Thermochemistry of uranium compounds V. Standard enthalpies of formation of the monouranates of lithium,potassium, and rubidium

Enthalpies of reaction, ΔH_r, of the monouranates of lithium, potassium, and rubidium with 1 mol dm^?3 HCl have been measured calorimetrically. From these measurements, and auxiliary determinations of the enthalpies of solution in acid of the chlorides of lithium, potassium, and rubidium and of uranyl chloride, the standard enthalpies of formation of the uranates, ΔH_f^o, have been derived. The results obtained are as follows:

     

112.

Benzocyclobutene: The Impact of Fusing a Strained Ring onto Benzene     

Glasovac Z  Eckert-Maksic M  Broadus KM  Hare MC  Kass SR 《The Journal of organic chemistry》2000,65(6):1818-1824

The gas-phase acidities of the two aromatic sites in benzocyclobutene were measured in a Fourier transform mass spectrometer using a kinetic technique (i.e., the DePuy method). Fusion of a cyclobutane ring onto benzene is found to have a slight acidifying effect at the alpha-position (3.2 +/- 1.7 kcal mol(-)(1)) and little, if any, influence on the beta-site (0.8 +/- 1.9 kcal mol(-)(1)). Energetic data (DeltaH degrees (acid) = 386.2 +/- 3.0 kcal mol(-)(1), EA = 0.84 +/- 0.11 eV, and C-H BDE = 92 +/- 4 kcal mol(-)(1)) for the benzylic position were obtained via the bracketing technique and application of a thermodynamic cycle. Differences in the reactivities of the three conjugate bases also were explored. Ab initio and density functional theory calculations were carried out to provide geometries, energies, and insights into the carbanions' electronic structures.     

113.

    

J W Hare  E I Solomon  H B Gray 《Journal of the American Chemical Society》1976,98(11):3205-3209

     

114.

Improved measurement of the positive-muon lifetime and determination of the Fermi constant     

Chitwood DB  Banks TI  Barnes MJ  Battu S  Carey RM  Cheekatmalla S  Clayton SM  Crnkovic J  Crowe KM  Debevec PT  Dhamija S  Earle W  Gafarov A  Giovanetti K  Gorringe TP  Gray FE  Hance M  Hertzog DW  Hare MF  Kammel P  Kiburg B  Kunkle J  Lauss B  Logashenko I  Lynch KR  McNabb R  Miller JP  Mulhauser F  Onderwater CJ  Ozben CS  Peng Q  Polly CC  Rath S  Roberts BL  Tishchenko V  Wait GD  Wasserman J  Webber DM  Winter P  Zołnierczuk PA;MuLan Collaboration 《Physical review letters》2007,99(3):032001

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).     

115.

Precise measurement of the positive muon anomalous magnetic moment     

Brown HN  Bunce G  Carey RM  Cushman P  Danby GT  Debevec PT  Deile M  Deng H  Deninger W  Dhawan SK  Druzhinin VP  Duong L  Efstathiadis E  Farley FJ  Fedotovich GV  Giron S  Gray F  Grigoriev D  Grosse-Perdekamp M  Grossmann A  Hare MF  Hertzog DW  Hughes VW  Iwasaki M  Jungmann K  Kawall D  Kawamura M  Khazin BI  Kindem J  Krienen F  Kronkvist I  Larsen R  Lee YY  Logashenko I  McNabb R  Meng W  Mi J  Miller JP  Morse WM  Nikas D  Onderwater CJ  Orlov Y  Ozben CS  Paley JM  Polly C  Pretz J  Prigl R  zu Putlitz G  Redin SI  Rind O 《Physical review letters》2001,86(11):2227-2231

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.     

116.

  总被引：2，自引：0，他引：2  

Kevin G. Hare. 《Mathematics of Computation》2005,74(250):1003-1008

Let denote the sum of the positive divisors of . We say that is perfect if . Currently there are no known odd perfect numbers. It is known that if an odd perfect number exists, then it must be of the form , where are distinct primes and . Define the total number of prime factors of as . Sayers showed that . This was later extended by Iannucci and Sorli to show that . This paper extends these results to show that .

     

117.

         下载免费PDF全文

K. G. Hare  C. J. Smyth. 《Mathematics of Computation》2008,77(263):1869-1869

     

118.

Synthesis,structure and characterisation of rac and meso–ansa-bridged permethylindenyl cobalt complexes     

Paul Ransom  Andrew Ashley  Amber Thompson  Dermot O’Hare 《Journal of organometallic chemistry》2009,694(7-8):1059-1068

Disodium ethylene-bis-hexamethylindenyl, {(C₉Me₆)₂C₂H₄}Na₂ (EBI1Na₂), has been prepared in good yield by the reaction of lithium heptamethylindenyl with cyanogen bromide followed by treatment with sodium naphthalenide. EBI1Na₂ reacts with anhydrous Co(acac)₂ to give a mixture of rac and meso-ethylene-bis-hexamethylindenyl cobalt(II) (EBI1Co). The isomers can be separated by fractional crystallisation and the rac-isomer has been structurally characterised. Oxidation of the reaction mixture yields both rac and meso-ethylene-bis-hexamethylindenyl cobalt(III) which have both been structurally characterised.     

119.

Measurement of the negative muon anomalous magnetic moment to 0.7 ppm     

Bennett GW  Bousquet B  Brown HN  Bunce G  Carey RM  Cushman P  Danby GT  Debevec PT  Deile M  Deng H  Dhawan SK  Druzhinin VP  Duong L  Farley FJ  Fedotovich GV  Gray FE  Grigoriev D  Grosse-Perdekamp M  Grossmann A  Hare MF  Hertzog DW  Huang X  Hughes VW  Iwasaki M  Jungmann K  Kawall D  Khazin BI  Krienen F  Kronkvist I  Lam A  Larsen R  Lee YY  Logashenko I  McNabb R  Meng W  Miller JP  Morse WM  Nikas D  Onderwater CJ  Orlov Y  Ozben CS  Paley JM  Peng Q  Polly CC  Pretz J  Prigl R  Zu Putlitz G  Qian T  Redin SI  Rind O  Roberts BL 《Physical review letters》2004,92(16):161802

The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron. This result is based on data collected in 2001, and is over an order of magnitude more precise than the previous measurement for the negative muon. The result a(mu(-))=11 659 214(8)(3) x 10(-10) (0.7 ppm), where the first uncertainty is statistical and the second is systematic, is consistent with previous measurements of the anomaly for the positive and the negative muon. The average of the measurements of the muon anomaly is a(mu)(exp)=11 659 208(6) x 10(-10) (0.5 ppm).     

120.

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine     

Shubert VA  Baquero EE  Clarkson JR  James WH  Turk JA  Hare AA  Worrel K  Lipton MA  Schofield DP  Jordan KD  Zwier TS 《The Journal of chemical physics》2007,127(23):234315

Resonant two-photon ionization (R2PI), resonant ion-dip infrared (RIDIR), and UV-UV hole-burning spectroscopies have been employed to obtain conformation-specific infrared and ultraviolet spectra under supersonic expansion conditions for O-(2-acetamidoethyl)-N-acetyltyramine (OANAT), a doubly substituted aromatic in which amide-containing alkyl and alkoxy side chains are located in para positions on a phenyl ring. For comparison, three single-chain analogs were also studied: (i) N-phenethyl-acetamide (NPEA), (ii) N-(p-methoxyphenethyl-acetamide) (NMPEA), and (iii) N-(2-phenoxyethyl)-acetamide (NPOEA). Six conformations of OANAT have been resolved, with S(0)-S(1) origins ranging from 34,536 to 35,711 cm(-1), denoted A-F, respectively. RIDIR spectra show that conformers A-C each possess an intense, broadened amide NH stretch fundamental shifted below 3400 cm(-1), indicative of the presence of an interchain H bond, while conformers D-F have both amide NH stretch fundamentals in the 3480-3495 cm(-1) region, consistent with independent-chain structures with two free NH groups. NPEA has a single conformer with S(0)-S(1) origin at 37,618 cm(-1). NMPEA has three conformers, two that dominate the R2P1 spectrum, with origin transitions between 35,580 and 35,632 cm(-1). Four conformations, one dominate and three minor, of NPOEA have been resolved with origins between 35,654 and 36,423 cm(-1). To aid the making of conformational assignments, the geometries of low-lying structures of all four molecules have been optimized and the associated harmonic vibrational frequencies calculated using density functional theory (DFT) and RIMP2 methods. The S(0)-S(1) adiabatic excitation energies have been calculated using the RICC2 method and vertical excitation energies using single-point time-dependent DFT. The sensitivity of the S(0)-S(1) energy separation in OANAT and NPOEA primarily arises from different orientations of the chain attached to the phenoxy group. Using the results of the single-chain analogs, tentative assignments have been made for the observed conformers of OANAT. The RIMP2 calculations predict that interchain H-bonded conformers of OANAT are 25-30 kJ/mol more stable than the extended-chain structures. However, the free energies of the interchain H-bonded and extended structures calculated at the preexpansion temperature (450 K) differ by less than 10 kJ/mol, and the number of extended structures far outweighs the number of H-bonded conformers. This entropy-driven effect explains the presence of the independent-chain conformers in the expansion, and cautions future studies that rely solely on relative energies of conformers in considering possible assignments.     

[首页] « 上一页 [6] [7] [8] [9] [10] [11] 12 [13] [14] [15] 下一页 » 末  页»

	$\text{ΔH}{}_{\mathrm{r}}\text{/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$	$\text{ΔH}{}_{\mathrm{f}}{}^{\mathrm{o}}\text{(c, 298.15 K)/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$
α-Li2UO4	?(41.77±0.02)	?(463.31±0.84)
K2UO4	?(42.07±0.05)	?(451.39±0.83)
Rb2UO4	?(41.30±0.05)	?(452.00±0.85)

Benzocyclobutene: The Impact of Fusing a Strained Ring onto Benzene

The gas-phase acidities of the two aromatic sites in benzocyclobutene were measured in a Fourier transform mass spectrometer using a kinetic technique (i.e., the DePuy method). Fusion of a cyclobutane ring onto benzene is found to have a slight acidifying effect at the alpha-position (3.2 +/- 1.7 kcal mol(-)(1)) and little, if any, influence on the beta-site (0.8 +/- 1.9 kcal mol(-)(1)). Energetic data (DeltaH degrees (acid) = 386.2 +/- 3.0 kcal mol(-)(1), EA = 0.84 +/- 0.11 eV, and C-H BDE = 92 +/- 4 kcal mol(-)(1)) for the benzylic position were obtained via the bracketing technique and application of a thermodynamic cycle. Differences in the reactivities of the three conjugate bases also were explored. Ab initio and density functional theory calculations were carried out to provide geometries, energies, and insights into the carbanions' electronic structures.     

Improved measurement of the positive-muon lifetime and determination of the Fermi constant

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).     

Precise measurement of the positive muon anomalous magnetic moment

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.     

Synthesis,structure and characterisation of rac and meso–ansa-bridged permethylindenyl cobalt complexes

Disodium ethylene-bis-hexamethylindenyl, {(C₉Me₆)₂C₂H₄}Na₂ (EBI1Na₂), has been prepared in good yield by the reaction of lithium heptamethylindenyl with cyanogen bromide followed by treatment with sodium naphthalenide. EBI1Na₂ reacts with anhydrous Co(acac)₂ to give a mixture of rac and meso-ethylene-bis-hexamethylindenyl cobalt(II) (EBI1Co). The isomers can be separated by fractional crystallisation and the rac-isomer has been structurally characterised. Oxidation of the reaction mixture yields both rac and meso-ethylene-bis-hexamethylindenyl cobalt(III) which have both been structurally characterised.     

Measurement of the negative muon anomalous magnetic moment to 0.7 ppm

The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron. This result is based on data collected in 2001, and is over an order of magnitude more precise than the previous measurement for the negative muon. The result a(mu(-))=11 659 214(8)(3) x 10(-10) (0.7 ppm), where the first uncertainty is statistical and the second is systematic, is consistent with previous measurements of the anomaly for the positive and the negative muon. The average of the measurements of the muon anomaly is a(mu)(exp)=11 659 208(6) x 10(-10) (0.5 ppm).     

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Resonant two-photon ionization (R2PI), resonant ion-dip infrared (RIDIR), and UV-UV hole-burning spectroscopies have been employed to obtain conformation-specific infrared and ultraviolet spectra under supersonic expansion conditions for O-(2-acetamidoethyl)-N-acetyltyramine (OANAT), a doubly substituted aromatic in which amide-containing alkyl and alkoxy side chains are located in para positions on a phenyl ring. For comparison, three single-chain analogs were also studied: (i) N-phenethyl-acetamide (NPEA), (ii) N-(p-methoxyphenethyl-acetamide) (NMPEA), and (iii) N-(2-phenoxyethyl)-acetamide (NPOEA). Six conformations of OANAT have been resolved, with S(0)-S(1) origins ranging from 34,536 to 35,711 cm(-1), denoted A-F, respectively. RIDIR spectra show that conformers A-C each possess an intense, broadened amide NH stretch fundamental shifted below 3400 cm(-1), indicative of the presence of an interchain H bond, while conformers D-F have both amide NH stretch fundamentals in the 3480-3495 cm(-1) region, consistent with independent-chain structures with two free NH groups. NPEA has a single conformer with S(0)-S(1) origin at 37,618 cm(-1). NMPEA has three conformers, two that dominate the R2P1 spectrum, with origin transitions between 35,580 and 35,632 cm(-1). Four conformations, one dominate and three minor, of NPOEA have been resolved with origins between 35,654 and 36,423 cm(-1). To aid the making of conformational assignments, the geometries of low-lying structures of all four molecules have been optimized and the associated harmonic vibrational frequencies calculated using density functional theory (DFT) and RIMP2 methods. The S(0)-S(1) adiabatic excitation energies have been calculated using the RICC2 method and vertical excitation energies using single-point time-dependent DFT. The sensitivity of the S(0)-S(1) energy separation in OANAT and NPOEA primarily arises from different orientations of the chain attached to the phenoxy group. Using the results of the single-chain analogs, tentative assignments have been made for the observed conformers of OANAT. The RIMP2 calculations predict that interchain H-bonded conformers of OANAT are 25-30 kJ/mol more stable than the extended-chain structures. However, the free energies of the interchain H-bonded and extended structures calculated at the preexpansion temperature (450 K) differ by less than 10 kJ/mol, and the number of extended structures far outweighs the number of H-bonded conformers. This entropy-driven effect explains the presence of the independent-chain conformers in the expansion, and cautions future studies that rely solely on relative energies of conformers in considering possible assignments.