Search results for "Benzene"
showing 10 items of 1701 documents
ChemInform Abstract: Multi-Arm 1,2,3-Thiadiazole Systems.
2010
Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.
Bedeutung von Assoziationsphänomenen quartärer Oniumverbindungen in der organischen Phase für den Ablauf phasentransferktalysierter Reaktionen
1980
Quartare Oniumsalze sind, wie dampfdruckosmometrische Messungen zeigen, in Benzol und Chloroform assoziiert [in Benzol starker (Faktor 4–15) als in Chloroform (Faktor 1.2 – 2.4)]. Im Homogen- und Zweiphasensystem laufen die Modellreaktionen (1) und (2) mit steigendem Assoziationsgrad schneller ab — langsamer im Zweiphasensystem wegen des Wassergehaltes der organischen Phase (Verminderung des Assoziationsgrades). Assoziationsphanomene sind offensichtlich fur die “Katalyse” im Zweiphasensystem wesentlich. Importance of Association Phenomena of Quaternary Onium Salts in the Organic Phase Responsible for the Course of Phase-Transfer-Catalysed Reactions As shown by vapour pressure osmometry quat…
Comparative study on the column performance of microparticulate 5-μm C18-bonded and monolithic C18-bonded reversed-phase columns in high-performance …
1999
In this paper we report on the results of a comparative study on the performance of Purospher RP 18e, 5 μm, columns and prototypes of monolithic columns named SilicaROD from Merck, Darmstadt, Germany. The studies were performed on HPLC equipment with minimum extra column contribution. The plate height linear velocity dependency of the Purospher RP 18e column showed a minimum of H of about 10–15 μm at a linear velocity of 1 mm/s. The H versus u curves of the monolithic columns followed the same course. Yet, the curves remained flat up to a linear velocity of about 7 mm/s, where the Purospher RP 18e column could not be operated anymore due to the extremely high back-pressure. In conclusion th…
A bis-exTTF macrocyclic receptor that associates C60 with micromolar affinity
2010
An exTTF-based macrocyclic receptor that associates C(60) with a binding constant10(6) M(-1) in chlorobenzene at room temperature is described. This represents an improvement of 3 orders of magnitude with respect to the previous examples of exTTF-based receptors and one of the highest binding constants toward C(60) reported to date.
Tetrakis(tert-butylammonium) benzene-1,2,4,5-tetracarboxylate octahydrate
2007
In the crystal structure of the title compound, 4C4H12N+·C10H2O8 4−·8H2O, there is a centre of symmetry at the centre of the benzene ring; the asymmetric unit comprises one half-anion, two cations and four water molecules. The pyromellitate tetraanion is nonplanar; it and the cations exhibit normal geometry. The two unique carboxylate groups are twisted out of the plane of the benzene ring by about 40 and 50°. The network formed by the ions and water molecules is based on eight O—H...O and six N—H...O strong hydrogen bonds.
Photoinduced switching of electrical properties in thin films of polar indandione type organic molecules
2006
The optically induced switching of organic materials with large dipole moments consisting of acceptor and donor groups bridged by a delocalized π-electron system is important for investigations of optoelectronic effects. To the contrary of azobenzene molecule, photoinduced change of dipole moment of indandione molecule does not need free volume in thin films. To modify the dipole moment and also to optimise properties of film formation, a number of novel indandione derivatives is investigated. Reversible switching of the surface potential of polymer films with incorporated or chemically attached indandione molecules is observed at irradiation in photoinduced intramolecular electron transfer…
1977
Deuteron relaxation times T1 of polystyrenes deuterated at the backbone (PS-d3) and the phenyl ring (PS-d5), respectively, have been measured in solutions of benzene and diethyl malonate as a function of concentration and temperature. We conclude that the motion of the phenyl ring is faster than that of the backbone, the difference being smallest at high temperatures around 180°C. The temperatures dependence is discussed in relation to the activation energies in polystyrene.
Dielektrische Relaxation und aromatischer Bindungszustand der Amino- und Hydroxylgruppe
1965
Bei funf Wellenlangen im Bereich von 60 cm bis 7 mm wurde in benzolischer Losung bei 20 °C die dielecktrische Absorption von Benzolderivaten gemessen, die Amino- oder Hydroxylgruppen enthalten. Danach erfolgt die elektrische Dipolorientierung bei N, N'-Dimethylanilin, Diphenylamin und ver wandten Molekulen in der Art, das die drei Bindungen des Stickstoffs uber die ebene Anordnung hinweg umklappen. Ebenso kann auch das Relaxationsverhalten von Anilin beschrieben werden. Voraussetzung fur diese Inversion ist die mesomere Wechselwirkung zwischen dem Stickstoff und einem aromatischen ϕ-Elektronen-system. Dagegen ergeben die Meswerte keinen Hinweis darauf, das bei der Hydroxylgruppe auch eine s…
IR-und UV-spektroskopische Eigenschaften einer homologen Reihe von molekulareinheitlichen, 12gliedrige Ringe enthaltenden Leiteroligomeren
1984
The reactions of multiple acrylates of oligo[(hydroxyphenylene)methylene] s (2a–2f), strongly diluted in boiling benzene, with 2,2′-azoisobutyronitrile in a mole ratio of 1:10, were investigated. The elemental analysis and the determination of relative molar masses of the resulting products (3, 4, 5, 6a, 6b, 7a and 7b) demonstrate that their molecules contain two nitrile groups. These data, together with the IR and UV spectra, show that the products are molecularly uniform ladder oligomers with two 1-cyano-1-methylethyl groups on both ends.
Task Specific Dicationic Ionic Liquids: Recyclable Reaction Media for the Mononuclear Rearrangement of Heterocycles
2014
Nine functionalized dicationic ionic liquids were used to study the base catalyzed mononuclear rearrangement of (Z)-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into the corresponding triazole at 363 K. Ionic liquids were characterized by the presence of 1-(1-imidazolylmethyl)-3,5-di[1-(3'-octylimidazolylmethyl)]benzene cation, bearing on the structure a neutral imidazole unit as basic functionality. Besides anions generally used for monocationic ionic liquids, such as [Br(-)], [BF4(-)], and [NTf2(-)], also dianions having a rigid aromatic spacer such as 1,4-benzenedicarboxylate, 2,6-naphthalenedicarboxylate, and 1,5- and 2,6-naphthalenedisulfonate were taken into account. Further…