresol isomers on concentration, temperature, and pressure is obtained from experiments in the ternary system, o-cresol+p-cresol+carbon dioxide. The influence of ethanol added to each of the binary systems, cresol isomer+carbon dioxide, in order to enhance the solubility of the cresols in the carbon dioxide-rich phase is also shown. The experimental data have been correlated using seven different equations of state, whereof four explicitly account for intermolecular association: Statistical Association Fluid Theory (SAFT) by Chapman, Gubbins, Huang and Radosz, the SAFT modification by Pfohl and Brunner for near-critical fluids, a modified cubic-plus-association equation of state (CPA EOS) according to the ideas by Tassios et al., and one of the EOS by Anderko. The mixing rule proposed by Mathias, Klotz, and Prausnitz, with two binary interaction parameters per binary system influencing intermolecular attractive forces, is used for all EOS as a basis for an objective comparison of the EOS.     

Gas phase thermolysis of aryl t-butyl amines

N-t-butylaniline, N-t-butyl-p-anisidine, and N-t-butyl-p-nitroaniline have been pyrolyzed in a stirred-flow reactor at 510–620°C, 8–15 torr total pressure, and 0.5–1.5 s contact time, using toluene as carrier gas. An order one kinetics was observed for the consumption of the amines. The reactions yielded 95 ± 2% isobutene plus the corresponding anilines as reaction products. The rate coefficients followed the Arrhenius equations N–t–butylaniline N-t-butyl-p-anisidine N-t-butyl-p-nitroaniline The results are consistent with an unimolecular elimination of isobutene involving polar four-center cyclic transition states. © John Wiley & Sons, Inc.     

Effect of olefins on the thermal decomposition of propane part I. The model reaction

Study of the thermal decomposition of propane at very low conversions in the temperature range 760–830 K led to refinement of the mechanism of the reaction. The quotient V/V characterizing the two decomposition routes connected with the 1- and 2-propyl radicals proved to depend linearly on the initial propane concentration. This suggested the occurrence of intermolecular radical isomerization: in competition with decomposition of the 2-propyl radical: The linearity led to the conclusion that the selectivity of H-abstraction from the methyl and methylene groups by the methyl radical is practically the same as that by the H atom. The temperature-dependence of this selectivity ( μ = kCH₃/kCH₂) was given by Further evaluation of the dependence gave the Arrhenius representation for the ratio of the rate coefficients of the above isomerization and decomposition reactions. Steady-state treatment resulted in the rate equation of the process, comparison of which with measurements gave further Arrhenius dependences.     

Neue,ungewöhnlich verlaufende Arylierungen der 1,5-Dihydroxy-4,8-diaminoanthrachinon-2,6-disulfonsäure mit Kresolen

A novel course of a phenylation reaction of 1,5-dihydroxy-4,8-diaminoanthraquin-one-2,6-disulfonic acid with cresols . The arylation of 1,5-dihydroxy-4,8-diaminoanthraquinone-2,6-disulfonic acid with m-cresol in conc. sulfuric acid gives in the presence of boric acid a mixture of monosulfonic acids which differ in the substitution of the m-cresol moiety. The main product ( 8 , 95%) is substituted at the p-position to the methyl group, the side product ( 12 , 5%) at the p-position to the OH group. The monosulfonic acid 8 , which could not be isolated is further sulfonated under the reaction conditions to the disulfonic acid 9 . In the case of o-cresol, the cresol moiety is substituted in the p-position ( 16 ) to OH group and in the case of p-cresol in the o-position ( 20 ) to OH group. The obtained monosulfonic acids 16 and 20 resp. are partially sulfonated further under the reaction conditions. The new structures are elucidated by ¹H- and ¹³C-NMR. spectroscopy and the pattern of arylation reaction with phenol is discussed.     

The kinetics of free radical chain reactions in solutions of trichlorofluorethylene in cyclohexane

The kinetics of the gamma-radiation-induced free radical chain reaction in solutions of C₂Cl₃F in cyclohexane (RH) was investigated over a temperature range of 87.5–200°C. The following rate constants and rate constant ratios were determined for the reactions: In competitive experiments in ternary solutions of C₂Cl₄ and C₂Cl₃F in cyclohexane the rate constant ratio k_2c/k_2a was determined By comparing with previous data for the addition of cyclohexyl radicals to other chloroethylenes it is shown that in certain cases the trends in activation energies for cyclohexyl radical addition can be correlated with the C? Cl bond dissociation energies in the adduct radicals.     

An FTIR product study of the reaction between HCO and NO2

The product distribution of the reaction (1a) $$\rm\longrightarrow OH+NO+CO$$ (1b) $$\rm\longrightarrow HNO+CO_{2}$$ (1c) $$\rm\longrightarrow H+NO+CO_{2}$$ (1d) $$\rm\longrightarrow HCO_{2}+NO$$ (1e) (1f) (1g) was investigated at room temperature in the gas phase in Ar buffer gas at 570 mbar pressure by Fourier transform infrared (FTIR) spectroscopy. Mixtures of NO₂/H₂CO/Ar were photolyzed under stationary conditions using a high‐pressure Hg lamp at λ = 300–340 nm. NO, CO, CO₂, HONO, and H₂O were found as major reaction products. A small amount of N₂O was detected at long reaction times. From the yields of CO and CO₂, branching ratios were found to be (k_1a + k_1b)/k₁ = (0.66 ± 0.10) and (k_1c + k_1d + k_1e)/k₁ = (0.34 ± 0.10). The formation of HONO was attributed to reaction ( 1a ) and/or reaction ( 1c ) followed by the reaction HNO + NO₂ → NO + HONO with a combined branching ratio of (k_1a + k_1c)/k₁ = (0.28 ± 0.10). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 136–145, 2000     

Hammerstein integral equivalent of Riccati's equation

A transformation exists which allows the general Riccati equation to be written in a simpler form: The transformed equation has the equivalent nonlinear Hammerstein integral equation if the kernel N(r, r′) satisfies three conditions: and and A solution of the nonlinear integral equation is devised by repeatedly integrating the Hammerstein equation. During this procedure the kernel generates an equation that contains only coefficients of β(r)⁰ and β(r)¹. As a result, after truncating at the end of the nth cycle, it is a simple matter to write down a Padé-type approximation: all coefficients in this approximation are capable of being evaluated in terms of simple algebraic formulations of P(r), R(r), and integrals over P(r). The zeroes of the denominator of the Padé-type approximation define the points where singularities occur in β(r).     

The rate constant for t-C4H9 → H + i-C4H8 and the thermodynamic parameters of t-C4H9

The rate of the reverse reaction of the system has been measured in the range of 584–604 K from a study of the azomethane sensitized pyrolysis of isobutane. Assuming the published value for the rate constant of recombination of t-butyl we obtain Combination with our published data for k₁ permits the evaluation We have modified a previously published structural model of t-butyl by the inclusion of a barrier to free rotation of the methyl groups in order to calculate values of the entropy and enthalpy of t-butyl as a function of temperature. Using standard data for H and for i-C₄H₈ we obtain We have obtained other, independent values of this quantity by a reworking of published data using our new calculations of the entropy and enthalpy of t-butyl. There is substantial agreement between the different values with one exception, namely, that derived from published data on the equilibrium which is significantly lower than the other values. We conclude that the value obtained from the present work and a reworking of published data which involves the use of experimental data on t-butyl recombination is incompatible with the result based on iodination data.     

H2S-promoted thermal isomerization of butene-2 CIS to butene-1 or butene-2 trans around 500°C

H₂S increases the thermal isomerization of butene-2 cis (B_c) to butene-1 (B₁) and butene-2 trans (B_t) around 500°C. This effect is interpreted on the basis of a free radical mechanism in which buten-2-yl and thiyl free radicals are the main chain carriers. B₁ formation is essentially explainedby the metathetical steps: whereas the free radical part of B_t formation results from the addition–elimination processes: . It is shown that the initiation step of pure B_c thermal reaction is essentially unimolecular: and that a new initiation step occurs in the presence of H₂S: . The rate constant ratio has been evaluated: and the best values of k₁ and k_1', consistent with this work and with thermochemical data, are . From thermochemical data of the literature and an “intrinsic value” of E_?3 ? 2 kcal/mol given by Benson, further values of rate constants may be proposed: is shown to be E₄ ? 3.5 ± 2 kcal/mol, of the same order as the activation energy of the corresponding metathetical step.