scholarly journals Quantum chemical study of the structure, spectroscopy and reactivity of NO + .(H 2 O) n =1−5 clusters

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170152 ◽  
Author(s):  
Kirsty A. Linton ◽  
Timothy G. Wright ◽  
Nicholas A. Besley
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Ab Initio Molecular Dynamics ◽  
Structure Theory ◽  
Energy Structure ◽  
Hartree Fock ◽  
Quantum Chemical Methods ◽  
Moller Plesset

Quantum chemical methods including Møller–Plesset perturbation (MP2) theory and density functional theory (DFT) have been used to study the structure, spectroscopy and reactivity of NO + .(H 2 O) n =1−5 clusters. MP2/6-311++G** calculations are shown to describe the structure and spectroscopy of the clusters well. DFT calculations with exchange–correlation functionals with a low fraction of Hartree–Fock exchange give a binding energy of NO + .(H 2 O) that is too high and incorrectly predict the lowest energy structure of NO + .(H 2 O) 2 , and this error may be associated with a delocalization of charge onto the water molecule directly binding to NO + . Ab initio molecular dynamics (AIMD) simulations were performed to study the NO + .(H 2 O) 5 H + .(H 2 O) 4 + HONO reaction to investigate the formation of HONO from NO + .(H 2 O) 5 . Whether an intracluster reaction to form HONO is observed depends on the level of electronic structure theory used. Of note is that methods that accurately describe the relative energies of the product and reactant clusters did not show reactions on the timescales studied. This suggests that in the upper atmosphere the reaction may occur owing to the energy present in the NO + .(H 2 O) 5 complex following its formation. This article is part of the theme issue ‘Modern theoretical chemistry’.

Quantum chemical study on the formation of isopropyl cyanide and its linear isomer in the interstellar medium

2020 ◽  
pp. 1-11
Author(s):  
Keshav Kumar Singh ◽  
Poonam Tandon ◽  
Alka Misra ◽  
Shivani ◽  
Manisha Yadav ◽  
...  
Keyword(s):  
Amino Acids ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dark Cloud ◽  
Water Ice ◽  
Hydrocarbon Radicals

Abstract The formation mechanism of linear and isopropyl cyanide (hereafter n-PrCN and i-PrCN, respectively) in the interstellar medium (ISM) has been proposed from the reaction between some previously detected small cyanides/cyanide radicals and hydrocarbons/hydrocarbon radicals. n-PrCN and i-PrCN are nitriles therefore, they can be precursors of amino acids via Strecker synthesis. The chemistry of i-PrCN is especially important since it is the first and only branched molecule in ISM, hence, it could be a precursor of branched amino acids such as leucine, isoleucine, etc. Therefore, both n-PrCN and i-PrCN have significant astrobiological importance. To study the formation of n-PrCN and i-PrCN in ISM, quantum chemical calculations have been performed using density functional theory at the MP2/6-311++G(2d,p)//M062X/6-311+G(2d,p) level. All the proposed reactions have been studied in the gas phase and the interstellar water ice. It is found that reactions of small cyanide with hydrocarbon radicals result in the formation of either large cyanide radicals or ethyl and vinyl cyanide, both of which are very important prebiotic interstellar species. They subsequently react with the radicals CH2 and CH3 to yield n-PrCN and i-PrCN. The proposed reactions are efficient in the hot cores of SgrB2 (N) (where both n-PrCN and i-PrCN were detected) due to either being barrierless or due to the presence of a permeable entrance barrier. However, the formation of n-PrCN and i-PrCN from the ethyl and vinyl cyanide always has an entrance barrier impermeable in the dark cloud; therefore, our proposed pathways are inefficient in the deep regions of molecular clouds. It is also observed that ethyl and vinyl cyanide serve as direct precursors to n-PrCN and i-PrCN and their abundance in ISM is directly related to the abundance of both isomers of propyl cyanide in ISM. In all the cases, reactions in the ice have smaller barriers compared to their gas-phase counterparts.

HYDRATION AND DISSOCIATION OF CALCIUM HYDROXIDE IN WATER CLUSTERS: A QUANTUM CHEMICAL STUDY

2007 ◽  
Vol 06 (03) ◽  
pp. 595-609 ◽  
Author(s):  
CLARA JIAYUN MEN ◽  
FU-MING TAO
Keyword(s):  
Calcium Hydroxide ◽  
Quantum Chemical ◽  
Density Functional ◽  
Water Clusters ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Structure Stability ◽  
Water Molecules ◽  
Aerosol Formation ◽  
Hydrated Clusters

The structure, stability, and properties of the hydrated clusters of calcium hydroxide, Ca ( OH )2( H 2 O )n, n = 1–6, were investigated using density functional and ab initio quantum chemical methods. The results show that six water molecules are needed to result in the complete dissociation of Ca ( OH )2. The stable and ionic conformer of Ca ( OH )2( H 2 O )6 has C 3 symmetry. Its surprising stability and high IR activity render hydrated clusters of Ca ( OH )2 potentially significant in the nucleation of noctilucent clouds in the mesosphere. Trends in the interaction energies (ΔEe) of the complexes show that water molecules in the first shell of Ca 2+ are highly stable, further alluding to the role of hydrated Ca ( OH )2 in aerosol formation.

scholarly journals The transition metal to ligand bonding nature: A quantum chemical study of π-allyl-ruthenacycle molecule

2018 ◽  
Vol 58 (3) ◽  
Author(s):  
Aušra Vektarienė
Keyword(s):  
Transition Metal ◽  
Physical Properties ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Decomposition Analysis ◽  
Computational Procedure ◽  
Chemical Study ◽  
Hartree Fock ◽  
Charge Decomposition Analysis ◽  
The Density Functional Theory

Understanding of the transition metal (TM) to ligand (L) bonding nature is important for characterization of experimental observations. One of the methods to explain the TM to L interactions is the Dewar–Chatt–Duncanson (DCD) model. However, in most applications the validity of the DCD model is based on assumptions in order to explain trends in vibrational spectroscopy or other physical properties of TM complexes. In this paper the computational methodology for treatment of the π-allyl-ruthenacycle complex based on the density functional theory, restricted Hartree–Fock method, natural bond orbital and charge decomposition analysis is reported. It is shown how the DCD model emerges from the presented calculation scheme and how it relates with the physical properties and stability of this complex. It is important to note that in this work the determination of the DCD model operation is based on the defined computational procedure, not postulated beforehand. The calculated geometry parameters, vibrational frequencies and electron density arrangement for the π-allyl-ruthenacycle complex are in good agreement with the experiment and support the DCD model.

scholarly journals A quantum chemical study on ˙Cl-initiated atmospheric degradation of acrylonitrile

RSC Advances ◽  
2017 ◽  
Vol 7 (33) ◽  
pp. 20574-20581 ◽  
Author(s):  
Jingyu Sun ◽  
Youxiang Shao ◽  
Wenzhong Wu ◽  
Yizhen Tang ◽  
Yunju Zhang ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Atmospheric Degradation ◽  
Atomic Chlorine

Degradation of acrylonitrile (CH2CHCN) by reaction with atomic chlorine was studied using quantum chemical methods.

scholarly journals A quantum chemical study on gas phase decomposition pathways of triethylgallane (TEG, Ga(C2H5)3) and tert-butylphosphine (TBP, PH2(t-C4H9)) under MOVPE conditions

2014 ◽  
Vol 16 (32) ◽  
pp. 17018-17029 ◽  
Author(s):  
Andreas Stegmüller ◽  
Phil Rosenow ◽  
Ralf Tonner
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Phase Decomposition ◽  
Chemical Methods ◽  
Decomposition Products ◽  
Elementary Reactions ◽  
Quantum Chemical Methods ◽  
Precursor Molecules

Gas phase decomposition products of MOVPE precursor molecules TEG and TBP were identified via thermodynamic and kinetic data from a catalogue of 61 elementary reactions as calculated by quantum chemical methods.

Quantum Chemical Study of Thermal Dehydrochlorination of Poly(vinyl chloride) Containing Aldehyde Groups

1995 ◽  
Vol 60 (8) ◽  
pp. 1310-1315
Author(s):  
Jaroslav Burda
Keyword(s):  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Aldehyde Group ◽  
Point Of View ◽  
Chemical Methods ◽  
Poly Vinyl Chloride ◽  
Quantum Chemical Methods ◽  
Aldehyde Groups ◽  
Force Potential

Thermal dehydrochlorination of syndiotactic oligomeric models of PVC with aldehyde groups is studied using semiempirical quantum chemical methods AM1 and MNDO. The possibility of both radical and ionic mechanism of HCl elimination is examined. From the results it follows that the homolytic detachment of chlorine from the carbon in β-position to the aldehyde group is preferred, followed by hydrogen splitting off. Hydrogen atom detachment from the carbon in α-position to the aldehyde group as the first step is found energetically less convenient. The dehydrochlorination of aldehyde-containing PVC model, especially of the first molecule from the chain, is remarkably easier in comparison with regular PVC model. However, the energetical preference is smaller for further HCl splitting off and, from the kinetic point of view, this process seems to be slower. The influence of the aldehyde group inductive effect on the driving force potential m(Ca-Cw) is apparent from the partial charge distributions.

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