What Is P-Cymene?
p-Cymene is an organic compound in which two hydrogens of benzene are replaced by methyl and isopropyl groups.
Usually, p-Cymene (paracymene) has a structure in which a methyl group and an isopropyl group are substituted at the para-positions (1 and 4) of the benzene ring.
The CAS registration number is 99-87-6. However there are two positional isomers, o-cymene (CAS No. 527-84-4) and m-cymene (CAS No. 535-77-3), neither of which is found in nature.
Uses of P-Cymene
In nature, p-Cymene is found in the essential oils of shell ginger, cumin, and thyme. It is commonly used as a fragrance and is used in soaps. The substance has a citrus odor with a volatile oil smell.
p-Cymene is a useful substance as an organic synthetic raw material. It is used as a raw material for the synthesis of terephthalic acid and thymol.
Among the intermediates and building blocks that can be synthesized from p-Cymene are p-Cymene hydroperoxide, 4-methylacetophenone, 4-isopropylbenzyl alcohol, 4-isopropylbenzaldehyde, and 4-isopropylbenzoic acid. These substances are sometimes used to study oxidation reactions under various conditions.
Properties of P-Cymene
p-Cymene is an organic compound classified as a monoterpene (a 10-carbon hydrocarbon produced by plants, insects, fungi, and bacteria) and an aromatic hydrocarbon.
Its molecular formula is C10H14 and its molecular weight is 134.22. It has a melting point of -68.9°C, a boiling point of 177.10°C, and is a clear, colorless liquid at room temperature.
It has a characteristic aroma, sometimes described as citrusy, reminiscent of lemon. It is miscible with ethanol, acetone, benzene, carbon tetrachloride, and petroleum ether, but is virtually insoluble in water. It has a density of 0.857 g/mL.
Although p-Cymene is stable under normal handling conditions, it reacts with oxidizing agents and is believed to attack rubber. During storage, it is necessary to avoid mixing with these substances. p-Cymene is also used as a ligand for ruthenium. A typical example is dichloro(p-Cymene)ruthenium(II) (η6-cymene)2Ru2Cl4), which is usually sold in dimer form (CAS registration number 52462-29-0).
This complex is synthesized from ruthenium trichloride and α-ferlandrene and is used as a precursor to various ruthenium-cymene complexes. Other p-Cymene complexes of osmium are also known.
Types of P-Cymene
p-Cymene is commonly sold as an industrial raw material substance in reagent products for research and development and in fragrances. As mentioned above, p-Cymene is the most common.
p-Cymene is available as an R&D reagent product in a variety of capacities, including 25 mg, 25 mL, 500 mL, 1 kg, 8 kg, and 20 kg. Typically, these reagent products can be handled at room temperature.
Some reagent manufacturers offer o-Cymene and m-Cymene, but in small quantities of only a few hundred milligrams, and the price is also effective. As an industrial raw material, it is offered in units of 100 g, 1 kg, 25 kg, etc., and may also be customized to meet other demands.
Other Information on P-Cymene
1. P-Cymene Synthesis
p-Cymene is industrially produced by dehydrogenation of α-pinene with iodine (I2) or phosphorus trichloride (PCl3) or by the Friedel-Crafts alkylation reaction of toluene and propene.