Excess enthalpies of binary mixtures of 2-, 3-, 4-picoline+n-alkane (C6H14-C10H22) at 298.15 K. Comparison with theory

The molar excess enthalpies measured for binary mixtures of 2-, 3-, 4-picoline +n-alkane (C₆H₁₄-C₁₀H₂₂) at 298.15 K have been compared with the Prigogine-Flory-Patterson theory and the Extended Real Associated Solution model estimations.

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Zusammenfassung Die bei 298.15 K gemessenen molaren Zusatzenthalpien binärer Mischungen aus 2-,3-,4-Picolin und einemn-Alkan (C₆H₁₄-C₁₀H₂₂) wurden mit den nach der Prigonine-Flory-Patterson-Theorie und den nach dem erweiterten Modell real assoziierter Lösungen (ERAS) berechneten Weiten verglichen.

     

Unexpected Chemistry from the Reaction of Naphthyl and Acetylene at Combustion‐Like Temperatures

The hydrogen abstraction/acetylene addition (HACA) mechanism has long been viewed as a key route to aromatic ring growth of polycyclic aromatic hydrocarbons (PAHs) in combustion systems. However, doubt has been drawn on the ubiquity of the mechanism by recent electronic structure calculations which predict that the HACA mechanism starting from the naphthyl radical preferentially forms acenaphthylene, thereby blocking cyclization to a third six‐membered ring. Here, by probing the products formed in the reaction of 1‐ and 2‐naphthyl radicals in excess acetylene under combustion‐like conditions with the help of photoionization mass spectrometry, we provide experimental evidence that this reaction produces 1‐ and 2‐ethynylnaphthalenes (C₁₂H₈), acenaphthylene (C₁₂H₈) and diethynylnaphthalenes (C₁₄H₈). Importantly, neither phenanthrene nor anthracene (C₁₄H₁₀) was found, which indicates that the HACA mechanism does not lead to cyclization of the third aromatic ring as expected but rather undergoes ethynyl substitution reactions instead.     

Gas-Phase Synthesis of Triphenylene (C18H12)

For the last decades, the hydrogen-abstraction−acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C₁₄H₉]^.) with vinylacetylene (C₄H₄), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH – triphenylene (C₁₈H₁₂) – via an unconventional hydrogen abstraction–vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level.     

Rates of reaction of atomic oxygen with C2H3F,C2H3Cl,C2H3Br, 1,1-C2H2F2, and 1,2-C2H2F2

Rate constants for the reactions of atomic oxygen (O³P) with C₂H₃F, C₂H₃Cl, C₂H₃Br, 1,1-C₂H₂F₂, and 1,2-C₂H₂F₂ have been measured at 307°K using a discharge-flow system coupled to a mass spectrometer. The rate constants for these reactions are (in units of 10¹¹ cm³ mole^?1 s^?1) 2.63 ± 0.38, 5.22 ± 0.24, 4.90 ± 0.34, 2.19 ± 0.18, and 2.70 ± 0.34, respectively. For some of these reactions, the product carbonyl halides were identified.     

Rate constants for the reactions of C2H5O,i‐C3H7O,and n‐C3H7O with NO and O2 as a function of temperature

The rate constants of the reactions of ethoxy (C₂H₅O), i‐propoxy (i‐C₃H₇O) and n‐propoxy (n‐C₃H₇O) radicals with O₂ and NO have been measured as a function of temperature. Radicals have been generated by laser photolysis from the appropriate alkyl nitrite and have been detected by laser‐induced fluorescence. The following Arrhenius expressions have been determined: (R₁) C₂H₅O + O₂ → products k₁ = (2.4 ± 0.9) × 10⁻¹⁴ exp(−2.7 ± 1.0 kJmol⁻¹/RT) cm³ s⁻¹ 295K < T < 354K p = 100 Torr (R₂) i‐C₃H₇O + O₂ → products k₂ = (1.6 ± 0.2) × 10⁻¹⁴ exp(−2.2 ± 0.2 kJmol⁻¹/RT) cm³ s⁻¹ 288K < T < 364K p = 50–200 Torr (R₃) n‐C₃H₇O + O₂ → products k₃ = (2.5 ± 0.5) × 10⁻¹⁴ exp(−2.0 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 289K < T < 381K p = 30–100 Torr (R₄) C₂H₅O + NO → products k₄ = (2.0 ± 0.7) × 10⁻¹¹ exp(0.6 ± 0.4 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 388K p = 30–500 Torr (R₅) i‐C₃H₇O + NO → products k₅ = (8.9 ± 0.2) × 10⁻¹² exp(3.3 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 389K p = 30–500 Torr (R₆) n‐C₃H₇O + NO → products k₆ = (1.2 ± 0.2) × 10⁻¹¹ exp(2.9 ± 0.4 kJmol⁻¹/RT) cm³s⁻¹ 289K < T < 380K p = 30–100 Torr All reactions have been found independent of total pressure between 30 and 500 Torr within the experimental error. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 860–866, 1999     

Reactivity of the Indenyl Radical (C9H7) with Acetylene (C2H2) and Vinylacetylene (C4H4)

The reactions of the indenyl radicals with acetylene (C₂H₂) and vinylacetylene (C₄H₄) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C₉H₇^.) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C₆H₅^.) and acetylene forming phenylacetylene (C₆H₅CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol⁻¹) and slow, contrary to the exoergic (−38 kJ mol⁻¹) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces.     

Isotropic C6, C8 and C10 interaction coefficients for CH4, C2H6, C3H8, n-C4H10 and cyclo-C3H6

The non-empirical generalized Kirkwood, Unsöld, and the single-Δ Unsöld methods (with double-zeta quality SCF wave-functions) are used to calculate isotropic dispersion (and induction) energy coefficients C_2n, with n ? 5, for interactions involving ground state CH₄, C₂H₆, C₃H₈, n-C₄H₁₀ and cyclo-C₃H₆. Results are also given for the related multipole polarizabilities α_l, multipole sums S₁/(0) and S₁(?1) which are evaluated using sum rules, and the permanent multipole moments. for l = 1 (dipole) to l = 3 (octupole). Estimates of the reliability of the non-empirical methods, for the type of molecules considered, are obtained by a comparison with accurate literature values of α₁S₁(?1) and C₆. This, and the asymptotic properties of the multipolar expansion of the dispersion energy, the use to discuss recommended representation for the isotropic long range interaction energies through R^?10 where R is the intermolecular separation.     

Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO

The rate coefficients for the gas-phase reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O₂, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C₂H₅ radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C₃H₇O₂ + NO reaction, yielding k_{298 K} = (9.1 ± 1.5) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10⁻¹² exp{(380 ± 70)/T} cm³ molecule⁻¹ s⁻¹ and k(T) = (2.9 ± 0.5) × 10⁻¹² exp{(350 ± 60)/T} cm³ molecule⁻¹ s⁻¹ for the reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for C₂H₅O₂ radicals and k = (9.4 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for n-C₃H₇O₂ radicals. © 1996 John Wiley & Sons, Inc.     

Kinetics of the reactions of C2H5, n‐C3H7, and n‐C4H9 radicals with Cl2 at the temperature range 190–360 K

The kinetics of the C₂H₅ + Cl₂, n‐C₃H₇ + Cl₂, and n‐C₄H₉ + Cl₂ reactions has been studied at temperatures between 190 and 360 K using laser photolysis/photoionization mass spectrometry. Decays of radical concentrations have been monitored in time‐resolved measurements to obtain reaction rate coefficients under pseudo‐first‐order conditions. The bimolecular rate coefficients of all three reactions are independent of the helium bath gas pressure within the experimental range (0.5–5 Torr) and are found to depend on the temperature as follows (ranges are given in parenthesis): k(C₂H₅ + Cl₂) = (1.45 ± 0.04) × 10^?11 (T/300 K)^{?1.73 ± 0.09} cm³ molecule^?1 s^?1 (190–359 K), k(n‐C₃H₇ + Cl₂) = (1.88 ± 0.06) × 10^?11 (T/300 K)^{?1.57 ± 0.14} cm³ molecule^?1 s^?1 (204–363 K), and k(n‐C₄H₉ + Cl₂) = (2.21 ± 0.07) × 10^?11 (T/300 K)^{?2.38 ± 0.14} cm³ molecule^?1 s^?1 (202–359 K), with the uncertainties given as one‐standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are ±20%. Current results are generally in good agreement with previous experiments. However, one former measurement for the bimolecular rate coefficient of C₂H₅ + Cl₂ reaction, derived at 298 K using the very low pressure reactor method, is significantly lower than obtained in this work and in previous determinations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 614–619, 2007     

Tests of a free-volume model for the permeation of gas mixtures through polymer membranes. CO2-C2H4, CO2-C3H8, and C2H4-C3H8 mixtures in polyethylene

Steady-state permeability coefficients have been measured for equimolar mixtures of CO₂-C₂H₄, CO₂-C₃H₈, and C₂H₄-C₃H₈, as well as for a mixture of 74.9 mol % CO₂ and 25.1 mol % C₂H₄ in polyethylene membranes. The measurements were made at 20, 35, and 50°C and at pressures of up to 28 atm. Each component of the permeating mixtures studied had the effect of increasing the permeability coefficient for the other component. Furthermore, at equal partial pressures and at the same temperature, the component exhibiting the highest solubility in the polymer had the largest effect in increasing the permeability coefficient of the other component. This behavior is in agreement with the predictions of a free-volume model for the permeation of gas mixtures proposed by Fang, Stern, and Frisch. From a quantitative viewpoint, the permeability coefficients for the components of the mixtures agreed, on the average, to better than 25% with the predicted values. The theoretical permeability coefficients can be estimated from the model by using parameters determined with the pure components only.     

Dynamics simulation and reaction pathway analysis of characteristics of soot particles in ethylene oxidation at high temperature

Soot particles characteristics were investigated numerically for high temperature oxidation of C₂H₄/O₂/N₂ (C/O ratio of 2.2) in a closed jet-stirred/plug-flow reactor (JSR/PFR) system. Based on the growth mechanism of polycyclic aromatic hydrocarbons (PAHs), two mechanisms were used to explore the formation pathways of soot precursors and soot. Numerical results were compared with the experimental and reference data. The simulation results show that the value predicted for small molecule intermediates within A1 gives a strong regularity, consistent trend with reference data. However, with the hydrogen-abstraction-carbon-addition (HACA) growth mechanism, the predicted value for beyond-A1 PAH macromolecules and soot volume fraction are smaller than the experimental data. The results also show that the predicted soot volume fraction is in good agreement with experimental data when a combination of the HACA and PAHs condensation (HACA + PAH-PAH) growth mechanisms is used. Analyses of the A1 sensitivity and reaction pathway elucidated that A1 are mainly formed from C₂H₃, C₂H₂, C₃H₃, C₆H₅OH, A1C₂H and A1-. The reaction 2C₃H₃ → A1 is the dominant route of benzene formation. The prediction results and an analysis of the A3 reaction pathway indicate that the growth process from benzene to larger aromatic hydrocarbons (beyond two-ring polycyclic aromatic hydrocarbons [PAHs]) goes by two pathways, i.e., HACA combined with the PAH-PAH radical recombination and addition reaction growth mechanisms.     

Isomerization reactions of the n-C4H9O and n-OOC4H8OH radicals in oxygen

Reactions of n-C₄H₉O radicals have been investigated in the temperature range 343–503 K in mixtures of O₂/N₂ at atmospheric pressure. Flow and static experiments have been performed in quartz and Pyrex vessels of different diameters, walls passivated or not towards reactions of radicals, and products were analyzed by GC/MS. The main products formed are butyraldehyde, hydroperoxide C₄H₈O₃ of MW 104, 1-butanol, butyrolactone, and n-propyl hydroperoxide. It is shown that transformation of these RO radicals occurs through two reaction pathways, H shift isomerization (forming C₄H₈OH radicals) and decomposition. A difference of activation energies ΔE = (7.7 ± 0.1 (σ)) kcal/mol between these reactions and in favor of the H-shift is found, leading to an isomerization rate constant k_isom (n-C₄H₉O) = 1.3 × 10¹² exp(− 9,700/RT). Oxidation, producing butyraldehyde, is proposed to occur after isomerization, in parallel with an association reaction of C₄H₈OH radicals with O₂ producing OOC₄H₈OH radicals which, after further isomerization lead to an hydroperoxide of molecular weight 104 as a main product. Butyraldehyde is mainly formed from the isomerized radical HOCCCC˙ + O₂ ··· → O (DOUBLE BOND) CCCC + HO₂, since (i) the ratio butyraldehyde/(butyraldehyde + isomerization products) = 0.290 ± 0.035 (σ) is independent of oxygen concentration from 448 to 496 K, and (ii) the addition of small quantities of NO has no influence on butyraldehyde formation, but decreases concentration of the hydroperoxides (that of MW 104 and n-propyl hydroperoxide). By measuring the decay of [MW 104] in function of [NO] added (0–22.5 ppm) at 487 K, an estimation of the isomerization rate constant OOC₄H₈OH → HOOC₄H₇OH, κ₅ ≅ 10¹¹exp(−17,600/RT) is made. Implications of these results for atmospheric chemistry and combustion are discussed. © 1996 John Wiley & Sons, Inc.     

Syntheses of(C_8H_8)Ln(C_9H_7)·(THF)_2(Ln=Pr,Nd)and crystal structure of(C_8H_8)Pr(C_9H_7)·(THF)_2

This paper reports two lanthanide complexes of formula (C_9H_7)Ln(C_8H_8)·(THF)_2 whereLn is Pr or Nd,C_9H_7 is indenyl,and C_8H_8 is cyclooctatetraene (COT).The complexes were preparedby the reaction of LnCl_3 with K(C_9H_7) and K_2(C_8H_8) in THF.(C_9H_7)Pr(C_8H_8)·(THF)_2 crystallizes inTHF at - 15℃ in the monoclinic space group P2_1:with unit cell dimensions a=8.446(0),b=10.083(2),c=13.407(3),β=105.48(1)°,V=1100.43(35)~3,Dc=1.52g/cm~3 and Z=2.The final R valueis 0.033,R_w value is 0.030,respectively.In (C_9H_7)Pr(C_8H_8)·(THF)_2 a five-membered ring centroid ofC_9H_7,the C_8H_8 ring centroid and the two oxygen atoms from the two THF molecules form a distortedtetrahedral geometry around the metal.     

Thermodynamic Properties of the n-Alkanes C19H40 to C26H54 and Their Binary Phase Diagrams

The shapes of the C₂₂H₄₆-C₂₄H₅₀ and C₂₃H₄₈-C₂₄H₅₀ binary phase diagrams were analyzed. In the C₂₂H₄₆-C₂₄H₅₀ binary system the increased stability of the binary compounds with increasing temperature can be explained by the much larger heat capacity and entropy of the binary compounds compared to that of the components C₂₂H₄₆ and C₂₄H₅₀. In the C₂₃H₄₈-C₂₄H₅₀ system this effect is much less pronounced. The measured enthalpy data of n-alkanes C₁₉H₄₀ to C₂₄H₅₀ and of the binary system C₂₂H₄₆-C₂₄H₅₀ were analyzed to obtain the ‘excess’ heat capacity per atom of carbon {[C _p/(Rm)]-3} (Rm being the number of carbon atoms). The ‘excess’ heat capacity per carbon atom is the value of the heat capacity above the Debye high temperature value of 3R. At low temperatures (below 280 K) one is in the Debye temperature θ_D region. At higher temperatures the large ‘excess’ heat capacity of the solids explains the movements in the carbon chains. In the liquid the excess heat capacity is small and corresponds numerically to the anharmonic vibrations in low melting metals. In contrast to metals, where the difference in heat capacity between liquid and solid below the melting point is positive C _p(L-s)>0, in the alkanes studied it is strongly negative C _p(L-s)?0. This explains the shape of the binary phase diagrams C₂₂H₄₆-C₂₄H₅₀, C₂₄H₅₀-C₂₆H₅₄, C₂₂H₄₆-C₂₃H₄₈ and C₂₃H₄₈-C₂₄H₅₀.     

New Thioantimonates(III) with Different Sb:S Ratios: Solvothermal Syntheses and Crystal Structures of [(C3H10NO)(C3H10N)][Sb8S13], [(C2H8NO)(C2H8N)(CH5N)][Sb8S13], [(C6H16N2)(C6H14N2)][Sb6S10], and [C8H22N2][Sb4S7]

Four new thioantimonates(III) with compositions [(C₃H₁₀NO)(C₃H₁₀N)][Sb₈S₁₃] ( 1 ) (C₃H₉NO = 1‐amino‐3‐propanol, C₃H₉N = propylamine), [(C₂H₈NO)(C₂H₈N)(CH₅N)][Sb₈S₁₃] ( 2 ) (C₂H₇NO = ethanolamine, C₂H₇N = ethylamine, CH₅N = methylamine), [(C₆H₁₆N₂)(C₆H₁₄N₂)][Sb₆S₁₀] ( 3 ) (C₆H₁₄N₂ = 1,2‐diaminocyclohexane) and [C₈H₂₂N₂][Sb₄S₇] ( 4 ) (C₈H₂₀N₂ = 1,8‐diaminooctane) were synthesized under solvothermal conditions. Compound 1 : triclinic space group P$\bar{1}$ , a = 6.9695(6) Å, b = 13.8095(12) Å, c = 18.0354(17) Å, α = 98.367(11), β = 96.097(11) and γ = 101.281(11)°; compound 2 : monoclinic space group P2₁/m, a = 7.1668(5), b = 25.8986(14), c = 16.0436(11) Å, β = 96.847(8)°; compound 3 : monoclinic space group P2₁/n, a = 11.6194(9), b = 10.2445(5) Å, c = 27.3590(18) Å, β = 91.909(6)°; compound 4 : triclinic space group P$\bar{1}$ , a = 7.0743(6), b = 12.0846(11), c = 13.9933(14) Å, α = 114.723(10), β = 97.595(11), γ = 93.272(11)°. The main structural feature of the two atoms thick layered [Sb₈S₁₃]^2– anion in 1 are large nearly rectangular pores with dimensions 11.2 × 11.7 Å. The layers are stacked perpendicular to [100] to form tunnels being directed along [100]. In contrast to 1 the structure of 2 contains a [Sb₈S₁₃]^2– chain anion with Sb₁₂S₁₂ pores measuring about 8.9 × 11.5 Å. Only if longer Sb–S distances are considered as bonding interactions a layered anion is formed. The chain anion [Sb₆S₁₀]^2– in compound 3 is unique and is constructed by corner‐sharing SbS₃ pyramids. Two symmetry‐related single chains consisting of alternating SbS₃ units and Sb₃S₃ rings are bound to Sb₄S₄ rings in chair conformation. Finally, in the structure of 4 the SbS₃ and SbS₄ moieties are joined corner‐linked to form a chain of alternating SbS₄ units and (SbS₃)₃ blocks. Neighboring chains are connected into sheets that contain relatively large Sb₁₀S₁₀ heterorings. The sheets are further connected by sulfur atoms generating four atoms thick double sheets.     

Synthesis of some new mono- and di-substituted o-carborane derivatives with thiolate and carbamate moieties: crystal structure of 1-(SNC5H4)-1,2-C2B10H11

Some new o-carborane derivatives of stoichiometry 1,2-(SR)₂-1,2-C₂B₁₀H₁₀ [SR=S₂NC₇H₄, S₂CNEt₂] have been synthesised by reaction of 1,2-Li₂-1,2-C₂B₁₀H₁₀ with the corresponding disulfide derivatives RSSR (RSSR=(C₇H₄NS₂)₂, 2,2′-dithiobis(benzothiazole); (Et₂NCS₂)₂, tetraethylthiuram disulfide) in molar ratio 1:2. The reaction of 1-Li-2-Si^tBuMe₂-1,2-C₂B₁₀H₁₀ with RSSR (RSSR=(C₅H₄NS)₂, 2,2′-dithiodipyridine; (C₇H₄NS₂)₂) in molar ratio 1:1 has afforded the new mixed di-substituted compounds 1-SR-2-Si^tBuMe₂-1,2-C₂B₁₀H₁₀ (SR=SNC₅H₄; S₂NC₇H₄). The reaction of 1-SNC₅H₄-2-Si^tBuMe₂-1,2-C₂B₁₀H₁₀ with NBu₄F in THF in molar ratio 1:2 has afforded the mono-substituted derivative 1-SNC₅H₄-1,2-C₂B₁₀H₁₁, whereas the treatment of 1,2-(C₇H₄NS₂)₂-1,2-C₂B₁₀H₁₀ with NBu₄F in THF in molar ratio 1:5 has led to the partially degraded derivative NBu₄[7,8-(S₂NC₇H₄)₂-7,8-C₂B₉H₁₀]. The crystal structure of 1-SNC₅H₄-1,2-C₂B₁₀H₁₁ has been determined by X-ray diffraction.     

A study of [C7H8]+˙ and [C7H8]2+ ions formed from different precursor molecules

On the basis of unimolecular and collisionally activated decompositions, as well as their charge stripping behaviour, [C₇H₈]⁺˙ and [C₇H₈]²⁺ ions from a variety of precursors have been studied. In particular, structural characteristics of molecular ions of toluene, cycloheptatriene, norborna-2,5-diene and quadricyclane have been compared to those of [C₇H₈]⁺˙ and [C₇H₈]²⁺ rearrangement fragment ions obtained from n-butylbenzene, 2-phenylethanol and n-pentylbenzene. Severe interferences from [C₇H₇]^2+˙ ion fragmentations have been observed and rationalized.     

Transition-metal mediated heteroatom removal by reactions of FeL+ [L=O,C4H6, c-C5H6, c-C5H5, C6H6, C5H4(=CH2)] with furan,thiophene, and pyrrole in the gas phase

Reactions of Fe⁺ and FeL⁺ [L=O, C₄H₆, c-C₅H₆, C₅H₅, C₆H₆, C₅H₄(=CH₂)] with thiophene, furan, and pyrrole in the gas phase by using Fourier transform mass spectrometry are described. Fe⁺, Fe(C₅H₅)⁺, and FeC₆H ₆ ⁺ yield exclusive rapid adduct formation with thiophene, furan, and pyrrole. In addition, the iron-diene complexes [FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺], as well as FeC₅H₄(=CH₂)⁺ and FeO⁺, are quite reactive. The most intriguing reaction is the predominant direct extrusion of CO from furan by FeC₄H₆ ⁺, Fe(c-C₅H₆)⁺, and FeC₅H₄(=CH₂)⁺. In addition, FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺ cause minor amounts of HCN extrusion from pyrrole. Mechanisms are presented for these CO and HCN extrusion reactions. The absence of CS elimination from thiophene may be due to the higher energy requirements than those for CO extrusion from furan or HCN extrusion from pyrrole. The dominant reaction channel for reaction of Fe(c-C₅H₆)⁺ with pyrrole and thiophene is hydrogen-atom displacement, which implies D^O(Fa(N₅H₅)⁺-C₄H₄X)>D^O(Fe(C₅H₅)⁺-H)=46±5 kcal mol^?1. D^O(Fe⁺-C₄H₄S) and D^O(Fe⁺-C₄H₅N)=D^O(Fe⁺-C₄H₆)=48±5 kcal mol^?1. Finally, 55±5 kcal mol^?1=D^O(Fe⁺-C₆H₆)>D^O(Fe⁺-C₄H₄O)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mol^?1. FeO⁺ reacts rapidly with thiophene, furan, and pyrrole to yield initial loss of CO followed by additional neutral losses. D^O(Fe⁺-CS)>D^O(Fe⁺-C₄H₄S)≈48±5 kcal mol^?1 and D^O(Fe⁺-C₄H₅N)≈48±5 kcal mol^?1>D^O(Fe⁺-HCN)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mil^?1.     

Rate constants for the elementary reactions between CN radicals and CH4, C2H6, C2H4, C3H6, and C2H2 in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)ⁿ exp(?θ/T), yielding: for CH₄, A′(298) = 7.0 × 10^?13 cm³ molecule^?1 s^?1, n = 2.3, and θ = ?16 K; and for C₂H₆, A′(298) = 5.6 × 10^?12 cm³ molecule^?1 s^?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C₂H₄, C₃H₆, and C₂H₂ all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)ⁿ with k(298) = 2.5 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.24 for CN + C₂H₄; k(298) = 3.4 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.19 for CN + C₃H₆; and k(298) = 2.9 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.53 for CN + C₂H₂. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.     

Rearrangements and fragmentations of metastable [C13H9S]+, [C14H11]+, [C13H11]+ and [C8H7S]+ ions

[C₁₃H₉S]⁺, [C₁₄H₁₁]⁺, [C₁₃H₁₁]⁺ and [C₈H₇S]⁺ ions with unknown structures were generated from two [C₁₄H₁₂S]^+·precursor ions by fragmentation reactions that must be preceded by extensive rearrangements. Ions with the same compositions, each with several initial structures, were prepared by simple bond-breaking reactions. Metastable characteristics were compared for each of the four types of ions. It was found than in all cases fast isomerization reactions occur prior to fragmentation, so that no information about the unknown ion structures could be obtained by comparison of the observed fragmentations of metastable ions.