principle:
reagent:
1.8 g (0.08 mol) sodium metal, 10.2 g (10 ml, 0.08 mol) ethyl acetate, 11 g (10 ml, 0.086 mol) benzyl chloride, 25 ml absolute ethanol, 6.3 g (0.33 mol) sodium metabisulfite, sodium hydroxide, hydrochloric acid, 95% ethanol.
instrument:
Three-necked bottle, reflux condenser, drip funnel, dispensing funnel, Brinell funnel, extraction bottle, Erlenmeyer flask
steps:
1． Preparation of 4-phenyl-2-butanone
(1) Preparation of sodium ethanol. In a 250 ml dried three-mouth bottle, add 25 ml of absolute ethanol and fill the upper end of the condensing tube with a calcium chloride drying tube. Add 1.6 g of sodium metal cut into small pieces to the bottle in batches to maintain the solution micro-boiling.
(2) Benzylation reaction. After the metal sodium is finished, add 10ml of ethyl acetate dropwise at room temperature, and continue to stir for 10min after adding. Then slowly add 10 ml of benzyl chloride. It will be added in about 15 minutes. The water bath is heated and refluxed for 1.5h.
(3) Water relieves carboxylation. Slowly add a solution made of 4 g of sodium hydroxide and 30 ml of water to the above solution dropwise. Heated reflux for 2h. Stop heating, cool to below 40 ° C, slowly add about 10 ml of concentrated hydrochloric acid, until the PH is 1-2. Heated reflux for 1h decarboxylation until carbon dioxide-free bubbles escape.
(4) Crude product separation. The water bath distillates in addition to the low boiling point, and the residual distillate is transferred into a separating funnel to separate the reddish-brown organic phase (crude oil) of about 9-10g.
2． Preparation of sodium bisulfite additives
Add the above crude oil and 35 ml, 95% ethanol in a 100 ml Erlenmeyer flask and heat it on a water bath to make an ethanol solution for later use.
Add 6.3 g of sodium metabisulfite and 27.5 ml of water to the three-mouth bottle, heat to about 80 ° C, stir and dissolve using a solid. The ethanol solution of the above crude oil was slowly added from the top of the condensing tube to the three-necked bottle, and the reflux was heated for 15 minutes to obtain a transparent solution. Cool the crystals and filter them to obtain white flake crystals. Further purification can be recrystallized with 70% ethanol.
Experimental considerations
1． Metal sodium is burned and exploded when it meets water, so it should be strictly prevented from contact with water when used, and should be rapid during weighing or slicing to avoid erosion or oxidation of water vapor in the air.
2． When acidification, the acid acceleration should not be too fast to prevent a large amount of carbon dioxide from escaping during acid decomposition and punching.