A computational study on the thermal decomposition of di(tri)thiocarbonates

2016 ◽  
Vol 15 (07) ◽  
pp. 1650061 ◽  
Author(s):  
Jingjing Xia ◽  
Ping Wu
Keyword(s):  
Thermal Decomposition ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Reaction Progress ◽  
Bond Indices ◽  
Elimination Reactions ◽  
Wiberg Bond Indices

Alkyl methyl di(tri)thiocarbonates can be thermally decomposed into alkenes. In this paper, theoretical calculations were used to calculate the thermal decomposition procedures. Six compounds, including ethyl, isopropyl and [Formula: see text] dithiocarbonate and trithiocarbonate, were examined. For each decomposition, nine possible paths were considered, including the paths leading to the desired alkene products, as well as rearrangement and elimination reactions. This calculation was performed with the MP2/6-31G(d) method. Wiberg bond indices were also calculated to further reveal the reaction progress.

A theoretical study towards thermolysis process of thionesters and thiolesters

2018 ◽  
Vol 17 (02) ◽  
pp. 1850014 ◽  
Author(s):  
Xun Zhu ◽  
Xiuqin Zhou ◽  
Dongsheng Xiang ◽  
Ping Wu
Keyword(s):  
Theoretical Study ◽  
Theoretical Calculations ◽  
Transition States ◽  
Membered Ring ◽  
Basis Set ◽  
Reaction Progress ◽  
Alkyl Groups ◽  
Thermal Elimination ◽  
Bond Indices ◽  
Wiberg Bond Indices

This paper focuses on the thermal elimination of alkenes from methyl alkyl thionacetates and thiolacetates. Three alkyl groups are calculated: ethyl, isopropyl and tert-butyl. Possible elimination mechanisms are considered, including six- and four-membered ring transition states for alkene elimination, four-membered ring isomerization and a possible five-membered ring decomposition. Theoretical calculations are performed with the MP2 method and the 6-31G* basis set. Wiberg bond indices are also summarized to monitor the reaction progress.

Theoretical studies on the pyrolysis of (Thion)carbonates

2014 ◽  
Vol 13 (06) ◽  
pp. 1450051 ◽  
Author(s):  
Ping Wu ◽  
Jiaxing Li
Keyword(s):  
Theoretical Calculations ◽  
Theoretical Studies ◽  
Nucleophilic Substitutions ◽  
Alkyl Groups ◽  
Thermal Elimination ◽  
Bond Indices ◽  
Wiberg Bond Indices

MP2/6-31G(d) was employed to investigate the theoretical calculations on the pyrolysis of alkyl methyl (thion)carbonates, where alkyl groups referred to ethyl, isopropyl and t-butyl groups. Nine possible pathways were considered for the pyrolysis of alkyl methyl thioncarbonates, while only seven possible pathways were found to pyrolyze alkyl methyl carbonates. Both of them had three pathways to generate the desired alkene products. Not only thermal elimination pathways were calculated, other possible mechanisms, such as rearrangements and nucleophilic substitutions, were also considered. The progress of the reactions was also investigated by the calculation of Wiberg bond indices at MP2/6-31G(d) level.

Thermal decomposition of 2-phenylethanol: A computational study on mechanism

2013 ◽  
Vol 556 ◽  
pp. 29-34 ◽  
Author(s):  
Yasuyuki Sakai ◽  
Hiromitsu Ando ◽  
Tatsuo Oguchi ◽  
Yoshinori Murakami
Keyword(s):  
Thermal Decomposition ◽  
Computational Study

Conformational structures of jet-cooled acetaminophen–water clusters: a gas phase spectroscopic and computational study

2017 ◽  
Vol 19 (6) ◽  
pp. 4840-4848 ◽  
Author(s):  
Ahreum Min ◽  
Ahreum Ahn ◽  
Cheol Joo Moon ◽  
Ji Hoon Lee ◽  
Yeon Guk Seong ◽  
...  
Keyword(s):  
Gas Phase ◽  
Water Clusters ◽  
Computational Study ◽  
Theoretical Calculations

Jet-cooled acetaminophen (AAP)–water clusters, AAP–(H2O)1, have been investigated by a combination of theoretical calculations and R2PI, UV–UV HB, IR-dip, IR–UV HB techniques in the gas phase.

scholarly journals Detection of Chemical Weapon Agents Using Spectroscopic Probes: A Computational Study

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Letícia S. Braga ◽  
Érika F. Silva ◽  
Daiana T. Mancini ◽  
Eduardo P. da Rocha ◽  
Elaine F. F. da Cunha ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Organophosphorus Compounds ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Spectroscopic Properties ◽  
Acetylcholinesterase Inhibition ◽  
Chemical Weapon ◽  
Fast Detection ◽  
Absorption Wavelength

Organophosphorus compounds are organic compounds widely employed in agriculture as well as in chemical weapons. The use in agriculture is due to their insecticidal properties. However, in chemical warfare, the use of organophosphorus is associated with acetylcholinesterase inhibition, which promotes the cholinergic syndromes. In this line, the fast detection of this class of compound is crucial for the determination of environmental exposure. This improved detection will naturally allow for more prompt courses of treatment depending on the contaminant findings. In this perspective, the dipyrrinone oxime (1) was employed for the detection of organophosphorus compounds that are employed as nerve agents, such as cyclosarin, sarin, soman, diethyl chlorophosphate, diisopropylfluorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, O-ethyl-S-[2-(diethylamino)ethyl]methylphosphonothioate, O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate, through fluorescent emission. The thermodynamics and kinetic parameters as well as spectroscopic properties of the complexes formed for 1 and all organophosphorus compounds previously cited were investigated by means of theoretical calculations. From our findings, only the diethyl chlorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate emitted fluorescence in the hexane, toluene, chloroform, dichloromethane, methanol, acetonitrile, water, and dimethyl sulfoxide solvents. The study of the absorption wavelength with the most polar solvent showed higher values compared to apolar solvents. In the same solvent, for instance, soman in hexane showed the lowest absorption wavelength value, 324.5 nm, and DCP the highest value, 330.8 nm. This behavior was observed in other tested solvents. The thermodynamic parameters indicate negative Gibbs free energy (ΔG) values for the O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate with 1 reaction. On the other hand, the sarin and cyclosarin revealed the lowest Gibbs free energy (ΔG‡) values, being kinetically favorable and presenting more reactivity.

Identifying Thermal Decomposition Products of Nitrate Ester Explosives Using Gas Chromatography–Vacuum Ultraviolet Spectroscopy: An Experimental and Computational Study

2020 ◽  
Vol 74 (12) ◽  
pp. 1486-1495 ◽  
Author(s):  
Courtney A. Cruse ◽  
Jingzhi Pu ◽  
John V. Goodpaster
Keyword(s):  
Thermal Decomposition ◽  
Gas Chromatography ◽  
Density Functional ◽  
Vacuum Ultraviolet ◽  
Computational Study ◽  
Ultraviolet Spectroscopy ◽  
Decomposition Products ◽  
Nitrate Ester ◽  
Vacuum Ultraviolet Spectroscopy ◽  
Synchrotron Spectroscopy

Analysis of nitrate ester explosives (e.g., nitroglycerine) using gas chromatography–vacuum ultraviolet spectroscopy (GC–VUV) results in their thermal decomposition into nitric oxide, water, carbon monoxide, oxygen, and formaldehyde. These decomposition products exhibit highly structured spectra in the VUV that is not seen in larger molecules. Computational analysis using time-dependent density functional theory (TDDFT) was utilized to investigate the excited states and vibronic transitions of these decomposition products. The experimental and computational results are compared with those in previous literature using synchrotron spectroscopy, electron energy loss spectroscopy (EELS), photoabsorption spectroscopy, and other computational excited state methods. It was determined that a benchtop GC–VUV detector gives comparable results to those previously reported, and TDDFT could predict vibronic spacing and model molecular orbital diagrams.

scholarly journals Understanding the Lack of Reactivity of 2,4-Dihydroxybenzaldehyde Towards the Biginelli Adduct Using Density Functional Theory Molecular Modeling

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 521
Author(s):  
Virginia Flores-Morales ◽  
Eduardo D. Ayala-Medrano ◽  
José García-Elías ◽  
Margarita L. Martínez-Fierro ◽  
Edgar Marquez ◽  
...  
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Activation Enthalpy ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Condensation Reaction ◽  
Biginelli Reaction ◽  
Hydroxyl Group ◽  
Functional Theory ◽  
Multiple Substitution

The Biginelli reaction is a multicomponent reaction for obtaining dihydropyrimidinthiones quickly, with multiple substitution patterns. The reaction mechanism remains unclear. Three possible pathways proposed for the reaction are the iminium route, an enamine intermediate, and the Knoevenagel pathway. However, when thiourea was used, no theoretical calculations were reported. Thus, based on the literature, the iminium pathway was used to obtain evidence explaining the lack of reactivity of 2,4-dihydroxybenzaldehyde towards the Biginelli adduct, compared with 4-hydroxybenzaldehyde. This computational study, carried out using the B3LYP/6-31++G(d,p) level of theory, showed an increment of 150 kJ/mol in the activation energy of the slowest pathway, due to the presence of a hydroxyl group in position 2 (ortho) of the aromatic aldehyde, decreasing its reactivity. Natural bond orbital (NBO) calculations suggest that the determinant steps are simultaneous, i.e., the polarization of the carbonyl group and its corresponding protonation by the hydrogen of the SH fragment of the thiourea tautomer. The activation enthalpy values suggest that the nucleophile attack takes place later on the compound 2,4-dihydroxybenzaldehyde compared to 4-hydroxybenzaldehyde-TS, confirming that the OH group in position 2 hinders the condensation reaction.

Thermal Decomposition of Branched Silanes: A Computational Study on Mechanisms

2012 ◽  
Vol 18 (29) ◽  
pp. 9106-9116 ◽  
Author(s):  
Wilhelm A. Eger ◽  
Alexander Genest ◽  
Notker Rösch
Keyword(s):  
Thermal Decomposition ◽  
Computational Study
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