4-chlorobenzoic acid Synthesis process

4-chlorobenzoic acid Synthesis process

Raw material:

Potassium Permanganate, p-chlorotoluene, industrial grade quaternary ammonium salt A-1, concentrated sulfuric acid, ethanol etc..

Instrument:

JJ-1 timing magnetic stirrer; SHB-3 the use of circulating water pumps, the digital melting point tester, 101A-1 type electrothermal blowing dry box, three neck bottle, condenser, funnel, suction flask, temperature control instrument, beaker.

Analysis method:

Determination of composition of 4-chlorobenzoic acid by infrared spectroscopy and x- ray diffraction instrument.

The experimental scheme:

The amount of catalyst A-1[4], Potassium Permanganate, water with 250 mL three neck bottle, connected according to the experimental set up good experimental instrument, using water bath heating, open at the same time condensation reflux device and agitator. The temperature rises to a certain temperature, 6 mL of toluene chloride was added drop wise three neck bottle (about 5 min), dropping temperature response is about 2 h. The change of temperature and time of three neck bottle purple strained attention during the reaction process.

After the reaction, while it is hot to filter in the funnel, the removal of manganese dioxide reaction precipitation. The filter cake with 100 mL of boiling water for washing 2 times, the washing liquid and filtrate. Such as liquid color is purple, then add a few milliliters of alcohol, heating the Potassium Permanganate decomposition, filtering, washing. The filtrate is concentrated merged to about 100 mL, cooled by adding 1 ∶ 1 sulfuric acid for acidification, immediately appear a lot of white precipitate.

Mixing, placed 20 min after cooling, and then a Buchner funnel cake filtration, washed with distilled water and cold, dry and put into the constant temperature drying box. After drying and weighing, measuring its melting point.

1 Influence Factors of the reaction and discussed

In the experimental process, many influencing factors, catalyst dosage, stirring intensity, reaction temperature, reaction time etc will affect the yield. Below for several main factors were discussed.

Effects of catalyst dosage of 1.1 A-1

In the PTC reaction, mole fraction of PTC reagent is generally 0.5% ~ 10%[5] substrate. Therefore, the effects of amount of catalyst on the reaction.

This column is about 18.970 g reaction Potassium Permanganate, p-chlorotoluene 6 mL, H2O216 mL, catalyst A-1, catalyst A-1, the Potassium Permanganate, water with three neck bottle, at about 80 ℃ into p-chlorotoluene, temperature 90 ℃, reaction at 2 h for reference.

Without catalyst reaction is extremely slow, with the increased dosage of catalyst A-1, 4-chlorobenzoic acid yield was also increased to maximum yield is 1.5, catalyst mL. When the amount of catalyst is close to 1.5 mL, yield increases more slowly, taking into account the cost of the catalyst, and the product cost etc.,

The choice of 1.25 mL was the best dosage.

1.2 effect of the dosage of KMnO4

This column experiments of A-1 1.25 mL, p-chlorotoluene 6 mL, H2O 216 mL, KMnO4 = 15.805 g, 17.284 g, 20.545 g, 23.706 G. At about 80 ℃ into 6 mL p-chlorotoluene, temperature 92 ～ 96 ℃, the Potassium Permanganate fade as a reference.

1.3 effect of reaction time

With the increase of the content of the Potassium Permanganate yield increased gradually, but 20.545 g yield increased speed slow, in order to reduce the cost as much as possible, Potassium Permanganate cannot consume too much, so the same reaction conditions, Potassium Permanganate dosage is 20.545 G.

1.4 effect of reaction temperature

The column experiment Potassium Permanganate 20.545 g, p-chlorotoluene 6mL, catalyst A-1 1.25 mL, water was 216 mL. Temperature control in 94 ℃, addition of chlorine toluene, reaction time was controlled to 1H, fade time, 2 h, 2.5 h, 3 h, 3.5 h.

Temperature has a great effect on the yield of 4-chlorobenzoic acid, at temperatures below 93 ℃, the yield increased with the increase of temperature, this is mainly because the temperature rise, increasing catalyst and reactant ions on the activity of each group, in the two-phase migration faster, increasing collision rate, the yield increased. More than 93 ℃, the yield decreased, mainly because of high temperatures can accelerate the decomposition Potassium Permanganate, for Potassium Permanganate oxidation of toluene chloride quantity is very few, and there will be a lot of side reactions, the higher the temperature electric energy consumption is more, so the temperature should be 93 ℃.

Impact of 1.5 water content

The column experiment Potassium Permanganate dosage is 20.54 g, 6 mL of toluene chloride, catalyst A-1 1.25 mL, water was 216 mL. The temperature was 70 ℃, 80 ℃, 90 ℃, 93 ℃ ~ 92, 95 ~ 96 ℃, 100 ℃. Join the p-chlorotoluene when bath temperature than the need to control the temperature low 10 ℃, reaction time was 2 h.

The yield increased with increasing the amount of water, more than 250 mL, the 4-chlorobenzoic acid yield increase was not obvious, taking into account the cost and impact on the separation of product, water should be controlled at around 250.

Optimization of reaction conditions and results of 1.6

P-chlorotoluene ∶ KMnO4 ∶ catalyst A-1 ∶ H2O ≈ 1 ∶ 2.56 ∶ 0.048 ∶ 278 (molar ratio), reaction temperature 93 ℃, reaction of 2.5 h, results show that the 4-chlorobenzoic and acid yield is 84.38%.

Knot theory

(1) through a series of experiments found that, with Potassium Permanganate synthesis of 4-chlorobenzoic acid and the suitable conditions for using phase transfer catalyst: reactant mole ratio and catalyst for toluene chloride catalyst KMnO4 ∶ A-1 ∶ H2O = 1 ∶ 2.56 ∶ 0.048 ∶ 278, reaction temperature 93 ℃, reaction time 2.5 h.

(2) by the method of preparing p-chlorotoluene acid mild reaction conditions, short reaction time, less corrosion to the apparatus, little environmental pollution, low production cost, simple operation, good industrialized prospect.

The synthesis process for production of more 4-chlorobenzoic acid, such as the need for further understanding, please contact us.