Theoretical Studies of Methyleneamino (CH2N) Radical Reactions. 1. Rate Constants and Product Branching Ratios for the CH2N + N2O Process by ab Initio Molecular Orbital/Statistical Theory Calculations

1999 ◽  
Vol 103 (5) ◽  
pp. 601-606 ◽  
Author(s):  
D. Chakraborty ◽  
M. C. Lin
Keyword(s):  
Statistical Theory ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Rate Constants ◽  
Branching Ratios ◽  
Radical Reactions ◽  
Theoretical Studies ◽  
Product Branching

scholarly journals Formation Mechanism of a Nonterrestrial C6H Radical: An Ab Initio/RRKM Study on the Reaction of Tetracarbon with Acetylene

2019 ◽  
Author(s):  
Tong Zhu ◽  
Chih-Hao Chin ◽  
John ZH Zhang
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Rate Constants ◽  
Kinetic Equations ◽  
Branching Ratios ◽  
The Other ◽  
Formation Mechanisms ◽  
Hydrogen Elimination ◽  
Carbon Carbon Bond ◽  
Product Branching

This study examined the formation mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/cc-pVTZ/B3LYP/6-311G(d,p) calculations, followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice–Ramsperger–Kassel–Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results show that the initial reaction begins with the formation of an intermediate t-i2, with entrance barriers of 3.8 kcal/mol, and an intermediate s-i1 without entrance barriers. On the triplet surface, the t-i2 rearranged the other C6H2 isomers, including t-i3, t-i4, and t-i6, through hydrogen migration; the t-i2, t-i3, t-i4, t-i5, and t-i6 isomers lost a hydrogen atom, and produced the most stable linear isomer of C6H, with an overall reaction exothermicity of 11 kcal/mol. Hydrogen elimination from the t-i10 isomer led to the formation of the annular C6H isomer, HC3C3 + H, at 23.9 kcal/mol above l-C4 + C2H2. On the singlet surfaces, s-i1 rearranged the other C6H2 isomers, including s-i2 and s-i4, through carbon–carbon bond cleavage. The s-i6 and s-i11 isomers also lost a hydrogen atom, and produced the linear C6H radical. Hydrogen elimination from the s-i4 isomer led to the formation of the annular C6H isomer. The s-i5 lost a hydrogen atom, and produced the six-member ring c-C6H isomer, at 2.1 kcal/mol higher than l-C4 + C2H2. The 1,1-H2 loss from the s-i10 isomer produced the linear hexacarbon l-C6 + H2 product, with an endothermicity of 2.3 kcal/mol and a 1,1-H2 loss from the s-i11 isomer, producing in the cyclic hexacarbon c-C6 + H2 product, with an exothermicity of 11.2 kcal/mol. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and VTST theories for determining the collision energies between 5 kcal/mol and 25 kcal/mol show that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products with branching ratios. The s-i6 isomer was calculated to be the most stable C6H2 species, even more favorable than t-i3 (by 76 kcal/mol).

scholarly journals Formation Mechanism of a Nonterrestrial C6H Radical: An Ab Initio/RRKM Study on the Reaction of Tetracarbon with Acetylene

2019 ◽  
Author(s):  
Tong Zhu ◽  
Chih-Hao Chin ◽  
John ZH Zhang
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Rate Constants ◽  
Kinetic Equations ◽  
Branching Ratios ◽  
The Other ◽  
Formation Mechanisms ◽  
Hydrogen Elimination ◽  
Carbon Carbon Bond ◽  
Product Branching

This study examined the formation mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/cc-pVTZ/B3LYP/6-311G(d,p) calculations, followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice–Ramsperger–Kassel–Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results show that the initial reaction begins with the formation of an intermediate t-i2, with entrance barriers of 3.8 kcal/mol, and an intermediate s-i1 without entrance barriers. On the triplet surface, the t-i2 rearranged the other C6H2 isomers, including t-i3, t-i4, and t-i6, through hydrogen migration; the t-i2, t-i3, t-i4, t-i5, and t-i6 isomers lost a hydrogen atom, and produced the most stable linear isomer of C6H, with an overall reaction exothermicity of 11 kcal/mol. Hydrogen elimination from the t-i10 isomer led to the formation of the annular C6H isomer, HC3C3 + H, at 23.9 kcal/mol above l-C4 + C2H2. On the singlet surfaces, s-i1 rearranged the other C6H2 isomers, including s-i2 and s-i4, through carbon–carbon bond cleavage. The s-i6 and s-i11 isomers also lost a hydrogen atom, and produced the linear C6H radical. Hydrogen elimination from the s-i4 isomer led to the formation of the annular C6H isomer. The s-i5 lost a hydrogen atom, and produced the six-member ring c-C6H isomer, at 2.1 kcal/mol higher than l-C4 + C2H2. The 1,1-H2 loss from the s-i10 isomer produced the linear hexacarbon l-C6 + H2 product, with an endothermicity of 2.3 kcal/mol and a 1,1-H2 loss from the s-i11 isomer, producing in the cyclic hexacarbon c-C6 + H2 product, with an exothermicity of 11.2 kcal/mol. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and VTST theories for determining the collision energies between 5 kcal/mol and 25 kcal/mol show that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products with branching ratios. The s-i6 isomer was calculated to be the most stable C6H2 species, even more favorable than t-i3 (by 76 kcal/mol).

The NCO + NO Reaction Revisited:  Ab Initio MO/VRRKM Calculations for Total Rate Constant and Product Branching Ratios

2000 ◽  
Vol 104 (46) ◽  
pp. 10807-10811 ◽  
Author(s):  
Rongshun Zhu ◽  
M. C. Lin
Keyword(s):  
Ab Initio ◽  
Rate Constant ◽  
Branching Ratios ◽  
Total Rate ◽  
Ab Initio Mo ◽  
Product Branching

Theoretical study of the C6H3 potential energy surface and rate constants and product branching ratios of the C2H(Σ+2)+C4H2(Σg+1) and C4H(Σ+2)+C2H2(Σg+1) reactions

2008 ◽  
Vol 128 (21) ◽  
pp. 214301 ◽  
Author(s):  
Alexander Landera ◽  
Sergey P. Krishtal ◽  
Vadim V. Kislov ◽  
Alexander M. Mebel ◽  
Ralf I. Kaiser
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Rate Constants ◽  
Energy Surface ◽  
Theoretical Study ◽  
Branching Ratios ◽  
Product Branching

Ab Initio Energies and Product Branching Ratios for the O + C3H6Reaction

2007 ◽  
Vol 111 (50) ◽  
pp. 12977-12984 ◽  
Author(s):  
Gary D. DeBoer ◽  
James A. Dodd
Keyword(s):  
Ab Initio ◽  
Branching Ratios ◽  
Product Branching
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