(E)-Stilbene, commonly known as trans-stilbene, is an
organic compound represented by the
condensed structural formula C6H5CH=CHC6H5. Classified as a
diarylethene, it features a central
ethylenemoiety with one
phenyl group
substituent on each end of the carbon–carbon
double bond. It has an
(E) stereochemistry, meaning that the phenyl groups are located on opposite sides of the double bond, the opposite of its
geometric isomer,
cis-stilbene. Trans-stilbene occurs as a white crystalline solid at room temperature and is highly soluble in organic solvents. It can be converted to cis-stilbene
photochemically, and further reacted to produce
phenanthrene.
Stilbene was discovered in 1843 by the French chemist
Auguste Laurent.[2] The name "stilbene" is derived from the
Greek word στίλβω (stilbo), which means "I shine", on account of the lustrous appearance of the compound.[3]
Isomers
Stilbene exists as two possible
stereoisomers. One is trans-1,2-diphenylethylene, called (E)-stilbene or trans-stilbene. The second is cis-1,2-diphenylethylene, called
(Z)-stilbene or cis-stilbene, and is
sterically hindered and less stable because the steric interactions force the aromatic rings out-of-plane and prevent
conjugation.[4]Cis-stilbene is a liquid at room temperature (melting point: 5–6 °C (41–43 °F)), while trans-stilbene is a crystalline solid which does not melt until around 125 °C (257 °F), illustrating the two isomers have significantly different physical properties.[5][6]
Preparation and reactions
Many syntheses have been developed. One popular route entails reduction of
benzoin using zinc amalgam.[6]
Both isomers of stilbene can be produced by decarboxylation of
α-phenylcinnamic acid, trans-stilbene being produced from the (Z)-isomer of the acid.[5]
Richard F. Heck[7] and Tsutomu Mizoroki[8] independently reported the synthesis of trans-stilbene by coupling of
iodobenzene and
styrene using a palladium(II) catalyst, in what is now known as the
Mizoroki-Heck reaction.[9][10] The Mizoroki approach produced the higher yield.
Stilbene undergoes reactions typical of alkenes. Trans-stilbene undergoes epoxidation with
peroxymonophosphoric acid, H3PO5, producing a 74% yield of trans-stilbene oxide in
dioxane.[11] The
epoxide product formed is a
racemic mixture of the two
enantiomers of 1,2-diphenyl
oxirane. The
achiralmeso compound (1R,2S)-1,2-diphenyloxirane arises from cis-stilbene, though peroxide epoxidations of the cis-isomer produce both cis- and trans-epoxide products. For example, using
tert-butyl hydroperoxide, oxidation of cis-stilbene produces 0.8% cis-stilbene oxide, 13.5% trans-stilbene oxide, and 6.1%
benzaldehyde.[12][13] Enantiopure stilbene oxide has been prepared by Nobel laureate
Karl Barry Sharpless.[14]
Bromination of trans-stilbene produces predominantly meso-1,2-dibromo-1,2-diphenylethane (sometimes called meso-stilbene dibromide), in line with a mechanism involving a cyclic
bromonium ion intermediate of a typical electrophilic
bromine addition reaction;[21]cis-stilbene yields a
racemic mixture of the two
enantiomers of 1,2-dibromo-1,2-diphenylethane in a non-polar solvent such as
carbon tetrachloride, but the extent of production of the
meso compound increases with solvent polarity, with a yield of 90% in
nitromethane.[22] The formation of small quantities of the two enantiomers of stilbene dibromide from the trans-isomer suggests that the bromonium ion intermediate exists in
chemical equilibrium with a carbocation intermediate PhCHBr–C+(H)Ph with a vacant
p orbital vulnerable to nucleophilic attack from either face.[21] The addition of bromide or tribromide salts restores much of the stereospecificity even in solvents with a
dielectric constant above 35.[23]
Disodium 4,4'-dinitrostilbene-2,2'-disulfonate is prepared by the
sulfonation of
4-nitrotoluene to form 4-nitrotoluene-2-sulfonic acid, which can then be oxidatively coupled using
sodium hypochlorite to form the (E)-stilbene
derivative[27] in a process originally developed by
Arthur George Green and André Wahl in the late nineteenth century.[28][29] Improvements to the process with higher yields have been developed, using air oxidation in liquid ammonia.[30] The product is useful as its reaction with
aniline derivatives results in the formation of
azo dyes. Commercially important dyes derived from this compound include Direct Red 76, Direct Brown 78, and Direct Orange 40.[26]
^Laurent, Auguste (1843).
"Mémoire sur la série stilbique" [Memoir on the stilbene series]. Comptes rendus (in French). 16: 856–860. From p. 857: "En soumettant ce sulfure à la distillation, il donne plusieurs produits, et entre autres, un composé fort remarquable que je nomme stilbène."
(On submitting this sulfide [i.e., phenyl thioaldehyde, C6H5(CS)H] to [dry] distillation, it gives several products, and among others, a very remarkable compound which I name "stilbene".)
^Heck, R. F.; Nolley, J. P. (1972). "Palladium-catalyzed vinylic hydrogen substitution reactions with aryl, benzyl, and styryl halides". J. Org. Chem.37 (14): 2320–2322.
doi:
10.1021/jo00979a024.
^Mizoroki, Tsutomu; Mori, Kunio; Ozaki, Atsumu (1971). "Arylation of Olefin with Aryl Iodide Catalyzed by Palladium". Bull. Chem. Soc. Jpn.44 (2): 581.
doi:
10.1246/bcsj.44.581.
^Ogata, Yoshiro; Tomizawa, Kohtaro; Ikeda, Toshiyuki (1979). "Oxidation of trans-stilbene with peroxymonophosphoric acid". J. Org. Chem.44 (14): 2362–2364.
doi:
10.1021/jo01328a006.
^Yin, Guochuan; Danby, Andrew M.; Kitko, David; Carter, John D.; Scheper, William M.;
Busch, Daryle H. (2007). "Olefin Epoxidation by Alkyl Hydroperoxide with a Novel Cross-Bridged Cyclam Manganese Complex: Demonstration of Oxygenation by Two Distinct Reactive Intermediates". Inorg. Chem.46 (6): 2173–2180.
doi:
10.1021/ic061957r.
PMID17295471.
^Buckles, Robert E.; Bader, Jane M.; Thurmaier, Roland J. (1962). "Stereospecificity of the Addition of Bromine to cis- and trans-Stilbene". J. Org. Chem.27 (12): 4523–4527.
doi:
10.1021/jo01059a097.
^Bianchini, Roberto; Chiappe, Cinzia (1992). "Stereoselectivity and reversibility of electrophilic bromine addition to stilbenes in chloroform: influence of the bromide-tribromide-pentabromide equilibrium in the counteranion of the ionic intermediates". J. Org. Chem.57 (24): 6474–6478.
doi:
10.1021/jo00050a021.
^Kwasniewski, S. P.; Claes, L.; François, J.-P.; Deleuze, M. S. (2003). "High level theoretical study of the structure and rotational barriers of trans-stilbene". J. Chem. Phys.118 (17): 7823–7836.
Bibcode:
2003JChPh.118.7823K.
doi:
10.1063/1.1563617.
^US patent 5041632, Guglielmetti, Leonardo, "Process for the preparation of 4,4'-dinitrostilbene-2,2-disulfonic acid", published 1991-08-20, issued 1991-08-20, assigned to
Ciba-Geigy Corporation
^Lide, David (1995). CRC Handbook of Chemistry and Physics (76th ed.). USA: CRC Press, Inc. pp. 6–107.
ISBN0-8493-0476-8.