Gas-phase structure, rotational barrier, and vibrational properties of methyl methanethiosulfonate, CH3SO2SCH3: an experimental and computational study

The molecular structure of methyl methanethiosulfonate, CH3SO2SCH3, has been determined in the gas phase from electron-diffraction data supplemented by ab initio (HF, MP2) and density functional theory (DFT) calculations using 6-31G(d), 6-311++G(d,p), and 6-311G(3df,3pd) basis sets. Both experimental and theoretical data indicate that although both anti and gauche conformers are possible by rotating about the S-S bond, the preferred conformation is gauche. The barrier to internal rotation in the CSSC skeleton has been calculated using the RHF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d) methods as well as MP2 with a 6-31G(3df) basis set on sulfur and 6-31G(d) on C, H, and O. A 6-fold decomposition of the rotational barrier has been performed in terms of a Fourier-type expansion, enabling us to analyze the nature of the potential function, showing that the coefficients V1 and V2 are the dominant terms; V1 is associated with nonbonding interactions, and V2 is associated with hyperconjugative interactions. A natural bond orbital analysis showed that the lone pair --> sigma* hyperconjugative interactions favor the gauche conformation. Furthermore, the infrared spectra for the liquid and solid phases and the Raman spectrum for the liquid have been recorded, and the observed bands have been assigned to the vibrational normal modes. The experimental vibrational data, along with calculated theoretical force constants, were used to define a scaled quantum mechanical force field for the target system that enabled us to estimate the measured frequencies with a final root-mean-square deviation of 6 cm-1.     

Vibrational analyses of vinylsulfonamide CH2CHSO2NH2

The structure and conformational stability of vinylsulfonamide CH2CHSO2NH2 were investigated by DFT-B3LYP/6-311+G** and ab initio MP2/6-311+G** calculations. From the calculations the molecule was predicted to exist predominantly in the gauche-syn (vinyl group nearly eclipses one of the SO bonds and the NH2 and the SO2 moieties eclipse each other) conformation with the possibility of low abundance of the cis-syn and the gauche-anti forms. The asymmetric potential function for the internal rotation about CS bond was determined for the molecule. The vibrational frequencies were computed at DFT-B3LYP level for the gauche-syn conformer of the molecule and its d2(C2H3SO2ND2) and d3(C2D3SO2NH2) deuterated species. Normal coordinate calculations were then carried out and the potential energy distributions were calculated for the molecule.     

Theoretical investigation on stability and isomerizations of CH3SO isomers

The stability and isomerizations of CH3SO isomers have been investigated at B3LYP/6-311G(d,p), MP2/6-311G(d,p), QCISD/6-311G(d,p), and CCSD(T)/6-311G(d,p) levels. Geometries of isomers and transition states (TS) have been optimized at the B3LYP/6-311G(d, p) level. Vibration analysis and the intrinsic reaction coordinate (IRC) calculated at the same level have been applied to validate the connection of the stationary points. The four different methods give similar results: 11 isomers and 9 isomerization channels were found. CH3SO and CH2(S)OH are the most stable species among the 11 isomers. Furthermore, the breakage and formation of the chemical bonds in isomerization reactions have been discussed by the topological analysis method of electronic density. The "energy transition state (ETS)" and the "structure transition state (STS)" of all the isomerizations have been found. The topological analysis shows that the relative positions of ETS and STS are determined by reaction energy. The nonplanar four-member ring structure transition state (STS), which was first found in this paper, extended the concept of ring STS.     

CH3CH2+O(3P)反应机理的理论研究

The reaction for CH3CH2+O(3P) 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 CH2O＋CH3, CH3CHO+H and CH2CH2+OH in the reaction. For the products CH2O＋CH3 and CH3CHO+H, the major production channels are A1: (R)→IM1→TS3→(A) and B1: (R)→IM1→TS4→(B), respectively. The majority of the products CH2CH2+OH are formed via the direct abstraction channels C1 and C2: (R)→TS1(TS2)→(C). In addition, the results suggest that the barrier heights to form the CO reaction channels are very high, so the CO is not a major product in the reaction.     

Kinetics of the multichannel reaction of methanethiyl radical (CH3S*) with 3O2

The CH3S* + O2 reaction system is considered an important process in atmospheric chemistry and in combustion as a pathway for the exothermic conversion of methane-thiyl radical, CH3S*. Several density functional and ab initio computational methods are used in this study to determine thermochemical parameters, reaction paths, and kinetic barriers in the CH3S* + O2 reaction system. The data are also used to evaluate feasibility of the DFT methods for higher molecular weight oxy-sulfur hydrocarbons, where sulfur presents added complexity from its many valence states. The methods include: B3LYP/6-311++G(d,p), B3LYP/6-311++G(3df,2p), CCSD(T)/6-311G(d,p)//MP2/6-31G(d,p), B3P86/6-311G(2d,2p)//B3P86/6-31G(d), B3PW91/6-311++G(3df,2p), G3MP2, and CBS-QB3. The well depth for the CH3S* + 3O2 reaction to the syn-CH3SOO* adduct is found to be 9.7 kcal/mol. Low barrier exit channels from the syn-CH3SOO* adduct include: CH2S + HO2, (TS6, E(a) is 12.5 kcal/mol), CH3 + SO2 via CH3SO2 (TS2', E(a) is 17.8) and CH3SO + O (TS17, E(a) is 24.7) where the activation energy is relative to the syn-CH3SOO* stabilized adduct. The transition state (TS5) for formation of the CH3SOO adduct from CH3S* + O2 and the reverse dissociation of CH3SOO to CH3S* + O2 is relatively tight compared to typical association and simple bond dissociation reactions; this is a result of the very weak interaction. Reverse reaction is the dominant dissociation path due to enthalpy and entropy considerations. The rate constants from the chemical activation reaction and from the stabilized adduct to these products are estimated as functions of temperature and pressure. Our forward rate constant and CH3S loss profile are in agreement with the experiments under similar conditions. Of the methods above, the G3MP2 and CBS-QB3 composite methods are recommended for thermochemical determinations on these carbon-sulfur-oxygen systems, when they are feasible.     

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.     

Lithiated hydrocarbons, their conjugate bases, and corresponding radicals: a computational study of RLi (R = CH3, CH3CH2, CH2=CH, and HC triple bond C)

Organolithium compounds RLi (R = CH(3), CH(3)CH(2), CH(2)=CH, and HC(triple bond)C) and their corresponding hydrocarbons were fully optimized at the MP2/6-311+G(2df,2pd) level. Single-point energy calculations also were carried out at the CCSD(T) and B3LYP levels with the same triple split-valence basis set. Acidities, electron affinities, and bond dissociation energies are reported, and the following general results were found: (1) Alpha-lithio anions are ground-state triplet molecules. (2) Lithium is an acid-enhancing substituent. (3) Conjugate bases of organolithiums are stable with respect to electron loss and therefore are attractive targets for mass spectrometry investigations. (4) Lithium weakens alpha- and beta-C-H bonds, the latter by approximately 25 kcal mol(-1). Consequently, radical chemistry of lithiated compounds at remote sites is a promising area for exploration.     

Methanesulfonates of high-valent metals: syntheses and structural features of MoO2(CH3SO3)2, UO2(CH3SO3)2, ReO3(CH3SO3), VO(CH3SO3)2, and V2O3(CH3SO3)4 and their thermal decomposition under N2 and O2 atmosphere

Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO(3), UO(2)(CH(3)COO)(2)·2H(2)O, Re(2)O(7)(H(2)O)(2), and V(2)O(5) with CH(3)SO(3)H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO(2)(CH(3)SO(3))(2) (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm(3), Z=8) contains [MoO(2)] moieties connected by [CH(3)SO(3)] ions to form layers parallel to (100). UO(2)(CH(3)SO(3))(2) (P2(1)/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, β=112.80(1)°, V=1.8937(3) nm(3), Z=8) consists of linear UO(2)(2+) ions coordinated by five [CH(3)SO(3)] ions, forming a layer structure. VO(CH(3)SO(3))(2) (P2(1)/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, β=113.66(1)°, V=0.8290(2) nm(3), Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO(3)(CH(3)SO(3)) (P1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), β=96.11(2), γ=99.04(2)°, V=1.1523(4) nm(3), Z=8) a chain structure exhibiting infinite O-[ReO(2)]-O-[ReO(2)]-O chains is formed. Each [ReO(2)]-O-[ReO(2)] unit is coordinated by two bidentate [CH(3)SO(3)] ions. V(2)O(3)(CH(3)SO(3))(4) (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, β=102.58(3), V=1.5637(5) pm(3), Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH(3)SO(3)] ligands. Additional methanesulfonate ions connect the [V(2)O(3)] groups along [001]. Thermal decomposition of the compounds was monitored under N(2) and O(2) atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N(2) the decomposition proceeds with reduction of the metal leading to the oxides MoO(2), U(3)O(7), V(4)O(7), and VO(2); for MoO(2)(CH(3)SO(3))(2), a small amount of MoS(2) is formed. If the thermal decomposition is carried out in a atmosphere of O(2) the oxides MoO(3) and V(2)O(5) are formed.     

Kinetic mechanism of the hydrogen abstraction reactions of the chlorine atoms with CH3CF2Cl and CH3CFCl2: a dual level direct dynamics study

The mechanisms of the reactions: CH(3)CFCl(2) + Cl (R1) and CH(3)CF(2)Cl + Cl (R2) are studied over a wide temperature range (200-3000 K) using the dual-level direct dynamics method. The minimum energy path calculation is carried out at the MP2/6-311G(d,p) and B3LYP/6-311G(d,p) levels, and energetic information is further refined by the G3(MP2) theory. The H-abstraction from the out-of-plane for (R1) is the major reaction channel, while the in-plane H-abstraction is the predominant route of (R2). The canonical variational transition-state theory (CVT) with the small-curvature tunneling (SCT) correction method is used to calculate the rate constants. Using group-balanced isodesmic reactions and hydrogenation reactions as working chemical reactions, the standard enthalpies of formation for CH(3)CFCl(2), CH(3)CF(2)Cl, CH(2)CFCl(2), and CH(2)CF(2)Cl are evaluated at the CCSD(T)/6-311 + G(3df,2p)//MP2/6-311G(d,p) level of theory. The results indicate that the substitution of fluorine atom for the chlorine atom leads to a decrease in the C-H bond reactivity with a small increase in reaction enthalpies. Also, for all reaction pathways the variational effect is small and the SCT effect is only important in the lower temperature range on the rate constants.     

Theoretical Studies of the Reaction Mechanisms of CH3S＋NO2

The potential energy surface for the CH3S NO2 reaction has been studied using the ab initio G3(MP2) method. A variety of possible complexes and saddle points along the minimum energy reaction paths have been characterized at UMP2 (full)/6-31G(d) level. The calculations reveal dominating reaction mechanisms of the title reaction: CH3S NO2 firstly produce intermediate CH3SONO,then break up into CH3SO NO. The results are valuable to understand the atmospheric sulfur compounds oxidation mechanism.     

Electronic properties of multifurcated bent hydrogen bonds CH3...Y and CH2...Y

H-bonding angle angleYHX has an important effect on the electronic properties of the H-bond Y...HX, such as intra- and intermolecular hyperconjugations and rehybridization, and topological properties of electron density. We studied the multifurcated bent H-bonds of the proton donors H3CZ (Z = F, Cl, Br), H2CO and H2CF2 with the proton acceptors Cl(-) and Br(-) at the four high levels of theory: MP2/6-311++G(d,p), MP2/6-311++G(2df,2p), MP2/6-311++G(3df,3pd) and QCISD/6-311++G(d,p), and found that they are all blue-shifted. These complexes have large interaction energies, 7-12 kcal mol(-1), and large blue shifts, delta r(HC) = -0.0025 --0.006 A and delta v(HC) = 30-90 cm(-1). The natural bond orbital analysis shows that the blue shifts of these H-bonds Y...HnCZ are mainly caused by three factors: rehybridization; indirect intermolecular hyperconjugation n(Y) -->sigma*(CZ), in that the electron density from n(Y) of the proton acceptor is transferred not to sigma*(CH), but to sigma*(CZ) of the donor; intramolecular hyperconjugation n(Z) -->sigma*(CH), in that the electron density in sigma*(CH) comes back to n(Z) of the donor such that the occupancy in sigma*(CH) decreases. The topological properties of the electron density of the bifurcated H-bonds Y...H2CZ are similar to those of the usual linear H-bonds, there is a bond critical point between Y and each hydrogen, and a ring critical point inside the tetragon YHCH. However, the topological properties of electron density of the trifurcated H-bonds Y...H3CZ are essentially different from those of linear H-bonds, in that the intermolecular bond critical point, which represents a closed-shell interaction, is not between Y and hydrogen, but between Y and carbon.     

反常蓝移单电子锂键Y…Li-CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]体系的结构与性质

在密度泛函理论B3LYP/6-311++G(d,p)及MP2/6-311++G(d,p)水平上研究了单电子锂键复合物Y…Li—CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]的结构与性质. 结果表明, 三种单电子锂键复合物H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III)和(H3C)3C…Li—CH3(IV)单电子锂键强度依II(-26.7 kJ·mol-1)相似文献   

The role of chalcogen-chalcogen interactions in the intrinsic basicity acidity of beta-chalcogenovinyl(thio)aldehydes HC([double bond]X)[bond]CH[double bond]CH[bond]CYH

The intrinsic acidity and basicity of a series of beta-chalcogenovinyl(thio)aldehydes HC([double bond]X)[bond]CH[double bond]CH[bond]CYH (X=O, S; Y=Se, Te) were investigated by B3LYP/6-311+G(3df,2p) density functional and G2(MP2) calculations on geometries optimized at the B3LYP/6-31G(d) level for neutral molecules and at the B3LYP/6-31+G(d) level for anions. The results showed that selenovinylaldehyde and selenovinylthioaldehyde should behave as Se bases in the gas phase, because the most stable neutral conformer is stabilized by an X[bond]H...Se (X=O, S) intramolecular hydrogen bond (IHB). In contrast the Te-containing analogues behave as oxygen or sulfur bases, because the most stable conformer is stabilized by typical X...Y[bond]H chalcogen-chalcogen interactions. These compounds have a lower basicity than expected because either chalcogen-chalcogen interactions or IHBs become weaker upon protonation. Similarly, they are also weaker acids than expected because deprotonation results in a significantly destabilized anion. Loss of the proton from the X[bond]H or Y[bond]H groups is a much more favorable than from the C[bond]H groups. Therefore, for Se compounds the deprotonation process results in loss of the X[bond]H...Se (X=O, S) IHBs present in the most stable neutral conformer, while for Te-containing compounds the stabilizing X...Y[bond]H chalcogen-chalcogen interaction present in the most stable neutral conformer becomes repulsive in the corresponding anion.     

Ab initio study of rearrangements on the (CH)2(BR)2, R=H, and NH2 potential energy surfaces

A comprehensive survey of the (CH)2(BH)2 potential energy surface was carried out at the [MP4/6-311 + G(d,p)]//MP2/6-31G(d) level. Many of the classical and nonclassical isomers of the carborane surface are separated by high activation barriers, which explains why derivatives of most isomers could be prepared as stable compounds at room temperature. The transition states are grouped into two types, hydrogen migration (terminal-to-bridge and bridge-to-terminal) and group migration (BH, CH, and CH2). The rearrangement of 1,3-diamino-1,3-diboretene (1-NH2) to 1,2-diamino-1,2-diboretene (2-NH2) was computed and compared to the rearrangement in the parent (1-->2). The effect of the amino group is to substantially increase the barrier height and stabilize the product, 2-NH2.     

Energetics of the O-H bond and of intramolecular hydrogen bonding in HOC6H4C(O)Y (Y = H, CH3, CH2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds

The energetics of the phenolic O-H bond in a series of 2- and 4-HOC 6H 4C(O)Y (Y = H, CH3, CH 2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH 3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds and of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y, was investigated by using a combination of experimental and theoretical methods. The standard molar enthalpies of formation of 2-hydroxybenzaldehyde (2HBA), 4-hydroxybenzaldehyde (4HBA), 2'-hydroxyacetophenone (2HAP), 2-hydroxybenzamide (2HBM), and 4-hydroxybenzamide (4HBM), at 298.15 K, were determined by micro- or macrocombustion calorimetry. The corresponding enthalpies of vaporization or sublimation were also measured by Calvet drop-calorimetry and Knudsen effusion measurements. The combination of the obtained experimental data led to Delta f H m (o)(2HBA, g) = -238.3 +/- 2.5 kJ.mol (-1), DeltafHm(o)(4HBA, g) = -220.3 +/- 2.0 kJ.mol(-1), Delta f H m (o)(2HAP, g) = -291.8 +/- 2.1 kJ.mol(-1), DeltafHm(o)(2HBM, g) = -304.8 +/- 1.5 kJ.mol (-1), and DeltafHm(o) (4HBM, g) = -278.4 +/- 2.4 kJ.mol (-1). These values, were used to assess the predictions of the B3LYP/6-31G(d,p), B3LYP/6-311+G(d,p), B3LYP/aug-cc-pVDZ, B3P86/6-31G(d,p), B3P86/6-311+G(d,p), B3P86/aug-cc-pVDZ, and CBS-QB3 methods, for the enthalpies of a series of isodesmic gas phase reactions. In general, the CBS-QB3 method was able to reproduce the experimental enthalpies of reaction within their uncertainties. The B3LYP/6-311+G(d,p) method, with a slightly poorer accuracy than the CBS-QB3 approach, achieved the best performance of the tested DFT models. It was further used to analyze the trends of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y evaluated by the ortho-para method and to compare the energetics of the phenolic O-H bond in 2- and 4-HOC 6H 4C(O)Y compounds. It was concluded that the O-H bond "strength" is systematically larger for 2-hydroxybenzoyl than for the corresponding 4-hydroxybenzoyl isomers mainly due to the presence of the intramolecular O...H hydrogen bond in the 2-isomers. The observed differences are, however, significantly dependent on the nature of the substituent Y, in particular, when an intramolecular H-bond can be present in the radical obtained upon cleavage of the O-H bond.     

Ab initio study of the interaction of CHX3 (X = H, F, Cl, or Br) with benzene and hexafluorobenzene

In this paper, the results of a study of the interaction of methane, fluoroform, chloroform, and bromoform with benzene and hexafluorobenzene are presented. The benzene complexes were studied at the MP2/6-31G(d) and MP2/6-311++G(2d,p) levels, and the hexafluorobenzene complexes were only studied at the MP2/6-31G(d) level. The optimized geometries, stabilization energies, potential energy surfaces, harmonic frequencies, and vibrational intensities are reported. A net attraction is predicted for all four benzene complexes, whereas for the CHX3.C6F6 complexes, it was found that MP2/6-31G(d) predicts a net attraction for the CH4, CHCl3, and CHBr3 complexes and does not predict a stable complex for CHF3.C6F6. The three complexes with net attractions all have blue-shifts of the CHX3 CH stretching wavenumber and a slight contraction (0.001-0.003 A) of the CH bond in CHX3. The MP2/6-31G(d) level predicts that the intensity of the CHX3 CH stretch will vary widely. For CH4.C6H6 and CHF3.C6H6, it is predicted that the intensity will be smaller for the complexes than the free molecules, whereas for the other complexes, anywhere from a 30% increase to an increase of 87 times is predicted. The atoms in molecules analysis showed that only three of the eight criteria for normal hydrogen bonding are satisfied for all eight complexes studied. Criterion 3 (value of the Laplacian at the bond critical point) is not satisfied for any of the eight complexes.     

Synthesis and structures of beta-diketiminatotin(II) halides, an amide and of Sn(=E)[{N(R)C(Ph)}2CH](NR2) (E = S or Se, R = SiMe3)

Treatment of [Li(L1)]2 (1) or K(L2) (2) with SnX2 in Et2O yielded the heteroleptic beta-diketiminatotin(II) halides Sn(L1)Cl (3a), Sn(L1)Br (3b) or Sn(L2)Cl (4), even when an excess of the alkali metal beta-diketiminate was used [L1={N(R)C(Ph)}2CH, L2={N(R)C(Ph)CHC(But)N(R)}, R = SiMe3]. From and half an equivalent each of SnCl2.2H2O and SnCl2, or one equivalent of SnCl2.2H2O, the product was Sn(L3)Cl (5) or Sn(L4)Cl (6), in which one or both of the N-R bonds of L1 had been hydrolytically cleaved; the compound Sn(L5)Cl (7) was similarly obtained from and an equivalent portion of SnCl2.2H2O [L3={N(R)C(Ph)CHC(But)N(H)}, L4={N(H)C(Ph)CHC(But)N(H)} and L5={N(H)C(Ph)}2CH]. The halide exchange between 3a and 3b, studied by two-dimensional (119)Sn{1H}-NMR spectroscopy, is attributed to implicate a (mu-Cl)(mu-Br)-dimeric intermediate or transition state. The 13C{1H}-NMR spectra of or showed two distinct resonances for each group, which coalesced on heating, corresponding to DeltaG(338 K)= 69.4 (3a) or 72.8 (3b) kJ mol(-1). The chloride ligand of was readily displaced by treatment with NaNR2, CF3SO3H or CH2(COPh)2, yielding Sn(L1)X [X = NR2 (8), O3SCF3 (9) or {OC(Ph)}2CH (10)]. Oxidative addition of sulfur or selenium to gave the tin(IV) terminal chalcogenides Sn(E)(L1)(NR2)[E = S (11) or Se (12)]. The X-ray structures of the cocrystal of 3a/3b and of the crystalline compounds 5, 6, 8, 11 and are presented, as well as multinuclear NMR spectra of each of the new compounds.     

Delta(DeltaS) and Delta(DeltaS) for the competing bond cleavage reactions in (CH3CN)(ROH)H+ [R = CH3, C2H5, C3H7, (CH3)2CH

Microcanonical variational transition-state theory was used to determine the entropies of activation for hydrogen-bond cleavage reactions leading to CH(3)CN + ROH(2)(+) in a series of acetonitrile-alcohol proton-bound pairs (CH(3)CN)(ROH)H(+) (where R = CH(3), CH(3)CH(2), CH(3)CH(2)CH(2), and (CH(3))(2)CH). In each case, the dissociation potential surface was modelled at the MP2/6-31 + G(d) level of theory. The dissociating configurations having the minimum sums-of-states were identified in each case and the resulting entropies of activation were calculated. Combined with previous work on the competing reaction leading to CH(3)CNH(+) + ROH, the results permitted the determination of the Delta(DeltaS) in each proton-bound pair. For the (CH(3)CN)(CH(3)OH)H(+) and (CH(3)CN)(CH(3)CH(2)OH)H(+) proton-bound pairs, the entropies of activation for the two dissociating channels are essentially the same [i.e., Delta(DeltaS) = 0], while Delta(DeltaS) for the propanol-containing pairs ranged between 40 and 45 J K(-1) mol(-1). The latter non-zero values are due to a combination of the location of the dividing surface in each dissociation and the rapidity with the frequencies of the vanishing vibrational modes go to zero as they are converted to product translations and rotations during the dissociation.     

Novel cation [N(SO2NMe3)2]+ and its synthesis and crystal structure. Dichloride of imido-bis(sulfuric) acid HN(SO2Cl)2. Part 1. Crystal structures of KN(SO2Cl)2.(1/2)CH3CN, KN(SO2Cl)2.(1/6)CH2Cl2, and [PCl4][N(SO2Cl)2

Several salts of bis(chlorosulfonyl)imide HN(SO2Cl)2 (1), namely, two solvates of its potassium salt, KN(SO2Cl)2.(1/2)CH3CN (1K1), KN(SO2Cl)2.(1/6)CH2Cl2 (1K2), and its tetrachlorophosphonium salt, [PCl4][N(SO2Cl)2] (2), were prepared and structurally characterized. The reaction of HN(SO2Cl)2 with Me3N gives the [N(SO2Cl)2]- salt of a novel cation, [N(SO2NMe3)2]+. This cation is analogous to the [HC(SO2NMe3)2]+ cation, but in contrast to the latter, it is fairly stable to hydrolysis. The salt [N(SO2NMe3)2]+[N(SO2Cl)2]- (3) can be converted into salts of other anions by being treated with diluted aqueous solutions of the respective acids, and thus NO3-, Cl-.H2O, SeO3(2-), CH3COO-, HSO4-, (COO)2(2-) salts were prepared. Treatment of 3 with concentrated HNO3 gave the [N(SO2NMe3)2]+ [O2NO-H-ONO2]- salt, and the addition of an HCl-acidified FeCl3 aqueous solution yielded the FeCl4- salt. Methanolysis resulted in the formation of MeOSO3- and [MeOSO2NSO2OMe]- salts. All salts have been characterized by chemical analysis, vibrational spectroscopy, and X-ray structure determinations.     

Protonated nitro group: structure, energy and conjugation

Structure of protonated nitro compounds was investigated by calculations at the levels MP2(FC)/6-311++G(2d,2p)//MP2(FC)/6-311++G(2d,2p)(nitromethane and reference compounds) or B3LYP/6-311+G(d,p)//B3LYP/6-311+G(d,p)(nitrobenzene and its 18 meta- and para-substituted derivatives). The group NO2H+ reveals many similarities with the isoelectronic group CO2H as the preferred conformation, conformational equilibrium, and stabilization by interaction (resonance) within the group quantified by means of isodesmic reactions. However, there is a difference in the interaction with donor groups (for instance in 4-nitroaniline) that is much stronger with NO2H+ than with CO2H. This interaction may be called resonance and may be described by standard resonance formulas, but these formulas predict only partially the geometry and cannot explain the great interaction energy.