173,446 research outputs found
Shock Wave Study of the Thermal Dissociations of C3F6 and c-C3F6. I. Dissociation of Hexafluoropropene
No full textThe thermal dissociation of C3F6 was studied between 1330 and 2210 K in shock waves monitoring the UV absorption of CF2. CF2 yields of about 2.6 per parent C3F6 were obtained at reactant concentrations of 500-1000 ppm in the bath gas Ar. These yields dropped to about 1.8 when reactant concentrations were lowered to 60 ppm. The increase of the CF2 yield with increasing concentration was attributed to bimolecular reactions between primary and secondary dissociation products. Quantum-chemical and kinetic modeling calculations helped to estimate the contributions from the various primary dissociation steps. It was shown that the measurements correspond to unimolecular reactions in their falloff range. Falloff representations of the rate constants are given, leading to an overall high pressure rate constant k∞ = 2.0 × 10(17)(-104 kcal mol(-1)/RT) s(-1) and a relative rate of about 2/3:1/3 for the reactions C3F6 → CF3CF + CF2 versus C3F6 → C2F3 + CF3.Fil: Cobos, Carlos Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Sölter, L.. Universitat of Gottingen; AlemaniaFil: Tellbach, E.. Universitat of Gottingen; AlemaniaFil: Troe, J.. Max-Planck-Institut für Biophysikalische Chemie; Alemania. Universitat of Gottingen; Alemani
Shock wave and modeling study of the thermal decomposition reactions of Pentafluoroethane and 2-H Heptafluoropropane
No full textThe thermal decomposition reactions of CF3CF2H and CF3CFHCF3 have been studied in shock waves by monitoring the appearance of CF2 radicals. Temperatures in the range 1400-2000 K and Ar bath gas concentrations in the range (2-10) × 10(-5) mol cm(-3) were employed. It is shown that the reactions are initiated by C-C bond fission and not by HF elimination. Differing conclusions in the literature about the primary decomposition products, such as deduced from experiments at very low pressures, are attributed to unimolecular falloff effects. By increasing the initial reactant concentrations in Ar from 60 to 1000 ppm, a retardation of CF2 formation was observed while the final CF2 yields remained close to two CF2 per C2F5H or three CF2 per C3F7H decomposed. This is explained by secondary bimolecular reactions which lead to comparably stable transient species like CF3H, releasing CF2 at a slower rate. Quantum-chemical calculations and kinetic modeling help to identify the reaction pathways and provide estimates of rate constants for a series of primary and secondary reactions in the decomposition mechanism.Fil: Cobos, Carlos Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Sölter, L.. Universitat of Gottingen; AlemaniaFil: Tellbach, E.. Universitat of Gottingen; AlemaniaFil: Troe, J.. Max-Planck-Institut für Biophysikalische Chemie; Alemani
Ectinogonia buqueti subsp. gutierrezi Cobos 1954
No full textEctinogonia buqueti gutierrezi Cobos, 1954:62 [Figures 4–30] Syntype: “ Caldera Coquimbo. X-38 Wagenknecht // PARATYPUS A. COBOS // EX COLECCION Dr. A. Cobos // Ectinogonia buqueti ssp. gutierrezi nov. A. Cobos det 1952 // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275869” Syntype: “ ♀ // Caldera Coquimbo. Chile Wagenknech coll. 10-1938 // EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275870” Syntype: “ Caldera Coquimbo. Chile Wagenknech coll. 10-1938 // EX COLECCION Dr.A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275871” Syntype: “ Caldera Coquimbo. Chile Wagenknecht coll. 10-1938 // EX COLECCION Dr.A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275872” Syntype: “ Caldera Coquimbo. Chile Wagenknecht c. X-1938 // EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275873” Syntype: “ Caldera Coquimbo. Chile Wagenknecht c. X-1938. // EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275874” Syntype: “ Caldera Coquimbo Chile Wagenknecht // EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275875” Syntype: “ Caldera Coquimbo. Chile Wagenknecht c. X-1938 // EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275876” Syntype: “ Caldera Coquimbo. Chile Wagenknecht coll. 10-1938// EX COLECCION Dr. A. Cobos // PARATYPUS A. COBOS // Sintipo MNCN Tipos N° 7941 // MNCN _Ent 275877” Current status: Ectinogonia (Ectinogonia) minor gutierrezi Cobos, 1954 (Bellamy, 2008; Moore & Vidal 2015). Comments: Cobos (1954) did not established a holotype and mentioned a great series studied. The nine specimens come from one of the localities mentioned in the original description and, despite their paratype labels, they should be considered as syntypes.Published as part of Pineda, Cristian & París, Mercedes, 2022, Types of species of Ectinogonia (Coleoptera: Buprestidae) described by Antonio Cobos Sánchez deposited in the Museo Nacional de Ciencias Naturales, Madrid, pp. 478-486 in Zootaxa 5175 (4) on page 480, DOI: 10.11646/zootaxa.5175.4.5, http://zenodo.org/record/700644
Ectinogonia buqueti subsp. speciosa var. obscuripennis Cobos 1954
No full textEctinogonia buqueti speciosa var. obscuripennis Cobos, 1954:65 [Figures 31–33, 49–51] Non-type specimen: “El Sauce Coquimbo. Chile R. Wagenknecht c. // Coll. Olave Chile. Amer. m. // EX COLECCION Dr. A. Cobos // Cotipo // Ectinogonia buqueti ssp. speciosa var. obscuripennis nov. A. Cobos det. 1.953 // ¿Sintipo? MNCN Tipos N° 7943 // MNCN_Ent 275887” Non-type specimen: “Laguna Maule, 15-Enero.48, Cord: Tlaca,. Coll: L.E. Pena. // Ex Colección Dr. A. Cobos. // MNCN_Ent 275888”. Non-type specimen: “Las Cabras, Cord. Chillan, 1100, 1480 m., 10.23-Dic.54, Coll: L.E. Pena // Ex Colección Dr. A. Cobos. // MNCN_Ent 275889”. Non-type specimen: “Las Cabras, Cord. Chillan, 1100, 1480 m., 10.23-Dic.54, Coll: L.E. Pena // Ex Colección Dr. A. Cobos. // MNCN_Ent 275890”. Non-type specimen: “ V. Venado-Vilches, Cord. Talca. 1600, 29-XII-1973, Col. P. Vidal // Ex Colección Dr. A. Cobos. // Ectinogonia buqueti ssp. speciosa f. obscuripennis m. A. Cobos det. 1976// MNCN _Ent 275891”. [Male. Genital structure removed and glued on card]. Current status: This taxon was recently raised to species level by Anguita-Salinas et al. (2019), but the name and authorship should be updated as Ectinogonia (Ectinogonia) oscuripennis Moore, 1994. Moore’s aim was to give a new status to the variety obscuripennis Cobos, but he wrote Ectinogonia speciosa oscuripennis, so oscuripennis and not obscuripennis is the correct spelling for this taxon. Comments: As the name obscuripennis Cobos was used as an infrasubspecific one is therefore not available according to Article 45.5. (ICZN 1999) (a name expressly proposed to denote an infrasubspecific entity is not an available name). The name oscuripennis Moore, 1994 is the available name for obscuripennis Cobos, 1954 in agreement with Article 45.5.1. (When a subsequent author applies the same word to a species or subspecies in a manner that makes it an available name, even if he or she attributes authorship of the name to the author of its publication as an infrasubspecific name, that subsequent author thereby establishes a new name with its own authorship and date). Moore (1994:154) raised the name obscuripennis Cobos to the subspecies level as Ectinogonia speciosa oscuripennis. He does not mention the specimens studied by Cobos (1954:65) and makes the diagnosis studying seven specimens from "Las Trancas, Chillán, VIII Región, Dic. 1983, 16/I/1987 y Dic. 1988 ”, which are the syntypes of this taxon. Regarding the specimens identified by Cobos as f. obscuripennis, in the collection of the Institut Royal des Sciences Naturelles de Belgique (RBINS) is currently deposited the specimen mentioned by Cobos (1954:65) as a blackish specimen, which was previously determined by Charles Kerremans as Ectinogonia fastidiosa. This specimen bears the following labels: “ Ectinogonia buqueti ssp. speciosa var. obscuripennis nov. A Cobos det. 1.953 COTIPO Cf.: Rev. Chil. Ent. 1953,3:52–64,5 Para-type // Kerremans det., 1890: Ectinogonia fastidiosa Fairm. // Determ 1890 Kerremans // Coll. R. I.Sc.N.B. Coll. Weyers ”. In the MNCN-CSIC collection are preserved five specimens identified by Cobos as f. obscuripennis. One of them (Fig. 31–33) is labelled as Cotipo, but this specimen is not type of any available taxon. The specimen deposited at the RBINS collection (Fig. 49–51), and four of the five specimens deposited at the MNCN-CSIC collection (MNCN _Ent 275888, 275889, 275890 and 275891) are conspecific with the specimens studied by Moore (1994:154). The specimen MNCN _Ent 275887 (Fig. 31–33) is an unidentified species of Ectinogonia, which is not conspecific with this taxon.Published as part of Pineda, Cristian & París, Mercedes, 2022, Types of species of Ectinogonia (Coleoptera: Buprestidae) described by Antonio Cobos Sánchez deposited in the Museo Nacional de Ciencias Naturales, Madrid, pp. 478-486 in Zootaxa 5175 (4) on pages 480-481, DOI: 10.11646/zootaxa.5175.4.5, http://zenodo.org/record/700644
Shock wave and modelling study of the dissociation kinetics of C₂F₅I
No full textThe thermal dissociation of C₂F₅I was studied in shock waves monitoring UV absorption signals from the reactant C₂F₅I and later formed reaction products such as CF, CF₂, and C₂F₄. Temperatures of 950–1500 K, bath gas concentrations of [Ar] = 3 × 10⁻⁵ –2 × 10⁻⁴ mol cm⁻³, and reactant concentrations of 100–500 ppm C₂F₅I in Ar were employed. Absorption-time profiles were recorded at selected wavelengths in the range 200–280 nm. It was found that the dissociation of C₂F₅I → C₂F₅ + I was followed by the dissociation C₂F₅ → CF₂ + CF₃, before the dimerization reactions 2CF₂ → C₂F₄ and 2CF₃ → C₂F₆ and a reaction CF₂ + CF₃ → CF + CF₄ set in. The combination of iodine atoms with C₂F₅ and CF₃ had also to be considered. The rate constant of the primary dissociation of C₂F₅I was analyzed in the framework of statistical unimolecular rate theory accompanied by a quantum-chemical characterization of molecular parameters. Rates of secondary reactions were modelled as well. Experimental rate constants for the dissociations of C₂F₅I and C₂F₅ agreed well with the modelling results. The comparably slow dimerization 2CF₂ → C₂F₄ could be followed both by monitoring reactant CF₂ and product C₂F₄ absorption signals, while CF₃ dimerization was too fast to be detected. A competition between the dimerization reactions of CF₂ and CF₃, the recombination of CF₂ and CF₃ forming C₂F₅, and CF-forming processes like CF₂ + CF₃ → CF + CF₄ finally was discussed.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada
Falloff curves and mechanism of thermal decomposition of CF3I in shock waves
No full textThe falloff curves of the unimolecular dissociation CF3I (+Ar) - CF3 + I (+Ar) are modelled by combining quantum-chemical characterizations of the potential energy surface for the reaction, standard unimolecular rate theory, and experimental information on the average energy transferred per collision between excited CF3I and Ar. The (essentially) parameter-free theoretical modelling gives results in satisfactory agreement with data deduced from earlier shock wave experiments employing a variety of reactant concentrations (between a few ppm and a few percent in the bath gas Ar). New experiments recording absorption–time signals of CF3I, I2, CF2 and (possibly) IF at 450–500 and 200–300 nm are reported. By analysing the decomposition mechanism, besides the unimolecular dissociation of CF3I, these provide insight into the influence of secondary reactions on the experimental observations.Fil: Cobos, Carlos Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Sölter, L.. Universität Göttingen; AlemaniaFil: Tellbach, E.. Universität Göttingen; AlemaniaFil: Troe, J.. Universität Göttingen; Alemania. Institut Max Planck fuer Bioanorganische Chemie; Alemani
On the optimality of compactness results for interpolation methods associated to polygons
No full textAbstractCompactness results of Cobos and Peetre [3] guarantee that the interpolated operator is compact assuming that all but two restrictions of the operator (located in adjacent vertices) are compact. Comparing these results with others in the literature, one might expect that the same conclusion holds under weaker compactness conditions. However, the Cobos—Peetre results are best possible as we show by means of counterexamples
Experimental and modeling study of the reaction C2F4 (+M) = CF2 + CF2 (+M)
No full textThe thermal dissociation reaction C2F4(+ M) → 2CF2(+ M) was studied in shock waves monitoring CF2 radicals by their UV absorption. The absorption coefficients as functions of wavelength and temperature were redetermined and are represented in analytical form. Dissociation rate constants as functions of bath gas concentration [M] and temperature, from previous and the present work, are presented analytically employing falloff expressions from unimolecular rate theory. Equilibrium constants are determined between 1200 and 1500 K. The data are shown to be consistent, with a C–C bond energy of 67.5 (±0.5) kcal mol–1. High-pressure limiting rate constants for dissociation and recombination are found to be unusually small. This phenomenon can be attributed to an unusually pronounced anisotropy of the potential energy surface, such as demonstrated by quantum-chemical calculations of the potential energy surface.Fil: Cobos, Carlos Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Croce, Adela Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Luther, K.. Universität Göttingen. Institut für Physikalische Chemie; AlemaniaFil: Sölter, L.. Universität Göttingen. Institut für Physikalische Chemie; AlemaniaFil: Tellbach, E.. Universität Göttingen. Institut für Physikalische Chemie; AlemaniaFil: Troe, J.. Universität Göttingen. Institut für Physikalische Chemie; Alemania. Max-Planck-Institut für Biophysikalische Chemie; Alemani
Gynandrophthalma (Otiocephala) maroccana Cobos 1957
No full textGynandrophthalma (Otiocephala) maroccana Cobos, 1957 Gynandrophthalma (Otiocephala) maroccana Cobos, 1957: 181 (original description). Type material in PJCP. SYNTYPES: ♂, ‘ Christian [p] 3.53 [h] / (Maroc) (Roulleau) [w, p] // [small blue round label, blank] // HOLOTIPO [r, p] // Otiocephala / maroccana / Holotipo nov. sp. [h] / A. Cobos det. 1.956 [w, p]’; ♀, ‘ Air Regada / M. At. c. III 47 [h] / Maroc (Antoine) [w, p] // [small blue round label, blank] // ALOTIPO [r, p] // Otiocephala / maroccana / m. nov. sp. / Alotipo [h] / A. Cobos det. 1.956 [w, p]’. Current status. Otiocephala maroccana (Cobos, 1957). Comments. Described from unspeciħed number of specimens of both sexes and the Institut scientiħque chériħen in Rabat was indicated as depository. Because holotype and allotype are not mentioned in the original description we treat the specimens as syntypes.Published as part of Bezdċk, Jan & Regalin, Renato, 2015, Identity of species-group taxa of the Western Palaearctic Clytrini (Coleoptera: Chrysomelidae) described by Maurice Pic and Louis Kocher, pp. 1-114 in Acta Entomologica Musei Nationalis Pragae (suppl.) (suppl.) 55 on pages 68-69, DOI: 10.5281/zenodo.427277
Shock wave studies of the pyrolysis of fluorocarbon oxygenates. II. the thermal dissociation of C4F8O
No full textThe thermal decomposition of octafluorooxalane, C4F8O, to C2F4 + CF2 + COF2 has been studied in shock waves highly diluted in Ar between 1300 and 2200 K. The primary dissociation was shown to be followed by secondary dissociation of C2F4 and dimerization of CF2. The primary dissociation was found to be in its falloff range and falloff curves were constructed. The limiting low and high pressure rate constants were estimated and compared with modelling results. Quantum-chemical calculations identified possible reaction pathways, either leading directly to the final products of the reaction or passing through an open-chain CF2CF2CF2 intermediate which dissociates in a second step.Fil: Cobos, Carlos Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Hintzer, K.. Dyneon GmbH; AlemaniaFil: Sölter, L.. Universität Göttingen; AlemaniaFil: Tellbach, E.. Universität Göttingen; AlemaniaFil: Thaler, A.. Dyneon GmbH; AlemaniaFil: Troe, J.. Universität Göttingen; Alemania. Max-Planck-Institut für Biophysikalische Chemie; Alemani
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