Cyclodimerization of styrene

Taylor, Arnold R.; Keen, G. W.; Eisenbraun, E. J.

doi:10.1021/jo00442a005

Cited by 31 publications

(12 citation statements)

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“…The mechanistic route of caffeic acid decomposition under acid or thermal conditions is a reaction via decarboxilation and ciclysation of vinylcatechol intermediate as described for styrene (Rizzi & Boekley, 1992;Taylor, Keen, & Eisenbraun, 1977). In particular, caffeic acid has a proclivity to lose carbon dioxide readily forming nucleophilic p-vinylcatechol which easily beget pro-oxidant cations (Clarke & Macrae, 1983;Henrich & Baltes, 1987;Stadler et al, 1996).…”

Section: Redox Potential (Mv)mentioning

confidence: 99%

Caffeic acid decomposition products: Antioxidants or pro-oxidants?

Andueza

Manzocco

Peña

et al. 2009

Food Research International

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a b s t r a c tThe potential of phenol antioxidants to suffer decomposition reactions leading to the formation of products exerting pro-oxidant activity was studied. A hydroalcoholic solution containing caffeic acid was assessed for antioxidant and pro-oxidant activity during heating at 90°C to simulate the heat maintenance of the coffee brews in thermos. Decomposition products were also evaluated by HPLC analysis. In the early steps of caffeic acid decomposition, a decrease in antioxidant capacity was detected, associated to a significant increase in pro-oxidant activity because the development of pro-oxidant compounds. On further heating, an increase in antioxidant activity associated to a decrease in pro-oxidant molecules previously formed and the formation of polymers with higher antioxidant activity was observed. A mechanistic route of caffeic acid decomposition under thermal conditions according to the HPLC analysis was proposed. This study clearly showed that caffeic acid, a well known antioxidant, may also act as pro-oxidant due to thermal decomposition.

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Section: Redox Potential (Mv)mentioning

confidence: 99%

Caffeic acid decomposition products: Antioxidants or pro-oxidants?

Andueza

Manzocco

Peña

et al. 2009

Food Research International

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“…The two olefinic protons as broad singlets at d 4.61 and 4.78 and a methyl linked to the double bond at d 1.70 as well as a significant ion in the mass spectrum at m/z 41 indicated the presence of an isopropenyl moiety in the side chain [15]. The other two olefinic proton multiplets at d 5.35 and 5.45 were due to the heteroannular diene of the ring system [16][17][18]. The presence of a heteroannular diene excluded the possibility of the usual 5,6 double bond.…”

Section: Resultsmentioning

confidence: 99%

Chemical constituents fromClerodendron serratum

Ravikumar¹,

Lakshmanan²,

Ravi³

2008

Journal of Asian Natural Products Research

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“…For the identification of the styrene dimers, the cyclic dimer 1 methyl 3 phenylindane was synthesized as a mixture of two isomers according to an earlier described procedure. 15 Linear dimers were identified in a mixture of all the four isomers with the following compositions (wt.%): (Z) 1,3 diphenylbut 1 ene (1a), 1.7; (E) 1,3 diphenylbut 1 ene (1b), 74.1; cis 1 methyl 3 phenylindane (2a), 10.9; trans 1 methyl 3 phenylindane (2b), 13.3.…”

Section: Methodsmentioning

confidence: 99%

Dimerization and oligomerization of styrene in the presence of pentasils

et al. 2009

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Styrene is converted to dimers under the action of zeolite ZSM 12 both in the presence and absence of the solvent (chlorobenzene). This transformation is characterized by a high conver sion of the monomer (up to 100 wt.%) and selective formation of linear isomers (70-75%). In the presence of zeolites ZVN and VKZ in chlorobenzene, styrene forms a mixture of oligomers (n = 2-7), among which the dimers prevailed, while without the solvent oligomers with an average molecular weight of ∼1510 are formed.Styrene dimers are promising as regulators of polymer chain growth, plasticizers of polymers and Plexiglas, a basis of synthetic lubricants, and components of epoxide, varnish and paint, and poly(vinyl chloride) materials. 1-4 Strong acids, namely, AcClO 4 , CF 3 SO 3 H, and p MeC 6 H 4 SO 3 H are usually used 5-7 for the synthesis of styrene dimers, although it is shown 8,9 that zeolites Y and Beta are highly active in styrene dimerization. The linear dimer of styrene, viz., (E) 1,3 diphenylbut 1 ene, was obtained with the selectivity up to 80% in the presence of zeolite Y at 70°C, whereas zeolite Beta is more selective (84-90%) with respect to the formation of cyclic styrene dimers: cis and trans 1 methyl 3 phenylindanes.The use of pentasils in styrene dimerization is unknown. Since these zeolites possess 10 stronger acid sites than zeo lites Y and Beta, it was of interest to study the catalytic properties of the pentasils in styrene dimerization.In the present work, we studied the transformations of styrene in the presence of pentasils of two different struc tural types: MTW (zeolite ZSM 12) and MFI (zeolites ZVN 11,12 and VKZ 13,14 ). The data obtained on the activity and selectivity of the catalysts in styrene dimerization were compared to their acidic properties and molecular sieve characteristics. ExperimentalSamples of the pentasils in the H form were studied: industrial catalysts ZSM 12 (SiO 2 /Al 2 O 3 = 34) and ZVN (SiO 2 / * Dedicated to Academician A. I. Konovalov on his 75th birth day. Al 2 O 3 = 28) produced at the OAO ''Angarskii zavod katalizatorov i organicheskogo sinteza'' and VKZ (SiO 2 /Al 2 O 3 = 40) synthesized by the hydrothermal method from alkaline aluminosilicate gel using hexamethylenediamine as an organic additive.Before experiments on styrene oligomerization, the catalyst samples were heated in air for 4 h at 540°C. Styrene (OAO ''Salavatnefteorgsintez'') were distilled. Chlorobenzene was dehydrated using a standard method.Styrene oligomerization was carried out in a periodical isothermal reactor at 80-130°C in the presence of 5-40 wt.% catalyst in chlorobenzene and without a solvent. The initial styrene concentration in chlorobenzene [M] 0 was 2.2 mol L -1 . 1 H and 13 C NMR spectra were recorded on a Bruker AVANCE 400 spectrometer ( 1 H, 400.13 MHz; 13 C, 100.62 MHz) in CDCl 3 . High resolution mass spectra were measured on a Fisons Trio 1000 instrument, whose chromatograph was equipped with a DB 560 quartz column (50 m); the temperature of the column was increased from 50 to 320°C with a...

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Cyclodimerization of styrene

Cited by 31 publications

References 1 publication

Caffeic acid decomposition products: Antioxidants or pro-oxidants?

Caffeic acid decomposition products: Antioxidants or pro-oxidants?

Chemical constituents fromClerodendron serratum

Dimerization and oligomerization of styrene in the presence of pentasils

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