4-Chloro-2-methylphenol

Chemical Properties

Off-white to slightly brownish crystalline solid

Uses

4-Chloro-2-methylphenol is a transformation/degredation product of herbicides found in the environment through landfills and runoff.

Definition

ChEBI: 4-chloro-2-methylphenol is a member of the class of phenols that is o-cresol in which the hydrogen para to the hydroxy group is replaced by a chlorine. It is a member of phenols and a member of monochlorobenzenes. It is functionally related to an o-cresol.

Application

4-Chloro-2-methylphenol is an important pharmaceutical intermediate ingredient used in the manufacture of herbicides (Mecoprop, MCPA, and MCPB), as an additive tracer for resist plasma etching. It is used as a closed system intermediate in the production of phenoxy herbicides. It is also used as a disinfectant or bactericide.

Synthesis Reference(s)

Tetrahedron Letters, 30, p. 5215, 1989 DOI: 10.1016/S0040-4039(01)93745-1

General Description

Dark red flakes with waxy texture. Insoluble in water.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

4-Chloro-2-methylphenol can react vigorously with concentrated sodium hydroxide solutions. Also reacts with other bases, acid chlorides, acid anhydrides, and oxidizing agents. Corrodes steel, brass, copper and copper alloys [NTP, 1992)]. A large quantity left in contact with concentrated sodium hydroxide solution for 3 days reacted violently, attaining red heat and evolving fumes that ignited explosively. The heat of reaction dissipated poorly because of the high viscosity of the mixture [Quart. Safety Summ., 1957, 28, 39].

Fire Hazard

4-Chloro-2-methylphenol is probably combustible.

Flammability and Explosibility

Non flammable

Synthesis

GENERAL STEPS: After the oven-dried Schlenk flask was cooled to room temperature, 2-methyl-4-chlorophenylboronic acid (1 mmol), acetonitrile (3.0 mL), and silicon chloride (0.5 mmol) were added sequentially. Subsequently, the reaction was activated by the addition of 30% H2O2 (1.0 eq.) and the reaction mixture was stirred at 30-35 °C for the time referred to in Table 5.The reaction progress was monitored by thin layer chromatography (TLC). After complete conversion of the feedstock, the reaction mixture was filtered to remove silica gel. The reaction mixture was neutralized with 5% NaHCO3 solution (5 mL), followed by extraction of the product with ethyl acetate (30 mL) and washing the organic phase with distilled water (10 mL). The organic extract was dried with anhydrous Na2SO4 and concentrated under reduced pressure to remove the solvent. The resulting crude product was purified by silica gel column chromatography with the eluent being a solvent mixture of hexane and ethyl acetate to give purified 4-chloro-2-methylphenol. The structure of the product was confirmed by gas chromatography-mass spectrometry (GC-MS), melting point determination (M.P.) and 1H nuclear magnetic resonance (1H NMR) spectroscopic techniques.

Purification Methods

Purify the phenol by crystallisation from pet ether (m 51o) and by zone melting. [Beilstein 6 H 359, 6 I 174, 6 II 332, 6 III 1264, 6 IV 1987.]

References

[1] Tetrahedron Letters, 2017, vol. 58, # 33, p. 3323 - 3326
[2] Organic Letters, 2012, vol. 14, # 13, p. 3494 - 3497