ortho-Cresol, also 2-methylphenol, is an organic compound with the formula CH3C6H4(OH). It is a colourless solid that is widely used intermediate in the production of other chemicals. It is a derivative of phenol, an isomer of p-cresol and m-cresol.

Appearance and properties: Transparent to slightly amber liquid

Density: 1.04

Boiling point: 191oC

Melting point: 30-32oC

Flash point: 81oC

Refractive index: 1.5361

Stability: Stable, but light and air sensitive. Combustible. Incompatible with oxidizing agents, bases.

Storage conditions: the warehouse is ventilated and dry at low temperature, and stored separately from oxidants

Production method

The cresol fraction cut from the phenol oil obtained from coal coking contains o-cresol 6%, m-cresol 49.4%, p-cresol 32.1%, xylenol and a small amount of phenol. The boiling point of o-cresol is 10℃ lower than that of M-cresol and p-cresol, and it is possible to separate it by ordinary distillation column. The o-cresol fraction cut by crude phenol distillation was distilled in a distillation column with no less than 40 theoretical plates, the reflux ratio was 14-15:1, and the cutting range was 188-192℃. The melting point of o-cresol obtained was about 29℃, and the purity was greater than 97%. The main synthesis methods are as follows:

1. Phenol alkylation method is prepared by methylation of phenol and methanol at about 4.14MPa surface pressure and in the presence of aluminum oxide catalyst.

2. O-toluidine method This method is used for reagent production, which is obtained by diazotization and hydrolysis of o-toluidine.

3. Toluene hydroxylation method

4. Add o-toluidine into sulfuric acid solution, stir and cool to obtain o-toluidine sulfate, add ice cubes to cool to 0 ~ 5℃, maintain this temperature range, slowly add saturated sodium nitrite solution while stirring until starch - potassium iodide test paper does not discolor as the reaction end point. The obtained diazo salt is fully mixed with concentrated sulfuric acid, and the stirring is stopped until the reactant reacts violently and then heated by steam until complete hydrolysis. Let the layer stand, take the lower oil, add 5% sodium hydroxide, filter out the insoluble impurities, and then neutralize with 25% sulfuric acid until the ph value is. Stand stratification, take the oil layer, wash it with water twice, the obtained crude product is distilled under vacuum, and the fraction of 74 ~ 75.5℃ is collected at 1333Pa to obtain the finished product.

Use

O-cresol is an important fine chemical intermediate for the synthesis of pesticides, dyes, plastic antioxidants, polymers and spices. In the past few years, there is basically no production equipment for o-cresol in China, and the demand is completely dependent on imports. It is one of the fine intermediates that needs to be developed urgently in China and has broad application prospects.