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Anisole, or methoxybenzene, 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. T ...
with the formula CH3OC6H5. It is a
color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are assoc ...
less liquid with a smell reminiscent of anise seed, and in fact many of its derivatives are found in natural and artificial fragrances. The compound is mainly made synthetically and is a
precursor Precursor or Precursors may refer to: * Precursor (religion), a forerunner, predecessor ** The Precursor, John the Baptist Science and technology * Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of u ...
to other synthetic compounds. It is an
ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
. Anisole is a standard reagent of both practical and pedagogical value. It can be prepared by the
Williamson ether synthesis The Williamson ether synthesis is an organic reaction, forming an ether from an organohalide and a deprotonated alcohol (alkoxide). This reaction was developed by Alexander Williamson in 1850. Typically it involves the reaction of an alkoxide io ...
; sodium phenoxide is reacted with a methyl halide to yield anisole.


Reactivity

Anisole undergoes
electrophilic aromatic substitution Electrophilic aromatic substitution is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitutions are aromatic n ...
reaction at a faster speed than
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
, which in turn reacts more quickly than nitrobenzene. The methoxy group is an ortho/para directing group, which means that electrophilic substitution preferentially occurs at these three sites. The enhanced nucleophilicity of anisole vs.
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
reflects the influence of the
methoxy In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula . On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position a ...
group, which renders the ring more electron-rich. The methoxy group strongly affects the pi cloud of the ring as a mesomeric electron donor, more so than as an inductive electron withdrawing group despite the
electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
of the
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
. Stated more quantitatively, the Hammett constant for para-substitution of anisole is -0.27. Illustrative of its nucleophilicity, anisole reacts with acetic anhydride to give :CH3OC6H5 + (CH3CO)2O → CH3OC6H4C(O)CH3 + CH3CO2H Unlike most acetophenones, but reflecting the influence of the methoxy group, methoxyacetophenone undergoes a second acetylation. Many related reactions have been demonstrated. For example, P4S10 converts anisole to Lawesson's reagent, CH3OC6H4)PS2sub>2. Also indicating an electron-rich ring, anisole readily forms π-complexes with
metal carbonyl Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe c ...
s, e.g. Cr(η6-anisole)(CO)3. The ether linkage is highly stable, but the
methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...
can be removed with
hydroiodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hy ...
: :CH3OC6H5 + HI → HOC6H5 + CH3I
Birch reduction The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditionally ...
of anisole gives 1-methoxycyclohexa-1,4-diene.


Preparation

Anisole is prepared by methylation of sodium phenoxide with dimethyl sulfate or methyl chloride: : 2 C6H5ONa+ + (CH3O)2SO2 → 2 C6H5OCH3 + Na2SO4


Applications

Anisole is a precursor to
perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...
s, insect
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s, and pharmaceuticals.Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki, Yasuhiro Fujita, Hans-Josef Buysch, Dorothea Garbe, Wilfried Paulus “Phenol Derivatives“ in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. For example, synthetic anethole is prepared from anisole.


Safety

Anisole is relatively nontoxic with an of 3700 mg/kg in rats.MSDS
Its main hazard is its flammability.


See also

* Anethole * Bromoanisole * Butylated hydroxyanisole *
Ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
*
Ethyl phenyl ether Ethyl phenyl ether (or phenetole) is an organic compound that belongs to a class of compounds called ethers. Ethyl phenyl ether has the same properties as some other ethers, such as volatility, explosive vapors, and the ability to form peroxides. ...
*
Phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...
*
2,4,6-Trichloroanisole 2,4,6-Trichloroanisole (TCA) is a chemical compound that is a chlorinated derivative of anisole. TCA is a fungal metabolite of 2,4,6-trichlorophenol, which is used as a fungicide. It can be found in minute traces on packaging materials stored in ...
(cork taint)


References


External links

*
Pherobase
pheromone database entry {{Authority control Flavors Pheromones Phenol ethers Phenyl compounds