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521.
522.
Abstract
The crystal structures of the 1:1 proton-transfer compounds of 4,5-dichlorophthalic acid with the aliphatic Lewis bases diisopropylamine and hexamethylenetetramine, viz. diisopropylaminium 2-carboxy-4,5-dichlorobenzoate (1) and hexamethylenetetraminium 2-carboxy-4,5-dichlorobenzoate hemihydrate (2), have been determined. Crystals of both 1 and 2 are triclinic, space group P − 1, with Z = 2 in cells with a = 7.0299(5), b = 9.4712(7), c = 12.790(1) ?, α = 99.476(6), β = 100.843(6), γ = 97.578(6)° (1) and a = 7.5624(8), b = 9.8918(8), c = 11.5881(16) ?, α = 65.660(6), β = 86.583(4), γ = 86.987(8)° (2). In each, one-dimensional hydrogen-bonded chain structures are found: in 1 formed through aminium N+–H…Ocarboxyl cation–anion interactions. In 2, the chains are formed through anion carboxyl O···H–Obridging water interactions with the cations peripherally bound. In both structures, the hydrogen phthalate anions are essentially planar with short intra-species carboxylic acid O–H…Ocarboxyl hydrogen bonds [O…O, 2.381(3) ? (1) and 2.381(8) ? (2)]. 相似文献523.
咪唑基离子液体的物理化学性质估算及预测(英文) 总被引:1,自引:0,他引:1
根据经验和半经验方程及空隙模型理论,可以估算及预测离子液体在298.15K的物理化学性质.本文讨论了离子液体的分子体积,密度,标准熵,晶格能,表面张力,等张比容,摩尔蒸发焓,空隙体积,空隙率和热膨胀系数.通过实验测得的三种离子液体1-乙基-3-甲基咪唑硫酸乙酯([C2mim][EtSO4)]),1-丁基-3-甲基咪唑硫酸辛酯([C4mim][OcSO4])和1-乙基-3-甲基咪唑双三氟甲磺酰亚胺盐([C2mim][NTf2])的密度和表面张力估算了它们的其它物理化学性质.由这三种离子液体的分子体积及等张比容预测了同系列中其它离子液体[Cnmim][EtSO4],[Cnmim][OcSO4]和[Cnmim][NTf2](n=1-6)的分子体积及等张比容,由此计算出它们的密度及表面张力.进而预测了它们的物理化学性质.将预测的离子液体[C4mim][NTf2]和[C2mim][OcSO4]的密度值与文献报导的实验值进行比较,其偏差在实验误差范围内.最后,将由Kabo经验方程计算的七个离子液体[C2mim][EtSO4]、[C4mim][OcSO4]、[C2mim][NTf2]、[C4mim][NTf2]、丁基三甲基铵双三氟甲磺酰亚胺盐([N4111][NTf2])、甲基三辛基铵双三氟甲磺酰亚胺盐([N8881][NTf2])和1-辛基-3-甲基吡啶四氟硼酸盐([m3opy][BF4])的摩尔蒸发焓与由Verevkin简单规则预测的摩尔蒸发焓进行比较,发现两者符合很好.因此,在缺乏密度和表面张力实验数据的情况下,可以用Verevkin简单规则来预测离子液体的摩尔蒸发焓. 相似文献
524.
Antonio Amantea Markus Walser Urs Squin Peter Strazewski 《Helvetica chimica acta》1995,78(5):1106-1111
The 5-methyl(15N2)[O2,O4-17O2]uridine (= (15N2)[O2,O4-17O 2]ribosylthymine; 15 ) was synthesized and analyzed by 15N- and 17O-NMR spectroscopy. (15N2)Urea was condensed with 2,3-dibromo-2-methylpropanoyl chloride ( 3 ) and cyclized to form (15N2)thymine ( 5 ). After glycosidation, the 17O isotopes were introduced in two separate steps: hydrolytic ring opening of 2,5′-anhydro derivative 9 and hydrolysis of 3-nitro-1H-1,2,4-triazole derivative 12 with labelled water in the presence of a strong base. The 15N- and 17O-NMR spectra (Fig.) of 15 in phosphate-buffered water serve as references for heteronuclear NMR spectra of labelled RNA fragments. 相似文献
525.
Graham Smith Urs D. Wermuth 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(9):o327-o331
The structures of the open‐chain amide carboxylic acid rac‐cis‐2‐[(2‐methoxyphenyl)carbamoyl]cyclohexane‐1‐carboxylic acid, C15H19NO4, (I), and the cyclic imides rac‐cis‐2‐(4‐methoxyphenyl)‐3a,4,5,6,7,7a‐hexahydroisoindole‐1,3‐dione, C15H17NO3, (II), chiral cis‐3‐(1,3‐dioxo‐3a,4,5,6,7,7a‐hexahydroisoindol‐2‐yl)benzoic acid, C15H15NO4, (III), and rac‐cis‐4‐(1,3‐dioxo‐3a,4,5,6,7,7a‐hexahydroisoindol‐2‐yl)benzoic acid monohydrate, C15H15NO4·H2O, (IV), are reported. In the amide acid (I), the phenylcarbamoyl group is essentially planar [maximum deviation from the least‐squares plane = 0.060 (1) Å for the amide O atom] and the molecules form discrete centrosymmetric dimers through intermolecular cyclic carboxy–carboxy O—H...O hydrogen‐bonding interactions [graph‐set notation R22(8)]. The cyclic imides (II)–(IV) are conformationally similar, with comparable benzene ring rotations about the imide N—Car bond [dihedral angles between the benzene and isoindole rings = 51.55 (7)° in (II), 59.22 (12)° in (III) and 51.99 (14)° in (IV)]. Unlike (II), in which only weak intermolecular C—H...Oimide hydrogen bonding is present, the crystal packing of imides (III) and (IV) shows strong intermolecular carboxylic acid O—H...O hydrogen‐bonding associations. With (III), these involve imide O‐atom acceptors, giving one‐dimensional zigzag chains [graph‐set C(9)], while with the monohydrate (IV), the hydrogen bond involves the partially disordered water molecule which also bridges molecules through both imide and carboxy O‐atom acceptors in a cyclic R44(12) association, giving a two‐dimensional sheet structure. The structures reported here expand the structural database for compounds of this series formed from the facile reaction of cis‐cyclohexane‐1,2‐dicarboxylic anhydride with substituted anilines, in which there is a much larger incidence of cyclic imides compared to amide carboxylic acids. 相似文献
526.
Graham Smith Urs D. Wermuth 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(7):o259-o264
The structures of the 1:1 proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with 4‐nitrophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4‐nitrobenzoate, C6H13N2O8+·C8H4O6−, (I)], 4,5‐dichlorophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4,5‐dichlorobenzoate, C6H13N2O8+·C8H3Cl2O4−, (II)] and 5‐nitroisophthalic acid [4‐carbamoylpiperidinium 3‐carboxy‐5‐nitrobenzoate, C6H13N2O8+·C8H4O6−, (III)], as well as the 2:1 compound with terephthalic acid [bis(4‐carbamoylpiperidinium) benzene‐1,2‐dicarboxylate dihydrate, 2C6H13N2O8+·C8H4O42−·2H2O, (IV)], have been determined at 200 K. All salts form hydrogen‐bonded structures, viz. one‐dimensional in (II) and three‐dimensional in (I), (III) and (IV). In (I) and (III), the centrosymmetric R22(8) cyclic amide–amide association is found, while in (IV) several different types of water‐bridged cyclic associations are present [graph sets R42(8), R43(10), R44(12), R33(18) and R64(22)]. The one‐dimensional structure of (I) features the common `planar' hydrogen 4,5‐dichlorophthalate anion, together with enlarged cyclic R33(13) and R43(17) associations. In the structures of (I) and (III), the presence of head‐to‐tail hydrogen phthalate chain substructures is found. In (IV), head‐to‐tail primary cation–anion associations are extended longitudinally into chains through the water‐bridged cation associations, and laterally by piperidinium–carboxylate N—H...O and water–carboxylate O—H...O hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. An additional example of cation–anion association with this cation is also shown in the asymmetric three‐centre piperidinium–carboxylate N—H...O,O′ interaction in the first‐reported structure of a 2:1 isonipecotamide–carboxylate salt. 相似文献
527.
John A. Schlueter Urs Geiser Jamie L. Manson 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(1):m1-m3
The crystal structure of [Mn(C4H2N3O)2(H2O)4]·2H2O, conventionally abbreviated [Mn(cdm)2(H2O)4]·2H2O, where cdm is carbamoyldicyanomethanide, is described. The bond lengths and distances are comparable to those previously reported for the isomorphous Ni and Co analogs. Molecular units are formed by coordination of the nitrile N atoms of two cdm anions and four water molecules to the manganese(II) cation. Although these mononuclear molecular species are connected via hydrogen bonding, no magnetic ordering was observed down to 1.55 K. 相似文献
528.
John A. Schlueter Urs Geiser 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):m146-m148
The crystal structure of the title compound, [Mn(C9H5N4O)2(H2O)2], conventionally denoted Mn(EtO‐TCA)2(H2O)2, where EtO‐TCA is 2‐ethoxy‐1,1,3,3‐tetracyanopropenide, is described. The EtO‐TCA anions bridge MnII centers through one of the nitrile N atoms of each of their two dicyanomethanide groups, thus forming dibridged chains along ab. These chains are linked into two‐dimensional sheets through hydrogen bonding. The seven‐atom bridge, which results in a long Mn⃛Mn intrachain interaction [9.0044 (4) Å], as well as the large interchain separations [8.3288 (4) and 8.5220 (4) Å] prohibit long‐range magnetic ordering down to temperatures as low as 1.55 K. 相似文献
529.
Verevkin SP Zaitsau DH Tong B Welz-Biermann U 《Physical chemistry chemical physics : PCCP》2011,13(28):12708-12711
Activity coefficients at infinite dilution of some common solvents in a protic ionic liquid ethylammonium nitrate have been measured using well established gas-chromatography-method. This method was possible to apply due to extremely low vapour pressure of ethylammonium nitrate at temperatures below 100 °C. Activity coefficients and separation factors were compared with those for aprotic ionic liquids. A new window for intensive accumulation of thermodynamic properties of protic ionic liquids has been opened. 相似文献
530.
Kirkpatrick ND Zou C Brewer MA Brands WR Drezek RA Utzinger U 《Photochemistry and photobiology》2005,81(1):125-134
Cancer chemopreventive agents such as N-4-(hydroxyphenyl)retinamide (4HPR) are thought to prevent cancers by suppressing growth or inducing apoptosis in precancerous cells. Mechanisms by which these drugs affect cells are often not known, and the means to monitor their effects is not available. In this study endogenous fluorescence spectroscopy was used to measure metabolic changes in response to treatment with 4HPR in ovarian and bladder cancer cell lines. Fluorescence signals consistent with nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD) and tryptophan were measured to monitor cellular activity through redox status and protein content. Cells were treated with varying concentrations of 4HPR and measured in a stable environment with a sensitive fluorescence spectrometer. Results suggest that redox signal of all cells changed in a similar dose-dependant manner but started at different baseline levels. Redox signal changes depended primarily on changes consistent with NADH fluorescence, whereas the FAD fluorescence remained relatively constant. Similarly, tryptophan fluorescence decreased with increased drug treatment, suggesting a decrease in protein production. Given that each cell line has been shown to have a different apoptotic response to 4HPR, fluorescence redox values along with changes in tryptophan fluorescence may be a response as well as an endpoint marker for chemopreventive drugs. 相似文献