| 摘要 |
#CMT# #/CMT# Preparation of pure, halogen-free O-phthalaldehyde (OPA) involves hydrolyzing tetrahalo-o-xylene at 155 - 160[deg]C and at a pressure of 2 - 5 bar in presence of phase-transfer catalyst to form o-phthalaldehyde, which is converted in an acidic alcoholic solution at 0 to reflux temperature into corresponding dialkoxyphthalane and, subsequently an acetal cleavage is effected by acid hydrolysis at a pH of 1.5 - 7, resulting in high-purity, halogen-free o-phthalaldehyde. #CMT#USE : #/CMT# For the preparation of O-phthalaldehyde (claimed) useful as intermediate for preparing dyes, optical brighteners or specific polymers, in the biocide or photographic industry, and for synthesizing pharmaceutical chemicals. #CMT#ADVANTAGE : #/CMT# The improved process prepares high purity, halogen free o-phthalaldehyde (OPA). The OPA is obtained in very high, halogen-free quality (greater than 99.5 GC area %) and in very high yield of up to over 92% by the purification process. The pure OPA exhibits a constant color, and no decolorization using Tonsil or carbon is necessary. In addition, the process avoids losses of yield of OPA. The reaction time is shortened by comparison with the prior art. #CMT#ORGANIC CHEMISTRY : #/CMT# Preferred Process: The hydrolyzing of tetrahalo-o-xylene is carried out in 1-4C carboxylic acid in presence of base and water. The conversion of o-phthalaldehyde to corresponding dialkoxyphthalane takes place at a pH of 0 - 3. The cleavage of acetal takes place at a pH of 1.6 - 2.5. Preferred Components: The amount of carboxylic acid used is 4 - 20 mol. eq, based on tetrahalo-O-xylene. #CMT#EXAMPLE : #/CMT# Tetrachloro-o-xylene (TCX) (61 g) (purity 99%) was introduced into an autoclave, and acetic acid (300 g) was added. A solution of sodium hydroxide (44 g) and deionized water (198 g) was added, and the mixture was heated to 160[deg]C and at a pressure of 3.8 - 3.9 bar for 1 hour. It was cooled to 40[deg]C and the autoclave was emptied to give a crude o-phthalaldehyde (OPA) solution. The crude OPA solution (606 g) was first mixed with deionized water (50 ml) and extracted with tert-butylmethyl ether (MTBE) (93 g). After work-up, residue (54 g) obtained from evaporation was mixed with methanol (375 ml), and concentrated sulfuric acid (2 ml) was added to adjust to pH 0.5. After 2 hours at 50[deg]C, 50% strength sodium hydroxide (10 ml) was added. After work-up, a crude acetal (42.4 g) was obtained. The crude acetal was distilled at a bath temperature of 135 - 140[deg]C, bottom temperature of 113 - 114[deg]C and overhead temperature of 110 - 111[deg]C and a pressure of 8 - 10 mbar, to give an o-phthalaldehyde (OPA) dimethoxy acetal (41.2 g). The o-phthalaldehyde (OPA) dimethoxy acetal (200 g) was added to deionized water (500 g), which was adjusted to pH 2.0 with sulfuric acid, and the pressure was reduced to 150 mbar. After work-up, and addition of diisopropyl ether (DIPE) (500 ml), the OPA was extracted at 50[deg]C. After work-up, a high-purity, halogen-free O-phthalaldehyde (greater than 99.8%) was obtained. |
