(E)-stilbene
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(''E'')-Stilbene, commonly known as ''trans''-stilbene, is an
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
represented by the
condensed structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bond ...
CHCH=CHCH. Classified as a diarylethene, it features a central
ethylene Ethylene ( IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene ...
moiety Moiety may refer to: Chemistry * Moiety (chemistry), a part or functional group of a molecule ** Moiety conservation, conservation of a subgroup in a chemical species Anthropology * Moiety (kinship), either of two groups into which a society is ...
with one
phenyl In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6 H5, and is often represented by the symbol Ph. Phenyl group is closely related to benzene and can be viewed as a benzene ring, minus a hydroge ...
group
substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and '' functional group'', as well as '' ...
on each end of the carbon–carbon
double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...
. 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 Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) with formula C14H10, consisting of three fused benzene rings. It is a colorless, crystal-like solid, but can also appear yellow. Phenanthrene is used to make dyes, plastics and pesticides, ...
. Stilbene was discovered in 1843 by the French chemist Auguste Laurent. The name "stilbene" is derived from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
word ''στίλβω'' (''stilbo''), which means "I shine", on account of the lustrous appearance of the compound.


Isomers

Stilbene exists as two possible
stereoisomer In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms i ...
s. One is ''trans''-1,2-diphenylethylene, called (''E'')-stilbene or ''
trans Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Arts, entertainment, and media * Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom * ''Trans'' (fil ...
''-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 Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change ...
. ''Cis''-stilbene is a liquid at room temperature (melting point: ), while ''trans''-stilbene is a crystalline solid which does not melt until around , illustrating the two isomers have significantly different physical properties.


Preparation and reactions

Many syntheses have been developed. One popular route entails reduction of benzoin using zinc amalgam. : CH–CH(OH)–C(=O)–CH   -> ce\ce \text \ce]   ''trans''-CH–CH=CH–CH Both isomers of stilbene can be produced by decarboxylation of alpha-phenylcinnamic acid, α-phenylcinnamic acid, ''trans''-stilbene being produced from the of the acid. Richard F. Heck and Tsutomu Mizoroki independently reported the synthesis of ''trans''-stilbene by coupling of
iodobenzene Iodobenzene is an organoiodine compound consisting of a benzene ring substituted with one iodine atom. It is useful as a synthetic intermediate in organic chemistry. It is a volatile colorless liquid, although aged samples appear yellowish. Prepa ...
and
styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
using a palladium(II) catalyst, in what is now known as the Mizoroki-Heck reaction. The Mizoroki approach produced the higher yield. : Stilbene undergoes reactions typical of alkenes. ''Trans''-stilbene undergoes epoxidation with
peroxymonophosphoric acid Peroxymonophosphoric acid () is an oxyacid of phosphorus. It is a colorless viscous oil. Its salts are called peroxymonophosphates. Another peroxyphosphoric acid is peroxydiphosphoric acid, . Preparation Peroxyphosphoric acids were first synt ...
, HPO, producing a 74% yield of ''trans''-stilbene oxide in
dioxane 1,4-Dioxane () is a heterocyclic organic compound, classified as an ether. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane because the other dioxane isomers ( 1,2- ...
. The
epoxide In organic chemistry, an epoxide is a cyclic ether () with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. They are produced on a large scale ...
product formed is a
racemic mixture In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...
of the two
enantiomers In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...
of 1,2-diphenyl
oxirane Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
. The achiral ''meso'' compound (1''R'',2''S'')-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 Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...
. Enantiopure stilbene oxide has been prepared by Nobel laureate
Karl Barry Sharpless Karl Barry Sharpless (born April 28, 1941) is an American chemist and a two-time Nobel laureate in Chemistry known for his work on stereoselective reactions and click chemistry. Sharpless was awarded half of the 2001 Nobel Prize in Chemistry " ...
. : Stilbene can be cleanly oxidised to benzaldehyde by
ozonolysis In organic chemistry, ozonolysis is an organic reaction where the unsaturated bonds of alkenes (), alkynes (), or azo compounds () are cleaved with ozone (). Alkenes and alkynes form organic compounds in which the multiple carbon–carbon bon ...
or Lemieux–Johnson oxidation, and stronger oxidants such as acidified
potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...
will produce
benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, w ...
. Vicinal
diol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is ...
s can be produced via the Upjohn dihydroxylation or enantioselectively using
Sharpless asymmetric dihydroxylation Sharpless asymmetric dihydroxylation (also called the Sharpless bishydroxylation) is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol. The reaction has been applied to alk ...
with
enantiomeric excess In stereochemistry, enantiomeric excess (ee) is a measurement of purity used for chiral substances. It reflects the degree to which a sample contains one enantiomer in greater amounts than the other. A racemic mixture has an ee of 0%, while a s ...
es as high as 100%. 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; ''cis''-stilbene yields a
racemic mixture In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...
of the two
enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...
s of 1,2-dibromo-1,2-diphenylethane in a non-polar solvent such as
carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVACR) is an organic compound with the chemi ...
, but the extent of production of the ''meso'' compound increases with solvent polarity, with a yield of 90% in
nitromethane Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as i ...
. 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 In a chemical reaction, chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the ...
with a carbocation intermediate PhCHBr–C(H)Ph with a vacant
p orbital In atomic theory and quantum mechanics, an atomic orbital is a function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in a ...
vulnerable to nucleophilic attack from either face. The addition of bromide or tribromide salts restores much of the stereospecificity even in solvents with a
dielectric constant The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric constant of an insulat ...
above 35. Upon UV irradiation it converts to ''cis''-stilbene, a classic example of a
photochemical reaction Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...
involving ''trans''-''cis'' isomerization, and can undergo further reaction to form
phenanthrene Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) with formula C14H10, consisting of three fused benzene rings. It is a colorless, crystal-like solid, but can also appear yellow. Phenanthrene is used to make dyes, plastics and pesticides, ...
. :


Derivatives and uses


Synthetic

(''E'')-Stilbene itself is of little value, but it is a precursor to other derivatives used as
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...
s,
optical brightener Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the ...
s,
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...
s, and
scintillator A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbe ...
s. Stilbene is one of the gain mediums used in
dye laser A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 ...
s. Disodium 4,4'-dinitrostilbene-2,2'-disulfonate is prepared by the
sulfonation Aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution. Aryl sulfonic acids are used as detergents, dye, and drugs. Stoichiometry ...
of 4-nitrotoluene to form 4-nitrotoluene-2-sulfonic acid, which can then be oxidatively coupled using
sodium hypochlorite Sodium hypochlorite (commonly known in a dilute solution as bleach) is an inorganic chemical compound with the formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may also be viewed as the sodium salt of ...
to form the (''E'')-stilbene
derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...
in a process originally developed by
Arthur George Green Arthur George Green FRS (1864 – 12 September 1941) was a British organic chemist. Career He was educated at Lancing College and University College London. In 1887, Green was working in London for the Brooke, Simpson and Spiller company when ...
and André Wahl in the late nineteenth century. Improvements to the process with higher yields have been developed, using air oxidation in liquid ammonia. The product is useful as its reaction with
aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile start ...
derivatives results in the formation of
azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C- ...
s. Commercially important dyes derived from this compound include Direct Red 76, Direct Brown 78, and Direct Orange 40.


Natural stilbenes

The
stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are prod ...
s are naturally occurring stilbene derivatives. Examples include
resveratrol Resveratrol (3,5,4′-trihydroxy-''trans''-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacteria or fungi. Sources ...
and its cousin, pterostilbene. The stilbestrols, which are structurally but not synthetically related to (''E'')-stilbene, exhibit
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal a ...
ic activity. bMembers of this group include
diethylstilbestrol Diethylstilbestrol (DES), also known as stilbestrol or stilboestrol, is a nonsteroidal estrogen medication, which is presently rarely used. In the past, it was widely used for a variety of indications, including pregnancy support for those with a ...
, fosfestrol, and
dienestrol Dienestrol (, ) (brand names Ortho Dienestrol, Dienoestrol, Dienoestrol Ortho, Sexadien, Denestrolin, Dienol, Dinovex, Follormon, Oestrodiene, Synestrol, numerous others), also known as dienoestrol (), is a synthetic nonsteroidal estrogen of the ...
. Some such derivative are produced by
condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...
of coenzyme A derivatives of
cinnamic acid Cinnamic acid is an organic compound with the formula C6H5-CH=CH- COOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxylic acid, it occurs n ...
or 4-hydroxycinnamic acid and the malonic acid.


Appendix

Table 1. Vapor pressures


References


External links


(E)-Stilbene on ChemExper
{{DEFAULTSORT:Stilbene, (E)- Luminescence Fluorescent dyes Phosphors and scintillators Laser gain media Stilbenoids Phenyl compounds