Collision of molecular anions of benzenedicarboxylic esters with oxygen in a triple quadrupole mass spectrometer

A series of symmetrical phthalate, isophthalate, and terephthalate ester molecular anions were reacted with oxygen in the collision cell of a triple quadrupole mass spectrometer to produce characteristic [M − R]⁻ fragments that can be used to identify these compounds. The [M − R]⁻/M^−· intensity ratios decreased for homologous esters in the following order: phthalates > isophthalates terephthalates. Based on the [M − R]⁻ ion intensities for different alkyl substituents, on ¹⁸O₂ labeling experiments, and on the reactivity of bis(t-butylcyclohexyl)phthalates, it was concluded that M − R anions are generated through an S_N2 nucleophilic displacement at the alpha carbon of the saturated alkyl substituent. For the phenyl ester, the reaction proceeds through attack at the carbonyl carbon.     

Aggregation behavior and chromonic liquid crystal phase of a dye derived from naphthalenecarboxylic acid

Polarizing microscopy, X-ray scattering, and absorption spectroscopy are used to investigate the aggregation process and chromonic liquid crystal of the anionic compound Bordeaux dye, a product of the sulfonation of the dibenzimidazole derivative of naphthalenetetracarboxylic acid. Polarizing microscopy reveals that the liquid crystal phase forms at room temperature when the concentration is only about 6 wt%, a value lower than what is found in many aggregating systems. The X-ray results indicate that the aggregation is via columns, with a cross-sectional area about 2.5 times larger than the individual molecule. Absorption spectroscopy shows a significant change in the absorption spectrum due to aggregation, which is nicely explained by a simple theory of isodesmic aggregation and excitonic coupling between the molecules in an aggregate. The "stacking free energy change" for a molecule in an aggregate relative to a molecule in solution is estimated to be about 9 kBT, a larger value than that found in the one other system where it has been estimated.     

Kinetics of benzene nitration by nitric acid

The kinetics of benzene mononitration in excess of 45–70 wt % nitric acid in a homogeneous liquid phase was studied. The data on the effects of temperature and nitric acid concentration on the reaction rate were obtained.     

脂肪酶催化合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯

用固定化脂肪酶Lipozyme 435作催化剂,分别用直接酯化法和酯交换法合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯.产物结构经IR、1HNMR、13CNMR和MS表征.结果表明,对于同一目标化合物,相似条件下,直接酯化法的效果优于酯交换法,原料脂肪酸和脂肪酸甲酯均可回收循环使用.     

Synthesis of the naphthalenecarboxylic acid derivative obtained from neocarzinostatin (NCS): A structure revision

The structure of the naphthalenecarboxylic acid derivative obtained from neocarzinostatin (NCS) was revised as methyl 2-hydroxy-7-methoxy-5-methyl-1-naphthalenecarboxylate (2a) by its synthesis.     

Use of phosphoric anhydride and metaphoshoric acid for nitration of toluene

Possibility of obtaining a 2,4-dinitrotoluene-enriched mixture of dinitrotoluenes in a single stage by nitration of toluene at 0°C with a mixture of nitric acid and phosphoric anhydride or metaphosphoric acid was examined.     

Transesterification of oxalic acid esters

Conclusions Transesterification of some lower oxalate esters with alcohols in the presence of acidic or basic catalysts gave the corresponding higher esters in good yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1102–1105, May, 1968.     

Preparation of nitropyridines by nitration of pyridines with nitric acid

Nitration of pyridines 1a-o with nitric acid in trifluoroacetic anhydride, gave the corresponding 3-nitropyridines 6a-n in yields of 10-83%.     

Ammonolysis of aziridinecarboxylic acid esters

The ammonolysis of 1-(2-methoxycarbonylvinyl)- and 1-(1,2-dimethoxycarbonylvinyl)-2-methoxycarbonylaziridines at normal pressure leads to 1-(2-methoxycarbonylvinyl)-and 1-(1,2-dicarbamoylvinyl)-2-carbamoylaziridines, respectively, whereas 1,3-diazabicyclo[3.1.0]hexan-4-one derivatives are formed under pressure.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 350–352, March, 1983.     

Intramolecular esters of alginic acid

The intramolecular ester (lactone) of alginic acid and of the polyuronide obtained on its fractionating were synthesized, and the effects of temperature and reaction duration on the number of ester groups formed in the polymer were studied.     

Macrocyclic organotin(IV) carboxylates based on benzenedicarboxylic acid derivatives: Syntheses, crystal structures and antitumor activities

Six new organotin carboxylates based on 1,3-benzenedicarboxylic acid and 1,4-benzenedicarboxylic acid derivatives, namely (Ph₃Sn)₂(2,5-L¹)(C₂H₅OH)₂ (1) (2,5-H₂L¹ = 2,5-dibenzoylterephthalic acid), (Ph₃Sn)₂(2,5-L²)(C₂H₅OH)₂ (2) (2,5-H₂L² = 2,5-bis(4-methylbenzoyl)terephthalic acid), (Ph₃Sn)₂(2,5-L³)(C₂H₅OH)₂ (3) (2,5-H₂L³ = 2,5-bis(4-ethylbenzoyl)terephthalic acid), [(n-Bu₂Sn)₄(4,6-L¹)O₂(OH)(OC₂H₅)]₂·2(C₂H₅OH) (4) (4,6- H₂L¹ = 4,6-dibenzoylisophthalic acid), [(n-Bu₂Sn)₄(4,6-L¹)O₂(OH)(OC₄H₉)]₂·2(C₄H₉OH) (5) and [(n-Bu₂Sn)₄(4,6-L²)O₂(OH)(OC₂H₅)]₂·2(C₂H₅OH) (6) (4,6-H₂L² = 4,6-bis(4-methylbenzoyl)isophthalic acid), have been synthesized. All the organotin carboxylates have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy and X-ray crystallography diffraction analyses. The structural analysis reveals that complexes 1-3 show similar structures, containing binuclear triorganotin skeletons. The significant intermolecular O-H?O hydrogen bonds linked the complexes 1-3 to form a novel 2D network polymer with 38-member macrocycles. In complexes 4-6, two Sn₄O₄ ladders are connected by two 1,3-benzenedicarboxylic acid derivatives to yield ladder-like octanuclear architectures and form macrocycle with 24 atoms. In addition, the antitumor activities of complexes 1-6 have been studied.     

Kinetics of benzonitrile nitration with mixed acid under homogeneous conditions

Chemical kinetics of benzonitrile nitration with mixed acid is investigated in the temperature range 283–299 K. Pseudo-first-order rate constants are evaluated by means of rate experiments on homogeneous reacting mixtures having large stoichiometric excesses of nitric acid. The second-order kinetic constants for nitronium ion attack to the aromatic substrate are derived on the basis of the assessed nitration mechanism. An activation energy of 604 ± 37 kJ mol^?1 is calculated for this reaction step. © 1993 John Wiley & Sons, Inc.     

Reaction of dibenzylphosphinous acid with formic acid esters

Summary The reaction of dibenzylphosphinous acid with formic acid esters was studied in the presence of sodium. Here we obtained dibenzylmethylolphosphine oxide and the enol form of the phenylalkoxybenzylphosphorylacetaldehyde.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1085–1088, June, 1965     

Sensitized photooxygenation of 2,4-hexadienoic acid esters and 2,4,6-octatrienoic acid esters. Unusual solvent and temperature effects

Sensitized photooxygenation of the title compounds were remarkably affected by the solvent used and the reaction temperature.     

Synthesis of esters of iminocarbonic acid

The first syntheses of asymmetrical esters of iminocarbonic acid are reported. These syntheses were carried out without the separation of intermediates. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, p. 23, October, 1989.