Showing papers on "Acetonitrile published in 2004"
TL;DR: Lower limiting film thicknesses and surface coverages for films prepared in aqueous conditions is attributed to growth of inherently more blocking films and is supported by examination of the response of the Fe(CN)6(3-/4-) couple at NP-modified surfaces.
Abstract: Electrochemical reduction of the diazonium salts of 4-nitrobenzene and 4-nitroazobenzene-4‘- has been investigated in aqueous acid and acetonitrile media at carbon surfaces. Using pyrolyzed photoresist films as the substrate, we have examined the deposited films using electrochemistry and atomic force microscopy (AFM). Film thicknesses were measured by scratching through the film with an AFM tip. The procedure employed two AFM cantilevers with different lengths, located on the one device. When the shorter cantilever engages the surface in tapping mode, the longer cantilever (which is not resonating) imbeds into the surface with a constant force. For both modifiers and modification media, film thicknesses increase with deposition time to a limiting value. With equivalent modification conditions, films prepared in aqueous acid medium have lower limiting thicknesses than those prepared in acetonitrile. For nitrophenyl (NP) films, the same trends are found when calculating surface coverages from the charge as...
399 citations
TL;DR: In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported, and a reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
Abstract: A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is catalysed using a [copper(II)-(N ligand)n] complex with TEMPO and a base as co-catalysts. In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported. Best results are obtained in acetonitrile/water as solvent using a copper(II) catalyst generated in situ from a Cu(II) salt with weak or non-coordinating anions and bipyridine ligands with electron-donating substituents. A reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
311 citations
TL;DR: In solvents with dielectric constants of 10 or less, ion association constants, K(A), are as much as 2 orders of magnitude lower with [B(C(6)F(5))(4)](-), TFAB, as the electrolyte anion and the degree of this lowering is related to the acceptor property of the solvent.
Abstract: Cyclic voltammetry experiments at minielectrodes exhibit less ohmic error for lower polarity solvents when the supporting electrolyte anion is [B(C6F5)4]- rather than one of the smaller traditional anions such as [BF4]-, [PF6]-, or [ClO4]-. Conductance measurements have been performed for [NBu4][B(C6F5)4] in tetrahydrofuran, dichloromethane, benzotrifluoride, and acetonitrile and compared with results for [NBu4]+ salts of several traditional anions in the same solvents. In solvents with dielectric constants of 10 or less, ion association constants, KA, are as much as 2 orders of magnitude lower with [B(C6F5)4]-, TFAB, as the electrolyte anion and the degree of this lowering is related to the acceptor property of the solvent. Analyses carried out on the basis of a Fuoss model attribute this fact to differences in concentrations of contact ion pairs rather than of solvent-separated ion pairs. The greater dissociation of the TFAB ion is attributed to its highly delocalized charge.
281 citations
TL;DR: Results from molecular dynamics simulations of surfactant-solubilized subtilisin BPN' in three organic solvents (octane, tetrahydrofuran, and acetonitrile) and in pure water indicate that the behavior of hydration water on the enzyme surface and in the active site is an important determinant of biological function especially in low water media.
218 citations
TL;DR: In this paper, the electrochemical reduction of oxygen is reported in four room temperature ionic liquids (RTILs) based on quaternary alkyl -onium cations and heavily fluorinated anions in which the central atom is either nitrogen or phosphorus.
Abstract: The electrochemical reduction of oxygen is reported in four room temperature ionic liquids (RTILs) based on quaternary alkyl -onium cations and heavily fluorinated anions in which the central atom is either nitrogen or phosphorus Data were collected using cyclic voltammetry and potential step chronoamperometry at gold, platinum, and glassy carbon disk electrodes of micrometer dimension under water-free conditions at a controlled temperature Analysis via fitting to appropriate theoretical equations was then carried out to obtain kinetic and thermodynamic information pertaining to the electrochemical processes observed In the quaternary ammonium electrolytes, reduction of oxygen was found to occur reversibly to give stable superoxide, in an analogous manner to that seen in conventional aprotic solvents such as dimethyl sufoxide and acetonitrile The most significant difference is in the relative rate of diffusion; the diffusion coefficients of oxygen in the RTILs are an order of magnitude lower than in c
216 citations
TL;DR: In this article, the authors describe the oxidation of several model S-containing molecules with hydrogen peroxide in a two liquid-liquid (L-L) phase system with a phase transfer catalyst under atmospheric pressure in the 333-353 K temperature range.
210 citations
TL;DR: In this paper, a diode-array detector was used to identify a series of polyynes having the general chemical structure: HA(CBC)mAH (with m an integer 1; 2; 3;... m).
136 citations
TL;DR: The dinuclear copper(II) cryptate [Cu2L](ClO4)4 (1) cleaves the C-C bond of acetonitrile at room temperature to produce a cyanide bridged complex of [ Cu2L(CN)](ClO 4)3.2CH3CN.4H2O (2).
Abstract: The dinuclear copper(II) cryptate [Cu2L](ClO4)4 (1) cleaves the C−C bond of acetonitrile at room temperature to produce a cyanide bridged complex of [Cu2L(CN)](ClO4)3·2CH3CN·4H2O (2). The cleavage mechanism is presented on the basis of the results of the crystal structure of 2, electronic absorption spectra, ESI-MS spectroscopy, and GC spectra of 1, respectively.
123 citations
TL;DR: In this article, a silyl iron complex Cp(CO)2Fe(SiMe3) (1) in acetonitrile in the presence of P(NMeCH2)2(OMe) (L) yielded CpL2FeMe (2), CpC 2Fe(CN) (3), and CpCO(LFeMe) (4), showing that carbon−carbon bond cleavage was achieved.
111 citations
TL;DR: These compounds are moderate hydride donors as compared to previously determined compounds and require significant revisions of the hydricities reported for related NADH analogues and metal hydrides.
Abstract: The thermodynamic hydride donor abilities of 1-benzyl-1,4-dihydronicotinamide (BzNADH, 59 ± 2 kcal/mol), C5H5Mo(PMe3)(CO)2H (55 ± 3 kcal/mol), and C5Me5Mo(PMe3)(CO)2H (58 ± 2 kcal/mol) have been measured in acetonitrile by calorimetric and/or equilibrium methods. The hydride donor abilities of BzNADH and C5H5Mo(PMe3)(CO)2H differ by 13 and 24 kcal/mol, respectively, from those reported previously for these compounds in acetonitrile. These results require significant revisions of the hydricities reported for related NADH analogues and metal hydrides. These compounds are moderate hydride donors as compared to previously determined compounds.
106 citations
TL;DR: Self-complexing molecular systems are obtained when an arm component is covalently linked to a preformed macrocycle (a pi-acceptor) and have the potential to undergo reversible movements, i.e., the arm can be driven out of or into the cavity of the linked macrocycle in response to temperature or applied voltage.
Abstract: Self-complexing molecular systems are obtained when an arm component (a π-donor) is covalently linked to a preformed macrocycle (a π-acceptor). The resulting self-complexing compounds are not only ...
TL;DR: In this article, a new methodology for functionalization of single-walled carbon nanotubes (SWNTs), using 1,3-dipolar cycloaddition of nitrile imines to the sidewalls of SWNTs, has been used to synthesize two soluble, photoactive single walled carbon Nanotubes containing n-pentyl esters at the tips and 2,5-diaryl pyrazoline units at the walls of the tubes.
Abstract: A new, versatile methodology for functionalization of single-walled carbon nanotubes (SWNTs), using 1,3-dipolar cycloaddition of nitrile imines to the sidewalls of SWNTs has been used to synthesize two soluble, photoactive single walled carbon nanotubes containing n-pentyl esters at the tips and 2,5-diarylpyrazoline units at the walls of the tubes. The success of the synthesis has been demonstrated by solution 1H and 19F NMR as well as UV−vis and FT-IR spectroscopy. These two compounds have been selected to have soluble single wall carbon nanotubes substituted either with an electron-poor 3,5-bis(trifluoromethyl)phenyl or electron-rich 4-(N,N-dimethylamino)phenyl on the C atom of the pyrazoline ring. Laser flash photolysis in dynamic flow of these carbon nanotubes in acetonitrile reveals the formation of several transient species decaying in the microsecond time scale. All the available data, including the photochemistry of model compounds, quenching experiments with electron donors and acceptors, and inf...
TL;DR: The cobalt-catalyzed carbocyclization reaction was successfully extended to the synthesis of indene derivatives, and when 7e was employed for the carbocylization, reductive decyanation occurred to give an indene derivative without the cyano functionality.
Abstract: An efficient cobalt-catalyzed carbocylization for the synthesis of indenols and indenes and a new method for reductive decyanation are described. 2-Iodophenyl ketones and aldehydes 1a−g undergo carbocyclization with various disubstituted alkynes 2a−k in the presence of Co(dppe)I2 and zinc powder in acetonitrile at 80 °C for 3 h to afford the corresponding indenol derivatives 3a−s and 4a−m in good to excellent yields. For some unsymmetrical alkynes, the carbocyclization was remarkably regioselective, affording a single regioisomer. The cobalt-catalyzed carbocyclization reaction was successfully extended to the synthesis of indene derivatives. Thus, the reaction of 2-iodophenyl ketones and aldehydes (1) with acrylates H2CCHCO2R (7a−d) and acrylonitrile H2CCHCN (7e) proceeds smoothly in the presence of Co(dppe)Cl2/dppe and zinc powder in acetonitrile at 80 °C for 24 h to afford the corresponding indenes 8a−k and 9a−c in moderate to good yields. Interestingly, when 7e was employed for the carbocylization, red...
TL;DR: The addition of TMSCN to a variety of arylaldimines (Strecker reaction) in the presence of LiClO 4 or BF 3 ·Et 2 O in acetonitrile has been studied in this article.
TL;DR: In this paper, the catalytic asymmetric chlorination of β-keto esters was performed by the [Ti(TADDOLato)] complex, whereby α-chlorinated products were obtained in moderate to good yields and enantioselectivities of up to 71%.
Abstract: (Dichloroiodo)toluene (=dichloro(4-methylphenyl)iodine; 2) was found to be a suitable chlorinating agent in the catalytic asymmetric chlorination of β-keto esters 3 catalyzed by the [Ti(TADDOLato)] complex 1 (=bis(acetonitrile)dichloro[(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(naphthalen-1-yl)-1,3-dioxolane-4,5-dimethanolato(2−)-κO,κO′]titanium), whereby α-chlorinated products were obtained in moderate to good yields and enantioselectivities of up to 71% (Scheme 2, Table 2) The enantioselectivity of the reaction shows a remarkable temperature dependence, the maximum selectivity being obtained at ca 50°
TL;DR: In this article, the synthesis of 1,2,3-triazoles with aryl substituents at the ring carbon atoms was described by Khisamutdinov and co-workers.
Abstract: It is known that some 1,2,3-triazole derivatives possess practically important properties. For example, 4-(4-methoxyphenyl)-5-nitro-1,2,3-triazole exhibits antifungal activity, and 4-(4-bromophenyl)and 4-(4nitrophenyl)-5-nitro-1,2,3-triazoles are tuberculostatic and fungicide agents [1]. Some 1,2,3-triazoles can be used as photostabilizers and optical bleaching agents [2, 3], and they may be regarded as precursors of azapurines which are potential carcinostatic agents [2]. The synthesis of nitro-1,2,3-triazoles having aryl substituents at the ring carbon atoms was described by Khisamutdinov and co-workers [1, 4]. It is based on the reaction of 2-aryl-1-bromo-1-nitroethenes or 2-aryl-1,2-dibromo-2-nitroethanes with sodium azide in aprotic (DMF, DMSO) or protic (ethanol) solvents. 1,1-Dinitroethene derivatives, specifically β,β-dinitrostyrenes, are highly reactive compounds [5–8] which can be used in the synthesis of nitro-1,2,3triazoles. We have shown that β,β-dinitrostyrenes I–III react with 2 equiv of sodium azide under fairly mild conditions, in anhydrous acetonitrile at room temperature. The reaction takes 2.5–4.5 h, and the products are 4-aryl-5-nitro-1,2,3-triazoles VII–IX which are formed in 59–77% yield. Compounds VII–IX were also synthesized by independent method from the corresponding β-bromo-β-nitrostyrenes and sodium azide in DMF, following a slightly modified procedure
TL;DR: In this paper, the cyclic voltammetry and the electrochemical impedance spectroscopy responses of p-doped poly(3,4-ethylenedioxythiophene) (PEDOT) electrodeposited on platinum electrode surface were studied in a room-temperature ionic liquid, 1ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (EMITFSI).
TL;DR: In this paper, cyclometalated derivatives of ring-substituted N,N-dimethylbenzylamines with controlled redox potentials are reported as potent mediators of bioelectrochemical electron transport.
TL;DR: In this paper, a comparative study of the electrochemical behavior of several transition metal substituted polyoxotungstates in acetonitrile solution with tetra-n-butylammonium perchlorate as a supporting electrolyte is presented.
Abstract: A comparative study of the electrochemical behaviour of several transition metal substituted polyoxotungstates in acetonitrile solution with tetra-n-butylammonium perchlorate as a supporting electrolyte is presented. Tetra-n-butylammonium salts of Keggin-type polyoxoanions, α-[(C4H9)4N]4Hx[XW11M(H2O)O39]·nH2O, X = P, Si; MII = Co, Ni, MIII = Fe, Mn, x = 0−2, n = 0−2, and sandwich-type polyoxoanions, α-B-[(C4H9)4N]7H3[M4(H2O)2(PW9O34)2], MII = Co, Mn, have been studied by cyclic voltammetry and spectroelectrochemistry. Under the conditions used, the tungsten-oxo framework of the metal substituted Keggin anions could accept up to three electrons in quasi-reversible one-electron consecutive processes. Comparison with the corresponding lacunary anions is presented. Redox processes at the metal centre have been detected for all metals M except Ni. For the anions α-[XW11M(H2O)O39]m−, the co-existence of species with a different degree of protonation was deduced from cyclic voltammetry results whenever protons were included in the molecular formula. The influence of the solids’ composition on the electrochemical results is stressed. For the sandwich anions, cyclic voltammetry revealed redox processes occurring on the W atoms and also on the metallic belt. Two metal atoms in the belt of the α-B-[CoII4(H2O)2(PW9O34)2]10− anion could be electrochemically oxidised to CoIII in two separate steps. A similar result was observed for the MnII analogue, but the corresponding first step was not as well defined. Re-oxidation was only detected for the Co anion. This work is the first comparative study of the electrochemical behaviour of such transition metal substituted polyoxotungstates in an organic medium. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
TL;DR: Aprotic polar solvents such as DMF, acetonitrile or DMSO can be protonated to form stable triflate salts when treated with triflic acid as discussed by the authors.
TL;DR: It is shown that the rate of electron transfer of a single compound in different alkyl cyanides is determined by the longitudinal dielectric relaxation properties of the solvent, while differences in rate between the substituted anthracenes in acetonitrile can be quantitatively rationalized by considering their relative hydrodynamic radii.
Abstract: The validity of Marcus theory for outer-sphere heterogeneous electron transfer for the electro-oxidation of a range of anthracene derivatives in alkyl cyanide solvents is investigated. The precision measurement of these fast electron transfers (k(0) >or= 1 cm s(-1)) is achieved by use of the high-speed channel electrode and, where necessary, fast-scan cyclic voltammetry. First, the solvent effect on the rate of electron transfer is studied by considering the first oxidation wave of 9,10-diphenylanthracene in the alkyl cyanide solvents: acetonitrile, propionitrile, butyronitrile, and valeronitrile. Second, the variation of k(0) for a series of substituted anthracenes is investigated by analyzing the voltammetric response of the one-electron oxidations of 9-phenylanthracene, 9,10-dichloroanthracene, 9-chloroanthracene, 9,10-dicyanoanthracene, 9-cyanoanthracene, 9-nitroanthracene, 9,10-diphenylanthracene, and anthracene in acetonitrile. It is shown that the rate of electron transfer of a single compound in different alkyl cyanides is determined by the longitudinal dielectric relaxation properties of the solvent, while differences in rate between the substituted anthracenes in acetonitrile can be quantitatively rationalized by considering their relative hydrodynamic radii. This makes possible the accurate prediction of electron-transfer rates for a molecule by interpolation of rate constants known for related molecules.
TL;DR: In this paper, the first-order and second-order rate constants of CH2I-I were obtained for femtosecond photolysis in acetonitrile at an excitation wavelength of 266nm.
Abstract: Femtosecond and nanosecond photolysis of CH2I2 in acetonitrile at an excitation wavelength of 266-nm yield the ground-state CH2I-I isomer product in similar to70% quantum yield. High isomer formation quantum yields (> 70%) were measured also in n-hexane, dichloromethane, methanol, and ethanol using nanosecond photolysis. The CH2I-I product is formed biphasically within similar to15 ps after excitation and can survive on a nanosecond to microsecond time scale before it decays via a mixture of first- and second-order processes. At 21 degreesC, the first-order rate constants are 1.8 x 10(5) s(-1) in n-hexane, with the measured apparent activation energy of 41 +/- 2 kJ mol(-1) (5-55 degreesC), and 4.3 x 10(6) s(-1) in acetonitrile. These rate constants correspond to intramolecular decomposition Of CH2I-I into a CH2I. radical and an I atom, with the additional formation of I- in acetonitrile. In methanol and ethanol, the CH2I-I isomer decays faster with the pseudo-first-order rate constants of 2.0 x 10(8) and 1.3 x 10(8) s(-1), respectively, and as in acetonitrile, I-3(-) and I-2(-) ion products dominate the absorption of photolyzed CH2I2 samples at long times. The thermodynamics of the CH2I2 system and its implication for the CH2I-I formation mechanism are discussed. A possible role of the CH2I-I isomer as a methylene transfer agent in photocyclopronation of olefins is investigated. Vibrationally relaxed CH2I-I is demonstrated to react with cyclohexene yielding an I-2 leaving group with the second-order rate constants similar to4.4 x 10(5) M-1 s(-1) in n-hexane, 3.4 x 10(6) M-1 s(-1) in dichloromethane, and 4.2 x 10(6) M-1 s(-1) in acetonitrile. (Less)
TL;DR: In this paper, the authors applied CO 2 -expanded liquid (CXL) solvent media to heterogeneously catalyzed oxidations and showed that it significantly reduces the use of conventional organic solvents as reaction media and also enhances catalyst stability.
Abstract: CO 2 -expanded liquid (CXL) solvents are known to provide optimum reaction and environmental benefits for certain homogeneously catalyzed oxidations. In this work, CXL solvent media are applied to heterogeneously catalyzed oxidations. The oxidation of cyclohexene is investigated as a model reaction. Conversion/selectivity measurements were made in a stirred batch reactor on a MCM-41 encapsulated iron porphyrin chloride complex ( p =1–127 bar, T =25–50 °C, t =4–12 h), using either dioxygen or iodosylbenzene as oxidant. Neat acetonitrile and CO 2 -expanded acetonitrile are used as reaction media. The pressures required for reaction studies in CO 2 -based media were determined by expansion studies as well as cloud point measurements. For the oxidation with dioxygen, conversion and product yields in CO 2 -expanded acetonitrile (∼30% CO 2 ) almost doubled compared to the neat organic solvent. In contrast, CO 2 -replacement of the organic solvent had a negligible effect on conversion and selectivity values when using iodosylbenzene as oxidant. Our results indicate that CXLs significantly reduce the use of conventional organic solvents as reaction media and also enhance catalyst stability against leaching. These advantages suggest that CXLs are promising media for developing green heterogeneous catalytic processes.
TL;DR: In this article, a series of common synthesis gas contaminants were evaluated to determine their effect on catalyst activity, and the following representative species were found to adversely affect the rate of methanol synthesis: phosphine (PH3), carbonyl sulfide (COS), carbon disulfide (CS2), thiophene (C4H4S), methyl thiocyanate (CH3SCN), methyl chloride (CH 3Cl), and methyl fluoride (CH
Abstract: The liquid phase methanol (LPMEOH™) process has successfully produced methanol from coal-derived synthesis gas on an industrial scale. This process uses a standard copper, zinc oxide, and alumina catalyst suspended in an inert mineral oil in a slurry bubble column reactor. A series of common synthesis gas contaminants were evaluated to determine their effect on catalyst activity. The following representative species were found to adversely affect the rate of methanol synthesis: phosphine (PH3), carbonyl sulfide (COS), carbon disulfide (CS2), thiophene (C4H4S), methyl thiocyanate (CH3SCN), methyl chloride (CH3Cl), and methyl fluoride (CH3F). The nitrogen-containing contaminants hydrogen cyanide (HCN), acetonitrile (CH3CN), and methylamine (CH3NH2) had no effect on catalyst activity. The surprising inactivity of HCN is likely attributable to its hydrogenation under methanol synthesis conditions. An approximate order of decreasing catalyst poison potency was obtained: C4H4S≅AsH3>CH3Cl>CH3SCN>CS2>COS>PH3>CH3F. Based on catalyst surface area and molar effectiveness for each poison, catalyst poisoning cannot be attributed solely to a loss of copper surface area. Although this study involved the liquid phase process, the results should be applicable to methanol synthesis by a gas phase, fixed bed process. A rationalization of contaminant/catalyst reactivity is presented.
TL;DR: Steady-state measurements, EPR evidence, deuteration experiments and attempted intramolecular trapping of the adduct radical support the mechanistic proposal.
Abstract: Alkyl radical obtained by irradiation of tetrabutylammonium decatungstate in acetonitrile in the presence of cycloalkanes (C5H10, C6H12, C7H14) are efficiently trapped by electrophilic alkenes (acrylonitrile, isopropylydenmalonitrile, isopropylydencyanoacetate) to give the corresponding alkylated aliphatic nitriles. The reaction can be carried out up to complete conversion of the alkene with reasonable (in most cases 60-65 %) yields. Addition of the radicals to the alkene is followed by electron transfer from reduced decatungstate regenerating the sensitizer (turn over number up to 60). Steady-state measurements, EPR evidence, deuteration experiments and attempted intramolecular trapping of the adduct radical support the mechanistic proposal.
TL;DR: The syn-isomer of 1,8-bis(4,4′-diisopropyl-9,9′-diacridyl)naphthalene, 1, has been prepared by two consecutive Pd(PPh3)4-catalyzed Stille cross-coupling steps as discussed by the authors.
TL;DR: The potential of packed-bed reactors for the treatment of a concentrated mixture of volatile pollutants is confirmed and microbial characterization of the biofilm resulted in the isolation of a Comamonas sp.
Abstract: A 20-l packed-bed reactor filled with foamed glass beads was tested for the treatment of acetonitrile HPLC wastes. Aeration was provided by recirculating a portion of the reactor liquid phase through an aeration tank, where the dissolved oxygen concentration was kept at 6 mg/l. At a feeding rate of 0.77 g acetonitrile l−1 reactor day−1, 99% of the acetonitrile was removed; and 86% of the nitrogen present in acetonitrile was released as NH3, confirming that acetonitrile volatilization was not significant. Increasing the acetonitrile loading resulted in lower removal efficiencies, but a maximum removal capacity of 1.0 g acetonitrile l−1 reactor day−1 was achieved at a feeding rate of 1.6 g acetonitrile l−1 reactor day−1. The removal capacity of the system was well correlated with the oxygenation capacity, showing that acetonitrile removal was likely to be limited by oxygen supply. Microbial characterization of the biofilm resulted in the isolation of a Comamonas sp. able to mineralize acetonitrile as sole carbon, nitrogen and energy source. This organism was closely related to C. testosteroni (91.2%) and might represent a new species in the Comamonas genus. This study confirms the potential of packed-bed reactors for the treatment of a concentrated mixture of volatile pollutants.
TL;DR: A novel and practical procedure for preparation of imides is described using chromium(VI) oxide to catalyze the oxidation of N-alkylamides with periodic acid in the presence of acetic anhydride in acetonitrile.
TL;DR: In this paper, the vibrational spectra of acetonitrile solutions containing lithium iodide and tetrabutylammonium iodide have been studied using ATR-FTIR spectroscopy.
Abstract: The vibrational spectra of acetonitrile solutions containing lithium iodide and tetrabutylammonium iodide have been studied using ATR-FTIR spectroscopy. The focus of interest was the effect of the iodide anion on the important vibrational bands of acetonitrile. The main effect of the LiI electrolyte is to shift the C⋮N stretching frequency in the blue direction due to interaction of the Li+ cation with the electronegative C⋮N group. However, a small red shift of the C⋮N stretching mode due to the interaction of I- with the methyl group of acetonitrile is found in both electrolytes. On the other hand, the symmetic and asymmetric stretching modes of the methyl group are significantly red shifted in the presence of LiI. Ab initio quantum chemical calculations were carried out to determine the optimum location of the Li+ and I- ions in ion−solvent complexes containing a varying number of solvent molecules. These calculations correctly predict the direction of the observed shifts for all the principal bands of...
TL;DR: 2D free energy surfaces V = V(rOH, rO...O) for the intramolecular H-bond in the title compound were calculated by the DFT method and used in the calculation of primary and secondary chemical shifts of the compound dissolved in chloroform and acetonitrile.
Abstract: 2D free energy surfaces V = V(rOH, rO...O) for the intramolecular H-bond in the title compound were calculated by the DFT method and used in the calculation of primary and secondary chemical shifts of the compound dissolved in chloroform and acetonitrile. Solvent effects were accounted for by the SCRF/PCM method. The corresponding two-dimensional chemical shift surfaces with included solvent reaction field were obtained using the Continuous Set of Gauge Transformations approach at the B3LYP/6-311+G(2d,2p) level of theory. The chemical shifts were estimated as quantum averages along the two internal coordinates in the hydrogen bond and along several vibrational levels according to the Boltzmann distribution at room temperature. Fairly good agreement between the experimental and calculated isotope effects was obtained. 1D and 2D NMR spectra of solutions of picolinic acid N-oxide and its deuterated analogue were recorded and assigned.