What Is Anisole?
Anisole, also called methoxybenzene, is an aromatic ether with the molecular formula C7H8O and the CAS registry number 100-66-3. Its structure consists of a benzene ring substituted with one methoxy group, -OCH3. At room temperature it is a colorless liquid with a pleasant, characteristic odor reminiscent of anise seed.
As the simplest member of the aromatic ether family, anisole combines the stability of an aromatic ring with the reactivity of an ether linkage, which makes it useful both as a solvent and as a synthetic building block. It has a relatively high boiling point of about 154 °C and is essentially immiscible with water, but it dissolves readily in ethanol, ether, and most organic solvents.
Function as an Organic Synthesis Solvent
Industrial anisole is widely used as a solvent in organic synthesis. Its high boiling point allows reactions to be run at elevated temperatures without the need for pressurized equipment, while its ether structure makes it compatible with a broad range of organometallic and organic reagents. Because anisole is aprotic and chemically resistant under many conditions, it serves as a stable reaction medium for couplings, substitutions, and rearrangements.
In addition, anisole is used as a solvent for recrystallization and extraction in the production of fine chemicals, where its immiscibility with water simplifies work-up procedures.
Function as a Chemical Intermediate
The methoxy group of anisole is a versatile handle for further chemistry. Anisole is an intermediate or precursor in the synthesis of numerous value-added compounds:
Pharmaceutical intermediates: many drug molecules contain the anisole framework or are built from anisole-derived building blocks.
Fragrance and flavor compounds: anisole derivatives such as anisaldehyde and anethole are important aroma chemicals.
Agrochemical intermediates: the anisole ring appears in certain herbicides, insecticides, and fungicides.
Dye and polymer additives: substituted anisoles are used in specialty colorants and stabilizers.
In these applications, the electron-rich aromatic ring of anisole directs electrophilic substitution to the para position, giving chemists predictable regiochemistry in further transformations.
Function in Specialty and Laboratory Applications
In the laboratory, anisole is a common solvent for microwave-assisted reactions and for processes that require a high-boiling, low-polarity medium. It is also used as a standard in NMR spectroscopy, where its proton signals are well characterized. In specialty industrial processes, anisole appears as a component in heat-transfer fluids and as a solvent for high-performance coatings where conventional solvents are unsuitable.
Physical Properties at a Glance
| Property | Typical Value |
|---|---|
| CAS number | 100-66-3 |
| Molecular formula | C7H8O |
| Appearance | Colorless liquid |
| Boiling point | About 154 °C |
| Density at 20 °C | About 0.995 g/cm³ |
| Water solubility | Practically immiscible |
These reference values are consistent with standard chemical handbooks. Minor variations may appear depending on measurement conditions and purity.
Safety and Handling
Anisole is a flammable liquid and should be stored away from ignition sources in well-ventilated areas. It can irritate the eyes, skin, and respiratory tract on contact or inhalation, so appropriate personal protective equipment is recommended during handling. Spills should be contained and absorbed with inert material, and waste should be disposed of through licensed channels in accordance with local environmental regulations.
Frequently Asked Questions
What is the function of industrial anisole?
Industrial anisole functions as a high-boiling organic synthesis solvent, a chemical intermediate for pharmaceuticals, fragrances, and agrochemicals, and a stable reaction medium in specialty processes.
What is the CAS number of anisole?
Anisole has the CAS registry number 100-66-3 and the molecular formula C7H8O. Its common name is methoxybenzene.
Is anisole soluble in water?
Anisole is practically immiscible with water, but it is miscible with ethanol, ether, benzene, and most organic solvents.
What is anisole used for in perfumery?
Anisole itself is used as an intermediate for aroma chemicals such as anisaldehyde and anethole, which contribute anise and sweet notes to fragrances and flavors.
Is anisole flammable?
Yes. Anisole is a flammable liquid and must be stored and handled away from heat, sparks, and open flames.
Why is anisole used as a reaction solvent?
Because of its high boiling point, aprotic nature, and chemical resistance, anisole allows reactions to run at elevated temperatures with minimal side reactions, and it is easily separated from aqueous phases.
