Gas‐Phase Radical–Radical Reaction Dynamics of O(³P)+C₂H₃→C₂H₂+OH

Abstract

BACKGROUND The authors assessed the biologic behavior of differentiated thyroid carcinoma in patients age 70 years or older and evaluated factors that influenced long‐term survival. METHODS Among 1448 patients with differentiated thyroid carcinoma who were treated at the authors' institution over the past 60 years, 111 patients were identified who were age 70 years or older at the time of their initial diagnosis (range, 70–93 years). The authors conducted a retrospective analysis of the outcome of these 111 patients, who had a median follow‐up of 9 years (range, 2–9 years). RESULTS There were 83 female patients and 28 male patients (female to male ratio, 3:1). Fifty‐eight tumors were papillary, 46 tumors were follicular, and 7 tumors were Hürthle cell carcinoma. Eighty percent of patients presented with a thyroid mass, and 70% of tumors were pathologic stage T3 (pT3) or pT4. Lymph node disease was evident at presentation in 44% of patients, and distant metastases were documented at diagnosis in 23% of patients. Forty‐six patients underwent total thyroidectomy, and the remaining patients underwent subtotal thyroidectomy or biopsy only. Radioiodine was administered to 80 patients, and external beam radiotherapy was administered to 19 patients. The cause specific survival rates were 75%, 50%, and 50% at 5 years, 10 years, and 15 years, respectively. Multivariate analysis showed that the presence of metastases was the most important independent prognostic factor for survival. External beam radiotherapy was associated with a poorer prognosis, in that it was reserved for patients with either inoperable disease or residual disease after surgery and patients with no uptake of radioiodine. CONCLUSIONS A large proportion of thyroid tumors showed extrathyroid spread and distant metastases, which frequently were not iodine‐avid. The prevalent histologic type was papillary, often with features of poor differentiation. Thyroid carcinoma in the elderly appears to behave more aggressively, and they have a less favorable prognosis compared with younger adults. Cancer 2003;97:2736–42. © 2003 American Cancer Society. DOI 10.1002/cncr.11410

Analysis of Nascent Rotational Energy Distributions and Reaction Mechanisms of the Gas‐Phase Radical–Radical Reaction O(3P)+(CH3)2CH→C3H6+OH

“…Experimental Studies: The lab-made crossed-beam apparatus for investigating gas-phase reaction dynamics has been described in detail elsewhere. [1,[5][6][7][8][9][10][11][12][13][14][15][16][17] It consists of two radical-source chambers, each pumped by a 6-inch (1400 L s À1 ) baffled diffusion pump, and a scattering chamber, pumped by a 10-inch (3000 L s À1 ) baffled diffusion pump. The average base pressure in the scattering chamber was kept below 2.0 10 À6 Torr.…”

“…It builds on previous gas-phase crossed-beam studies. [5][6][7][8][9][10][11][12][13][14][15][16][17] Radical-radical reaction dynamics were investigated as part of ongoing efforts to elucidate the mechanistic and dynamic attributes of the reactions of O( 3 P) with a series of prototypal alkyl radicals, such as allyl, propargyl, tert-butyl (t-C 4 H 9 ), and vinyl, and to identify the general principles that determine their reactivity and mechanisms. Some hydrocarbon species showed intrinsic stability due to resonance stabilization or hyperconjugation.…”

Study of the Gas-Phase Oxygen–Hydrogen Exchange Reaction of O(3P) + i-C3H7 → H(2S) + CH3COCH3

“…The lab-made crossed-beam apparatus employed in this study was described in detail elsewhere. ,− In brief, a pulsed supersonic O( 3 P) beam was produced by irradiating He samples seeded with 12% NO 2 with a 30 mJ pulse –1 of a 355 nm laser beam near the throat of the supersonic expansion. A second pulsed (CH 3 ) 2 CH radical beam was generated by the supersonic flash pyrolysis of the precursor isopropyl bromide, (CH 3 ) 2 CHBr, seeded in He at 2 atm, which underwent quantitative thermal decomposition into (CH 3 ) 2 CH + Br.…”

“…Recently, this lab reported a series of combined crossed-beam and ab initio investigations of the elementary reactions of O( 3 P) with several prototypal alkyl radicals as model systems, including allyl (C 3 H 5 ), propargyl (C 3 H 3 ), tert -butyl ( t -C 4 H 9 ), ethyl (C 2 H 5 ), isopropyl ( i -C 3 H 7 ), and vinyl (C 2 H 3 ). − The radicals were generated in a supersonic flash pyrolysis source, wherein the labile precursor molecules underwent rapid thermal decomposition inside a high-temperature tube, thereby producing clean, jet-cooled alkyl radical beams without recombination and/or secondary dissociation . The nascent state distributions of various reaction products have revealed characteristic reactivity and mechanistic aspects unobserved in the reactions of O( 3 P) + closed-shell hydrocarbon molecules.…”