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How is the peroxide in Tetrahydrofuran(THF) produced and removed - part 2

Views: 0     Author: Site Editor     Publish Time: 2022-04-29      Origin: Site

Preparation of anhydrous toluene, anhydrous Tetrahydrofuran and anhydrous dioxane

Reagents required: sodium (except water), benzophenone (indicator, which appears blue in absolute anhydrous conditions).

Dosage: 1000ml of solvent needs up to 10 grams of sodium, benzophenone needs about 5 grams.

Operation: Dry, cool, and set aside the required equipment (usually: 1000ml round bottom bottle, ball condensing tube, straightTHF cost - YuanfarChemicals condensing tube, tail nozzles, triangular bottle, tee, glass plug). Toluene and benzophenone are added to the round bottom bottle, and the sodium block is added with tweezers, and the kerosene on the surface of the sodium block is wiped by cotton. Then the sodium is cut into small pieces with scissors, and added to toluene through the feeding funnel. Then set up the device, the air in the device is replaced with nitrogen, including the receiving bottle, heated reflux 2 ~ 3h, reflux blue, slightly cold (no reflux can be), instead of distillation device, with a small amount of the former fraction, collect the needed part. Stop post-heat treatment when the liquid in the round-bottomed flask remains about 50mL: Add anhydrous ethanol to the remaining sodium balls in the round-bottomed flask and stir at room temperature until they decompose completely. Pour into the waste liquid bottle.  

Note: THF must not be dried, it will produce peroxide, easy to explode!

Preparation of anhydrous DMF (N, N-dimethylformamide) 

DMF was dried with anhydrous magnesium sulfate one day in advance (25g/L); Will need the device (usually required: 1000ml round bottom bottle, straight condensate pipe, tail pipe, triangle bottle, tee, glass plug, water pump), drying, cooling, set aside. Add dried DMF to round bottle. then set up the unit and check the tightness of the unit with a nitrogen ball. Then 60℃-70℃ vacuum distillation followed by a small amount of the front fraction, collection of the required part.

Preparation of anhydrous dichloromethane

(1) Calcium hydroxide: in addition to water;

Usage: 50 g/L

Operation: after 3-4 hours of reflux, distillation, 4A molecular sieve preservation.

Post-treatment: The remaining CaH2 in a round-bottom flask is stirred with anhydrous ethanol at room temperature until it is completely decomposed. Pour into the waste liquid bottle.

② Anhydrous calcium chloride, molecular sieve;

Operation: Room temperature agitation overnight, distillation out with molecular sieve preservation

Preparation of anhydrous ether

Sodium: dry;

Dosage: 7-8g /500mL

Operation: Cut the sodium into small pieces to dry for 24 hours, and then use it. The 500mL reagent bottle is sealed with 19# rubber plug, and the deflated balloon is inserted.

Note: the temperature should not be too high, not more than 30℃; Ether left too long cannot be heated because it contains peroxide and tends to explode.

Preparation of anhydrous methanol and ethanol

Less than 1% can be dried with 4A molecular sieve;

Anhydrous calcium sulfate is heated, reflow and distilled.

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