Reactions of Titanocene Derivatives with Molecular Carboxylic Acids and Copolymers Bearing Carboxylic Acid Groups

Linear, soluble copolymers containing titanium are of interest for use in targets for inertial-confinement fusion (ICF) experiments because the titanium is a useful spectroscopic probe for studying the nuclear fusion process. We have studied the reactions of dichloro- titanocene and diphenyltitanocene with carboxylic acids to determine if these can be used to prepare such polymers. Model reactions of dichlorotitanocene with p -toluic acid show that both mono- and di-carboxylates are formed. We have prepared a soluble titanium-containing copolymer via the reaction of poly(styrene- co -methacrylic acid) with an excess of dichlorotitanocene but attempts to remove the excess molecular titanocene from the copolymer result in crosslinking of the copolymer. Model reactions of benzoic and pivalic acids with diphenyltitanocene demonstrate that monosubstituted carboxylato(phenyl)titanocenes are formed but that these products are stable only at low temperatures and decompose readily at ambient temperature. Proton NMR studies of the reaction of diphenyltitanocene and benzoic acid at −20 °C indicate that this reaction is second order, suggesting that the reaction does not proceed through a benzyne intermediate. © 1997 by John Wiley & Sons, Ltd.     

Characterization of Aromatic Polyamide Particles Containing Carboxylic Acid and Carboxylic Acid Chloride Groups and Their Modification in Water

Two types of aromatic polyamide particles were prepared from 4,4′-diphenyldicarbonyl chloride and 3,5-diaminobenzoic acid in a reaction solution containing water or pyridine. Particles obtained using water (PA-water) were coarse spheres containing COOH groups with a diameter of 1 µm. Particles obtained using pyridine (PA-pyridine) were smooth spheres containing COOH and COCl groups with a diameter of 80 nm. The molecular weight of PA-pyridine was less than that of PA-water. During modification of PA-pyridine using 4′-aminobenzo-15-crown-5-ether, the COCl groups reacted with NH₂ groups of the crown ether in water, resulting in attachment of the crown ether to the particle surface.     

Application of Triphenylamine-Based Sensitizers with Two Carboxylic Acid Groups to Dye-Sensitized Solar Cells

Two triphenylamine-based dyes (TPAR3 and TPAR6) containing two carboxylic acid groups with different conjugated lengths were synthesized and characterized with regard to their photophysical and photoelectrochemical properties. Experimental results showed that the λ_max of TPAR6 either in methanol solution or on TiO₂ film was red-shifted and broadened by extending the π-conjugated bridge. However, the performance of TPAR3-based dye-sensitized solar cell (DSC) was superior to that of TPAR6. This reason was due to the serious self-quenching of the electronically excited state in TPAR6 molecule, resulting from its cis-trans isomerization. The effects of addition of guanidinium thiocyanate (GT) in the electrolyte on the performance of DSCs based on TPAR3 were also investigated, revealing a maximum energy conversion efficiency of 4.02% at 0.100 mol·L⁻¹ GT.     

含双吸电子基团的三苯胺染料在太阳电池中的应用

合成了两种具有不同共轭链长度的双吸电子基团的三苯胺类染料TPAR3和TPAR6, 研究了它们的光物理与光电化学性质, 并将它们用作TiO2纳米晶电极的光敏化剂引入太阳电池. 结果表明, 与含有乙烯基共轭桥的染料TPAR3相比, 含有丁二烯基共轭桥的染料TPAR6在甲醇溶液和TiO2膜上的最大吸收均发生一定程度的红移和宽化; 但TPAR6表现出比TPAR3差的光电性能, 主要是因为前者更易发生顺反异构化, 电子不能够顺利地从染料激发态注入到TiO2导带中, 光电流的产生得到抑制. 考察了基于TPAR3的太阳电池在电解液中加入不同浓度的硫氰酸胍(GT)对光电性能的影响, 发现在GT浓度为0.100 mol·L-1时效率达到最大(4.02%).     

Chemoselectivity and the Curious Reactivity Preferences of Functional Groups

Achieving high levels of chemoselectivity has been the Achilles’ heel of chemical synthesis. The excitement generated by the successful realization of chemoselective strategies underscores the painstaking efforts to define a set of conditions conducive to selection among the available reaction pathways. We discuss in this Review various aspects of chemoselectivity that have been addressed in a range of synthetic methods over the past decade. We have focused on the proposed mechanistic basis of the reactions under consideration in an attempt to categorize them and highlight the key concepts that have been emerging on the basis of these studies. Our overview of recent advances in chemoselective processes suggests that significant progress has been made, but a lot of challenges lie ahead.     

New Poly(Bismaleimide-Ether)s Containing Functional Pendant Carboxylic Groups

Abstract

New poly(bismaleimide-ether)s with functional pendant groups were synthesized by Michael addition polymerization of two monomers with functionality f > 2 (DL tartaric acid and methylene-5,5′disalicylic acid) to various bismaleimides with flexible groups (N,N'-4,4′-diphenyl-methanebismaleimide, N,N'-4,4′-diphenyletherbismaleimide and N,N'-4,4′-dibenzylbismaleimide). The polymerization occurred in solution, through the addition of the OH groups to the C[dbnd]C double bond of the maleimide rings. The polymers were obtained in good yields and they were characterized by elemental analysis, IR and ¹H NMR spectra, thermogravimetric analysis and viscozimetry.     

Two-State Reactivity in Organometallic Gas-Phase Ion Chemistry

In contrast to organic reactions, which can almost always be described in terms of a single multiplicity, in organometallic systems, quite often more than one state may be involved. The phenomenon of two states of different multiplicities that determine the minimum-energy pathway of a reaction is classified as two-state reactivity (TSR). As an example, the ion/molecule reactions of ‘bare’ transition-metal-monoxide cations with dihydrogen and hydrocarbons have been analyzed in terms of the corresponding potential-energy hypersurfaces. It turns out that, besides classical factors, such as the barrier heights, the spin-orbit coupling factor is essential, since curve crossing between the high- and low-spin states constitutes a distinct mechanistic step along the reaction coordinates. Thus, TSR may evolve as a new paradigm for describing the chemistry of coordinatively unsaturated transition-metal complexes. This concept may contribute to the understanding of organometallic chemistry in general and for the development of oxidation catalysts in particular.     

Water Sorption to Hydroxyl and Carboxylic Acid Groups in Carboxymethylcellulose (CMC) Studied with NIR-spectroscopy

In carbohydrate systems which contain polar groups such as hydroxyl and carboxylic acid groups, water molecules are adsorbed in a specific way which varies with the type of polar group. Near infrared Spectroscopy (NIR) combined with multivariate statistical analysis was used to study the interactions between water molecules and carboxymethylated cellulose (CMC) with various degrees of substitution of the carboxylic acid groups, in two ionic forms (CMC-Na and CMC-Ca). The adsorbed water molecules were clearly influenced by the counterion; i.e. the nature of the ion-pair. A principle component analysis (PCA) identified variations in the registered spectra related to: the nature of the counter-ion, the degree of substitution (DS), the relative humidity (RH) and the type of polar group to which water was adsorbed. It was, possible furthermore, through the use of partial least square analysis (PLS), to extract spectral information related to the non-freezing bound water adsorbed on hydroxyl and carboxyl groups respectively. Loading spectra indicated that the obtained spectral information indeed correlated to the two kinds of polar groups studied (hydroxyl groups and carboxylic acid groups). The results support the view that, in the humidity range of 0–100%, water molecules are specifically adsorbed to individual polar groups, which characteristics are dependent on the nature of the polar group.     

Influence of Comonomer Functional Groups on the Reactivity Ratios of Some Phenolic Monomers

The reactivity ratios of some halogen-substituted phenolic monomers have been determined by the linear graphical method of Kelen and Tüdöls. The nature of functional groups present in the comonomer influence the order of reactivity of p-chlorophenol, p-bromophenol, and p-iodophenol. The behavior of these monomers during copolymerization reaction has been interpreted in terms of 1) different degrees of resonance stabilization of the monomers, and 2) opposite polarization caused by the substituents present in the comonomer.     

羟基和甲氧基对羧酸酸性的影响分析

归纳和演绎法是有机化学学习中的重要方法,通过分析讨论羟基和甲氧基在几种体系中对羧酸酸性的影响,得出了氢键效应在不同体系中对羧酸酸性的影响并不一致的结论.     

Reaction of an Introverted Carboxylic Acid with Carbodiimide

The reaction of carboxylic acids with carbodiimides is reviewed, and an ‘introverted’ carboxylic acid is proposed as a means of trapping reactive intermediates along the reaction pathway. The introverted acid is a cavitand with the carboxylic function directed toward the floor of the cavity. Its reaction with diisopropyl carbodiimide gives a covalent adduct that is either the elusive O-acylisourea or the commonly encountered N-acylurea.     

New Fluorene-Based Conjugated Copolymers Bearing Carboxylic Groups

Summary: New conjugated copolymers containing 9,9-dioctylfluorene and terephthalate units (as dimethyl ester or free acid) were synthesized by the Suzuki coupling and characterized by GPC and NMR, FT-IR and UV-VIS spectroscopies. These copolymers proved to be good luminescent materials showing emissions in the blue region of the visible spectrum both in solution (λ_em = 450 nm) and in thin layers. Differences in the luminescence properties were attributed to various extents of aggregation. It was shown that interchain interaction can be avoided by the formation of the copolymer sodium salt. The copolymers were tested as active layers in light-emitting devices and the formation of their Eu(III) complexes was studied.     

Reaction of N-Phenyltrifluoromethanesulfonamide with Carbodiimides

Russian Journal of Organic Chemistry - N-Phenyltrifluoromemanesulfonamide reacted with N,N′-dicyclohexylcarbodiimide in methylene chloride to give exchange products,...     

可溶性的含羧基苝酰亚胺类化合物的合成及其光谱性质研究

本文主要以酐(1)为起始物,通过在环母体结构的1、6、7、12位上引入苯氧基和对甲基苯氧基合成了另外两种酐化合物(2a和2b);所得到的酐化合物与6-氨基已酸进行反应,合成了3种可溶性的含有羧基的酰亚胺化合物(3a、3b和3c),使用红外、紫外、荧光、¹H-NMR,元素分析对所合成的化合物进行了表征.经研究发现,环母体结构的1、6、7、12位上苯氧基和对甲基苯氧基的引入,能使得所合成的含羧基酰亚胺类化合物的最大吸收波长分别红移了44.1 nm和50.1 nm;Stokes位移变大,分别为34.1 nm和30.0 nm;而荧光量子产率有所降低但下降趋势不明显.     

含L-氨基酸基团的手性功能单体及与N-异丙基丙烯酰胺共聚物的合成

以L-苯丙氨酸（L-Phe）、L-色氨酸（L-Trp）和L-亮氨酸（L-Leu）3种常见的氨基酸为手性源,经过酯化、缩合等步骤制备3种手性功能单体AAc-L-Phe(AAc:丙烯酸)、AAc-L-Trp和AAc-L-Leu,其结构经过IR、1H NMR确证。 并将手性单体AAc-L-Phe与温敏材料N-异丙基丙烯酰胺(NIPAam)共聚,制备了手性共聚物P(NIPAam-co-AAc-L-Phe),结构经IR确证,示差扫描量热分析测试证明其具有温敏性。 这些手性功能单体有可能用于制备环境响应性手性高分子聚合物。     

Mutual Effect of Functional Groups and the Radical Center on the Reactivity of Nitroxyl Radicals

This review considers the correlation between the reactivity of nitroxyl radicals (piperidine, pyrroline, pyrrolidine, imidazoline, dihydroquinoline, tetrahydroquinoline, diphenyl nitroxide, etc.) and their chemical structure in terms of the rate constants of reactions between these radicals and hydrazobenzene. 4,4′-Di(tert-butyl)diphenyl nitroxyl has the highest reactivity, and the nitroxyl radical of benzoindolopyrrolidine is the least reactive (the difference is a factor of ∼10⁴). The effects of the metal atom in stable organometallic nitroxyl radicals and of the halogen atom in halogenated nitroxyl radicals on the reactivity of the nitroxyl center are considered. Data on the effect of the nitroxyl center on the reactivity of functional groups in the piperidine nitroxyl radical are generalized. Nitroxyl radicals with an activated double bond are shown by quantum chemical calculations to form cyclic transition complexes with amines, involving both the paramagnetic center and a double bond. This explains why the activated double bond in nitroxyl radicals is more reactive in nucleophilic additions of amines than the same bond in their diamagnetic analogues. The rate constants of nitroxyl reduction with hydrazobenzene and of nitroxyl oxidation with tetranitromethane are related to the σ_ESR constant derived from isotropic hyperfine coupling constants HFC_(aN), and their correlation with Hammett constants is demonstrated. The role of solvents in the reduction and oxidation of the nitroxyl radicals is considered. The influence of hydroxyl radical-polar solvent complexes and hydroxylamine-polar solvent H complexes on the course of reactions is considered for hydrogen atom transfer in systems of a sterically hindered nitroxyl radical and hydroxylamine.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 506–528.Original Russian Text Copyright © 2005 by Malievskii, Shapiro.     

新型含氨基酸官能团的香豆素衍生物的合成

以L-苯丙氨酸、L-色氨酸、L-酪氨酸和组氨酸为原料,在Me₃SiCl-MeOH(Ⅲ)体系中反应合成了相应的甲酯盐酸盐（2a~2d）;以7-羟基香豆素为原料,经两步反应制得7-(乙酸氧基)香豆素（6）; 6与3a经酰胺化反应合成了一种新型的香豆素衍生物--N-乙酰基-(氧-7-香豆素)-3-苯基-2-氨基-丙酸甲酯,其结构经¹H NMR, ¹³C NMR和FT-IR表征。     

反式环己烷羧酸衍生物的合成

低档液晶显示中所用的液晶材料,如联苯氰类、酯类等,具有高的粘度,低的清亮点及低的光化学、化学稳定性等缺点．随着液晶显示技术的发展,对高档液晶材料的要求越来越迫切．为了降低液晶材料的粘度指数,改造液晶分子的方法之一是用环己烷环代替分子中的苯环［１］．因...     

Synthesis of Phosphorus-Containing Carboxylic Acid Derivatives

Abstract

Phosphorus-containing carboxylic acids are of great interest as potential antiviral substances (1). Thus, the search for the simple and technological methods of their synthesis draws much attention.