Reaction of Methylmalonyl Dichloride with Unsaturated Carboxamides

Methylmalonyl dichloride reacts with (2E)-3-phenylacrylamides and (2E)-3-(2-furyl)acrylamide to give the corresponding E-isomeric 2-substituted 4-hydroxy-5-methyl-6H-1,3-oxazin-6-ones. The reaction of methylmalonyl dichloride with acrylamide afforded N-(3-chloropropionyl)-2-methylmalonamic acid. The structure of the products was confirmed by the ¹H and ¹³C NMR, IR, and UV spectra.     

Reaction of Dextran Polyaldehyde with Aminohydroxypyrimidines

Reaction of dextran polyaldehyde with aminohydroxypyrimidines is proposed as a procedure for modifying polysaccharides with low-molecular-weight compounds. The influence exerted by the reaction temperature and time and by solution pH on the number of incorporated heterocyclic fragments was examined.     

化学法修饰碳纳米管

综述了化学法修饰碳纳米管表面反应的研究进展,从酸化及其衍生反应、环加成反应、氟化反应、原子转移自由基聚合反应、卡宾加成反应等几种反应入手着重介绍了碳纳米管表面修饰的方法和研究状况。     

(烷基环戊二烯基)环戊二烯基二氯化钛的合成与反应

Richard在1959年合成了第一个环戊二烯基(取代环戊二烯基)钛衍生物,(CH₃C₅H₄)(C₅H₅)T1Cl₂^[1].我们曾报道了环戊二烯基(烯烃基环戊二烯基)二卤化钛的合成和反应^[2]。     

Enhancement of the Antioxidant and Antimicrobial Activities of Porphyran through Chemical Modification with Tyrosine Derivatives

The chemical modification of porphyran hydrocolloid is attempted, with the objective of enhancing its antioxidant and antimicrobial activities. Sulfated galactan porphyran is obtained from commercial samples of the red algae Porphyra dioica using Soxhlet extraction with water at 100 °C and precipitation with isopropyl alcohol. The extracted porphyran is then treated with modified L-tyrosines in aqueous medium in the presence of NaOH, at ca. 70 °C. The modified tyrosines L1 and L2 are prepared through a Mannich reaction with either thymol or 2,4-di-tert-butylphenol, respectively. While the reaction with 2,4-di-tert-butylphenol yields the expected tyrosine derivative, a mixture of products is obtained with thymol. The resulting polysaccharides are structurally characterized and the respective antioxidant and antimicrobial activities are determined. Porphyran treated with the N-(2-hydroxy-3,5-di-tert-butyl-benzyl)-L-tyrosine derivative, POR-L2, presents a noticeable superior radical scavenging and antioxidant activity compared to native porphyran, POR. Furthermore, it exhibited some antimicrobial activity against S. aureus. The surface morphology of films prepared by casting with native and modified porphyrans is studied by SEM/EDS. Both POR and POR-L2 present potential applicability in the production of films and washable coatings for food packaging with improved protecting characteristics.     

Propagation of Oscillating Chemical Signals through Reaction Networks

Akin to electronic systems that can tune to and process signals of select frequencies, systems/networks of chemical reactions also “propagate” time‐varying concentration inputs in a frequency‐dependent manner. Whereas signals of low frequencies are transmitted, higher frequency inputs are dampened and converted into steady‐concentration outputs. Such behavior is observed in both idealized reaction chains as well as realistic signaling cascades, in the latter case explaining the experimentally observed responses of such cascades to input calcium oscillations. These and other results are supported by numerical simulations within the freely available Kinetix web application we developed to study chemical systems of arbitrary architectures, reaction kinetics, and boundary conditions.     

Effect of Chemical Modification on Hydrolysis and Condensation Reaction of Zirconium Alkoxide

Chemical modification effect of acetic acid was examined to control the hydrolysis and following condensation reaction of zirconium alkoxide. When acetic acid was added to zirconium alkoxide solution, acetic acid coordinated to a zirconium alkoxide to form a stable bidentate chelating compound if molar ratio of acetic acid to zirconium alkoxide (here after abbreviated as RA) was less than two. In the case of simultaneous addition of acetic acid and water into a zirconium alkoxide solution, acetic acid immediately reacted with alkoxide. Water reacted with residual functional alkoxy groups to proceed the following condensation. Changing the degree of chelating the acetic acid to a zirconium alkoxide led to the control of the hydrolysis and condensation by decreasing the alkoxy groups of zirconium alkoxide. Polymeric transparent monolithic gels could be successfully prepared in the range from RA = 1 to RA = 1.5, and from RW = 1 to RW = 1.5 (here RW means molar ratio of water to zirconium alkoxide), respectively.     

Thermal Diffusion with Chemical Reaction: A Carrier System

The heat of transport of oxygen across a membrane mediated by hemoglobin (Hb) as a carrier is iuvestigated by the method of irreversible thermodynamics. It is assumed that oxygen combines with hemoglobin molecules to form oxyhemoglobin according to the reaction nO₂ + Hb=HbO_zn. The oxyhemoglobin molecule HbO_zn then migrates to a new position and is reconverted to Hb by releasing oxygen. It is shown that the heat of transport of oxygen consists of two contributions; one due to the reaction and the other from thermal diffusion of individual species present. Total oxygen flux across the membrane is also calculated in terms of temperature and the chemical potential difference of oxygen across the membrane. The use of the heat of transport as a measure of the efficiency of the heat pump for the carrier-mediated transport process is investigated.     

Chemical Modification of Plant Alkaloids. 4. Reaction of Cotarnine with Bifunctional NH- and CH-Acids

1-Substituted 1,2,3,4-tetrahydroisoquinoline systems were prepared by reaction of cotarnine with the NH-and CH-acids methyl- and acyl derivatives of pyrazole and 1,3-dicarbonyl reagents. Depending on the structure and reaction conditions, bifunctional pyrazole nucleophiles can give substitution products at the N atom, methyl, or acyl group; 1,3-diketones, at the terminal methyl. Rearrangements occurring during the reaction of cotarnine with bifunctional substrates were studied. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 360–364, July–August, 2005.     

Influence of the Solution Acidity and pK a of the Amine on the Reaction of Dextran Polyaldehyde with Amines

The influence exerted by the solution pH and pK _a of the amine on the reaction of dextran polyaldehyde with aromatic and aliphatic amines was studied.     

Aromatic Fluorine as a Chemical Label for Detecting Reaction Mechanism

This article explains how nucleophilically activated fluorine can be used for the detection of ion-pair formation during the decomposition of various aryl radical generators. Thus a concurrent dual mechanism for the breakdown of certain aryl radical sources can be experimentally demonstrated by fluorine labeling. The bearing of this information on the mechanism of diazo coupling is also discussed. In addition, labeling with aromatic fluorine is applied to the thermolysis of aryl azides, the aminolysis of 3-aryl-4-bromosydnones, and the hydrolysis of 3-arylsydnone imines. Finally some mechanistic problems are posed which may possibly be solved by this labeling technique.     

甲基钙黄绿素与二氯化双(甲氧羰乙基)锡的显色反应及其应用

在pH10.5的NH3 NH4Cl缓冲溶液中,有溴化十六烷基三甲基铵(CTMAB)和Tri tonX 100存在下,二氯化双(甲氧羰乙基)锡与甲基钙黄绿素形成1∶2的有色络合物。络合物的最大吸收波长为500mm,表观摩尔吸光系数为1.90×104L·mol-1·cm-1,Sn浓度在0～2.5mg/L范围内符合比耳定律。方法用于PVC中间产品中R2SnCl4的测定,结果满意,相对标准偏差和回收率分别在0.61%～1.58%和97.2%～100.1%之间。     

Reaction of Phenylmalonyl Dichloride with 3-Phenylpropynamide and Transformations of the Product by the Action of Some Nucleophiles

Phenylmalonyl dichloride reacted with 3-phenylpropynamide to give 4-hydroxy-5-phenyl-2-phenylethynyl-6H-1,3-oxazin-6-one. Treatment of the latter with hydrazine afforded 3,5-disubstituted 1,2,4-triazole. Reactions of 4-hydroxy-5-phenyl-2-phenylethynyl-6H-1,3-oxazin-6-one with methanol and ethanol led to formation of the corresponding malonamic acid esters. The structure of the products was proved by the ¹H and ¹³C NMR and IR spectra, quantum-chemical calculations (PM3, MNDO, MINDO3), and some chemical transformations.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 815–819.Original Russian Text Copyright © 2005 by Komarov, Yakovlev, Zakhs, Prep’yalov.     

Chemical Reactions on Polymers. II. Modification of Diene Polymers with Triazolinediones via the Ene Reaction

A wide variety of polymers and copolymers of 1,3-dienes have been modified at low temperatures via the ene reaction with 4-substituted l,2,4-triazoline-3,5-diones. The resulting modified polymers were characterized via infrared spectroscopy, nuclear magnetic resonance, intrinsic viscosity, gel-permeation chromatography, differential scanning calorimetry, solubility tests, and tensile measurements. Physical properties measurements support the postulate that the highly polar pendant urazole groups contribute inter molecular and intramolecular hydrogen-bonding interactions and thus impart to the modified polymers thermoplastic elastomer properties. Changes in the solubility character, thermal behavior, and tensile properties of the modified polymers are in accord with this postulate. Since the association between molecules is physical in nature, the modified polymers remain soluble in appropriate solvents. They also show dramatic decreases in molecular size; for example, the average molecular size of polymers at 1% modification is about one tenth that of the unmodified polymer due to intramolecular interactions, a size reduction of the same order of magnitude as that of chemically crosslinked polymers. Poly-1,2-butadiene, when modified to the extent of 5%, gave values for elongation to break, Young's modulus, and tensile strength twice those for the parent polymer, while tensile recoveries were > 90%.     

化学修饰提高核酸适体结合亲和力的研究进展

核酸适体(Aptamer)是通过体外筛选得到的短单链DNA或RNA寡核苷酸, 具有与抗体相当或更优异的特异性及亲和力, 且具有靶标范围广、 易制备和灵活可控修饰、 免疫原性低、 批次差异性小以及易于运输保存等优势, 为食品、 环境和生物医学等领域提供了全新的分子识别工具, 获得了研究者的广泛关注. 但是目前其商业应用的数量仍有限. 为了增强核酸适体的应用性能, 研究者对核酸适体进行了大量的改性研究. 本文系统总结了核酸适体筛选前、 后采用非共价或共价方式对其进行化学修饰, 以增加核酸适体与靶标的结合亲和力的相关研究进展, 并对未来发展前景进行了展望.     

Induced Alkene Reactions with Sulfur Dichloride. System Sulfur Dichloride-Dimethyl Sulfide as a Reagent for Polysulfonation and Conjugate Chlorination of Alkenes

In reaction of unsaturated compounds with sulfur dichloride in the presence of dimethyl sulfide radically new induced directions are realized: the reagent is involved as dimer or trimer (formation of di- and trisulfides). Alongside this process a conjugate chlorination occurred with participation of external nucleophiles, dimethyl sulfide and acetonitrile, furnishing sulfonium chlorides and N-substituted acetamides respectively. The relative importance of these alternative reactions depends on solvent, alkene structure, and order of reagents addition.     

稀土和磷改性对裂化催化剂反应性能的影响

我们采用稀土以及稀土和磷两种方式对Y型沸石表面进行修饰，NH3-TPD测试表明稀土和磷复合改性Y沸石(P—RE—USY)的酸性分布更集中在中强酸范围．在固定床和提升管装置上评价了含有P—RE-USY沸石催化剂的反应性能．经过稀土和磷复合改性，增强了沸石孔道的酸性中心，而表面活性中心在磷和稀土相互作用的改性中得以减少和弱化．这种修饰作用引导更多的烃分子进入沸石孔道中进行反应，减少了烃分子通过表面反应形成大量烯烃分子的几率．同时，由于烯烃的降低不完全来自二次氢转移反应的饱和过程，所以，适度降低二次反应有效地减少了中间馏分油的裂解，提高了柴油收率．