Theoretical study of reaction channels for the weakly bound complex systems created with HF, CO2, and various amines

2005 ◽  
Vol 103 (2) ◽  
pp. 198-214
Author(s):  
Shyh-Jong Chen ◽  
Cheng Chen ◽  
Yaw-Shun Hong
Keyword(s):  
Complex Systems ◽  
Theoretical Study ◽  
Weakly Bound ◽  
Reaction Channels

Analysis of fragment distribution and associated effects in 12,13C induced reactions

2014 ◽  
Vol 23 (05) ◽  
pp. 1450030
Author(s):  
Manpreet Kaur ◽  
Mahesh K. Sharma ◽  
Manoj K. Sharma
Keyword(s):  
Cross Sections ◽  
Heavy Ion ◽  
Evaporation Residue ◽  
Incomplete Fusion ◽  
Cluster Decay ◽  
Weakly Bound ◽  
Wide Range ◽  
Reaction Channels ◽  
Nice Agreement ◽  
Fragment Distribution

The decay of 220 Ra * nucleus formed in two different entrance channels 12 C +208 Pb and 13 C +207 Pb is investigated over a wide range of incident energies using the dynamical cluster decay model (DCM). The DCM is a non-statistical model used to account for the decay of hot and rotating nuclei formed in low energy heavy ion reactions. The excitation functions are calculated by considering quadrupole (β2) deformations with optimum orientations [Formula: see text] of decaying fragments. The DCM-based cross-sections for evaporation residue (ER), fusion–fission, αxn and neutron decay processes find nice agreement with the reported experimental data over wide range of incident energies. The cross-sections corresponding to different decay mechanism are worked out within DCM by fitting neck length parameter (ΔR). The entrance channel and angular momentum effects are investigated in reference to the above-mentioned reaction channels. In addition to this, the fragment mass distribution is worked out by colliding 13 C weakly bound stable projectile with a variety of target nuclei resulting in 13 C +159 Tb , 13 C +181 Ta and 13 C +207 Pb reactions. At comparable projectile energies, the increase in target mass is shown to favor asymmetric fragmentation in the fissioning region. Besides this, the incomplete fusion (ICF) contribution is worked out for 12 C and 13 C channels by applying necessary energy corrections in the framework of DCM.

Computational studies of gas-phase accretion product formation involving RO2

2020 ◽  
Author(s):  
Theo Kurtén ◽  
Siddharth Iyer ◽  
Vili-Taneli Salo ◽  
Galib Hasan ◽  
Matti Rissanen ◽  
...  
Keyword(s):  
Physical Chemistry ◽  
Gas Phase ◽  
Product Formation ◽  
Peroxy Radicals ◽  
Dimer Formation ◽  
Weakly Bound ◽  
Alkoxy Radicals ◽  
Reaction Channels ◽  
A Minor ◽  
Simple Systems

<p>Field and laboratory studies have indirectly but conclusively established that reactions involving peroxy radicals (RO<sub>2</sub>) play a key role in the gas-phase formation of accretion products, also commonly referred to as “dimers”, as they typically contain roughly twice the number of carbon atoms compared to their hydrocarbon precursors. Using computational tools, we have recently presented two different potential mechanisms for this process.</p><p>First, direct and rapid recombination of peroxy and alkoxy (RO) radicals, analogous to the recently characterized RO<sub>2</sub> + OH reaction, leads to the formation of metastable RO<sub>3</sub>R’ trioxides, which may have lifetimes on the order of a hundred seconds. [1] However, due to both the limited lifetime of the trioxides, and the low concentration of alkoxy radicals, the RO<sub>2</sub> + R’O pathway is likely to be a minor, though not necessarily negligible, pathway for atmospheric dimer formation.</p><p>Second, we have shown that recombination of two peroxy radicals – phenomenologically known to be responsible for the formation of ROOR’ – type dimers – very likely occurs through a multi-step mechanism involving an intersystem crossing (ISC). [2]  In contrast to earlier predictions, we find that the rate-limiting step for the overall RO<sub>2</sub>  + R’O<sub>2</sub> reaction is the initial formation of a short-lived RO<sub>4</sub>R’ tetroxide intermediate. For tertiary RO<sub>2</sub>, the barrier for the tetroxide formation can be substantial. However, for all studied species the tetroxide decomposition is rapid, forming ground-state triplet O<sub>2</sub>, and a weakly bound triplet complex of two alkoxy radicals. The branching ratios of the different RO<sub>2</sub> + R’O<sub>2</sub> reaction channels are then determined by a three-way competition of this complex. For simple systems, the possible channels are dissociation (leading to RO + R’O), H-abstraction on the triplet surface (leading to RC=O + R’OH), and ISC and subsequent recombination on the singlet surface (leading to ROOR’). All of these can potentially be competive with each other, with rates very roughly on the order of 10<sup>9</sup> s<sup>-1</sup>. For more complex RO<sub>2</sub> parents, rapid unimolecular reactions of the daughter RO (such as alkoxy scissions) open up even more potential reaction channels, for example direct alkoxy – alkyl recombination to form (either singlet or triplet) ether-type (ROR’) dimers.</p><p>[1] Iyer, S., Rissanen, M. P. and Kurtén, T. Reaction Between Peroxy and Alkoxy Radicals can Form Stable Adducts. Journal of Physical Chemistry Letters, Vol. 10, 2051-2057, 2019.</p><p>[2] Valiev, R., Hasan, G., Salo, V.-T., Kubečka, J. and Kurtén, T. Intersystem Crossings Drive Atmospheric Gas-Phase Dimer Formation. Journal of Physical Chemistry A, Vol. 123, 6596-6604, 2019.</p><p> </p>

scholarly journals Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

2014 ◽  
Vol 10 ◽  
pp. 259-270 ◽  
Author(s):  
Shinichi Yamabe ◽  
Guixiang Zeng ◽  
Wei Guan ◽  
Shigeyoshi Sakaki
Keyword(s):  
Dft Calculations ◽  
Phenyl Ring ◽  
Theoretical Study ◽  
Bond Formation ◽  
Reduction Reaction ◽  
Base Catalyst ◽  
Reaction Channels ◽  
Catalyzed Reactions ◽  
First Time

Wolff–Kishner reduction reactions were investigated by DFT calculations for the first time. B3LYP/6-311+G(d,p) SCRF=(PCM, solvent = 1,2-ethanediol) optimizations were carried out. To investigate the role of the base catalyst, the base-free reaction was examined by the use of acetone, hydrazine (H2N–NH2) and (H2O)8. A ready reaction channel of acetone → acetone hydrazine (Me2C=N–NH2) was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N2 extrusion step from the isopropyl diimine intermediate (Me2C(H)–N=N–H). Two base-catalyzed reactions were investigated by models of the ketone, H2N–NH2 and OH−(H2O)7. Here, ketones are acetone and acetophenone. While routes of the ketone → hydrazone → diimine are similar, those from the diimines are different. From the isopropyl diimine, the N2 extrusion and the C–H bond formation takes place concomitantly. The concomitance leads to the propane product concertedly. From the (1-phenyl)ethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene product. For both ketone substrates, the diimines undergoing E2 reactions were found to be key intermediates.

A Theoretical Study of Silanol Polymerization

1986 ◽  
Vol 73 ◽  
Author(s):  
Larry W. Burggraf ◽  
Larry P. Davis
Keyword(s):  
Complex Systems ◽  
Molecular Orbital ◽  
Anionic Polymerization ◽  
Theoretical Study ◽  
State Of The Art ◽  
Activation Barrier ◽  
Polymerization Process ◽  
Nucleophilic Attack ◽  
Semi Empirical ◽  
Coordinate Structures

ABSTRACTWe have applied state-of-the-art semi-empirical molecular orbital methods to a study of the anionic polymerization of silanols to form silica. In particular, we have considered nucleophilic attack on silanols and subsequent reactions of the products. Hydroxide addition proceeds without activation to form five-coordinate silicate anions. Five-coordinate structures can also be formed by oligomerization following the attack of hydroxide on neutral silanols to abstract a proton. These five-coordinate structures are predicted to play a key role as intermediates in the polymerization process. Water can be eliminated from these anions, but with a substantial activation barrier. The activation barrier appears to be lower for the larger, more complex systems. These predictions are consistent with a rapid pre-equilibrium to form dimer anions followed by the slower reaction to form higher oligomers.

Theoretical study on the unimolecular decomposition of 2-chlorinated ethyl hydroperoxide

2016 ◽  
Vol 15 (01) ◽  
pp. 1650008 ◽  
Author(s):  
Ya Li ◽  
Na Wang ◽  
Chunzhang Wang ◽  
Xin Wang ◽  
Jinglai Zhang ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Bond Cleavage ◽  
Coupled Cluster ◽  
Unimolecular Decomposition ◽  
Coupled Cluster Theory ◽  
Major Interest ◽  
Coefficient Corrélation ◽  
Reaction Channels ◽  
Equilibrium Structures ◽  
Optimized Geometries

Chlorine-containing organic compounds have been of major interest since such compounds would serve as temporary reservoirs for HOX, ROX and ClOX radicals. Moreover, it would transport chlorine species to the atmosphere and stratosphere. However, limited studies have been performed on the 2-chlorinated ethyl hydroperoxide. In this work, the mechanism of unimolecular dissociation of 2-chlorinated ethyl hydroperoxide is theoretically studied. The equilibrium structures are optimized at the Boese–Martin for kinetics (BMK) level. And the energies are further refined at the Balanced multi-coefficient correlation-coupled cluster theory with single and double excitations (BMC-CCSD) level on the basis of the optimized geometries. Fifteen reaction channels are finally confirmed including the direct C–O, O–O, O–H, and C–C bond cleavage or the H2-, H2O-, H2O2-, and CH3Cl-elimination.

Theoretical influence of third molecule on reaction channels of weakly bound complex CO2… HF systems

2006 ◽  
Vol 106 (7) ◽  
pp. 1640-1652 ◽  
Author(s):  
Shyh-Jong Chen ◽  
Cheng Chen ◽  
Yaw-Shun Hong
Keyword(s):  
Weakly Bound ◽  
Reaction Channels

Theoretical Study of the H3PNH + H2CO Reaction Mechanism via Five Reaction Channels

1999 ◽  
Vol 103 (8) ◽  
pp. 1078-1083 ◽  
Author(s):  
Wen Cai Lu ◽  
Cheng Bu Liu ◽  
Chia Chung Sun
Keyword(s):  
Reaction Mechanism ◽  
Theoretical Study ◽  
Reaction Channels
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