IR Spectrum of C8H2: Integrated Band Intensities and Some Observational Implications

Shindo, F.; Bénilan, Y.; Chaquin, Patrick; Guillemin, Jean‐Claude; Jolly, A.; Raulin, F.

doi:10.1006/jmsp.2001.8459

Cited by 35 publications

(35 citation statements)

References 27 publications

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“…The chemical shifts computed with the CAM-B3LYP functional compare well with earlier experimental and computed values reported for PY chains [35][36][37][38] . For PY with n=16, the chemical shift we predict ranges between 56-65 ppm, which compares very well to the experimental value reported by Tykwinski (57-69 ppm) 38 .…”

Section: Methodssupporting

confidence: 80%

Impact of Donor–Acceptor Functionalization on the Properties of Linearly π-Conjugated Oligomers: Establishing Quantitative Relationships for the Substituent and Substituent Cooperative Effect Based on Quantum Chemical Calculations

et al. 2013

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To understand better the impact of donor-acceptor substitution on the properties of linearly -conjugated compounds, we performed a computational study on a series of variably substituted transpolyacetylenes, polyynes, and polythiophenes. The focus of this work is on how rapidly the impact of a given substituent or a given combination of substituents vanishes along the -conjugated chain. The response of the structural (bond-length alternation, rotational barrier) and molecular properties ((hyper)polarizability, chemical shift) to substitution is analyzed using different protocols, including a superposition model for the evaluation of the cooperative effect of substituents in homo-and heterosubstituted oligomers. With the exception of the (hyper)polarizability, the impact of donor-acceptor substitution is found to vanish following an exponential. The rate of decay of the substituent impact is found to be characteristic for each backbone, whereas the choice of substituent determines the absolute value of the respective property. The combination of substituents is shown to determine whether the substituent cooperative effect on a property is of an enhancing or damping nature. The rate of decay of the cooperative effect on most properties, including the (hyper)polarizability, is also found to follow an exponential law. With the exception of the (hyper-)polarizability, the impact of donor-acceptor substitution is found to vanish following an exponential. The rate of decay of the substituent impact is found to be characteristic for each backbone, whereas the choice of substituent determines the absolute value of the respective property. The combination of substituents is shown to lead whether the substituent cooperative effect on a property is of enhancing or damping nature. The rate of decay of the cooperative effect on most properties, including the (hyper-)polarizability, is also found to follow an exponential law.

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Section: Methodssupporting

confidence: 80%

Impact of Donor–Acceptor Functionalization on the Properties of Linearly π-Conjugated Oligomers: Establishing Quantitative Relationships for the Substituent and Substituent Cooperative Effect Based on Quantum Chemical Calculations

et al. 2013

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“…H(-C≡C-) m H, H(-C≡C) m or (C≡C) m ). Khlifi et al (1995); (i) Shindo et al (2001Shindo et al ( , 2003. Comparing our UV-VIS spectra to spectra obtained by arcing of graphitic electrodes submerged in water (Cataldo 2004), also shown in Fig.…”

Section: Polymerizationmentioning

confidence: 64%

“…The aforementioned reaction products have known vibrational transitions both in the short wavelength range of the C-H stretching mode and around the C-H bending mode. Shindo et al (2001Shindo et al ( , 2003 and A83, page 4 of 11 Zhou et al (2009) have observed other stronger features at 600, ∼620, 664, ∼3330, and 3386 cm −1 . Owing to a combination of the water baseline and worsened signal-to-noise ratios in these parts of the spectrum, these features are not unambiguously identified in our spectra.…”

Section: Polymerizationmentioning

confidence: 98%

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Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

Cuylle

Zhao

Strazzulla

et al. 2014

A&A

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Aims. Gas phase acetylene (C 2 H 2 ) and polyynes (H(-C≡C-) m H) are ubiquitous in the interstellar medium. However, astrochemical models systematically underestimate the observed abundances, supporting the idea that enrichment from the solid state takes place. In this laboratory-based study, we investigate the role C 2 H 2 plays in interstellar ice chemistry and we discuss the way its photoproducts may affect gas phase compositions. Methods. C 2 H 2 ice is investigated under vacuum ultraviolet (VUV) irradiation in its pure form as present in the atmosphere of Titan and in a water-dominated ice as present on grain mantles in molecular clouds and on comets. To disentangle the photochemical network, a unique, complementary combination of infrared and ultraviolet-visible (UV-VIS) spectroscopy is used. Results. From the experimental results, it can be concluded that the VUV-induced solid state C 2 H 2 reaction network is dominated by polymerization resulting in the formation of polyynes at least up to C 20 H 2 and larger polyyne-like molecules. At low temperatures, this process takes place very efficiently and suggests low barriers. When extending this reaction scheme to a water-rich environment, the dominant reaction products are CO and CO 2 but the simultaneous detection of polyyne like molecules is evidence that the reactions as observed in pure C 2 H 2 ice persist. Conclusions. From the spectroscopic evidence as presented in this laboratory study, it is concluded that the formation of polyynes upon VUV irradiation of interstellar ices is a process that may contribute to at least part of the observed gas phase enrichment in space.

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“…Finally, investigations of the atmosphere of Titan, a moon of Saturn, have shown that photochemistry in its upper atmosphere leads to significant concentrations of polyynes, assumed to be produced in similar reaction sequences to those involved in the terrestrial formation of PAHs and soot, and including ethynyl-like intermediates in a chain reaction synthetic pathway. [12][13][14] In support of the extensive reaction network modeling in multiple environments, rate constants have been measured for reactions of ethynyl radicals with various partners over a range of temperatures. [15][16][17][18][19][20][21][22][23][24][25] Following the astronomical observation of the ethynyl radical, 9 the gas-phase microwave spectrum was recorded and the molecular structure determined in the 1980's.…”

Section: Introductionmentioning

confidence: 99%

The near-infrared spectrum of ethynyl radical

Hall

Sears

2016

J. Chem. Phys.

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Transient diode laser absorption spectroscopy has been used to measure three strong vibronic bands in the near infrared spectrum of the C 2 H, ethynyl, radical not previously observed in the gas phase. The radical was produced by ultraviolet excimer laser photolysis of either acetylene or (1,1,1)-trifluoropropyne in a slowly flowing sample of the precursor diluted in inert gas, and the spectral resolution was Doppler- (2004)), the vibronic character of these levels was also assigned. The observed states contain both X 2 Σ + and A 2 Π electronic character. Several local rotational level perturbations were observed in the excited states. Kinetic measurements of the time-evolution of the ground state populations following collisional relaxation and reactive loss of the radicals formed in a hot, nonthermal, population distribution were made using some of the strong rotational lines observed. The case of C 2 H may be a good place to investigate the behavior at intermediate pressures of inert colliders, where the competition between relaxation and reaction can be tuned and observed to compare with master equation models, rather than deliberately suppressed to measure thermal rate constants.

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IR Spectrum of C8H2: Integrated Band Intensities and Some Observational Implications

Cited by 35 publications

References 27 publications

Impact of Donor–Acceptor Functionalization on the Properties of Linearly π-Conjugated Oligomers: Establishing Quantitative Relationships for the Substituent and Substituent Cooperative Effect Based on Quantum Chemical Calculations

Impact of Donor–Acceptor Functionalization on the Properties of Linearly π-Conjugated Oligomers: Establishing Quantitative Relationships for the Substituent and Substituent Cooperative Effect Based on Quantum Chemical Calculations

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

The near-infrared spectrum of ethynyl radical

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