Novel products from C6H5 + C6H6/C6H5 reactions

To date only one product, biphenyl, has been reported to be produced from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions. In this study, we have investigated some unique products of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via both experimental observation and theoretical modeling. In the experimental study, gas-phase reaction products produced from the pyrolysis of selected aromatics and aromatic/acetylene mixtures were detected by an in situ technique, vacuum ultraviolet (VUV) single photon ionization (SPI) time-of-flight mass spectrometry (TOFMS). The mass spectra revealed a remarkable correlation in mass peaks at m/z = 154 {C(12)H(10) (biphenyl)} and m/z = 152 {C(12)H(8) (?)}. It also demonstrated an unexpected correlation among the HACA (hydrogen abstraction and acetylene addition) products at m/z = 78, 102, 128, 152, and 176. The analysis of formation routes of products suggested the contribution of some other isomers in addition to a well-known candidate, acenaphthylene, in the mass peak at m/z = 152 (C(12)H(8)). Considering the difficulties of identifying the contributing isomers from an observed mass number peak, quantum chemical calculations for the above-mentioned reactions were performed. As a result, cyclopenta[a]indene, as-indacene, s-indacene, biphenylene, acenaphthylene, and naphthalene appeared as novel products, produced from the possible channels of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions rather than from their previously reported formation pathways. The most notable point is the production of acenaphthylene and naphthalene from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via the PAC (phenyl addition-cyclization) mechanism because, until now, both of them have been thought to be formed via the HACA routes. In this way, this study has paved the way for exploring alternative paths for other inefficient HACA routes using the PAC mechanism.     

Rate constants for tsomerization of C6H5C(SC6H5)2 ĆH2 radicals to C6H5Ć(SC6H5)CH2SC6H5 radicals based on EPR data

Conclusions The parameters of the Arrhenius equation for the isomerization of PhC(SPh)₂H₂ radicals to Ph(SPh)CH₂. SPh radicals are in agreement with an intramolecular character of the rearrangement, with a 1,2-migration of the thiyl group. These parameters were calculated on the basis of the data that were obtained by the EPR method in the range 10–70°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2596–2597, November, 1982.     

Substitution and protonation effects on spin-spin coupling constants in prototypical aromatic rings: C6H6, C5H5N and C5H5P

Ab initio equation-of-motion coupled cluster calculations have been carried out to evaluate one-, two-, and three-bond 13C-13C, 15N-13C, 31P-13C coupling constants in benzene, pyridine, pyridinium, phosphinine, and phosphininium. The introduction of N or P heteroatoms into the aromatic ring not only changes the magnitudes of the corresponding X-C coupling constants (J, for X = C, N, or P) but also the signs and magnitudes of corresponding reduced coupling constants (K). Protonation of the heteroatoms also produces dramatic changes in coupling constants and, by removing the lone pair of electrons from the sigma-electron framework, leads to the same signs for corresponding reduced coupling constants for benzene, pyridinium, and phosphininium. C-C coupling constants are rather insensitive to the presence of the heteroatoms and protonation. All terms that contribute to the total coupling constant (except for the diamagnetic spin-orbit (DSO) term) must be computed if good agreement with experimental data is to be obtained.     

Ab initio kinetics for the unimolecular reaction C6H5OH --> CO + C5H6

The unimolecular decomposition of C(6)H(5)OH on its singlet-state potential energy surface has been studied at the G2M//B3LYP/6-311G(d,p) level of theory. The result shows that the most favorable reaction channel involves the isomerization and decomposition of phenol via 2,4-cyclohexadienone and other low-lying isomers prior to the fragmentation process, producing cyclo-C(5)H(6) + CO as major products, supporting the earlier assumption of the important role of the 2,4-cyclohexadienone intermediate. The rate constant predicted by the microcanonical RRKM theory in the temperature range 800-2000 K at 1 Torr--100 atm of Ar pressure for CO production agrees very well with available experimental data in the temperature range studied. The rate constants for the production of CO and the H atom by O-H dissociation at atmospheric Ar pressure can be represented by k(CO) = 8.62 x 10(15) T(-0.61) exp(-37,300/T) s(-1) and k(H) = 1.01 x 10(71) T(-15.92) exp(-62,800/T) s(-1). The latter process is strongly P-dependent above 1000 K; its high- and low-pressure limits are given.     

Computational study on the mechanism and rate constant for the C6H5 + C6H5NO reaction

The reaction mechanism of C6H5 + C6H5NO involving four product channels on the doublet-state potential energy surface has been studied at the B3LYP/6-31+G(d, p) level of theory. The first reaction channel occurs by barrierless association forming (C6H5)2NO (biphenyl nitroxide), which can undergo isomerization and decomposition. The second channel takes place by substitution reaction producing C12H10 (biphenyl) and NO. The third and fourth channels involve direct hydrogen abstraction reactions producing C6H4NO + C6H6 and C6H5NOH + C6H4, respectively. Bimolecular rate constants of the above four product channels have been calculated in the temperature range 300-2000 K by the microcanonical Rice-Ramsperger-Kassel-Marcus theory and/or variational transition-state theory. The result shows the dominant reactions are channel 1 at lower temperatures (T < 800 K) and channel 3 at higher temperatures (T > 800 K). The total rate constant at 7 Torr He is predicted to be k(t) = 3.94 x 10(21) T(-3.09) exp(-699/T) for 300-500 K, 2.09 x 10(20) T(-3.56) exp(2315/T) for 500-1000 K, and 1.51 x 10(2) T(3.30) exp(-3043/T) for 1000-2000 K (in units of cm3 mol(-1) s(-1)), agreeing reasonably with the experimental data within their reported errors. The heats of formation of key products including biphenyl nitroxide, hydroxyl phenyl amino radical, and N-hydroxyl carbazole have been estimated.     

Zur disproportionierung der phenylfluorphosphane (C6H5)2PF und (C6H5)PF2

Ph₂P-PF₂Ph₂ has been identified by means ¹⁹F- and ³¹P- NMR spectroscopy as an intermediate product of the disproportionation of Ph₂PF. The disproportionation is catalyzed by acids. The reaction mechanism is discussed. PhPF₂ disproportionates faster in solution in acetonitrile than neat, forming (PhP)₆, instead of (PhP)₅.     

A tandem mass spectrometry study of the gas phase RSC6H5Cr+L (R = H,C6H5; L = arene) and C6H5SSC6H5Cr+ ions

Ion-molecule reactions of chromium containing ions with arylsulfides have been studied in the gas phase and their products have been characterized by tandem mass spectrometry. C₆H₅SH and (C₆H₅)₂S react as typical aromatic compounds and give rise to Cr⁺C₆H₅SR] and RC₆H₅Cr⁺QH₅SR′ [R = H, CH₃, CH(CH₃)₂; R′ = H, C₆H₅] ions. Metastable ion mass spectra of the latter species show that the metal is more strongly bound to diphenylsulfide than to alkylbenzenes. C₆H₅SSC₆H₅ reacts with chromium-containing ions to form only Cr⁺(C₆H₅SSC₆H₅). The decomposition characteristics of this ion and, in particular, the presence of a recovery signal in the neutralization-reionization mass spectrum are in keeping with the formation of a 1,2-dithia[2]cyclophane complex ion, which rearranges into a structurel(s) that contains Cr?S bond(s). No evidence was found for metal atom insertion into S?S, C?S, or S?H bonds.     

Charge inversion as a structural probe for C6H 5 + and C6H 6 +· cations

Charge reversal (⁺CR⁻) of cations to anions can be used to structurally differentiate isomeric C₆H₅⁺ and C₆H₆^+· hydrocarbon ions by means of tandem mass spectrometry. In view of the manifold of possible isomers, only a few prototype precursors are examined. Thus, charge inversion demonstrates that electron ionization of 2,4-hexadiyne yields an intact molecular ion, whereas the charge inversion spectra of C₆H₆^+· obtained from benzene, 1,5-hexadiyne, and fulvene are identical within experimental error. Similarly, the ⁺CR⁻ spectrum of the C₆H₅⁺ cation generated by dissociative ionization of 2,4-hexadiyne is significantly different from the ⁺CR⁻ spectrum of C₆H₅⁺ obtained from iodobenzene, suggesting the formation of a 2,4-hexadiynyl cation from the former precursor. Although charge inversion of cations to anions has a low efficiency and requires large precursor ion fluxes, the particular value of this method is that the spectra may not just differ in fragment ion intensities, but these differences can directly be related to the underlying ion structures.     

Syntheses and crystal structures of [(C6H5CH2C5H4)2GdCl.THF]2 and (C6H5CH2C5H4)2ErCl.THF

[(C₆H₅CH₂C₅H₄)₂GdCl.THF]₂ (1) and (C₆H₅CH₂C₅H₄)₂ErCl.THF (2) were prepared by the reaction of LnCl₃ (Ln? Gd, Er) with benzylcyclopentadienyl sodium in THF and characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, MS and thermal gravimetry. The crystal structures of both compounds were determined. Complex 1 is dimeric and its structure belongs to the monoclinic, P2₁/c space group with a=1.1432(2), b=1.2978(2), c=1.7604(3) nm, β=108.75(2), V=2.4732(9) nm³, Z=2(four monomers), D_c“1.54 g.cm^?3. R=0.0342 and R_w“0.0362. Complex 2 is monomer and its structure belongs to the orthorhombic, P2₁2₁2₁ space group with a=0.8645(2), b=1.1394(3), c=2.5289(4) nm, V=2.4919(9) nm³, Z=4, D_c“1.56 g.cm^?3. R=0.0514, R_w“0.0529. The determination of the crystal structure shows that in complex 1 the benzyl groups on the cyclopentadienyls coordinated to Gd³⁺ are located in the opposite direction (139°); in complex 2 the benzyl groups on the cyclopentadienyls coordinated to Er³⁺ are located in the same direction (6.5°).     

用Grignard试剂C6H5MgBr合成苯甲醛

苯甲醛广泛用于医药、农药、染料、香料等行业[1] 。为了寻找产率高、成本低的新合成方法 ,人们进行了广泛的研究[1 7] 。本文用Ｇｒｉｇｎａｒｄ试剂与苯并咪唑盐[8] 合成苯甲醛。合成路线如下 :1　实验部分ＸＴ 2型数字显微熔点仪 (温度计未经校正 ) :ＰＥ 2 40 0ＣＨＮ元素分析仪 ;ＶａｒｉａｎＩＮＯＶＡ 40 0核磁共振仪 ;试剂均为化学纯。参考文献 [9]合成Ｇｒｉｇｎａｒｄ试剂Ｃ6 Ｈ5ＭｇＢｒ,以四氢呋喃作溶剂。1 1　苯并咪唑的合成在 1 0 0ｍｌ圆底烧瓶中加入 1 0 8ｇ(0 1ｍｏｌ)邻苯二胺和 8ｍｌ(0 2ｍｏｌ) 90 %甲酸 ,90℃下…     

Über die Kristallstruktur von (C6H5)3SiSH und (C6H5)3SiSBr und die Darstellung des Iodsulfans (C6H5)3SiSI

The Crystal Structure of (C₆H₅)₃SiSH and (C₆H₅)₃SiSBr and the Preparation of the Iodosulfane (C₆H₅)₃SiSI The preparation of the halogenosulfanes Ph₃SiSBr and Ph₃SiSI from Ph₃SiSH and N-halogenosuccinimide is reported. They are characterized by vibrational spectroscopic measurements. Ph₃SiSBr crystallizes in space group P1 with a = 899.3(8) pm, b = 941.3(7) pm, c = 1 051.4(7) pm, α = 109.88(5)°, β = 99.23(6)°, γ = 96.78(6)° and Z = 2. Ph₃SiSH crystallizes in space group P2₁/c with a = 1 879.4(8), b = 966.3(5), c = 1 845.2(9), β = 107.84(4), Z = 8. The halogenosulfanes decompose in polar solvents by formation of sulphur and triphenylsilanhalide.     

A kinetics study on reactions of C6H5O with C6H5O and O3 at 298 k

Kinetics for reactions of phenoxy radical, C₆H₅O, with itself and with O₃ were examined at 298 K and low pressure (1 Torr) using discharge flow coupled with mass spectrometry (DF/MS). The rate constant for the phenoxy radical self‐reaction was determined to be k₁ = (1.49 ± 0.53) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ defined by d[C₆H₅O]/dt=−2 k₁[C₆H₅O]². The rate constant for the C₆H₅O reaction with O₃ was measured to be k₂ = (2.86 ± 0.35) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, which may be a lower limit value. Because of much higher atmospheric abundance of ozone than that of both NO and phenoxy, the reaction of C₆H₅O with ozone may represent the principal fate of the phenoxy radical in the atmosphere. Products from reaction of C₆H₅O + C₆H₅O, NO, and NO₂ were also investigated, and (C₆H₅O)₂ (m/e = 186), C₆H₅O(NO) (m/e = 123), and C₆H₅O(NO₂) (m/e = 139) adducts were observed as products for the reactions of C₆H₅O with itself, NO, and NO₂, respectively. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 65–72, 1999     

Computational study on the kinetics and mechanism for the unimolecular decomposition of C6H5NO2 and the related C6H5 + NO2 and C6H5O + NO reactions

The kinetics and mechanisms for the unimolecular dissociation of nitrobenzene and related association reactions C(6)H(5) + NO(2) and C(6)H(5)O + NO have been studied computationally at the G2M(RCC, MP2) level of theory in conjunction with rate constant prediction with multichannel RRKM calculations. Formation of C(6)H(5) + NO(2) was found to be dominant above 850 K with its branching ratio > 0.78, whereas the formation of C(6)H(5)O + NO via the C(6)H(5)ONO intermediate was found to be competitive at lower temperatures, with its branching ratio increasing from 0.22 at 850 K to 0.97 at 500 K. The third energetically accessible channel producing C(6)H(4) + HONO was found to be uncompetitive throughout the temperature range investigated, 500-2000 K. The predicted rate constants for C(6)H(5)NO(2) --> C(6)H(5) + NO(2) and C(6)H(5)O + NO --> C(6)H(5)ONO under varying experimental conditions were found to be in good agreement with all existing experimental data. For C(6)H(5) + NO(2), the combination processes producing C(6)H(5)ONO and C(6)H(5)NO(2) are dominant at low temperature and high pressure, while the disproportionation process giving C(6)H(5)O + NO via C(6)H(5)ONO becomes competitive at low pressure and dominant at temperatures above 1000 K.