Cyanoacetylene Research Articles

Combined crossed molecular beams and computational study on the N(2D) + HCCCN(X1Σ+) reaction and implications for extra-terrestrial environments

The reaction of the nitrogen atom (N) in its first electronically excited state (2D) with cyanoacetylene (HC3N) has been investigated under single-collision conditions by using the crossed molecular beam method with mass spectrometric detection at a collision energy of 31 kJ mol−1. With the support of electronic structure calculations, we found that this reaction proceeds via the barrierless addition of the N(2D) atom to the carbon–carbon triple bond of HC3N, followed by the formation of a cyclic intermediate adduct HC(N)CCN, which dissociates to C(N)CCN + H products or isomerises to a more stable intermediate HNCCCN by H-migration and ring-opening processes. The long-lived HNCCCN complex produces the linear 3Σg – ground state dicyanocarbene (NCCCN) radical plus atomic hydrogen through a barrierless unimolecular dissociation accompanied by a negligible competitive channel forming the NCCCN radical (1A1) with a bent C 2v structure plus H. The main product of this neutral-neutral reaction is the 3NCCCN radical that could be a potential precursor to form other nitriles (C2N2, C3N) or more complex organic species in planetary atmospheres, such as that of Titan and Pluto, in cometary comas, and in UV irradiated interstellar environments.

Prebiotic Cytosine Synthesis from Urea in Interstellar Space: A Computational Mechanistic Study

Abstract The potential energy surfaces for the formation of cytosine (Cyt) and a protonated cytosine (CytH+) from reactions of urea with cyanoacetylene (CA), cyanoacetaldehyde (CAA), or their protonated ions, CAAH+ and CAH+ with or without H2O, have been determined from quantum chemical calculation using the CBS-QB3 method. The overall activation energies of the formation of Cyt or CytH+ from urea + CA, urea + CAA and, urea + CAH+ are 127, 211, and 31 kJ mol−1, respectively, which are too high for the thermal reactions to occur in the interstellar medium (ISM). The barrierless reaction pathways have been proposed for the formation of CytH+ from urea + CAH++ H2O and urea + CAAH+. A kinetic analysis shows that the synthesis of Cyt through the formation of CytH+ from urea, CAH+, and H2O would be possible in the ISM.

Angle-dependent strong-field ionization of triple bonded systems calculated by time-dependent configuration interaction with an absorbing potential

The angle dependence of strong field ionization has been studied for a set of molecules containing triple bonds: HCCH, HCN, HCC–CN, H2N–CCH, H2N–CN, and H2N–CC–CN. Time-dependent configuration interaction (TDCI) with a complex absorbing potential was used to model strong field ionization by a linearly polarized seven-cycle 800 nm cosine squared pulse. The ionization yields have been calculated as a function of the laser intensity and polarization direction and plotted as three-dimensional surfaces. At low field strengths, the angular dependence can be understood in terms of ionization from the highest occupied orbitals. At higher laser intensities, ionization occurs from lower lying orbitals as well as from the highest occupied orbitals, as indicated by changes in the angular dependence of the ionization yield and by variations in the population analysis of the TDCI wavefunction with the intensity of the laser field. The ionization yield for directions parallel to the molecular axis increases more rapidly than perpendicular to the axis as the conjugation length is increased. NH2 substitution substantially increases the ionization yield along the molecular axis but has only a small effect for perpendicular directions.

Combined IRAM andHerschel/HIFI study of cyano(di)acetylene in Orion KL: tentative detection of DC3N

We present a study of cyanoacetylene (HC3N) and cyanodiacetylene (HC5N) in Orion KL, through observations from two line surveys performed with the IRAM 30m telescope and the HIFI instrument on board the Herschel telescope. The frequency ranges covered are 80-280 GHz and 480-1906 GHz. We model the observed lines of HC3N, HC5N, their isotopologues (including DC3N), and vibrational modes, using a non-LTE radiative transfer code. To investigate the chemical origin of HC3N and DC3N in Orion KL, we use a time-dependent chemical model. We detect 40 lines of the ground state of HC3N and 68 lines of its 13C isotopologues. We also detect 297 lines of six vibrational modes of this molecule (nu_7, 2nu_7, 3nu_7, nu_6, nu_5, and nu_6+nu_7) and 35 rotational lines of the ground state of HC5N. We report the first tentative detection of DC3N in a giant molecular cloud with a DC3N/HC3N abundance ratio of 0.015. We provide column densities and isotopic and molecular abundances. We also perform a 2x2" map around Orion IRc2 and we present maps of HC3N lines and maps of lines of the HC3N vibrational modes nu_6 and nu_7. In addition, a comparison of our results for HC3N with those in other clouds allows us to derive correlations between the column density, the FWHM, the mass, and the luminosity of the clouds. The high column densities of HC3N obtained in the hot core, make this molecule an excellent tracer of hot and dense gas. In addition, the large frequency range covered reveals the need to consider a temperature and density gradient in the hot core in order to obtain better line fits. The high D/H ratio (comparable to that obtained in cold clouds) that we derive suggests a deuterium enrichment. Our chemical models indicate that the possible deuterated HC3N present in Orion KL is formed during the gas-phase. This fact provides new hints concerning the processes leading to deuteration.

C(sp3)–N(sp) Bond Cleavage of Isocyanides at a Cationic [CCH] Subunit in a Bisdisphenoidal Eight-atom Tetrairon–Tetracarbon Cluster

Abstract Reaction of [(η5-C5H4Me)4Fe4(HCCH)(HCC–NC4H4N)](PF6)2 (1) with tert-butyl isocyanide led to C(sp3)–N(sp) bond activation to give [(η5-C5H4Me)4Fe4(HCCH)(HCC–CN)](PF6) (2). The resulting tert-butyl cation was trapped as the adduct with pyrazine. Reactions of 1 with 2,6-dimethylphenyl isocyanide and cyclohexyl isocyanide led to the coordination of the isocyanides to the cationic [CCH] subunit. Thermolysis of [(η5-C5H4Me)4Fe4(HCCH)(HCC–CNCy)](PF6)2 (6) yielded 2.

VUV spectroscopy and photochemistry of five interstellar and putative prebiotic molecules

For many years, our group has been investigating the VUV spectroscopy and photochemistry of molecules of astrophysical (Jochims et al. 2006a,b; Leach et al. 2008; Schwell et al. 2012) and prebiotic interest (Schwell et al. 2006). Polyynes and cyano-polyynes that are abundant in the interstellar medium (ISM) and in planetary atmospheres, have been investigated too (e.g. Fray et al. 2010). An aerosol source for reactive and thermo-labile compounds has been developed (Gaie-Levrel et al. 2011) to perform gas-phase measurements. These are necessary to measure intrinsic molecular properties and to compare to quantum chemical calculations. Besides measuring absolute absorption and photoionization cross sections, dissociative channels and their involved excited states are identified for a number of molecules of interstellar interest. Branching ratios of the respective elementary photoreactions are determined in order to understand and model the photochemistry occurring in the ISM. Some very recent results on the dissociative photoionization of methylformate (MF), glycolaldehyde (GA), dimethylether (DIM), aminoacetonitrile (AAC) and cyanoacetylene (CA), are presented here.

PROSPECTS FOR THE DETECTION OF INTERSTELLAR CYANOVINYLIDENE

Prospects for the presence and detection of interstellar cyanovinylidene, CC(H)CN, a Y-shaped isomer of cyanoacetylene, are discussed. It is proposed that CC(H)CN can arise in interstellar clouds as one of the HC3NH+ + e – dissociative recombination products, by rearrangements of the neutral chain radical HC3NH into branched species HCCC(H)N, CC(H)C(H)N, and/or HCC(H)CN, and by the subsequent elimination of a hydrogen atom. It is deduced that the abundance of cyanovinylidene in molecular clouds should be confined between the abundances of its chain isomers HNCCC and HCNCC. Quantum chemical predictions regarding cyanovinylidene geometry, ground-state rotational constants, centrifugal distortion constants, spin-orbit coupling, IR absorption spectroscopy, and electric dipole moment are given. The spectroscopically observed molecules formyl cyanide, NC2(H)O, and propynal, HC3(H)O, with structures qualitatively resembling cyanovinylidene, served to prove the adequacy of the calculational procedures employed.

Effects of wave function modifications on calculated carbon–carbontriple bond lengths

Two-level factorial design (FD) and principal component (PC) models are used to determine the effects of wave function modifications on calculated carbon–carbon triple bond lengths for the HC CH, HC CF, HC CCH 3, CH 3C CCH 3 and HC CCCH molecules. Our results have shown that valence, diffuse and polarization main effects are significant at the three levels of calculation here employed: Hartree–Fock (HF), Møller–Plesset 2 (MP2) and density functional theory (DFT) with B3LYP exchange–correlation functional. The valence–polarization interaction effect is significant at only the HF and MP2 levels of calculation. When valence and polarization functions are introduced in the basis set, the calculated C C bond length values decrease, in contrast with the results obtained when diffuse functions are used. The latter increase the C C bond length by +0.0016 Å, at all levels of calculations. Changing the method from HF to B3LYP and from B3LYP to MP2 yields an increase (averaged values) of +0.0195 and +0.0169 Å, respectively, on the calculated C C bond length values. For each level of calculation it was possible to establish an algebraic model to explain how the calculated C C bond length values depend on the molecular orbital wave functions. Such algebraic models successfully reproduce calculated C C bond lengths for the HC CCN and HC CCl molecules, which were not included in our training set. Our FD and PC models lead to the B3LYP/6-31G(d,p) and B3LYP/6-311++G wave functions as the selected ones in order to better reproduce experimental C C bond lengths for all the seven molecules here studied (training and validation molecules). Their predicted values deviate by just 0.004 Å from the experimental ones.

Cyanoacetylene and Its Derivatives. 30. Reactions of 2,3-Dimercaptoquinoxaline with 3-Phenyl-2-propynonitrile and 4-Alkyl-4-hydroxy-2-alkynonitriles

The reaction of 2,3-dimercaptoquinoxaline with 3-phenyl-2-propynonitrile (~10 mass % KOH, 20-25°C, 5 h, dioxane) gave the S,S-diadduct (as with unsubstituted acetylene). 2,3-Dimercaptoquinoxaline reacted with 4-alkyl-4-hydroxy-2-alkynonitriles to give 2-cyanomethyl-2-(1-hydroxy-1-alkyl)-1,3-dioxolano[4,5-b]quinoxalines or 3-cyanomethylene-8-imino-2,2,6,6-tetramethyl-1,7-dioxa-4-thiaspiro[4.4]nonane.

The ν1Band System of H–CC–CN (Cyanoacetylene)

The ν1band system of cyanoacetylene (H–CC–CN) has been observed with an effective resolution of 0.006 cm−1. ν1= 3327.37085(3) cm−1,B1= 0.15149762(2) cm−1,D1= 1.8065(3) × 10−8cm−1. Several hot bands from the statesv5= 1,v6= 1,v7= 1, 2 (l= 0 and 2), 3 (l= 1 and 3), and 4 (l= 0 and 2),v6=v7= 1 (l= 0 and 2), andv6= 1 andv7= 2 (l= 3) have also been observed and analyzed. Many bands show strong local perturbations due to interactions with states which are combinations of the modes 4, 5, 6, and 7. These perturbing states are also described quantitatively, and rovibrational constants are given.

Photochemistry of Cyanoacetylene at 193.3 nm

Cyanoacetylene (CA) is an important minor constituent in the Titan atmosphere and is present in the interstellar medium. The absorption cross section of CA has been measured in the region from 190 to 255 nm with a resolution of 1 nm. The photochemistry of CA at 193.3 nm has been studied using a quadrupole mass spectrometer and a Fourier transform infrared spectrometer for product analysis. From the photolysis of HC3N−D2 and HC3N−CD4 mixtures and a plateau value of 0.3 for the quantum yield (QY) of DC3N (C3N + D2 → DC3N + D), it is concluded that the main dissociation process is HC3N + hν → H + C3N with a QY of 0.30 ± 0.05 and a minor process is HC3N + hν → C2H + CN with a QY equal to or less than 0.02. The remaining process is the formation of metastable CA (a triplet or carbene). The photolysis of CA induces a noticeable pressure decrease and a concomitant formation of a mist. The QY of CA disappearance is 4.5 ± 0.5, which is much higher than that of diacetylene (QY = 2.0 ± 0.5) and of acetylene (QY = 2.3). The rapid mist formation in CA may explain a haze observed in the Titan atmosphere. A detailed mist formation process is not known. The C3N radical disappears partially by C3N + HC3N → C6N2 + H and 2C3N → C6N2. To explain the formation of minor products, HCN, C2H2, HC5N, and C4N2, two processes involving an unspecified CA metastable state or states may be proposed: HC3N* + HC3N → HC5N + HCN and C4N2 + C2H2.

Three millimeter molecular line observations in Sagittarius B2. 1: Full synthesis mapping study of HNO, CCS, and HC(13)CCN

We present the first full synthesis maps of the small molecules HNO, CCS, and HC(13)CCN in Sgr B2. We have observed the 3.8 mm continuum, the HNO J(sub K(sub -1)K(sub 1)) = 1(sub O1)-0(sub OO), the CCS J(sub N) = 7(sub 6)-6(sub 5), and the HC(13)CCN J = 9-8 transitions in the core of the Sgr B2 molecular cloud, using the Berkeley Illinois Maryland Association (BIMA) millimeter array and the NRAO 12 m telescope. We have found that HNO exists in five major gas clumps in the Sgr B2 region, which we have labeled HNO(N), HNO(NW), HNO(E), HNO(M), and HNO(S). Of particular interest is HNO(M), a major molecular gas concentration approximately 15 sec west of Sgr B2(M) in a region of young star formation. HNO is found to be closely associated with the ionized gas and might be depleted around bright H II complexes. In general, the peak intensity of the HNO emission is found to be offset from the peak of the continuum emission. We found evidence for some chemical differentiation among the three species, HNO, CCS, and HC(13)CCN, but the abundance ratios are in fair agreement with theoretical models. Two unidentified lines, U81420 and U81518, were observed, and a previously unknown compact dust source was detected. Our HNO data indicate the presence of a rotating approximately (2.2-4.4) x 10(exp 3)solar mass gas envelope surrounding Sgr B2(N), a possible bipolar gas outflow in HNO(M), and possibly a large (approximately 4.2 x 10(exp 4)solar mass) extended rotating disk associated with HNO(S). In addition, the CCS and HC(13)CCN data approximately outline the extended component of Sgr B2 and clearly show that the southern continuum source Sgr B2(S) is actually a major molecular source as well. Consequently, the kinematics of the Sgr B2 molecular cloud is quite complex, but in moving from the northwest to south, the LSR velocity generally changes from 79 to 46 km/s.

Transition metal-cyanocarbon chemistry X. Reactions of monocyanoacetylene and dicyanoacetylene with organometallic compounds of cobalt(I) and nickel(II). Crystal structure of [Co(CCCN) 2(η 5-C 5H 5)(P(C 6H 5) 3)

The reaction of monocyanoacetylene (HCCCN) with [Co(η 5-C 5H 5)(P(C 6H 5) 3) 2] gives the vinylacetylide [Co(CCCN)(CHCH(CN))(η 5-C 5H 5)(P(C 6H 5) 3)] ( 1) and the diacetylide [Co(CCCN) 2(η 5-C 5H 5)(P(C 6H 5) 3)] ( 2). The crystal structure of the latter has been established by an X-ray diffraction study. Two conformers of 1 are formed in a ratio depending on conditions. In 1 a PPh 3 ligand can be replaced by (CH 3) 3SiCCSi(CH 3) 3, which acts as a π-bonded ligand in the product, [Co(CCCN)(CHCH(CN))(η 5-C 5H 5)(η 2-(CH 3) 3SiCCSi(CH 3) 3)] ( 3). Treatment of 1 with I 2 gave (Co(η 5-C 5H 5)(I) 2(P(C 6H 5) 3)] ( 6) and CH(CN)CH-C(CN)CHI ( 5). The major product of the reaction of [Co(η 5-C 5H 5)(P(C 6H 5) 3) 2] with dicyanoacetylene (NCCCCN) was the 1,6-diphosphorane (C 6H 5) 3PC(CN)C(CN)C(CN)C(CN)C(CN)C(CN)P(C 6H 5) 3. [Co(η 5-C 5H 5)(η 4-C 5H 5(CCCN))] ( 7) was isolated from the reaction of monocyanoacetylene with [Co(η 5-C 5H 5)(η 4-C 5H 6)]. Cyanoalkynes bridge two nickel atoms in [μ-(HCCCN)][Ni(η 5-C 5H 5)] 2 ( 8) and [μ-(NCCCCN)][Ni(η 5-C 5H 5)] 2 ( 9), which were formed in the reaction of nickelocene with HCCCN and NCCCCN, respectively.

Transition metal-cyanocarbon chemistry: IX. Reactions of monocyanoacetylene with dicarbonylcyclopentadienylmethylthiolatoiron(II). Crystal structures of [ [formula omitted]CH 3) (η 5-C 5H 5)(CO)] and of μ-η 2-Fe(CCCN)(η 5-C 5H 5)(CO) 2][Co(CO) 3] 2

The reaction of [Fe(η 5-C 5H 5)(SCH 3)(CO) 2] with monocyanoacetylene (HCCCN) in THF at room temperature gives the acetylide [Fe(CCCN)(η 5-C 5H 5)(CO) 2] ( 1, the acylic species [ FeC(O)C(CN)CH(S CH 3)(η 5-C 5H 5)(CO)] ( 2), the binuclear complex [Fe(η 5-C 5H 5)(CO) 2C(CN)C(SCH 3)Fe(η 5-C 5H 5)(CO) 2] ( 3), and the disubstituted olefin Z-(NC)CHCH((SCH 3) ( 4. If the HCCCN is condensed on to a frozen solution of the thiolato complex and the mixture then allowed to warm up, the acylic compound 2 is not isolated. Irradiation of 1 and 3 in the presence of PPh 3 in THF gives the substituted complex [Fe(CCCN)(η 5-C 5H 5)(CO)(PPh 3)] ( 6)_and [Fe(η 5-C 5H 5)(CO) 2C(CN)C(SCH 3)Fe(η 5-C 5H 5)(CO)(PPh 3)] ( 10). Cycloaddition of tetracyanoethylene on 1 and 6 gives the corresponding complexes [fe( CC(CN)C(CN) 2C (CN) 2(η 5-C 5H 5)(CO)(L)] (L = CO (7) or PPh 3 ( 8). Under UV irradiation 8 is converted into Fe(η 3-C(CN) 2C(CN)C C(CN) 2(η 5-C 5H 5)(PPh 3)] by loss of CO. Complex 1 reacts with Co 2(CO) 8 to form the [μ-η 2-Fe(CC-CN)(η 5-C 5H 5)(CO) 2][Co(CO) 3] 2 ( 5). The structures of 2 and 5 have been determined by X-ray diffraction.

Structure of HNO 3-intercalated graphite fiber prepared from cyanoacetylene

A highly conductive graphite fiber was prepared by chemical vapor deposition of cyanoacetylene (CA) on a carbon fiber substrate, followed by heat treatment. In order to discuss the graphitization process, the inhomogeneity of residual strain of the graphite fiber was investigated from the analysis of X-ray peak width. Peak analysis of 00 l reflections by use of Hall's method reveals that inhomogeneous strain decreases with increasing heat treatment temperature (HTT), and reaches to 5.0×10 −4 (or ± 35 K) at HTT 3000°C. The structural changes of HNO 3-intercalated graphite fibers prepared from CA were studied in air. HNO 3-graphite fiber from CA (HTT 3000°C) changes the structure from α-stage 3 ( Ic=14.50 A ̊ : di=7.80 A ̊ ) to β-stage 3 ( Ic=13.25 A ̊ : di=6.55 A ̊ ) in 8h after exposure to air, and retain β-stage 3 over 6 months. While, fibers from benzene are unstable in air and are transformed to mixed structure with pristine graphite and higher stage compounds in 1 month. It is suggested that residual nitrogen atoms in the graphite fibers (0.2 wt% even at HTT 3000°C) contribute to the structural stability of HNO 3-graphite fiber from CA.

Transition metal-cyanocarbon chemistry: VI. Insertions of cyano- and dicyano-acetylenes into the iron-hydride bonds in (C5H5)(CO)LFeH (L  CO, PPh3) and [(C5H5)(CO)FeH]2 [μ-(C6H5)2PCH2CH2P(C6H5)2] complexes

Monocyanoacetylene (HCCCN, mca) and dicyanoacetylene (NCCCCN, dca) have been shown to insert into the FeH bonds of various mononuclear and dinuclear iron hydrides. In the presence of dca, [(η5-C5H5)(CO)2FeH] and [(η5-C5H5)(CO)(PPh3)FeH] give [(η5-C5H5)(CO)2Fe(σ-(Z)-C(CN)CH(CN)] and [(η5-C5H5)(CO)(PPh3)Fe(σ-(Z)-C(CN)CH(CN)] respectively. The reaction involving [(η5-C5H5)(CO)(PPh3)FeH] provides the first evidence for non-regioselectivity of an insertion of mca; the isomers [(η5-C5H5)(CO)(PPh3)Fe(σ-(Z)-CHCH(CN)] and [(η5-C5H5)(CO)(PPh3)Fe(σ-C(CN)CH2)] being obtained in a 4/1 ratio. However regioselectivity is observed for insertion of mca into the FeH bonds of dinuclear [(η5-C5H5)(CO)FeH]2(μ-dppe) (dppe = 1,2-bis(diphenylphosphido)ethane); in this case the CN groups are attached only to the Cα carbon atom. The reaction of dca with the dinuclear hydride gives products analogous to those from the mononuclear ones. The mechanisms of these various insertions are discussed in terms of the degree of hydridic nature of the hydridic hydrogen in the initial iron complexes.

Properties and structures of graphite fibers prepared from cyanoacetylene

The structural change of nitrate intercalated graphite fibers prepared from cyanoacetylene (CA) were studied in air. Two kinds of 3rd stage graphite intercalation compounds are identified by X-ray diffraction measurements, one of which is a stable stage structure observed newly in this study. HNO 3-graphite fibers prepared from CA (H.T.T. 3000°C) change the structure from α-3rd stage ( Ic=14.50 A ̊ : di=7.80 A ̊ ) to β-3rd stage ( I=13.25 A ̊ : di=6.55 A ̊ ) in 8h after exposure to air, while the change occurs in less than 1h for fibers from benzene. The former retain β-3rd stage over 6 months, while the latter are unstable and are transformed into mixed structure with β-3rd stage compound and pristine graphite in a few days. Content of residual nitrogen in graphite fibers from CA (H.T.T. 3000°C) is estimated to be about 0.2 wt.% from elemental analysis. It is suggested that residual nitrogen atoms contribute to the structural stability of HNO 3-graphite fibers from CA.

Unexpected direct formation of a bridging 4-cyanobuta-1,3-dienylidene group from reaction of [(C 5H 5)Fe(CO)] 2(μ-CCH 2) with HCCCN

The ethenylidenediiron complex [C 5H 5Fe(CO)] 2 (μ-CO)(μ-CCh 2) reacts with the nitrile substituted alkyne HCCCn to give high yield of [(C 5H 5)Fe(CO)] 2 (μ-CO)(μ-CCHCHC(CN)H). It is suggested that this bridging 4-cyanobuta-1,3-dien-ylidenediiron complex is formed by attack of the electron rich double bond of the ethenylidenediiron complex on the electrophilic protonated carbon of the alkyne. An IR study has indicated that hydride reduction of the complex occurs selectively at the bridging vinylidene carbon atom to give am anionic bridging cyanovinylalkylidenediiron complex.

High electro-conductive product from cyanoacetylene

Polymerisation en phase vapeur sur un support de quartz ou un film de polyimide «Kapton»; obtention d'un film de conductivite electrique elevee

Structure and Electric Conductivity of Vapor Deposition Products of Cyano Acetylene

Abstract Cyanoacetylene can be polymerized from vapor state onto an inactive surface of substrate at a temperature as low as 200°C. The structure and electric conductivity of these cyanoacetylene products have been investigated.