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Molecular formula : C7H6O2
MW : No. # 122.12
CAS-08-0
nature : colorless crystalline powder. 115-116 ° C melting point, the relative density of 1.129 (30 / 4 ° C). In the air easily sublimated. Soluble in ethanol, ethyl ether, acetone, ethyl acetate, slightly soluble in water (30.5 ° C in the water solubility of 1.38g/100ml), soluble in benzene (at 65 ° C for benzene solubility 3.68g/ml). There aromatic odor.
Preparation Methods : HYDROXYBENZALDEHYDE the production of a number of routes, mainly industrial production of phenol, cresol, dinitrotoluene and other raw material routes. 1. France phenol phenol Act is divided into Reimer - Tiemann reaction, Gattermann reaction, phenol - chloroform line acetaldehyde, phenol-line acid, phenol - formaldehyde routes of synthesis of a variety of routes. Phenol Act process is characterized by easy to get raw materials, manufacturing technology is relatively simple, but low yield, the higher the cost. (1) Reimer - Tiemann reaction of phenol and chloroform in alkaline aqueous solution at 60-100 ° C reaction by heating 2-4h, while creating ,1,4 and neighbors hydroxybenzaldehyde (commonly called salicylaldehyde), the total yield was about 50%, the highest yield HYDROXYBENZALDEHYDE only 17%. This process is mainly used synthetic salicylaldehyde, right hydroxybenzaldehyde as a by-product, but it is the main process of production method. This process is the conversion of raw materials and product yields are very low, there are a lot of tar produced. Chloroform necessary excessive, the reaction of phenol not difficult recovery, product separation and purification difficulties. Therefore, we must vigorously develop new efficient catalysts, improving the selectivity of reaction, to develop simple and efficient separation and purification products, in order to reduce costs, improve product yield. (2) Gattermann reaction of phenol and HCN, in the presence of AlCl3, which leads to dry HCl, catalytic reaction, and the ice water decomposition been ,1,4, product yield is higher. Using HCN replace zinc cyanide, the yield is almost theoretical capacity. This selective high technology products, but the drawback First cyanide toxicity, the most technically demanding, difficult; 2 is due anhydrous operation, demanding reaction equipment, the high cost; Third, it is accompanied by a small number have salicylaldehyde, product purification difficulties, thus limiting mass production . 2. Right nitrotoluene Act of nitrotoluene production ,1,4 process of oxidation - reduction, and diazotization step for hydrolysis. (1) of dinitrotoluene redox pair of dinitrotoluene simultaneously using multiple sodium sulfide oxidation and reduction, to be p. Specific process : will nitrotoluene, ethanol solvent and surfactant (OP Twain, etc.) than by the quality of 1:5:0.02-0.04 evenly mixed, 80-85 ° C 71/92 sodium polysulfide solution, the reaction of 2-3h. Water steam distillation products, except for dinitrotoluene and amino toluene. The use of ether extraction in p. The conversion rate and the yield is above 90%. Polysulfide available sulfur sodium hydride, sodium and sulfur in the system for raw materials. (2) hydrolysis and will diazotization p 40% sulfuric acid, in the 0-3 ° C by adding 30% sodium nitrite solution, the reaction around 30 minutes, with a small amount of urea decomposition excessive sodium nitrite, to be p diazonium salt solution. This solution in the presence of sulfuric acid hydrolysis, temperature 80-85 ° C for 30 minutes, or so. The product extraction, purification, drying ,1,4 products, the yield of over 90%. This process has the advantage of cheap raw materials prices, but the drawback is the length of routes, equipment, the very large intermediate product of p toxic, diazotization low reaction temperature, high-frozen conditions. The current domestic Qixian County Fine Chemical Plant in Shanxi used for the production of hydroxybenzaldehyde. 3. Right cresol catalytic oxidation process is in the role of catalyst, using air or oxygen direct oxidation of cresol Synthesis of hydroxybenzaldehyde. 1980s of the 20th century, Japan, the United States, Germany and other routes this process conducted in-depth studies and reports. The late 1980s and early 1990s, the domestic Jiangsu, Shanghai, Dalian to several research and production units have this technology for research and development, and its industrial production. The specific process : will cresol and sodium hydroxide, methanol by adding stainless steel pressure vessel, stirring until completely dissolved, will join Cobalt Acetate sealed reactor, heating to 55 ° C to start the oxygen, so the pressure within the reactor in response to 1.5MPa conditions 8-10h, reaction strict control of the process oxygen rate, the vessel was equipped with a cooling system, when the reaction temperature can reach the reactor jacket cooling water, this time within the coil start the cooling water, strictly control the total oxygen, and keep the reactor temperature within 60 hours. Reaction materials at the end of the beginning of steaming kettle Add steamed, and to recycle solvent methanol and water after hydrochloric acid solution for salting out. Solid and liquid materials used to filter centrifuge, the solid obtained Add vacuum oven at 60 ° C dry around 3-5h, and can be content greater than 98% of p-cresol.
purposes : the goods for medicine, spices, the LCD intermediates. Right HYDROXYBENZALDEHYDE used in the production of antibacterial synergist TMP (trimethoprim), Amoxycillin, hydroxyl ammonia benzyl cephaloridine, artificial Tianma, Rhododend, Bezafibrate, esmolol; Fennel used in the production of spices, vanillin, ethyl vanillin, raspberry ketone.
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