A new rearrangement process in tert-amyl cation

13C NMR spectroscopy of the 2-methyl-2-butyl-1-13C cation (13C-labeled tert-amyl cation) indicates that interchange of the inside and outside carbons occurs via a barrier of 19.5 +/- 2.0 kcal/mol. A plausible mechanism involves hydride migration in the proposed 2-pentyl cation 4 to form 3-pentyl cation 5. Via the protonated cyclopropane intermediate 6, which undergoes degenerate corner-to-corner hydride shift, the secondary 3-pentyl cation 5' with the label shifted to the central carbon atom is formed. The tert-amyl cation obtained from 5' in the reverse process has the 13C label on an inside carbon atom. All intermediates and transition structures were located on the PES theoretically at the MP2/6-31G(d,p) level of theory. The rearrangement rate of the doubly labeled tert-amyl cation (methyl-13C-butyl-1-13C cation), followed by means of 13C NMR, revealed that the process that interchanges inside and outside carbons has the highest barrier. Comparison of the initial rates revealed that isotopomer 1e arises considerably more slowly than other isotopomers, indicating that in the overall rearrangement process transition structure 5-TS has the highest energy.     

电极/离子液体界面电容

用电化学阻抗方法研究了铂片电极在BMIMPF6,BMIMBF4,BMIMClO4,BMIMTf2N,BMIMCl,BMIMBr,C3OHMIMBF4,C3OHMIMClO4和BMMIMPF6(BMIM:1-butyl-3-methylimidazolium;C3OHMIM:1-(3-hydroxypropyl)-3-methylimidazolium;BMMIM:1-butyl-2-methyl-3-methylimidazolium;Tf2N:bis(trifluoromethylsulfonyl)amide)等离子液体中的界面电容及结构.结果表明:当阴、阳离子半径相差不大且不存在特性吸附时,在零电荷电势附近,电极/离子液体界面的电容-电势曲线将出现电容单峰或者双峰.电极的零电荷电势对应于单峰的峰电势或者双峰之间的谷电势.当电极电势远离零电荷电势时,电极/离子液体界面成紧密层结构,可由紧密层理论来描述.如果存在离子的特性吸附,相应的电容峰可能不再出现,而表现为双层电容随电极电势对零电荷电势的偏离而单调增加.还研究了添加小的Li+离子对电极/离子液体界面电容的影响.通过向BMIMTf2N中加入LiTf2N,发现Li+离子可以改变电极/离子液体界面的双层结构,但无助于界面电容的提高,甚至可能引起电容的降低.最后探讨了不同条件下,尤其考虑阴阳离子特性吸附时,电极/离子液体的界面结构.     

Structures of ionic liquids with different anions studied by infrared vibration spectroscopy

We investigated the structures of ionic liquids (1-butyl-3-methylimidazolium iodide [BMIM][I] and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]) and their aqueous mixtures using attenuated total reflection (ATR) infrared absorption and Raman spectroscopy. The ATR spectrum in the CHx (x = 1, 2, 3) vibration region from 2800 to 3200 cm-1 was very different between [BMIM][BF4] and [BMIM][I] even though all the spectral features in this region were from the butyl chain and the imidazolium ring of the same cation. The spectrum did not change appreciably irrespective of the water concentration for [BMIM][BF4], whereas the spectrum from [BMIM][I] showed significant changes as the water concentration was increased, especially in CH-vibration modes from the imidazolium ring. For very diluted solutions both aqueous mixtures of [BMIM][I] and [BMIM][BF4] showed very similar spectra. Mixing of [BMIM][I] with heavy water (D2O) facilitated the isotopic exchange of the proton attached to the most acidic carbon of the imidazolium ring into deuterium from D2O, whereas even prolonged exposure to D2O did not induce any isotopic exchange for [BMIM][BF4]. Raman spectra around 600 cm(-1) indicative of the butyl chain conformation also changed differently as the water concentration was increased between [BMIM][I] and [BMIM][BF4]. These differences are considered to come from the variation in the position of the anion, where I- is expected to be closer to the C(2) hydrogen of the imidazolium cation and interacting more specifically as compared to BF(4-).     

A Bloembergen–Purcell–Pound <Superscript>13</Superscript>C NMR relaxation study of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The molecular structure and rotational motion of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) were studied over a wide temperature range using the Bloembergen–Purcell–Pound ¹³C NMR spin–lattice relaxation method and NOE factors. Examination of the spin–lattice relaxation times (T ₁) and the rates (R ₁=1/T ₁) of the 1-butyl-3-methylimidazolium cation reveals the relative motions of each carbon in the imidazolium cation. The rotational characteristics of the [BMIM] cation are supported by ab-initio molecular structures of [BMIM][PF6] using density functional theory (DFT) and Hartree–Fock (HF) methods. The ab-initio gas phase structures of [BMIM][PF6] indicate that the 1-butyl-3-methylimidazolium C2 hydrogen, the ring methyl group, and the butyl side-chain hydrogen atoms form hydrogen bonds with the hexafluorophosphate anion.     

Surface tension of binary mixtures of imidazolium and ammonium based ionic liquids with alcohols, or water: cation, anion effect

The surface tensions were measured at atmospheric pressure, with use of a ring tensiometer, of a series of alcoholic solutions of closely related ionic liquids: 1-methyl-3-methylimidazolium methylsulfate, [MMIM][CH3SO4] in alcohol (methanol, or ethanol, or 1-butanol at 298.15 K), 1-butyl-3-methylimidazolium methylsulfate, [BMIM][CH3SO4] in alcohol (methanol, or ethanol, or 1-butanol at 298.15 K), 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OcSO4] in alcohol (methanol, or 1-butanol at 298.15 K) and of 1-hexyloxymethyl-3-methylimidazolium tetrafluoroborate, [C6H(13)OCH2MIM][BF4], 1,3-dihexyloxymethylimidazolium tetrafluoroborate, [(C6H13OCH2)2IM][BF4] in alcohol (methanol, or 1-butanol, or 1-hexanol at 308.15 and 318.5 K) and hexyl(2-hydroxyethyl)dimethylammonium bromide, C6Br in 1-octanol at 298.15 K. The set of ammonium ionic liquids of different cations and anions (C2Br, C2BF4, C2PF6, C2N(CN)2, C3Br, C4Br and C6Br) was chosen to show the influence of small amount of the ammonium ionic liquid on the surface tension of water at 298.15 K. The influence of the cation, or anion alkyl chain length on the properties under study (densities and surface tension) was tested.     

近红外菁染料敏化的准固态太阳电池的光电化学研究

一个新型的近红外五甲川菁染料敏化剂(Cy)通过3,3-二甲基-1-乙基-2-[4-(N-苯乙酰氨基]-1,3-丁二烯-1-基]-3H-苯并[e]吲哚碘盐和5-羧基-1-丁基-2,3,3-三甲基-3H-吲哚碘盐的Knoevenagel缩合反应合成, 其结构用核磁、质谱和紫外等方法进行了确定; 使用疏水性气相法纳米SiO2 R974固化1-丁基-3-丙基咪唑碘离子液体制备了一种新的准固态电解质, 将其应用于菁染料(Cy)敏化的太阳电池, 对该染料敏化的准固态太阳电池的光电化学性能进行了研究. 在AM1.5G标准光源下, 得到1.49%的光电转换效率. 此方法对拓展准固态染料敏化太阳电池的研究具有一定的意义.     

Comparison of dansylated aminopropyl controlled pore glass solvated by molecular and ionic liquids

We compare how (i) four ionic liquids (ILs) (1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpy][Tf2N]), and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P(C6)3C14][Tf2N])) and (ii) two conventional molecular liquids (methanol and 1-octanol) solvate/wet luminescent organic moieties that are covalently attached to the surface of silica controlled pore glass (CPG). A series of aminopropyl CPG particles that have been covalently tagged with the solvatochromic fluorescent probe group dansyl were used in this study. The results demonstrate that ILs solvate/wet the silica surface differently in comparison to molecular liquids (MLs). Specifically, when comparing ILs and MLs that appear to solvate the free probe, dansylpropylsulfonamide (DPSA), equally in solution, we find that ILs do not solvate/wet the silica surfaces as well as the corresponding MLs. The cation component in these ILs is the significant factor in how the ILs solvate/wet silica surfaces. Solvation/wetting of surface-bound species at a silica surface depends on the cation size. Chlorosilane end-capping of the surface silanol and amine residues attenuates the cation's affects.     

Synthesis,structure and antioxidant activity of sulfur-containing tetrakisphenol

3-[2-(3,5-Di-tert-butyl-4-hydroxyphenylsulfanyl)acetoxy]2,2-bis[2-(3,5-di-tert-butyl-4-hydroxyphenylsulfanyl) acetoxymethyl]propyl 3,5-di-tert-butyl-4-hydroxyphenylsulfanylacetate was synthesized. Its structure was determined by means of ¹H and ¹³C NMR spectroscopy and X-ray-diffraction analysis. This compound was found to possess high antioxidant activity in the conditions of auto-oxidation of low-pressure polyethylene.     

The enthalpies of vaporisation of ionic liquids: new measurements and predictions

The enthalpies of vaporisation, Δ(vap)H(298), of seven ionic liquids (ILs) (four imidazoliums, a pyridinium, a phosphonium and an isouronium) have been determined by temperature programmed desorption using line of sight mass spectrometry. They were: 1-ethyl-3-methylimidazolium bis(pentafluoroethyl)phosphinate, [C(2)C(1)Im][PO(2)(C(2)F(5))(2)]; 1-butyl-3-methylimidazolium octylsulfate, [C(4)C(1)Im][C(8)OSO(3)]; 1-butyl-3-methylimidazolium tetrafluoroborate, [C(4)C(1)Im][BF(4)]; 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [C(6)C(1)Im][FAP]; 1-butylpyridinium methylsulfate, [C(4)Py][C(1)OSO(3)]; trihexyl(tetradecyl)phosphonium tetrafluoroborate, [P(6,6,6,14)][BF(4)] and O-ethyl-N,N,N',N'-tetramethylisouronium trifluoromethanesulfonate, [C(2)(C(1))(4)iU][TfO]. The values were found to be consistent with a previously proposed, predictive, model in which Δ(vap)H(298) is decomposed into a Coulombic component (computable from the IL density) and van der Waals components from the anion and cation. Two previously predicted values of Δ(vap)H(298) were found to be within 6 kJ mol(-1) of the measured experimental values. Values for the van der Waals components are tabulated for eleven cations and twelve anions. Predictions are made for Δ(vap)H(298) for 13 ILs with as yet unmeasured Δ(vap)H(298) values (using experimental molar volumes), and for a further 44 ILs using estimated molar volumes.     

Characterization of the molecular reorientational dynamics of the neat ionic liquid 1-butyl-3-methylimidazolium bromide in the super cooled state using 1H and 13C NMR spectroscopy

The (13)C spectra and (13)C longitudinal relaxation times (T(1)) were measured to investigate the segmental motion of the neat ionic liquid 1-butyl-3-methylimidazolium bromide ([bmim]Br) in the super cooled state. The (13)C signals of the imidazole ring significantly broadened at 283 K, whereas many other signals were unchanged. In the process of lowering temperature, the [bmim]Br changed to the solid state at ca 273 K without showing the rapid phase transition. Only the (13)C signal of the terminal methyl group in the butyl chain was still observed at 263 K, indicating that the motion of the imidazole ring was extremely restricted, whereas the methyl group in the butyl chain was active even in the solid state. The (13)C-T(1) values measured as a function of temperature also supported the discrete segmental motions of the [bmim](+) cation.     

Fused s-triazino heterocycles. XVI. 13H-1,3,7,8,12a, 13c-hexaazabenzo[de]naphthacene and 1,3,7,8,11b, 12,14,14d-octaazadibenzo[de,hi]naphthacene,two new ring systems

The reaction of 7,9-dibromo-5-tribromomethyl-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1a ) with 2-amino-5-picoline is shown to give 4,6-dibromo-2-t-butyl-13-imino-11-methyl-13H-1,3,7,8,12a,13c-hexaazabenzo[de]naphthacene ( 3 ) and the isomeric 7,9-dibromo-2-t-butyl-4-cyano-5N-(5-methyl-2-pyridyl)amino-1,3,-6,9b-tetraazaphenalene ( 2a ). A related annulation reaction of 7,9-dibromo-2-t-butyl-5-chloro-4-cyano-1,3,6,9b-tetraazaphenalene ( 1g ) with 2-amino-6-trimethylacetamidopyridine leads in two steps to 4,6-dibromo-2,13-di-t-butyl-1,3,7,8,11b,12,14,14d-octaazadibenzo[de,hi]naphthacene ( 4a ). The preparation of 1g , 5-azido-7,9-dibromo-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1c ) and the reaction of the latter with pyrrolidine leading to 7,9-dibromo-2-t-butyl-4-cyano-5-(1-pyrrolidino)-1,3,6,9b-tetraazaphenalene ( 1e ) are also reported. Attempted displacement of the azido-group on 1c by 2,6-diaminopyridine affords surprisingly 5-amino-7,9-dibromo-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1d ).     

On the spontaneous carboxylation of 1-butyl-3-methylimidazolium acetate by carbon dioxide

The formation of 1-butyl-3-methylimidazolium-2-carboxylate in the mixture of CO(2) with 1-butyl-3-methylimidazolium acetate under mild conditions (298 K, 0.1 MPa) has been put in evidence in the liquid phase using Raman and infrared spectroscopy complemented by DFT calculations and NMR ((1)H, (13)C, (15)N) spectroscopy.     

In search of ionic liquids incorporating azolate anions

Twenty-eight novel salts with tetramethyl-, tetraethyl-, and tetrabutylammonium and 1-butyl-3-methylimidazolium cations paired with 3,5-dinitro-1,2,4-triazolate, 4-nitro-1,2,3-triazolate, 2,4-dinitroimidazolate, 4,5-dinitroimidazolate, 4,5-dicyanoimidazolate, 4-nitroimidazolate, and tetrazolate anions have been prepared and characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and single-crystal X-ray crystallography. The effects of cation and anion type and structure on the physicochemical properties of the resulting salts, including several ionic liquids, have been examined and discussed. Ionic liquids (defined as having m.p.<100 degrees C) were obtained with all combinations of the 1-butyl-3-methylimidazolium cation ([C(4)mim](+)) and the heterocyclic azolate anions studied, and with several combinations of tetraethyl or tetrabutylammonium cations and the azolate anions. The [C(4)mim](+) azolates were liquid at room temperature exhibiting large liquid ranges and forming glasses on cooling with glass-transition temperatures in the range of -53 to -82 degrees C (except for the 3,5-dinitro-1,2,4-triazolate salt with m.p. 33 degrees C). Six crystal structures of the corresponding tetraalkylammonium salts were determined and the effects of changes to the cations and anions on the packing of the structure have been investigated.     

3-氨基-4-氧代氰基呋咱捕获与表征

3,4-双(4-氨基呋咱-3-基)氧化呋咱由活性中间体3-氨基-4-氧代氰基呋咱分子间发生二聚获得,但3-氨基-4-氧代氰基呋咱不稳定,无法通过分离、纯化及光谱鉴定证实其存在.采用4种不同的烯烃与3-氨基-4-氧代氰基呋咱发生1,3-偶极环加成反应得到3-(4-氨基呋咱-3-基)-5-氰基-Δ2-异噁唑啉、3-(4-氨基呋咱-3-基)-5-乙酰氧基-Δ2-异噁唑啉、3-(4-氨基呋咱-3-基)-5-正丁基-Δ2-异噁唑啉及3-(4-氨基呋咱-3-基)-环己烷并-Δ2-异噁唑啉4种Δ2-异噁唑啉衍生物;采用苯甲酰氯为捕获剂,与3-氨基-4-氧代氰基呋咱反应获得了3-氨基-4-(N-苯甲酸基氨基羰基)呋咱化合物;通过红外光谱、核磁共振光谱、质谱、元素分析表征了5种新化合物的结构,提供了活性中间体3-氨基-4-氧代氰基呋咱存在的间接证据.     

Comparative study of the hypercoordinate ions C7H9+ and C8H9+ by the ab initio/GIAO-CCSD(T) method

A comparative study of the hypercoordinate square-pyramidal carbocations C7H9+ and C8H9+ was performed by the ab initio/GIAO-CCSD(T) method. The structures and 13C NMR chemical shifts of the cations were calculated at the GIAO-CCSD(T)/tzp/dz//MP2/cc-pVTZ level. The bishomo square pyramidal structure 1 was calculated for C7H9+ at the MP2/cc-pVTZ level. The calculated 13C NMR chemical shifts of structure 1 agree extremely well with the experimental values. However, unlike for C7H9+ both the bishomo square pyramidal structure 3 and the trishomocyclopropenium type structure 4 were found to be minima on the potential energy surface of C8H9+. They are very close energetically with cation 3, only 0.7 kcal/mol less stable than cation 4 at the MP2/cc-pVTZ//MP2/cc-pVTZ + ZPE level. Neither structure 3 nor 4 yields NMR spectra that agree with experiment. However, a weighted average of the two reproduces the observed NMR spectrum of C8H9+ (at -80 degrees C) quite well.     

Structural characterization of the 1-butyl-3-methylimidazolium chloride ion pair using ab initio methods

Ab initio theoretical methods are used to investigate the gas-phase ion pairs of the ionic liquid 1-butyl-3-methylimidazolium chloride. Multiple stable conformers with the chloride anion positioned (in-plane) around the imidazolium ring or above the C2-H bond are determined. The relative energy ordering of the conformers is examined at the B3LYP, MP2, and CCSD(T) levels. Zero-point energies, BSSE, and basis set effects are examined. For accurate results, correlation (dispersion) effects must be included. The most stable conformers are essentially degenerate and have the chloride H-bonding to, or lying above, the C2-H bond. Other conformers are found to lie approximately 30 and approximately 60 kJ mol(-1) higher in energy. Results are compared with those from recent simulations and experimental studies. The effect of the chloride anion on rotation of the butyl chain is investigated and found to lower some rotational barriers while enhancing others. The origin of the rotational barriers is determined. The number and type of hydrogen bonds formed between the imidazolium cation and chloride anion is found to vary significantly among conformers. No evidence of a possible intra C(alkyl)-H...pi interaction is obtained; however, hints of a Cl...pi interaction are found. The vibrational spectrum of each conformer is examined, and the origin of multiple (H-bonding) features in the vibrational spectrum of the ionic liquid explained.     

The vapour of imidazolium-based ionic liquids: a mass spectrometry study

Eight common dialkylimidazolium-based ionic liquids have been successfully evaporated in ultra-high vacuum and their vapours analysed by line of sight mass spectrometry using electron ionisation. The ionic liquids investigated were 1-alkyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide, [C(n)C(1)Im][Tf(2)N] (where n = 2, 4, 6, 8), 1-alkyl-3-methylimidazolium tetrafluoroborate, [C(n)C(1)Im][BF(4)] (where n = 4, 8), 1-butyl-3-methylimidazolium octylsulfate, [C(4)C(1)Im][C(8)OSO(3)] and 1-butyl-3-methylimidazolium tetrachloroferrate, [C(4)C(1)Im][FeCl(4)]. All ionic liquids studied here evaporated as neutral ion pairs; no evidence of decomposition products in the vapour phase were observed. Key fragment cations of the ionised vapour of the ionic liquids are identified. The appearance energies, E(app), of the parent cation were measured and used to estimate the ionisation energies, E(i), for the vapour phase neutral ion pairs. Measured ionisation energies ranged from 10.5 eV to 13.0 eV. Using both the identity and E(app) values, the fragmentation pathways for a number of fragment cations are postulated. It will be shown that the enthalpy of vaporisation, Δ(vap)H, can successfully be measured using more than one fragment cation, although caution is required as many fragment cations can also be formed by ionisation of decomposition products.     

The structure of thiophene sesquioxide: Syn,endo-3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b] thiophene 1,1,8-trioxide

Thiophene sesquioxide is shown to be syn, endo-3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1,8-trioxide (I) by ¹ H and ¹³ C nmr evidence. Assignment of the ¹³ C spectrum was facilitated by a cross-ring long-range ¹³ C-¹ H coupling. The mass spectrum of I is dominated by an unusual break-down to give benzene radical cation.     

Molecular ions of ionic liquids in the gas phase

Ionic liquids form neutral ion pairs (CA) upon evaporation. The softness of the gas-phase ionization of field ionization has been used to generate "molecular ions," CA(+*), of ionic liquids, most probably by neutralization of the anion. In detail, 1-ethyl-3-methylimidazolium-thiocyanate, [C(6)H(11)N(2)](+) [SCN](-), 1-butyl-3-methylimidazolium-tricyanomethide, [C(8)H(15)N(2)](+) [C(4)N(3)](-), N-butyl-3-methylpyridinium-dicyanamide, [C(10)H(16)N](+) [C(2)N(3)](-), and 1-butyl-1-methylpyrrolidinium-bis[(trifluormethyl)sulfonyl]amide, [C(9)H(20)N](+) [C(2)F(6)NO(4)S(2)](-) were used. The assignment as CA(+*) ions, which has been confirmed by accurate mass measurements and misassignments due to thermal decomposition of the ionic liquids, has been ruled out by field desorption and electrospray ionization mass spectrometry of the residues.     

Nuclear magnetic resonance data of pyrido[2,3-B] pyrazines and their σ-adducts with amide ion and water

¹³C nmr spectral data of the parent substance pyrido[2,3-b]pyrazine and several of its derivatives (containing one or more chloro, amino, oxo, bromo, fluoro, phenyl, methyl, hydrazino or t-butyl substituents) are reported. The ¹³C nmr spectrum of the parent substance has been assigned conclusively by ¹³C-labelling. Additionally we proved, the existence of anionic 1:1 σ-adducls i.e., 3-amino-3,4-dihydropyrido[2,3-b]pyrazine, the formation of 3-amino-2-t-butyl-6-chloro-3,4-dihydropyrido[2,3-b]pyrazinide ion and by ¹H nmr spectroscopy 2-amino-1,2-dihydro-3-phenylpyrido[2,3-b]pyrazinide ion. The ¹³C nmr data of the cation of the dihydrale 2,3-dihydroxy-1,2,3,4-tetrahydropyrido[2,3-b]pyrazine, present in a solution of the parent compound in N hydrochloric acid, are given.