Theoretical study of mechanism of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde

The mechanism of cycloaddition reaction between singlet dimethylmethylenesilylene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy surface, it can be considered in thermodynamics and dynamics that reaction (1) and reaction (4) are the two dominant competitive reaction channels of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde. The reaction process of reaction (1) is that: the two reactants (R1, R2) first form intermediates INT1a and INT1b through two reaction paths, a and b, which are barrier‐free exothermic reactions of 31.8 and 43.9 kJ/mol; then, INT1a and INT1b isomerize to a four‐membered ring product P1 via transition states TS1a and TS1b, with energy barriers of 26.3 and 24.4 kJ/mol. Reaction (4) also has two reaction paths, a and b, each of which consists of three steps are as follows: (i) the two reactants (R1, R2) first form intermediates INT3a and INT3b, which are barrier‐free exothermic reactions of 64.5 and 44.2 kJ/mol. (ii) INT3a and INT3b further react with formaldehyde (R2) to form intermediates INT4a and INT4b, through barrier‐free exothermic reactions of 22.9 and 22.2 kJ/mol. (iii) INT4a and INT4b then isomerize to form silapolycyclic product P4 via transition states TS4a and TS4b, with energy barriers of 39.7 and 29.3 kJ/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Non-catalytic hydroamination of alkenes: a computational study

The detailed reaction profiles of the neutral-neutral as well as the cation-neutral direct hydroamination reactions between ethylene and ammonia are analyzed using MP2 (Full)/6-31++G(2df,2p) and B3LYP/6-31++G(2df,2p) methodologies. Analysis shows that both neutral-neutral, as well as the cation-neutral reactions are exothermic and the latter is >100 kJ/mol more exothermic than the former. Calculations show that a very large barrier height (>200 kJ/mol), and very large negative reaction entropy prevent the neutral-neutral reaction from proceeding in the forward direction. Analysis of the cation-neutral reaction, which is barrierless (the transition state is more stable than the reactants) and highly exothermic, indicates that the direct hydroamination reaction is thermodynamically attainable via a cation-neutral reaction pathway without a catalyst. Our calculations also suggest that although the cation-neutral direct hydroamination reaction is very fast, the cation of either ethylene or ammonia goes through a structural relaxation process before reacting with the other neutral reactant.     

Thermochemistry and reaction paths in the oxidation reaction of benzoyl radical: C6H5C•(═O)

Alkyl substituted aromatics are present in fuels and in the environment because they are major intermediates in the oxidation or combustion of gasoline, jet, and other engine fuels. The major reaction pathways for oxidation of this class of molecules is through loss of a benzyl hydrogen atom on the alkyl group via abstraction reactions. One of the major intermediates in the combustion and atmospheric oxidation of the benzyl radicals is benzaldehyde, which rapidly loses the weakly bound aldehydic hydrogen to form a resonance stabilized benzoyl radical (C6H5C(?)═O). A detailed study of the thermochemistry of intermediates and the oxidation reaction paths of the benzoyl radical with dioxygen is presented in this study. Structures and enthalpies of formation for important stable species, intermediate radicals, and transition state structures resulting from the benzoyl radical +O2 association reaction are reported along with reaction paths and barriers. Enthalpies, ΔfH298(0), are calculated using ab initio (G3MP2B3) and density functional (DFT at B3LYP/6-311G(d,p)) calculations, group additivity (GA), and literature data. Bond energies on the benzoyl and benzoyl-peroxy systems are also reported and compared to hydrocarbon systems. The reaction of benzoyl with O2 has a number of low energy reaction channels that are not currently considered in either atmospheric chemistry or combustion models. The reaction paths include exothermic, chain branching reactions to a number of unsaturated oxygenated hydrocarbon intermediates along with formation of CO2. The initial reaction of the C6H5C(?)═O radical with O2 forms a chemically activated benzoyl peroxy radical with 37 kcal mol(-1) internal energy; this is significantly more energy than the 21 kcal mol(-1) involved in the benzyl or allyl + O2 systems. This deeper well results in a number of chemical activation reaction paths, leading to highly exothermic reactions to phenoxy radical + CO2 products.     

Theoretical studies on the mechanism of formation of a heteropolycyclic germanic compound between dimethyl‐germylidene and ethylene

Mechanism of the cycloadditional reaction between singlet dimethyl‐germylidene (R1) and ethylene (R2) has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction of forming a heteropolycyclic germanic compound between singlet dimethyl‐germylidene and ethylene consists of three steps: (1) the two reactants (R1, R2) first form a three‐membered intermediate (INT1) through a barrier‐free exothermic reaction of 39.6 kJ/mol. (2) Three‐membered intermediate (INT1) isomerizes to an active four‐membered intermediate (INT2) via a transition state (TS2), for which the barrier is 50.1 kJ/mol. (3) Four‐membered intermediate (INT2) reacts further with ethylene (R2) to form a heteropolycyclic germanic compound (P3), which is also a barrier‐free exothermic reaction of 87.7 kJ/mol. This dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

二氟亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究单重态二氟亚烷基卡宾与甲醛发生的环加成反应机理,采用MP2/6-31G^*方法计算了势能面上各驻点的构型参数、振动频率和能量.结果表明,单重态二氟亚烷基卡宾与甲醛的环加成反应主要有两种反应通道,通道1中,两个反应物经a,b和c三条反应途径生成三元环构型的产物P1,其中途径c是主反应途径,该途径有两步组成:(Ⅰ)二氟亚烷基卡宾与甲醛生成了1个富能中间体(INT1c),是无势垒放热反应,放出能量为219.18kJ/mol;(Ⅱ)中间体(INT1c)异构化为产物二氟亚烷基环氧乙烷,其势垒为134.71kJ/mol.通道2的反应途径由三步组成:(Ⅰ)反应物首先生成了1个富能中间体(INT1b),为无势垒的放热反应,放出的能量142.77kJ/mol;(Ⅱ)中间体(INT1b)异构化成另一中间体(INT2),其势垒为22.31kJ/mol;(Ⅲ)中间体(INT2)异构化成四元环构型产物P2,其势垒为11.98kJ/mol.     

Thermal reactions of lithiated graphite anode in LiPF6-based electrolyte

The thermal reactions of a lithiated graphite anode with and without 1.3 M lithium hexafluorophosphate (LiPF₆) in a solvent mixture of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were investigated by means of differential scanning calorimetry (DSC). The products of the thermal decomposition occurring on the lithiated graphite anode were characterized by Fourier transform infrared (FT-IR) analysis. The lithiated graphite anode showed two broad exothermic peaks at 270 and 325 °C, respectively, in the absence of electrolyte. It was demonstrated that the first peak could be assigned to the thermal reactions of PF₅ with various linear alkyl carbonates in the solid electrolyte interphase (SEI) and that the second peak was closely related to the thermal decomposition of the polyvinylidene fluoride (PVdF) binder. In the presence of electrolyte, the lithiated graphite anode showed the onset of an additional exothermic peak at 90 °C associated with the thermal decomposition reactions of the SEI layer with the organic solvents.     

Theoretical study of mechanism of cycloaddition reaction between dichloro‐germylene carbene (Cl2GeC:) and aldehyde

The mechanism of the cycloaddition reaction between singlet dichloro‐germylene carbene and aldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by zero‐point energy and CCSD (T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The channel (A) consists of four steps: (1) the two reactants (R1, R2) first form an intermediate INT2 through a barrier‐free exothermic reaction of 142.4 kJ/mol; (2) INT2 then isomerizes to a four‐membered ring compound P2 via a transition state TS2 with energy barrier of 8.4 kJ/mol; (3) P2 further reacts with aldehyde (R2) to form an intermediate INT3, which is also a barrier‐free exothermic reaction of 9.2 kJ/mol; (4) INT3 isomerizes to a germanic bis‐heterocyclic product P3 via a transition state TS3 with energy barrier of 4.5 kJ/mol. The process of channel (B) is as follows: (1) the two reactants (R1, R2) first form an intermediate INT4 through a barrier‐free exothermic reaction of 251.5 kJ/mol; (2) INT4 further reacts with aldehyde (R2) to form an intermediate INT5, which is also a barrier‐free exothermic reaction of 173.5 kJ/mol; (3) INT5 then isomerizes to a germanic bis‐heterocyclic product P5 via a transition state TS5 with an energy barrier of 69.4 kJ/mol. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

UV-light induced photodegradation of bisphenol a in water: Kinetics and influencing factors

The synthesis of dimethyl carbonate (DMC) from methanol and ethylene carbonate (EC) without using any solvent was investigated in the presence of ionic liquids as catalysts. The conversion of ethylene carbonate was affected by the structure of ionic liquid. For a series of 1-alkyl-3-methylimidazolium ionic liquids, the one with shorter alkyl chain and the one with more nucleophilic anion showed higher reactivity. The conversion of EC also increased with CO₂ pressure and reaction temperature. Esterification of EC and methanol can be considered as a pseudo-first order reaction with respect to EC concentration. The activation energy was estimated as 50.1 kJ/mol.     

Ab initio study on the mechanism of forming a germanic hetero-polycyclic compound between alkylidenegermylene and ethylene

The mechanism of the cycloaddition reaction of forming a germanic hetero-polycyclic compound between singlet alkylidenegermylene and ethylene has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the surface energy profile, it can be predicted that the dominant reaction pathway for this reaction consists of three steps: the two reactants first form a three-membered ring intermediate INT1 through a barrier-free exothermic reaction of 35.4 kJ/mol; this intermediate then isomerizes to an active four-membered ring product P2.1 via a transition-state TS2.1 with a barrier of 57.6 kJ/mol; finally, P2.1 further reacts with ethylene to form the germanic hetero-polycyclic compound P3, for which the barrier is only 0.8 kJ/mol. The rate of this reaction path considerably differs from other competitive reaction paths, indicating that the cycloaddition reaction has an excellent selectivity.     

Theoretical study of mechanism of forming a silapolycyclic compound between methylenesilylene and acetone

The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and acetone has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, we predict that the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and acetone has two competitive dominant reaction pathways. First dominant reaction pathway consists of four steps: (I) the two reactants (R1, R2) first form an intermediate (INT1) through a barrier‐free exothermic reaction of 46.2 kJ/mol; (II) intermediate (INT1) then isomerizes to a planar four‐membered ring product (P3) via transition state (TS3) with an energy barrier of 47.1 kJ/mol; (III) planar four‐membered ring product (P3) further reacts with acetone (R2) to form an intermediate (INT4), which is also a barrier‐free exothermic reaction of 40.0 kJ/mol; (IV) intermediate (INT4) isomerizes to a silapolycyclic compound (P4) via transition state (TS4) with an energy barrier of 57.0 kJ/mol. Second dominant reaction pathway consists of three steps: (I) the two reactants (R1, R2) first form a four‐membered ring intermediate (INT2) through a barrier‐free exothermic reaction of 0.5 kJ/mol; (II) INT2 further reacts with acetone (R2) to form an intermediate (INT5), which is also a barrier‐free exothermic reaction of 45.4 kJ/mol; (III) intermediate (INT5) isomerizes to a silapolycyclic compound (P5) via transition state (TS5) with an energy barrier of 49.3 kJ/mol. P4 and P5 are isomeric compounds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Ab initio study on the mechanism of forming a silapolycyclic compound between silylidene and formaldehyde

The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet silylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction process of forming the silapolycyclic compound (P₂) for this reaction consists of four steps: (I) the two reactants first form a semi-cyclic intermediate INT1a through a barrier-free exothermic reaction of 32.5 kJ mol⁻¹; (II) this intermediate then isomerizes to an active four-membered ring intermediate INT1 via a transition state TS1a with an energy barrier of 30.8 kJ mol⁻¹; (III) INT1 further reacts with formaldehyde to form an intermediate INT2, which is also a barrier-free exothermic reaction of 30.1 kJ mol⁻¹; (IV) INT2 isomerizes to a silapolycyclic compound P₂ via a transition state TS2 with a barrier of 50.6 kJ mol⁻¹. Comparing this reaction path with other competitive reaction paths, we can see that this cycloaddition reaction has an excellent selectivity.     

Density functional theory study of the role of anions on the oxidative decomposition reaction of propylene carbonate

The oxidative decomposition mechanism of the lithium battery electrolyte solvent propylene carbonate (PC) with and without PF(6)(-) and ClO(4)(-) anions has been investigated using the density functional theory at the B3LYP/6-311++G(d) level. Calculations were performed in the gas phase (dielectric constant ε = 1) and employing the polarized continuum model with a dielectric constant ε = 20.5 to implicitly account for solvent effects. It has been found that the presence of PF(6)(-) and ClO(4)(-) anions significantly reduces PC oxidation stability, stabilizes the PC-anion oxidation decomposition products, and changes the order of the oxidation decomposition paths. The primary oxidative decomposition products of PC-PF(6)(-) and PC-ClO(4)(-) were CO(2) and acetone radical. Formation of HF and PF(5) was observed upon the initial step of PC-PF(6)(-) oxidation while HClO(4) formed during initial oxidation of PC-ClO(4)(-). The products from the less likely reaction paths included propanal, a polymer with fluorine and fluoro-alkanols for PC-PF(6)(-) decomposition, while acetic acid, carboxylic acid anhydrides, and Cl(-) were found among the decomposition products of PC-ClO(4)(-). The decomposition pathways with the lowest barrier for the oxidized PC-PF(6)(-) and PC-ClO(4)(-) complexes did not result in the incorporation of the fluorine from PF(6)(-) or ClO(4)(-) into the most probable reaction products despite anions and HF being involved in the decomposition mechanism; however, the pathway with the second lowest barrier for the PC-PF(6)(-) oxidative ring-opening resulted in a formation of fluoro-organic compounds, suggesting that these toxic compounds could form at elevated temperatures under oxidizing conditions.     

Ab initio Study of Mechanism of Forming Germanic Hetero-Polycyclic Compound between Germylene Carbene (H2Ge=C: ) and Formaldehyde

The mechanism of the cycloaddition reaction of forming germanic hetero‐polycyclic compound between singlet germylene carbene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD (T)//MP2/6‐31G* method. From the potential energy profile, we predict that the cycloaddition reaction of forming germanic hetero‐polycyclic compound between singlet germylene carbene and formaldehyde has two competitive dominant reaction pathways. First dominant reaction pathway consists of four steps: (1) the two reactants (R1, R2) first form an intermediate (INT1) through a barrier‐free exothermic reaction of 117.5 kJ/mol; (2) intermediate (INT1) then isomerizes to a four‐membered ring compound (P2) via a transition state (TS2) with an energy barrier of 25.4 kJ/mol; (3) four‐membered ring compound (P2) further reacts with formaldehyde (R2) to form an intermediate (INT3), which is also a barrier‐free exothermic reaction of 19.6 kJ/mol; (4) intermediate (INT3) isomerizes to a germanic bis‐heterocyclic product (P3) via a transition state (TS3) with an energy barrier of 5.8 kJ/mol. Second dominant reaction pathway is as follows: (1) the two reactants (R1, R2) first form an intermediate (INT4) through a barrier‐free exothermic reaction of 197.3 kJ/mol; (2) intermediate (INT4) further reacts with formaldehyde (R2) to form an intermediate (INT5), which is also a barrier‐free exothermic reaction of 141.3 kJ/mol; (3) intermediate (INT5) then isomerizes to a germanic bis‐heterocyclic product (P5) via a transition state (TS5) with an energy barrier of 36.7 kJ/mol.     

亚烷基锡烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet alkylidenestannylene and ethylene has been investigated with MP2/3-21 G^* and B3LYP/3-21 G* methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD(T)//MP2/3-2 IG^* and CCSD(T)//B3LYP/3-21G^* methods, respectively. The results show that the dominant reaction pathway of the cycloaddition is that an intermediate (INT) is firstly formed between the two reactants through a barrier-free exothermic reaction of 39.7 kJ/mol, and the intermediate then isomerizes to a four-membered ring product (P2.1) via a transition state TS2.1 with a barrier of 66.8 kJ/mol.     

AIM Study on the Reaction of CH2SH Radical with Fluorine Atom

The reaction of CH2SH radical with fluorine atom was studied at the levels of B3LYP/6-311G(d,p) and MP2(Full)/6-311G(d,p). The computational results show that the reaction has three channels and proceeds by the addition of fluorine atoms on carbon or sulfur sites of CH2SH, forming initial intermediates. The calculated results show that the channel in which fluorine attaches to the carbon atom to form CH2S and HF, is the most likely reaction pathway. Topological analysis of electron density was carried out for the three channels. The change trends of the chemical bonds on the reaction paths were discussed. The energy transition states and the structure transition regions (states) of the three channels were found. The calculated results show that the structure transition regions are broad in unobvious exothermic reactions or unobvious endothermic reactions, and are narrow in obvious exothermic reactions or obvious endothermic reactions.     

Why are olefins oxidized by RuO4 under cleavage of the carbon-carbon bond whereas oxidation by OsO4 yields cis-diols?

Quantum chemical calculations using gradient-corrected (B3LYP) density functional theory have been carried out to investigate the mechanism of the oxidative cleavage of alkenes by ruthenium tetraoxide. The initial reaction of the tetraoxide with the olefin occurs via a [3+2] cycloaddition as in the case of osmium tetraoxide. The results clearly show that the bond cleavage does not take place at the primary adduct, but much later in the reaction path. After the formation of the ruthenium(VI)dioxo-2,5-dioxolane, the reaction proceeds with the addition of a second olefin to yield ruthenium(IV)-bis(2,5-dioxolane), which in turn becomes oxidized first to rutheniumoxo(VI)-bis(2,5-dioxolane) 6(Ru) and then to ruthenium(VIII)-dioxo-bis(2,5-dioxolane) 7(Ru). Only in complexes containing the metal center in the formal oxidation state +VIII are low activation barriers for C-C bond cleavage and exothermic formation of carbonyl compounds as products calculated. The lowest activation barrier, DeltaH(++) = 2.5 kcal/mol, is calculated for the C-C bond breaking reaction of 7(Ru) which is predicted as the pivotal intermediate of the oxidation reaction. The calculations of the oxidation reaction with OsO(4) show that those reactions where the oxidation state of the metal increases have larger activation barriers for M = Ru than for M = Os, while reactions which reduce the oxidation state have a lower activation barrier for ruthenium compounds. Also, reactions which increase the oxidation state of the metal are in the case of M = Os more exothermic than for M = Ru. In this work, all important points of the potential energy surface (PES) are reported, and the complete catalytic cycle for the oxidative cleavage of olefins by ruthenium tetraoxide is presented.     

Theoretical study on the mechanism of cycloaddition reaction between dimethyl germylidene and formaldehyde

The cycloaddition mechanism of the reaction between singlet dimethyl germylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated with CCSD (T)//MP2/6-31G* method. From the potential energy profile, we predict that the cycloaddition reaction between singlet dimethyl germylidene and formaldehyde has two dominant reaction pathways. First dominant reaction pathway consists of three steps: (1) the two reactants (R1, R2) firstly form an intermediate INT1a through a barrier-free exothermic reaction of 43.0 kJ/mol; (2) INT1a then isomerizes to a four-membered ring compound P1 via a transition state TS1a with an energy barrier of 24.5 kJ/mol; (3) P1 further reacts with formaldehyde(R2) to form a germanic heterocyclic compound INT3, which is also a barrier-free exothermic reaction of 52.7 kJ/mol; Second dominant reaction pathway is as following: (1) the two reactants (R1, R2) firstly form a planar four-membered ring intermediate INT1b through a barrier-free exothermic reaction of 50.8 kJ/mol; (2) INT1b then isomerizes to a twist four-membered ring intermediate INT1.1b via a transition state TS1b with an energy barrier of 4.3 kJ/mol; (3) INT1.1b further reacts with formaldehyde(R2) to form an intermediate INT4, which is also a barrier-free exothermic reaction of 46.9 kJ/mol; (4) INT4 isomerizes to a germanic bis-heterocyclic product P4 via a transition state TS4 with an energy barrier of 54.1 kJ/mol.     

亚甲基硅烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies of the involved conformers were calculated by CCSD（T）//MP2/6-31G＊ and CCSD（T）//B3LYP/6-31 G＊ methods, respectively. The results show that the dominant reaction pathway of the cycloaddition reaction is that a complex intermediate is firstly formed between the two reactants through a barrier-free exothermic reaction of 13.3 kJ/mol, and the complex is then isomefized to a four-membered ring product P2,1 via a transition state TS2.1 with a barrier of 32.0 kJ/mol.     

Development of many-body polarizable force fields for Li-battery applications: 2. LiTFSI-doped Oligoether, polyether, and carbonate-based electrolytes

A quantum chemistry study of Li(+) interactions with ethers, carbonates, alkanes, and a trifluoromethanesulfonylimide anion (TFSI(-)) was performed at the MP2, B3LYP, and HF levels using the aug-cc-pvDz basis set for solvents and TFSI(-) anion, and [8s4p3d/5s3p2d]-type basis set for Li. A classical many-polarizable force field was developed for the LiTFSI salt interacting with ethylene carbonate (EC), gamma-butyrolactone (GBL), dimethyl carbonate (DMC), acetone, oligoethers, n-alkanes, and perfluoroalkanes. Molecular dynamics (MD) simulations were performed for EC/LiTFSI, PC/LiTFSI, GBL/LiTFSI, DMC/LiTFSI, 1,2-dimethoxyethane/LiTFSI, pentaglyme/LiTFSI, and poly(ethylene oxide) (MW = 2380)/LiTFSI electrolytes at temperatures from 298 to 423 K and salt concentrations from 0.3 to 5 M. The ion and solvent self-diffusion coefficients, electrolyte conductivity, electrolyte density, LiTFSI apparent molar volumes, and structure of the Li(+) cation environment predicted by MD simulations were found in good agreement with experimental data.     

Theoretical studies of mechanism of cycloaddition reaction between germylidene and formaldehyde

Mechanism of the cycloadditional reaction between singlet germylidene (R1) and formaldehyde (R2) has been investigated with MP2/6‐31G* method, including geometry optimization, and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction between singlet germylidene and formaldehyde is reaction (4) , which consists of three steps: the two reactants (R1, R2) first form an intermediate INT1b through a barrier‐free exothermic reaction of 28.1 kJ/mol; this intermediate reacts further with formaldehyde (R2) to give an intermediate INT4, which is also a barrier‐free exothermic reaction of 37.2 kJ/mol; subsequently, the intermediate INT4 isomerizes to a heteropolycyclic germanic compound P4 via a transition state TS4, for which the barrier is 18.6 kJ/mol. The dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008