Fulvenallenyl Radical (C7H5·)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic C10H8 Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?

To understand the reactivity of resonantly stabilized radicals, often found in relevant concentrations in gaseous environments, it is important to determine their main reaction pathways. Here, it is investigated whether the fulvenallenyl radical (C7H5·) reacts preferentially with closed-shell molecules or radicals. Electronic structure calculations on the C10H9 potential energy surface accessed by the reactions of C7H5· with methylacetylene (CH3CCH) and allene (H2CCCH2) were combined with RRKM-ME calculations of temperature- and pressure-dependent rate constants using the automated EStokTP software suite and kinetic modeling to assess the reactivity of C7H5· with closed-shell unsaturated hydrocarbons. Experimentally, the reactions were attempted in a chemical microreactor heated to 998 ± 10 K by preparing fulvenallenyl radicals via pyrolysis of trichloromethylbenzene (C7H5Cl3) and seeding the radicals in methylacetylene or allene carrier gas, with product identification by means of photoionization mass spectrometry. The measured photoionization efficiency curve of m/z = 128 was assigned to a linear combination of the reference curves of two C10H8 isomers, azulene (minor) and naphthalene (major), presumably resulting from the C7H5· plus C3H4 reactions. However, the calculations demonstrated that these reactions are too slow, and kinetic modeling of processes in the reactor allowed us to conclude that the observation of naphthalene and azulene is due to the C7H5· plus C3H3· reaction, where propargyl is produced by direct hydrogen atom abstraction by chlorine (Cl) atoms from allene or methylacetylene and Cl stem from the pyrolysis of C7H5Cl3. Modeling results under the copyrolysis conditions of toluene and methylacetylene in high-temperature shock tube experiments confirmed the prevalence of the fulvenallenyl reaction with propargyl over its reactions with C3H4 even when the concentrations of allene and methylacetylene largely exceed that of propargyl. Overall, the reactions of fulvenallenyl with both allene and methylacetylene were found to be noncompetitive in the formation of naphthalene and azulene thus attesting the inefficiency of the fulvenallenyl radical reactions with the prototype closed-shell hydrocarbon species. In the meantime, the new reaction pathways revealed, including H-assisted isomerizations between C10H8 isomers and decomposition reactions of various C10H9 isomers, emerge as relevant and are recommended for inclusion in combustion kinetic models for naphthalene formation.

Gas-Phase Preparation of the 14π Hückel Polycyclic Aromatic Anthracene and Phenanthrene Isomers (C14H10) via the Propargyl Addition-BenzAnnulation (PABA) Mechanism.

Polycyclic aromatic hydrocarbons (PAHs) imply the missing link between resonantly stabilized free radicals and carbonaceous nanoparticles, commonly referred to as soot particles in combustion systems and interstellar grains in deep space. Whereas gas phase formation pathways to the simplest PAH - naphthalene (C10H8) - are beginning to emerge, reaction pathways leading to the synthesis of the 14π Hückel aromatic PAHs anthracene and phenanthrene (C14H10) are still incomplete. Here, by utilizing a chemical microreactor in conjunction with vacuum ultraviolet (VUV) photoionization (PI) of the products followed by detection of the ions in a reflectron time-of-flight mass spectrometer (ReTOF-MS), the reaction between the 1'- and 2'-methylnaphthyl radicals (C11H9⋅) with the propargyl radical (C3H3⋅) accesses anthracene (C14H10) and phenanthrene (C14H10) via the Propargyl Addition-BenzAnnulation (PABA) mechanism in conjunction with a hydrogen assisted isomerization. The preferential formation of the thermodynamically less stable anthracene isomer compared to phenanthrene suggests a kinetic, rather than a thermodynamics control of the reaction.

[The effect of RhoA/Rho kinase signal pathway on TGF-beta1-induced phenotypic differentiation of human dermal fibroblasts].

OBJECTIVE: To examine the effect of RhoA/Rho kinase signal pathway on TGF-beta1-induced phenotypic differentiation of human dermal fibroblasts. METHODS: The 4th generation of primary cultured human dermal fibroblasts were stimulated with TGF-beta1, (10 ng/ml). The expression of alpha-SMA was detected after treatment with TGF-beta1, for 0, 3, 6, and 24 h. The expression of alpha-SMA was also detected after treatment with different concentration of TGF-beta1 (0, 2, 10, 50 ng/ml). Then the human dermal fibroblasts (4th generation) were stimulated with TGF-beta1, (10 ng/ml) after being treated with the RhoA/Rho kinase signaling pathway inhibitor Y-27632 (10 umol/ml). The fibroblasts were treated with nothing as sham control, or with Y-27632 (10 umol/L) only as negative control group, or with TGF-beta1 (10 ng/ml) only as positive control group. The expression of alpha-SMA was detected in all the groups. Protein expression was analyzed with ANOVA statistical method. RESULTS: alpha-SMA expression in fibroblasts with 10 ng/ml TGF-beta1 stimulation for 0, 3, 6, 24 h was 1.0, 1.9 0.2, 2.1 +/- 0. 1, 3. 1 +/- 0.1, respectively. Alpha-SMA expression in 24 h group was significantly higher than that in other three groups (n = 4, P < 0.05). alpha-SMA expression in human dermal fibroblasts after stimulation with different concentration of TGF-beta1 (0, 2, 10, 50 ng/ml) was 1.0, 1.4 +/- 0.2, 3.2 + 0.1, 3.1 +/- 0.2, respectively. alpha-SMA expression in 10 ng/ ml group was significantly higher than that in 2 ng/ml group and control group (n = 4, P < 0.05). There was no statistical difference in alpha-SMA expression between 10 ng/ml group and 50 ng/ml group (n = 4, P > 0.05). With both Y-27632 (10 micromol/L) and TGF-beta1 stimulation, the cell phenotype differentiation was inhibited. Alpha-SMA expression in experimental group (1.2 +/- 0.2) was significantly reduced, when compared with that in positive control group (2.9 +/- 0.1) (n = 5, P < 0.05). There was no significant difference (n = 5, P > 0.05) in alpha-SMA expression between control group (1.0) and negative control group (1.1 +/- 0.1). CONCLUSIONS: RhoA/Rho kinase signaling pathway should be involved in TGF-beta1-induced phenotypic differentiation of human dermal fibroblasts.

[Analysis of misdiagnosis of laryngeal tuberculosis: a report of 16 cases].

OBJECTIVE: To further understand the clinical features of laryngeal tuberculosis and to reduce the rate of misdiagnosis. METHODS: Sixteen cases of laryngeal tuberculosis from Feb. 1998 to Aug 2006 were retrospectively studied. The clinical features and the causes underlying misdiagnosis were analyzed. RESULTS: The disease was more common in the elderly. The clinical manifestations of the infection were various and atypical. The lesions commonly involved the vocal cord (12/16 cases). Local manifestations were mainly proliferation lesions such as mass and granulation. CONCLUSION: Attention should be paid to the clinical features of laryngeal tuberculosis. Thorough examination should be carried out and early biopsy can avoid misdiagnosis.