Microwave Spectrum of Methoxyacetonitrile

Kewley, R.

doi:10.1139/v74-080

Cited by 21 publications

(18 citation statements)

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“…111 addition Hirota concluded that the energy difrere~ice between the two conformers is less than 1 kcal mol-I. In our laboratory it was deterniined that metlioxyacetonitrile, CH,OCH,CN, is predominantly in the gcruclle forni with a small amount of higher energy (by about 1.4 kcal mol-') trails form also present (2). By contrast we found that 3-nietlioxypropio~iitrile, CH,0CH2CH2CN, exists almost entirely as a fi~lly trmls conformer (3).…”

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confidence: 55%

Microwave spectrum of methylthioacetonitrile

Kewley¹

1978

Can. J. Chem.

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. Can. J. Cheni. 56,772 (1978). The microwave rotational spectrum of rncthylthioacetonitrile has been studied in the frequency range 18-37 GHz. The spectrum found is that of the grrrrclre conformer. The nonobservation of the spectrum of the !rc~tr.s conformer indicates that its abundance is less than about 5%. The rotational and centrifugal distortion constants for the ground vibrational state of the gcrr~clre confomier are: A = 7715.123 MHz, B = 2641.756 MHz, C = 2174.538 MHz, DK = 0.6824 MHz, DJK = -2.52 kHz, and DJ = 1.96 kHz. The observed rotational constants are compatible with a dihedral angle of 66 & 5" and a CSC angle of 104 & 2;. The dipole moment of the gcrriclre conformer has been determined as 3.02 D. Vibrational satellites due to S-CH, torsion have been observed and a torsional frequency of 101 cni-' has been estimated from relative intensity measurements. R. KEWLEY. Can. J. Chem. 56.772(1978). The present investigatioli represents an extension of our recent interest in straight chain rnethoxy derivatives. The first microwave spectroscopy study of a molecule closely related to methylthioacetonitrile, CH,SCH2CN, was Hirota's (1) work on butyronitrile, CH3CH2CH2CN, which was found to be present in the gas phase as both gnuclle and t r u l l .~ conformers, related by rotation around the CH,-CH2 bond. 111 addition Hirota concluded that the energy difrere~ice between the two conformers is less than 1 kcal mol-I. In our laboratory it was deterniined that metlioxyacetonitrile, CH,OCH,CN, is predominantly in the gcruclle forni with a small amount of higher energy (by about 1.4 kcal mol-') trails form also present (2). By contrast we found that 3-nietlioxypropio~iitrile, CH,0CH2CH2CN, exists almost entirely as a fi~lly trmls conformer (3). Recent niicrowave studies of niolecules of the type CH,OCH,X, X = F, C1, Br, and CECH, each resulted in the detection of a sole conformer, the guuclle (4-7). The Raman and infrared spectra of methyl propargyl ether, C H , 0 C H 2 C~C H , are explicable in terms of a predominant guuclle confornier in the solid, liquid, and vapor states (8). The infrared spectrum of metliylthioacetonitrile in the liquid, solid, and dissolved states has been investigated recently by Owen and co-workers (9). They were unable to obtain the gas phase infrared spectrum because of the low vapor pressure of CH3SCH2CN at room temperature. Solution infrared spectra were interpreted as showing 110 evidence of rotational isomerism. On the other hand spectral changes during warming and cooling between the solid and liquid phases did indicate that rotational isomerization was taking place. They also measured the dipole moment of CH,SCH,CN in solution in toluene. The observed value of 3.10 D is below the values of 3.2 and 5.0 D which they predicted from bond moments for the gcr~iche and trcnis conformers, I-espectively. This indicates that the proportion of gauclie confornier is close to 100%.In view of the ambiguous nature of the results of the infrared and dipole monient study a liiicrowave investigatio...

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confidence: 55%

Microwave spectrum of methylthioacetonitrile

Kewley¹

1978

Can. J. Chem.

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“…In addition to moving away from the Boltzmann peak of many large molecules at millimeter wavelengths, thus reducing the problem of line confusion (Sutton et al 1984;Crockett et al 2010), the THz window also allows the observation of low-lying torsional or vibrational states. Both methoxyacetonitrile and cyanoethanol have torsional states in the THz window, the lowest one at approximately 93 cm −1 for methoxyacetonitrile (Kewley 1974), and at approximately 108 cm −1 for cyanoethanol (Marstokk & Mollendal 1985). These torsions lie along the path to interconversion between the gauche and anti-conformers for both molecules, and in both cases the gauche and anti-conformers have large but differently oriented dipole moments (Kewley 1974;Marstokk & Mollendal 1985).…”

Section: Discussionmentioning

confidence: 99%

“…Both methoxyacetonitrile and cyanoethanol have torsional states in the THz window, the lowest one at approximately 93 cm −1 for methoxyacetonitrile (Kewley 1974), and at approximately 108 cm −1 for cyanoethanol (Marstokk & Mollendal 1985). These torsions lie along the path to interconversion between the gauche and anti-conformers for both molecules, and in both cases the gauche and anti-conformers have large but differently oriented dipole moments (Kewley 1974;Marstokk & Mollendal 1985). This indicates that these torsional modes should have significant intensity.…”

Section: Discussionmentioning

confidence: 99%

“…For both molecules the gauche conformer is lowest in energy by a significant margin over the next lowest conformer, 5.7 kJ mol −1 in the case of methoxyacetonitrile (Kewley 1974) and 2.7 kJ mol −1 in the case of cyanoethanol (Marstokk & Mollendal 1985). These conformers are therefore the focus of the present observational searches toward Sgr B2.…”

Section: Cyano-chemistrymentioning

confidence: 98%

“…Because these molecules are strongly prolate tops (κ = −0.844 for cyanoethanol and κ = −0.878 for methoxyacetonitrile) and effects of internal rotation are absent (or unimportant), both species are well-behaved asymmetric tops and their spectra can be accurately described using the parameters shown in Table 1. The rotational partition function merits some extra attention here due to the fact that both molecules have several low-lying torsional states in the ∼75-200 cm −1 range (Kewley 1974;Marstokk & Mollendal 1985). These states are significantly populated at room temperature and their inclusion in the partition function is known to be important in correctly modeling the room temperature spectra of both molecules (Braakman & Blake 2010a, 2010b.…”

Section: Cyano-chemistrymentioning

confidence: 99%

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Search for Interstellar Methoxyacetonitrile and Cyanoethanol: Insights Into Coupling of Cyano- To Methanol and Ammonia Chemistry

Braakman¹,

Беллоче²,

Blake³

et al. 2010

ApJ

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As part of an effort to study gas-grain chemical models in star-forming regions as they relate to molecules containing cyanide (-C≡N) groups, we present here a search for the molecules 2-cyanoethanol (OHCH 2 CH 2 CN) and methoxyacetonitrile (CH 3 OCH 2 CN) in the galactic center region SgrB2. These species are structural isomers of each other and are targeted to investigate the cross-coupling of pathways emanating from the photolysis products of methanol and ammonia with pathways involving cyano-containing molecules. Methanol and ammonia ices are two of the main repositories of the elements C, O, and N in cold clouds and understanding their link to cyanide chemistry could give important insights into prebiotic molecular evolution. Neither species was positively detected, but the upper limits we determined allow comparison to the general patterns gleaned from chemical models. Our results indicate the need for an expansion of the model networks to better deal with cyanochemistry, in particular with respect to pathways including products of methanol photolysis. In addition to these results, the two main observational routes for detecting new interstellar molecules are discussed. One route is by decreasing detection limits at millimeter wavelength through spatial filtering with interferometric studies at the Atacama Large Millimeter Array (ALMA), and the second is by searching for intense torsional states at THz frequencies using the Herschel Space Observatory. 2-cyanoethanol and methoxyacetonitrile would both be good test beds for exploring the capabilities of ALMA and Herschel in the study of complex interstellar chemistry.

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ChemInform Abstract: MICROWAVE SPECTRUM OF METHOXYACETONITRILE

Kewley¹

1974

Chemischer Informationsdienst

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Microwave Spectrum of Methoxyacetonitrile

Cited by 21 publications

References 3 publications

Microwave spectrum of methylthioacetonitrile

Microwave spectrum of methylthioacetonitrile

Search for Interstellar Methoxyacetonitrile and Cyanoethanol: Insights Into Coupling of Cyano- To Methanol and Ammonia Chemistry

ChemInform Abstract: MICROWAVE SPECTRUM OF METHOXYACETONITRILE

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