Search results for "Alkylation"
showing 10 items of 219 documents
Synthesis and characterization of amphiphilic comb-polymers via ring-opening metathesis polymerization of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[…
1994
A number of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[2.2.1]hept-2-enes (exo,exo-5,6-bis(alkoxymethyl)-7-oxanorbornenes) with long alkyl chains were prepared by reduction of the Diels-Alder adduct of furan and maleic anhydride, followed by alkylation with a series of different n-alkylbromides. These monomers were polymerized via ring-opening metathesis polymerization (ROMP) catalyzed by ruthenium trichloride in ethanolic solution. Contrary to a helical conformation as it was predicted by a previous molecular model study the poly(7-oxanorbornenes) adopt a coil conformation in solution. In bulk the materials show side chain crystallization.
The benefit of multipore zeolites: Catalytic behaviour of zeolites with intersecting channels of different sizes for alkylation reactions
2009
Abstract The catalytic behaviour of two multipore zeolites containing channels of different sizes, SSZ-33 (10 windows × 12 MR) and ITQ-22 (8 × 10 × 12 MR pores), for alkylation of benzene with ethanol and benzene with isopropanol or propylene, has been studied and compared to that of zeolites with intersecting channels of the same size, ZSM-5 (10 × 10 MR channels) and Beta (12 × 12 MR channels), which are industrially used for the above-mentioned process. For the alkylation of benzene with ethanol in gas phase, ITQ-22 behaves like the 10 MR ZSM-5 with respect to ethylbenzene selectivity, while the behaviour of SSZ-33 is close to that of a 12 MR zeolite such as Beta. For the alkylation of be…
Alkylation of Benzene with Short-Chain Olefins over MCM-22 Zeolite: Catalytic Behaviour and Kinetic Mechanism
2000
Abstract Benzene alkylation with ethene and propene has been carried out under liquid-phase reaction conditions over zeolites MCM-22, Beta, and ZSM-5. MCM-22 seems to be a good catalyst for benzene alkylation especially with propene, showing high activity and stability and good selectivity. Kinetic experiments show that alkylation with propene follows an Eley–Rideal type mechanism.
Alkylated dibenzothiophenes in pine needles from pulp and paper mill environment
1998
Abstract Concentrations of alkylated dibenzothiophenes (C n DBTs) in pine needles in a recipient area of the emissions from a pulp and paper mill where also waste combustion was done were measured. The concentrations (ng/g dry weight) of C 1 DBTs were in the range of 2 DBTs in the range of 3 DBTs in the range of 3 DBTs] > [C 2 DBTs] > [C 1 DBTs]. The pulp mill could not be shown to be the source of C 1 C 3 DBTs in the pine needles. Other possible sources are situated in the vicinity of the pulp and paper mill. Long-range transport, either, cannot be excluded as a possible source.
Synthesis of Pillar[6]arenes and Their Host–Guest Complexes
2015
Pillar[n]arenes are a fast-growing research topic in supramolecular chemistry. Originally the focus was predominantly on pillar[5]arenes; however, now more and more studies on pillar[6]arenes are being performed. The ability and selectivity of host–guest complexations depend strongly on the size of the inner cavities of these macrocycles. New results have stimulated us to compile the synthetic entries and the complexations of pillar[6]arenes with large cylindric cavities that offer space for many different guest molecules. 1 Introduction 2 Preparation of Pillar[6]arenes 2.1 Pillar[6]arenes by Macrocyclization Reactions 2.2 Hydroxypillar[6]arenes through Ether Cleavage 2.3 Hydroxypillar[6]ar…
ChemInform Abstract: Synthesis of Pillar[6]arenes and Their Host-Guest Complexes
2015
Pillar[n]arenes are a fast-growing research topic in supramolecular chemistry. Originally the focus was predominantly on pillar[5]arenes; however, now more and more studies on pillar[6]arenes are being performed. The ability and selectivity of host–guest complexations depend strongly on the size of the inner cavities of these macrocycles. New results have stimulated us to compile the synthetic entries and the complexations of pillar[6]arenes with large cylindric cavities that offer space for many different guest molecules. 1 Introduction 2 Preparation of Pillar[6]arenes 2.1 Pillar[6]arenes by Macrocyclization Reactions 2.2 Hydroxypillar[6]arenes through Ether Cleavage 2.3 Hydroxypillar[6]ar…
ChemInform Abstract: 3,4-Dihydro-2H-pyrrole-2-carbonitriles: Useful Intermediates in the Synthesis of Fused Pyrroles and 2,2′-Bipyrroles.
2016
Various heterocyclic structures containing the pyrrole moiety have been synthesized from easily accessible 3,4-dihydro-2H-pyrrole-2-carbonitriles in one-pot procedures. 5,6,7,8-Tetrahydroindolizines, 2,3-dihydro-1H-pyrrolizines as well as 6,7,8,9-tetrahydro-5H-pyrrolo[1,2-a]azepines were obtained from these precursors in high yields in an alkylation/annulation sequence. The same conditions were applied in the synthesis of a 5,8-dihydroindolizine, which could easily be transformed to the corresponding indolizine by dehydrogenation. Furthermore, oxidative couplings of 3,4-dihydro-2H-pyrrole-2-carbonitriles with copper(II)-salts furnished 2,2′-bipyrroles as well as 5,5′-bis(5-cyano-1-pyrroline…
Unveiling the reaction mechanism of novel copper N-alkylated tetra-azacyclophanes with outstanding superoxide dismutase activity.
2020
Quantum chemical and multiscale calculations reveal the mechanistic pathway of two superoxide dismutase mimetic N-alkylated tetra-azacyclophane copper complexes with remarkable activity. The arrangement of the binding site afforded by the bulky alkyl substituents and the coordinated water molecule as a proton source play key roles in the reaction mechanism.
The Mechanism of Diene Polymerisation by Organolanthanide Catalysts Deduced from Microwave Experiments
2005
Isoprene polymerisation performed under microwave irradiation with [Nd(BH 4 ) 3 (THF) 3 ]/Mg(Bu) 2 and [Nd-(BH 4 ) 3 (THE) 3 ]/Al(Et) 3 showed an enhancement in reactivity, with selectivity being only slightly modified. An explanation of the observed effect is proposed based on our current knowledge of the catalytic mechanism and by considering the alkylated complex as an ion pair. An analogy is proposed with the pseudoanionic polymerisation of oxygenated monomers. Finally, depolymerisation is observed under microwave irradiation at high temperature.
Reflux reactions for chromatography
1976
Reactions under pressure are mainly used to prepare derivatives before chromatographic analysis because of the lack of microequipment. A ml-refluxer has been designed to allow reactions under atmospheric pressure for volumes from 0.2 to 5 cm3. The reaction temperature is determined by the boiling point of the solvent thus derivatives of heat sensitive compounds can be made in the micro scale. With the aid of the ml-refluxer large series of derivatisations can be carried out and hence the reaction parameters can be optimized. This is shown at the example of the alkylation of barbituric acids for gas chromatography, where thus only N,N′-derivatives were obtained. The reliability of the appara…