Heats of formation and singlet-triplet separations of hydroxymethylene and 1-hydroxyethylidene

Thermochemical parameters of hydroxymethylene (HC:OH) and 1-hydroxyethylidene (CH3C:OH) were evaluated by using coupled-cluster, CCSD(T), theory, in conjunction with the augmented correlation consistent, aug-cc-pVnZ, basis sets, with n = D, T, Q, and 5, extrapolated to the complete basis set limit. The predicted value at 298 K for Delta Hf(CH2O) is -26.0 +/- 1 kcal/mol, as compared to an experimental value of -25.98 +/- 0.01 kcal/mol, and for Delta Hf(CH:OH) it is 26.1 +/- 1 kcal/mol. The hydroxymethylene-formaldehyde energy gap is 52.1 +/- 0.5 kcal/mol, the singlet-triplet separation of hydroxymethylene is Delta E(ST)(HC:OH) = 25.3 +/- 0.5 kcal/mol, the proton affinity is PA(HC:OH) = 222.5 +/- 0.5 kcal/mol, and the ionization energy is IEa(HC:OH) = 8.91 +/- 0.04 eV. The predicted value at 298 K for Delta Hf(CH3CHO) is -39.1 +/- 1 kcal/mol as compared to an experimental value of -40.80 +/- 0.35 kcal/mol, and for Delta Hf(CH3C:OH) it is 11.2 +/- 1 kcal/mol. The hydroxyethylidene-acetaldehyde energy gap is 50.6 +/- 0.5 kcal/mol, the singlet-triplet separation of 1-hydroxyethylidene is Delta E(ST)(CH3C:OH) = 30.5 +/- 0.5 kcal/mol, the proton affinity is PA(CH3C:OH) = 234.7 +/- 0.5 kcal/mol, and the ionization energy is IEa(CH3C:OH) = 8.18 +/- 0.04 eV. The calculated energy differences between the carbene and aldehyde isomers, and, thus, the heats of formation of the carbenes, differ from the experimental values by 2.5 kcal/mol.     

Total asymmetric syntheses of 3- and 4-deoxy-hexoses and derivatives

(1S,4S)-7-Oxabicyclo[2.2.1]hept-5-en-2-one ((−)-5, a “naked sugar”) has been converted to (−)-(1R,4S,6S)-6-endo-benzyloxy-2-bromo-7-oxabicyclo[2.2.1]hept-2-ene ((−)-12) in a highly stereoselective fashion. Double hydroxylation of the C=C double bond of (−)-12, followed by acetylation and Baeyer-Villiger oxidation of the resulting -acetoxyketone (−)-14 afforded (−)-5-O-acetyl-2-O-benzyl-3-deoxy-β-D-arabino-hexofuranurono-6,1-lactone ((−)-15). This compound was converted readily into (+)-methyl 3-deoxy--D-arabino-hexofuranoside ((+)-6 and (+)-methyl 3-deoxy-β-L-xylo-hexofuranoside ((+)-7) and partially protected derivatives. (−)-15 was also converted into 4-deoxy-D-lyxo-hexopyranose (34) and several partially protected derivatives such as (+)-methyl 4-deoxy-2,3-O-isopropylidene--D-lyxo-hexopyranoside ((+)-8).     

Kinetics and mechanisms of bromine chloride reactions with bromite and chlorite ions

Chloride ion catalyzes the reactions of HOBr with bromite and chlorite ions in phosphate buffer (p[H(+)] 5 to 7). Bromine chloride is generated in situ in small equilibrium concentrations by the addition of excess Cl(-) to HOBr. In the BrCl/ClO(2)(-) reaction, where ClO(2)(-) is in excess, a first-order rate of formation of ClO(2) is observed that depends on the HOBr concentration. The rate dependencies on ClO(2)(-), Cl(-), H(+), and buffer concentrations are determined. In the BrCl/BrO(2)(-) reaction where BrCl is in pre-equilibrium with the excess species, HOBr, the loss of absorbance due to BrO(2)(-) is followed. The dependencies on Cl(-), HOBr, H(+), and HPO(4)(2)(-) concentrations are determined for the BrCl/BrO(2)(-) reaction. In the proposed mechanisms, the BrCl/ClO(2)(-) and BrCl/BrO(2)(-) reactions proceed by Br(+) transfer to form steady-state levels of BrOClO and BrOBrO, respectively. The rate constant for the BrCl/ClO(2)(-) reaction [k(Cl)(2)]is 5.2 x 10(6) M(-1) s(-1) and for the BrCl/BrO(2)(-) reaction [k(Br)(2)]is 1.9 x 10(5) M(-1) s(-1). In the BrCl/ClO(2)(-) case, BrOClO reacts with ClO(2)(-) to form two ClO(2) radicals and Br(-). However, the hydrolysis of BrOBrO in the BrCl/BrO(2)(-) reaction leads to the formation of BrO(3)(-) and Br(-).     

Synthesis and Antimicrobial Evaluation of Some New 1,5-Benzothiazepine Derivatives and Their Ribofuranosides

( - )- cis -2(4-Methoxyphenyl)-3-hydroxy/methoxy-6,8-dichloro/6-chloro-2,3-dihydro-1,5-benzothiazepin-4[5H/5-chloroacetyl/5-(4'-methylpiperazino-1')acetyl]-ones have been synthesized by the condensation of 2-amino-3,5-dichloro/3-chloro benzenethiol with methyl-( - )- trans -3(4-methoxyphenyl)glycidate in xylene. Ribofuranosides viz ( - )- cis -2(4-methoxyphenyl)-3-methoxy-6,8-dichloro/6-chloro-2,3-dihydro-1,5-benzothiazepine-4-[5-(2',3',5'-tri- O -benzoyl- g -D-ribofuranosyl)-ones have been synthesized by the treatment of 3-methoxy derivatives of 1,5-benzothiazepines with sugar viz g -D-ribofuranose-1-acetate-2,3,5-tribenzoate in toluene at vacuo. Synthesized compounds have been characterized by elemental analysis, IR, 1 H NMR spectral studies and screened for their antimicrobial activity.     

Synthesis,Characterization, and Surface Properties of Cationic Gemini Surfactants

New pyridinium gemini surfactants have been synthesized by esterification of renewable fatty acids with mercaptoethanol furnishing respective esters (mercaptomethyl decanoate, mercaptomethyl dodecanoate, mercaptomethyl tetradecanoate, mercaptomethyl hexadecanoate) followed by their subsequent treatment with 4-dimethyl amino pyridine resulting in the formation of title gemini surfactants: 1-(5-(decanoyloxy)-2-hydroxypentyl)-4-((5-(decanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (9), 1-(5-(dodecanoyloxy)-2-hydroxypentyl)-4-((5-(dodecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (10), 1-(5-(tetradecanoyloxy)-2-hydroxypentyl)-4-((5-(tetradecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (11), and 1-(5-(hexadecanoyloxy)-2-hydroxypentyl)-4-((5-(hexadecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (12). Their identifications are based on infrared, ¹H NMR, ¹³C NMR, distortionless enhanced polarization transfer, co-relational spectroscopy (COSY), and mass spectral studies. Their surface active properties are also evaluated on the basis of surface tension and conductivity measurements. Thermal stability of these long chain cationic gemini surfactants have been measured by thermal gravimetric analysis under nitrogen atmosphere.     

Synthesis and mesomorphic properties of four-ring liquid crystals containing 2,3-difluorophenyl and 1,3-dioxane units

Two series of novel liquid crystalline materials were synthesized: 2-(2,3-difluoro-4-alkoxyphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (A_m-n) and 2-(2,3-difluoro-4-alkylphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (B_m-n). Their mesmorphic properties were characterized by polarizing optical microscopy and differential scanning calorimetry. All these compounds exhibit broad mesomorphic phases, and most of them show wide smectic C phases and the phase sequence Cr-SmC-SmA-N-I. The relationship between properties and chemical structures is discussed in detail.     

Gaseous rust: thermochemistry of neutral and ionic iron oxides and hydroxides in the gas phase

The experimental and theoretical thermochemistry of the gaseous neutral and ionic iron oxides and hydroxides FeO, FeOH, FeO(2), OFeOH, and Fe(OH)(2) and of the related cationic water complexes Fe(H(2)O)(+), (H(2)O)FeOH(+), and Fe(H(2)O)(2)(+) is analyzed comprehensively. A combination of data for the neutral species with those of the gaseous ions in conjunction with some additional measurements provides a refined and internally consistent compilation of thermochemical data for the neutral and ionic species. In terms of heats of formation at 0 K, the best estimates for the gaseous, mononuclear FeO(m)H(n)(-/0/+/2+) species with m = 1, 2 and n = 0-4 are Delta(f)H(FeO(-)) = (108 +/- 6) kJ/mol, Delta(f)H(FeO) = (252 +/- 6) kJ/mol, Delta(f)H(FeO(+)) = (1088 +/- 6) kJ/mol, Delta(f)H(FeOH) = (129 +/- 15) kJ/mol, Delta(f)H(FeOH(+)) = (870 +/- 15) kJ/mol, Delta(f)H(FeO(2)(-)) = (-161 +/- 13) kJ/mol, Delta(f)H(FeO(2)) = (67 +/- 12) kJ/mol, Delta(f)H(FeO(2)(+)) = (1062 +/- 25) kJ/mol, Delta(f)H(OFeOH) = (-84 +/- 17) kJ/mol, Delta(f)H(OFeOH(+)) = (852 +/- 23) kJ/mol, Delta(f)H(Fe(OH)(2)(-)) = -431 kJ/mol, Delta(f)H(Fe(OH)(2)) = (-322 +/- 2) kJ/mol, and Delta(f)H(Fe(OH)(2)(+)) = (561 +/- 10) kJ/mol for the iron oxides and hydroxides as well as Delta(f)H(Fe(H(2)O)(+)) = (809 +/- 5) kJ/mol, Delta(f)H((H(2)O)FeOH(+)) = 405 kJ/mol, and Delta(f)H(Fe(H(2)O)(2)(+)) = (406 +/- 6) kJ/mol for the cationic water complexes. In addition, charge-stripping data for several of several-iron-containing cations are re-evaluated due to changes in the calibration scheme which lead to Delta(f)H(FeO(2+)) = (2795 +/- 28) kJ/mol, Delta(f)H(FeOH(2+)) = (2447 +/- 30) kJ/mol, Delta(f)H(Fe(H(2)O)(2+)) = (2129 +/- 29) kJ/mol, Delta(f)H((H(2)O)FeOH(2+)) = 1864 kJ/mol, and Delta(f)H(Fe(H(2)O)(2)(2+)) = (1570 +/- 29) kJ/mol, respectively. The present compilation thus provides an almost complete picture of the redox chemistry of mononuclear iron oxides and hydroxides in the gas phase, which serves as a foundation for further experimental studies and may be used as a benchmark database for theoretical studies.     

Preparation and Standard Formation Enthalpy of 2－Amino－4,6－dimethylpyrimidine and Its Related Complexes of Copper

IntroductionThe pyrimidine and its derivatives are knownto possess extraordinary biological properties thatare generally distinguished qualitatively by havingbeen used as pesticide,herbicide,bactericide,andmedicine intermediates[1] .A survey of these appli-cations and a number of the related variations thathave been developed recently,such as the extraor-dinary effective herbicide of sulfonyl sulfourea,re-veals that the biological properties are just becauseof the wide existence of pyrimidine …     

Synthesis and1H NMR and13C spectroscopy of L-arabinopyranosyl biosides

Conclusions The 3-0- and 4-0-trityl ethers of the acetates of methyl -L- arid methyl -L-arabinopyranosides were synthesized. The glycosylation of the ethers with the aid of 3,4-di-0-acetyl-1,2-0-(1-exo-cyano)ethylidene--L-arabinopyranose and the subsequent deacetylation of the synthesized products yielded the disaccharides: methyl 4-0-(-L-arabinopyranosyl)-,methyl 4-0-(-L-arabinopyranosyl)-, and methyl 3-0-(-L-arabinopyranosyl)--L-arabinopyranoside; and methyl 4-0-(-L-arabinopyranosyl)-, methyl 4-0-(-L-arabinopyranosyl)-, methyl 3-0-(-L-arabinopyranosyl)-, and methyl 3-0-(-L-arabinopyranosyl)--L-arabinopyranoside.The assignment of the signals in the PMR and¹³C NMR spectra of the synthesized arabinopyranosyl biosides was carried out, allowing the determination of the type and configuration of the glycosidic bond by means of which the arabinopyranose residues are linked in the oligo- and polysaccharide chains.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 200–209, January, 1986.     

指示稳定性的反相超高效液相色谱评价原料药和制剂配方中奈必洛尔杂质的方法建立与验证(英文)

A sensitive,stability-indicating gradient reverse phase ultra performance liquid chromatographic method has been developed for the quantitative estimation of nebivolol impurities in active pharmaceutical ingredient(API)and pharmaceutical formulation.Efficient chromatographic separation was achieved on an Acquity BEH C18 column(100 mm×2.1 mm,1.7μm)with mobile phase of a gradient mixture.The flow rate of the mobile phase was 0.18 mL/min with column temperature of 30℃and detection wavelength of 281 nm.The relative response factor values of(R*)-2-(benzylamino)-1-((S*)-6-fluorochroman-2-yl)ethanol((R*S*)NBV-1),(R)-1-((R)-6-fluorochroman-2-yl)-2-((S)-2-((S)-6-fluoro-chroman-2-yl)-2-hydroxyethylamino)ethanol((RRSS)NBV-3),1-(chroman-2-yl)-2-(2-(6-fluorochroman-2-yl)-2-hydroxy ethyl amino)ethanol(monodesfluoro impurity),(S)-1-((R)-6-fluorochroman-2-yl)-2-((R)-2((S)-6-fluoro-chroman-2-yl)-2-hydroxyethylamino)ethanol hydrochloride((RSRS)NBV-3)and(R*)-1-((S*)-6-fluorochroman-2-yl)-2-((S*)-2-((S*)-6-fluoro-chroman-2-yl)-2-hydroxyethylamino)ethanol((R*S*S*S*)NBV-2)were 0.65,0.91,0.68,0.92 and 0.91 respectively.Nebivolol formulation sample was subjected to the stress conditions of acid,base,oxidative,hydrolytic,thermal,humidity and photolytic degradation.Nebivolol was found to degrade significantly under peroxide stress condition.The degradation products were well resolved from nebivolol and its impurities.The peak purity test results confirmed that the nebivolol peak was homogenous and pure in all stress samples and the mass balance was found to be more than 98%,thus proving the stability-indicating power of the method.The developed method was validated according to International Conference on Hormonization(ICH)guidelines with respect to specificity,linearity,limits of detection and quantification,accuracy,precision and robustness.     

Determination of absolute configuration of a metabolite (−)-hydroxyhexamide from acetohexamide, syntheses of (−)- and (+)-hydroxyhexamides and (−)- and (+)-acetoxyhexamides

Enantioselective acetylation of (±)-4-(1-hydroxyethyl)benzenesulfonamide 6 with ‘Acylase I’ (No. A 2156) from Aspergillus melleus in the presence of vinyl acetate gave (R)-4-(1-acetoxyethyl)benzenesulfonamide 7 (98% ee) and (S)-6 (98% ee). Both (S)-6 and (R)-7 were individually converted to the (S)-hydroxyhexamide 2 (>99% ee) and (R)-hydroxyhexamide 2 (>99% ee), respectively. The absolute configuration of a metabolite (−)-hydroxyhexamide 2 from acetohexamide 1 was found to be S based on unequivocal chemical methods including X-ray analysis.     

Chemoenzymatic synthesis of (+)-totarol, (+)-podototarin, (+)-sempervirol, and (+)-jolkinolides E and D

The enzymatic resolution products [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-7 (98% ee) and {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-9 (>99% ee)] obtained by the lipase-catalyzed enantioselective acetylation of (±)-7 in the presence of vinyl acetate as an acyl donor were converted to the ,β-unsaturated ketones (8aR)-6 and (8aS)-6, respectively. Concise syntheses of (+)-totarol 1, (+)-podototarin 2 and (+)-sempervirol 3 were achieved based on Michael reactions between (8aS)-6 and the appropriate β-keto ester followed by aldol condensation. The first chiral syntheses of (+)-jolkinolides E 4 and D 5 were achieved from (5R,10R,12R)-12-hydroxypodocarpa-8(14)-en-13-one 15 derived from (8aR)-6.     

Synthesis and Evaluation of Surface Active Properties of Ester-Based Cationic Imidazolium Monomeric Surfactants

New imidazolium cationic surfactants have been synthesized by esterification of halogenated carboxylic acids with long-chain fatty alcohols furnishing respective esters (dodecyl-2-chloroacetate, tetradecyl-2-chloroacetate, hexadecyl-2-chloroacetate, dodecyl-2-bromoacetate, tetradecyl-2-bromoacetate, and hexadecyl-2-bromoacetate) followed by their subsequent treatment with 1-trifluoro acetyl imidazole resulting into the formation of title monomeric surfactants: 3-(2-(hexadecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium chloride (7); 3-(2-(tetradecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium chloride (8); 3-(2-(dodecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium chloride (9); 3-(2-(hexadecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium bromide (10); 3-(2-(tetradecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium bromide (11) and 3-(2-(dodecyloxy)-2-oxoethyl)-1-(2,2,2-trifluoroacetyl)-1H-imidazol-3-ium bromide (12). Their identifications are based on IR, ¹H, ¹³C NMR, DEPT, and mass spectral studies. The dynamics of surface activity of these surfactants have also been investigated in the presence of sodium halides (NaCl and NaBr) by surface tension measurement. A series of useful parameters like critical micelle concentration (cmc), surface tension at the cmc (γ_cmc), adsorption efficiency (pC₂₀), effectiveness of surface tension reduction (Π_cmc), Gibbs free energy of the micellization (ΔG_0mic), and Gibbs free energy of adsorption (ΔG_0ads) have been determined from the measurements obtained by surface tension and conductivity method. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γ_max), and minimum surface area/molecule (A_min) at the air-water interface were also estimated. Thermal stability of these long-chain cationics have been measured by thermal gravimetric analysis under nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long-chain imidazoliums increase with an increase in chain length.     

Enantiodivergent synthesis of 3-amino-4,4-dimethyl-1-phenylpyrrolidin-2-one and derivatives: amino analogues of pantolactone

An enantiodivergent preparation of (+)-(R)- and (−)-(S)-3-amino-4,4-dimethyl-1-phenylpyrrolidin-2-one, (R)- and (S)-9, and several derivatives, from 4,4-dimethyl-1-phenylpyrrolidin-2,3-dione, 4, and (R)- or (S)-1-phenylethylamine, (R)- or (S)-5, as the chirality transfer agents, is described. Amine (S)-9 has also been used as a chiral auxiliary in a diastereoselective Michael reaction.     

Ab initio and density functional theory studies of the structure,gas-phase acidity and aromaticity of tetraselenosquaric acid

Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure,acidity (free energy of deprotonation,G0) and aro-maticity of tetraselenosquaric acid (3,4-diselenyl-3-cy-dobutene-1,2-diselenone,H2C4Se4) are reported.The global minimum found on the potential energy surface of tetraselenosquaric acid presents a planar conformation.The ZZ iso-mer was found to have the lowest energy among the three planar conformers and the ZZ and ZE isomers are very dose in energy.The optimized geometric parameters exhibit a bond length equalization relative to reference compounds,cyclobu-tanediselenone,and cydobutenediselenol.The computed aromatic stabilization energy (ASE) by homodesmotic reaction is -77.4 (MP2(fu)/6 - 311 G //RHF/6 - 311 G) and - 54.8 kJ/mol (B3LYP/6 - 311 G //B3LYP/6 -311 G).The aromaticity of tetraselenosquaric add is indicated by the calculated diamagnetic susceptibility exaltation (A) - 19.13 (CSGT(IGAEM) - RHF/6 - 311 G// RHF/6-     

苯并氧化呋咱稳定性和异构化的DFT和ab initio研究

运用B3LYP/6-31G(d)密度泛函理论（DFT）方法对苯并氧化呋咱、邻二亚硝基苯及其间的异构化反应进行了计算研究。结果表明,苯并氧化呋咱的分子总能量比邻二亚硝基苯的低;由苯并氧化呋咱异构为邻二亚硝基苯的正向反应活化能（Ea+=51.0kJ/mol）,与文献实测值（58.6kJ/mol）较接近,而其逆向反应活化能（Ea-=4.6kJ/mol）很小,从而揭示了苯并氧化呋咱比邻二亚硝基苯更稳定·此外,进行了HF/3-21G、HF/6-31G(d)和MP2/6-31G(d)//6-31G(d)水平下相应的计算,发现B3LYP-DFT的结果较abinitio为优。谐振动频率的B3LYP/6-31G(d)计算还支持了邻二亚硝基苯为苯并氧化呋咱“自-自”互变重排反应的中间体。     

Synthesis and characterisation of four- and eight-membered ring auralactam complexes

The reactions of the cyclo-aurated gold(III) dihalide complex [{C₆H₃(CH₂NMe₂)-2-(OMe)-5}AuCl₂] with N-cyanoacetylurethane [NCCH₂C(O)NHCO₂Et], 2-benzoylacetanilide [PhC(O)CH₂C(O)NHPh] and acetoacetanilide [MeC(O)CH₂C(O)NHPh], and [{C₆H₄(CH₂NMe₂)-2}AuCl₂] with acetoacetanilide in dichloromethane with excess silver(I) oxide gives the first examples of auralactam complexes, containing (O)---CHR′ four-membered rings. A single-crystal X-ray diffraction study on the complex [{C₆H₄(CH₂NMe₂)-2}A H(COMe)}] reveals similar structural features to related metallalactam complexes of platinum(II) and palladium(II). When a CDCl₃ solution of the complex [{C₆H₃(CH₂NMe₂)-2-(OMe)-5}A HCN}] is allowed to stand for 18 h, a novel dimerisation reaction occurs, giving the insoluble product [{C₆H₃(CH₂NMe₂)-2-(OMe)-5}Au{N(CO₂Et)C(O)CHCN}]₂·2CDCl₃, characterised by an X-ray structure determination. The dimer contains an eight-membered A

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ring.     

Experimental and theoretical determination of the dipole-quadrupole and dipole-octopole polarizabilities of the group IV tetrachlorides TiCl4, ZrCl4, and HfCl4

The dipole-quadrupole and dipole-octopole polarizabilities A and E of TiCl4, ZrCl4, and HfCl4 have been determined from collision-induced light-scattering experiments. Our respective experimental results for /A/ are (165+/-10), (110+/-30), and (140+/-20) e2a0 3Eh (-1), whereas /E/ is determined to be (675+/-125), (750+/-200), and (670+/-400) e2a0 4Eh (-1). Theory predicts values convincingly close to experiment, as A=(181.4+/-9.1), (167.6+/-8.4), and (139.8+/-7.0) e2a0 3Eh (-1), and E=(-671+/-67), (-688+/-69), and (-574+/-57) e2a0 4Eh (-1). In addition our quantum chemical ab initio calculations give reliable values for the dipole polarizability alpha, as well as for the octopole and hexadecapole moments Omega and Phi for all three substances.     

Inverse phase transfer catalysis. Kinetics of the pyridine 1-oxide-catalyzed reactions of dichlorobenzoyl chlorides and benzoate ions

The substitution reactions of 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoyl chloride (Cl₂C₆H₃COCl) and 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoate ion (Cl₂C₆H₅COO⁻) or benzoate ion (C₆H₅COO⁻) in a two-phase H₂O/CH₂Cl₂ medium using pyridine 1-oxide (PNO) as an inverse phase transfer catalyst were investigated. The reaction of Cl₂C₆H₃COCl and PNO in CH₂Cl₂ to produce the ionic intermediate, 1-(dichlorobenzoyloxy)-pyridinium chloride (Cl₂C₆H₃COONP⁺Cl⁻) is the rate-determining step. In the PNO-catalyzed two-phase reaction of Cl₂C₆H₃COCl and C₆H₅COONa, the order of reactivities of Cl₂C₆H₃COCl toward reaction with PNO is (2,3-, 2,4-)>3,5->3,4-2,6-Cl₂C₆H₃COCl, whereas it is 3,5->(2,3-, 3,4-)>2,4-Cl₂C₆H₃COCl in the PNO-catalyzed two-phase reaction of Cl₂C₆H₃COCl and the corresponding Cl₂C₆H₃COONa. The order of reactivities of Cl₂C₆H₃COO⁻ ions towards the reaction with 1-(benzoyloxy)-pyridinium (C₆H₅COONP⁺) ion is (3,4-, 3,5-)>(2,3-, 2,4-Cl₂C₆H₃COO⁻).     

Thermochemistry of the hypobromous and hypochlorous acids, HOBr and HOCl

The enthalpies of formation of HOBr and HOCl have been estimated by employing coupled cluster theory in conjunction with the correlation consistent basis sets and corrections for core-valence, relativistic, and anharmonic effects. We have employed three different reactions to estimate the DeltaH(o)(f,298)(HOBr), namely, the atomization reaction and two homodesmic reactions. Our best estimation is DeltaH(o)(f,298) (HOBr) = -15.3 +/- 0.6 kcal/mol and is very likely to lie toward the more negative values. The present value is 1.4 kcal/mol lower than the widely used experimental determination of Ruscic and Berkowitz (J. Chem. Phys. 1994, 101, 7795), DeltaH(o)(f,298)(HOBr) > -13.93 +/- 0.42 kcal/mol. However, it is closer to the more recent measurement of Lock et al. (J. Phys. Chem. 1996, 100, 7972), DeltaH(o)(f,298)(HOBr) = -14.8 +/- 1 kcal/mol. In the case of HOCl we have determined DeltaH(o)(f,298)(HOCl) = -18.1 +/- 0.3 kcal/mol, just in the middle of the two experimental values proposed, -17.8 +/- 0.5 kcal/mol (JANAF), obtained from equilibrium constant measurements, and -18.36 +/- 0.03 kcal/mol (Joens, J. A. J. Phys. Chem. A 2001, 105, 11041), determined from the measurements of the Cl-OH bond energy. If our conclusions are correct, several enthalpies of formation that have been determined by experimental chemists, Orlando and Burholder (J. Phys. Chem. 1995, 99, 1143), and theoretical chemists, Lee (J. Phys. Chem. 1995, 99, 15074), need to be revised, since a larger value was used for DeltaH(o)(f,298)(HOBr). Employing the results obtained by Orlando and Burkholder for Br(2)O we propose DeltaH(o)(f,298)(Br(2)O) = 24.9 +/- 0.6 kcal/mol, and employing Lee's enthalpies of reaction we propose the following DeltaH(o)(f,298): for BrBrO, HBrO, ClOBr, ClBrO, BrClO, BrCN, BrNC, BrNO, BrON, FOBr, and FBrO, 39.5 +/- 1, 41.0 +/- 1, 22.7 +/- 1.5, 34.2 +/- 1.5, 40.9 +/- 1.5, 43.7 +/- 1.5, 80.1 +/- 1.5, 22.3 +/- 1, 46.2 +/- 1, 17.3 +/- 1.5, and 6.3 +/- 1.5 kcal/mol, respectively. We expect that this work will stimulate new experimental measurements of the thermodynamic properties of HOBr and HOCl.