Analysis of the reaction force for a gas phase S(N)2 process: CH3Cl + H2O --> CH3OH + HCl

The "reaction force" F(R(c)) is the negative derivative of a system's potential energy V(R(c)) along the intrinsic reaction coordinate of a process. If V(R(c)) goes through a maximum, as is commonly the case, then F(R(c)) has a characteristic profile: a negative minimum followed by zero at the transition state and then a positive maximum. These features reflect four phases of the reaction: an initial one of reactant preparation, followed by two of transition to products, and then relaxation of the latter. In this study, we have analyzed, in these terms, a gas-phase S(N)2 substitution, selected to be CH3Cl + H2O --> CH3OH + HCl. We examine, at the B3LYP/6-31G level, the geometries, energetics, and molecular surface electrostatic potentials, local ionization energies, and internal charge separation.     

Vibrational spectroscopic study of the electron transfer for the Cl- + CH3Cl S(N)2 reaction in the gas phase

The vibrational spectra study of electron transfer of Cl- + CH3Cl --> ClCH3 + Cl- reaction has been examined by density function theory (DFT) calculations at 6-311 + +G** level in this paper. This reaction includes old bond rupture, new bond formation and electronic transfer in the intermolecular. The vibrational frequencies and vibrational modes of reactant, precursor complex, transition state, successor complex and product are analyzed. The relationship and the change among them can confirm the rupture of bond, the formation of bond and the process of electron transfer.     

Chemical reactions inside structured nano-environment: S(N)2 vs. E2 reactions for the F(-) + CH(3)CH(2)Cl system

A new receptor for S(N)2 transition states, named NPTROL, is proposed. This molecule has a cavity and four hydroxyl groups that are able to interact with ionic S(N)2 and E2 transition states. Its catalytic effect and selectivity was investigated through high level ab initio calculations using the fluoride ion plus ethyl chloride in DMSO solution as a model system. Calculations at the ONIOM[CCSD(T)/6-311+G(2df,2p)?:?MP2/BASIS1] level of theory and solvent effects, included through a continuum solvation model, indicate that NPTROL is able to catalyze the S(N)2 pathway and has an inverse effect on the E2 pathway. Inside the NPTROL cavity, the ΔG(?) for the S(N)2 transition state is 5.00 kcal mol(-1) lower than that for E2, and as a consequence this reaction becomes highly selective toward the S(N)2 product.     

Nonadiabatic dynamics in the CH3+HCl-->CH4+Cl(2PJ) reaction

Nonadiabatic dynamics in the title reaction have been investigated by 2+1 REMPI detection of the Cl(2P(3/2)) and Cl*(2P(1/2)) products. Reaction was initiated by photodissociation of CH(3)I at 266 nm within a single expansion of a dilute mixture of CH(3)I and HCl in argon, giving a mean collision energy of 7800 cm(-1) in the center-of-mass frame. Significant production of Cl* was observed, with careful checks made to ensure that no additional photochemical or inelastic scattering sources of Cl* perturbed the measurements. The fraction of the total yield of Cl(2P(J)) atoms formed in the J=1/2 level at this collision energy was 0.150+/-0.024, and must arise from nonadiabatic dynamics because the ground potential energy surface correlates to CH(4)+Cl(2P(3/2)) products.     

Vanadium complexes of the N(CH2CH2S)3(3-) and O(CH2CH2S)2(2-) ligands with coligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.     

CH3 CH2 +N(4S)反应机理的理论研究

The reaction for CH3CH2+N(4S) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The single point calculations for all the stationary points were carried out at the QCISD(T)/ 6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major products are the CH2CH2+3NH and H2CN＋CH3, and the minor products are the CH3CHN+H in the reaction. The majority of the products CH2CH2+3NH are formed via a direct hydrogen abstraction channel. The products H2CN＋CH3 are produced via an addition/dissociation channel. The products CH3CHN+H are produced via an addition/dissociation channel.     

State-to-state dynamics of the Cl + CH3OH --> HCl + CH2OH reaction

Molecular chlorine, methanol, and helium are co-expanded into a vacuum chamber using a custom designed "late-mixing" nozzle. The title reaction is initiated by photolysis of Cl2 at 355 nm, which generates monoenergetic Cl atoms that react with CH3OH at a collision energy of 1960 +/- 170 cm(-1) (0.24 +/- 0.02 eV). Rovibrational state distributions of the nascent HCl products are obtained via 2 + 1 resonance enhanced multiphoton ionization, center-of-mass scattering distributions are measured by the core-extraction technique, and the average internal energy of the CH3OH co-products is deduced by measuring the spatial anisotropy of the HCl products. The majority (84 +/- 7%) of the HCl reaction products are formed in HCl(v = 0) with an average rotational energy of [Erot] = 390 +/- 70 cm(-1). The remaining 16 +/- 7% are formed in HCl(v = 1) and have an average rotational energy of [Erot] = 190 +/- 30 cm(-1). The HCl(v = 1) products are primarily forward scattered, and they are formed in coincidence with CH2OH products that have little internal energy. In contrast, the HCl(v = 0) products are formed in coincidence with CH2OH products that have significant internal energy. These results indicate that two or more different mechanisms are responsible for the dynamics in the Cl + CH3OH reaction. We suggest that (1) the HCl(v = 1) products are formed primarily from collisions at high impact parameter via a stripping mechanism in which the CH2OH co-products act as spectators, and (2) the HCl(v = 0) products are formed from collisions over a wide range of impact parameters, resulting in both a stripping mechanism and a rebound mechanism in which the CH2OH co-products are active participants. In all cases, the reaction of fast Cl atoms with CH3OH is with the hydrogen atoms on the methyl group, not the hydrogen on the hydroxyl group.     

Rate constants and hydrogen isotope substitution effects in the CH3 + HCl and CH3 + Cl2 reactions

The kinetics of the CH3 + Cl2 (k2a) and CD3 + Cl2 (k2b) reactions were studied over the temperature range 188-500 K using laser photolysis-photoionization mass spectrometry. The rate constants of these reactions are independent of the bath gas pressure within the experimental range, 0.6-5.1 Torr (He). The rate constants were fitted by the modified Arrhenius expression, k2a = 1.7 x 10(-13)(T/300 K)(2.52)exp(5520 J mol(-1)/RT) and k2b = 2.9 x 10(-13)(T/300 K)(1.84)exp(4770 J mol(-1)/RT) cm(3) molecule(-1) s(-1). The results for reaction 2a are in good agreement with the previous determinations performed at and above ambient temperature. Rate constants of the CH3 + Cl2 and CD3 + Cl2 reactions obtained in this work exhibit minima at about 270-300 K. The rate constants have positive temperature dependences above the minima, and negative below. Deuterium substitution increases the rate constant, in particular at low temperatures, where the effect reaches ca. 45% at 188 K. These observations are quantitatively rationalized in terms of stationary points on a potential energy surface based on QCISD/6-311G(d,p) geometries and frequencies, combined with CCSD(T) energies extrapolated to the complete basis set limit. 1D tunneling as well as the possibility of the negative energies of the transition state are incorporated into a transition state theory analysis, an approach which also accounts for prior experiments on the CH3 + HCl system and its various deuterated isotopic substitutions [Eskola, A. J.; Seetula, J. A.; Timonen, R. S. Chem. Phys. 2006, 331, 26].     

Quantum chemical modeling of nucleophilic substitution reactions in the complexes cis-Pt(NH3)2Cl2 and cis-Pd(NH3)2Cl2

The B3LYP/6-31G** method was used for the study of nucleophilic substitution reaction in platinum and palladium square-planar cis-diaminate complexes. The processes under consideration take place in two steps through pentacoordinated transition states. Activation barriers for both steps of these processes in gaseous phase and aqueous solution were calculated. A major role in the increase in the activation energies is played by the formation of the intermediate electrostatic Van der Waals’ complexes. For the complex cis-[Pd(NH₃)₂Cl₂], the activation barriers in the nucleophilic substitution reaction are considerably lower than those for the complex cis-[Pt(NH₃)₂Cl₂].     

Syntheses and Structures of S4N4(OCH3)2 and CH3OS4N4(O)Cl

The reaction of S₄N₄Cl₂ with CH₃OH gives S₄N₄(OCH₃)₂, a simple dimethoxoderivative of S₄N₄. Its overall geometry is analogous to other compounds of the S₄N₄X₂ type. The chlorination of S₄N₄(OCH₃)₂ leads to the oxidation of one sulfur atom to S^VI and CH₃OS₄N₄(O)Cl is formed. The compounds were characterized by ir spectroscopy and their crystal structures were determined from single crystal diffraction data collected at ?153°C. The presence of S^VI in the molecule of CH₃OS₄N₄(O)Cl is manifested by a marked shortening of the bonds formed by this atom as compared with S₄N₄Cl₂ and S₄N₄(OCH₃)₂.     

Dual-level direct dynamics studies on the reaction Cl + CHBr(2)Cl

Theoretical investigations are carried out on the multichannel reaction CHBr(2)Cl + Cl by means of direct dynamics methods. The minimum energy path (MEP) is obtained at the BH&H-LYP/6-311G(d,p) level, and energetic information is further refined at the CCSD(T)/6-311+G(2df,2p) (single-point) level. The rate constants for three reaction channels, H-abstraction, Br-abstraction, and Cl-abstraction, are calculated by using the improved canonical variational transition state theory (ICVT) incorporating with the small-curvature tunneling (SCT) correction. The theoretical overall rate constants are in good agreement with the available experimental data and are found to be k=2.58 x 10(-15) T(1.18) exp(-861.17/T) cm(3)molecule(-1)s(-1) over the temperature range 200--2400 K. For the title reaction, H-abstraction reaction channel is the major channel at the lower temperatures, while as the temperature increases, the contribution of Br-abstraction reaction channel should be taken into account. At 2180 K, the rate constants of these two pathways are equal. Cl-abstraction reaction channel is minor channel over the whole temperature region.     

Ab initio studies on reaction H2C=C(OH)Li+CH3 + (CH3 -)

The possible structures and isomerizations of H₂C=C(OH)Li are studied theoretically by the gradient analytical method at RHF/6-31+G level. According to these results, reactions of H₂C=C(OH)Li with CH₃ ⁺ and CH ₃ ^- are investigated thoroughly. When H₂C=C(OH)Li reacts with CH ₃ ⁺ , H_zC=C(OH)Li firstly changes from structure1 to structure4, and then combines with CH₃ ⁺. In this reaction, the configuration of central carbon is retained. When H₂C=C(OH)Li reacts with CH ₃ ^- , structure1 firstly breaks its C-O bond to give contact ion-pair. Then through transition state16 which is similar to structure2, the attack of CH ₃ ^- from the opposite side of^-OH replaces^-OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid has close relationship with the stability of special structures. Project supported by the National Natural Science Foundation of China (Grant No. 29773025).     

4-Methyl-1,2,3,5-dithiadiazoliumsalze Die Kristallstrukturen von (CH3CN2S2)5[CoCl4]Cl3 und (CH3CN2S2)Cl

4-Methyl-1,2,3,5-dithiadiazolium Salts. Crystal Structures of(CH₃CN₂S₂)₅[CoCl₄]Cl₃ and (CH₃CN₂S₂)Cl 4-Methyl-1,2,3,5-dithiadiazolium tetrachlorocobaltate trichloride, (CH₃CN₂S₂)₅[CoCl₄]Cl₃, was obtained by reaction of trithiazyl chloride, (NSCl)₃, with CoCl₂ in acetonitrile; it forms brown, moisture sensitive crystals. With tetraphenylarsonium chloride in CH₂Cl₂ it yields yellow crystalline (CH₃CN₂S₂)Cl and (AsPh₄)₂CoCl₄. The IR spectra of the title compounds are reported and assigned. Theit crystal structures were determined by X-ray diffraction. Crystal data: (CH₃CN₂S₂)₅[CoCl₄]Cl₃, orthorhombic, P2₁2₁2₁, Z = 4, a = 830, b = 1603, c = 2443 pm at 180 K (structure determination with 1787 observed independent reflexions, R = 0.070); (CH₃CN₂S₂)Cl, triclinic, P2₁2₁2₁, Z = 4, a = 749, b = 819, c = 1015 pm, α = 84.9, β = 67.4, γ = 84.6° at 296 K (2653 reflexions, R = 0.040). Both compounds are ionic, having chloride and distorted tetrahedral CoCl₄^2? anions and planar 4-methyl-1,2,3,5-dithiadiazolium cations which nearly fulfill C_2v symmetry. The (CH₃CN₂S₂)₅[CoCl₄]Cl₃ structure contains five symmetry independent cations, (CH₃CN₂Cl has two symmetry independent cations, all being nearly equal. No nitrogen atom but all sulfur atoms of the cations have contact with three to five chlorine atoms, and as a rule there is one chloride ion which is coplanar with the cation and exhibits rather short distances to both S atoms (288 to 309 pm); therefore, the positive charge of the cations must be concentrated on the sulfur atoms.     

Schwingungsspektren und Kraftkonstanten von Cl3SiP(CH3)2 und Cl3SiAs(CH3)2

Vibrational Spectra and Force Constants of Cl₃SiP(CH₃)₂ and Cl₃SiAs (CH₃)₂ The i.r. and Raman spectra of Cl₃SiP(CH₃)₂ and Cl₃SiAs (CH₃)₂ have been recorded and assigned. A normal coordinate analysis has been made using a modified valence force field. The SiP force constant is slightly higher than those of alkylsilylphosphines, whereas a similar effect is not found for the SiAs bond.     

Kinetics of the CH2Cl + CH3 and CHCl2 + CH3 radical-radical reactions

The CH2Cl + CH3 (1) and CHCl2 + CH3 (2) cross-radical reactions were studied by laser photolysis/photoionization mass spectroscopy. Overall rate constants were obtained in direct real-time experiments in the temperature region 301-800 K and bath gas (helium) density (6-12) x 10(16) atom cm(-3). The observed rate constant of reaction 1 can be represented by an Arrhenius expression k1 = 3.93 x 10(-11) exp(91 K/T) cm3 molecule(-1) s(-1) (+/-25%) or as an average temperature-independent value of k1= (4.8 +/- 0.7) x 10(-11) cm3 molecule(-1) s(-1). The rate constant of reaction 2 can be expressed as k2= 1.66 x 10(-11) exp(359 K/T) cm3 molecule(-1) s(-1) (+/-25%). C2H4 and C2H3Cl were detected as the primary products of reactions 1 and 2, respectively. The experimental values of the rate constant are in reasonable agreement with the prediction based on the "geometric mean rule." A separate experimental attempt to determine the rate constants of the high-temperature CH2Cl + O2 (10) and CHCl2 + O2 (11) reaction resulted in an upper limit of 1.2 x 10(-16) cm(3) molecule(-1) s(-1) for k10 and k11 at 800 K.