The enthalpy of isomerisation of methyl isocyanide

1977 ◽  
Vol 55 (14) ◽  
pp. 2634-2636 ◽  
Author(s):  
Mohammad H. Baghal-Vayjooee ◽  
John L. Collister ◽  
Huw O. Pritchard
Keyword(s):  
Thermal Explosion ◽  
Enthalpies Of Formation ◽  
Methyl Cyanide ◽  
Methyl Isocyanide

A controlled thermal explosion in which methyl isocyanide isomerises quantitatively to methyl cyanide has been studied in a calorimeter at 300 K. The enthalpy of isomerisation ΔH = −23.70 ± 0.14 (2 sdm) kcal mol−1, from which values of the enthalpies of formation of both gaseous and liquid methyl isocyanide are calculated.Similar measurements for ethyl isocyanide yield ΔH = −21.5 ± 1.0 kcal mol−1.

Methyl Isocyanide as a Key Molecule in Thermal Explosion Theory

1973 ◽  
Vol 51 (23) ◽  
pp. 4001-4003 ◽  
Author(s):  
Huw O. Pritchard ◽  
Brian J. Tyler
Keyword(s):  
Thermal Explosion ◽  
Thermodynamic Data ◽  
Reaction System ◽  
Sufficient Accuracy ◽  
Temperature Range ◽  
Methyl Cyanide ◽  
Explosion Limits ◽  
Methyl Isocyanide ◽  
Thermal Explosion Theory

Thermal explosion limits have been measured in the temperature range 285–351 °C for methyl isocyanide and at 351 °C for mixtures of methyl isocyanide and methyl cyanide. We suggest that the methyl isocyanide isomerization is potentially the best reaction system against which to test thermal explosion theories, but at the present time certain kinetic, thermochemical, and thermodynamic data are not available with sufficient accuracy.

Failure of the scaling laws in the thermal explosion of methyl isocyanide

1977 ◽  
Vol 55 (22) ◽  
pp. 3815-3819
Author(s):  
John L. Collister ◽  
Huw O. Pritchard
Keyword(s):  
Thermal Explosion ◽  
Critical Parameter ◽  
Scaling Laws ◽  
Temperature Measurements ◽  
Methyl Cyanide ◽  
Explosion Limits ◽  
Methyl Isocyanide ◽  
Explosion Limit ◽  
Thermal Explosions ◽  
Reaction Vessels

Thermal explosions of methyl isocyanide have been studied in spherical reaction vessels with volumes in the range 300–5000 ml. The normal inverse dependence of the explosion limit on the square of the radius appears to hold over limited ranges, e.g. from 300–1000 ml and from 2000–3000 ml, but the explosion limits at 1000 ml and 2000 ml are characterized by markedly different values of the critical parameter δc. Temperature measurements were made at and near the vessel walls, but they do not reveal any abnormalities which could be used to explain these results.An appendix reports measurements of the thermal conductivities of methyl cyanide and methyl isocyanide from 200–350 °C.

Thermodynamic Properties of Methyl Cyanide and Methyl Isocyanide

1940 ◽  
Vol 8 (8) ◽  
pp. 635-636 ◽  
Author(s):  
Raymond H. Ewell ◽  
James F. Bourland
Keyword(s):  
Thermodynamic Properties ◽  
Methyl Cyanide ◽  
Methyl Isocyanide

Mixing of symmetry coordinates in methyl cyanide and methyl isocyanide

1964 ◽  
Vol 20 (6) ◽  
pp. 1065-1070 ◽  
Author(s):  
William H. Fletcher ◽  
Charles S. Shoup ◽  
William T. Thompson
Keyword(s):  
Methyl Cyanide ◽  
Symmetry Coordinates ◽  
Methyl Isocyanide

scholarly journals The ALMA-PILS survey: first detection of methyl isocyanide (CH3NC) in a solar-type protostar

2018 ◽  
Vol 617 ◽  
pp. A95 ◽  
Author(s):  
H. Calcutt ◽  
M. R. Fiechter ◽  
E. R. Willis ◽  
H. S. P. Müller ◽  
R. T. Garrod ◽  
...  
Keyword(s):  
Molecular Spectroscopy ◽  
Abundance Ratio ◽  
High Mass ◽  
Formation Mechanisms ◽  
Methyl Cyanide ◽  
Physico Chemical ◽  
Upper Limits ◽  
Methyl Isocyanide ◽  
Chemical Modelling ◽  
Solar Type

Context. Methyl isocyanide (CH3NC) is the isocyanide with the largest number of atoms confirmed in the interstellar medium (ISM), but it is not an abundant molecule, having only been detected towards a handful of objects. Conversely, its isomer, methyl cyanide (CH3CN), is one of the most abundant complex organic molecules detected in the ISM, with detections in a variety of low- and high-mass sources. Aims. The aims of this work are to determine the abundances of methyl isocyanide in the solar-type protostellar binary IRAS 16293–2422 and to understand the stark abundance differences observed between methyl isocyanide and methyl cyanide in the ISM. Methods. We use Atacama Large Millimeter/submillimeter Array (ALMA) observations from the Protostellar Interferometric Line Survey (PILS) to search for methyl isocyanide and compare its abundance with that of its isomer methyl cyanide. We use a new line catalogue from the Cologne Database for Molecular Spectroscopy (CDMS) to identify methyl isocyanide lines. We also model the chemistry with an updated version of the three-phase chemical kinetics model MAGICKAL, presenting the first chemical modelling of methyl isocyanide to date. Results. We detect methyl isocyanide for the first time in a solar-type protostar, IRAS 16293–2422 B, and present upper limits for its companion protostar, IRAS 16293–2422 A. Methyl isocyanide is found to be at least 20 times more abundant in source B compared to source A, with a CH3CN/CH3NC abundance ratio of 200 in IRAS 16293–2422 B and >5517 in IRAS 16293–2422 A. We also present the results of a chemical model of methyl isocyanide chemistry in both sources, and discuss the implications for methyl isocyanide formation mechanisms and the relative evolutionary stages of both sources. The chemical modelling is unable to match the observed CH3CN/CH3NC abundance ratio towards the B source at densities representative of that source. The modelling, however, is consistent with the upper limits for the A source. There are many uncertainties in the formation and destruction pathways of methyl isocyanide, and it is therefore not surprising that the initial modelling attempts do not reproduce observations. In particular, it is clear that some destruction mechanism of methyl isocyanide that does not destroy methyl cyanide is needed. Furthermore, these initial model results suggest that the final density plays a key role in setting the abundance ratio. The next steps are therefore to obtain further detections of methyl isocyanide in more objects, as well as undertaking more detailed physico-chemical modelling of sources such as IRAS16293.

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