principle:
Reagents: 25g (27.5ml, 0.38mol) ethyl acetate, 2.5g (0.11mol) sodium metal, 12.5ml xylene, acetic acid, saturated sodium chloride solution, sodium anhydrous sulfate
Instruments: 100ml round bottom flask, reflux condensate tube, drying tube, dispensing funnel, gram distillation bottle, vacuum distillation device
(Anhydrous drying reflux device; reduced pressure distillation device.) ）
steps:
1． Beat the sodium beads. Quickly cut na into thin slices on a surface dish, immediately place in a reflux bottle with a drying tube (12.5 ml xylene inside), heat and melt it. Shake the mouth of the bottle to make it a sodium bead. Recovery of xylene.
2． Condensation reaction. Quickly add 27.5 ml of ethyl acetate and the reaction begins. If slow, it can be warmed. Reflux for 1.5h until the sodium basically disappears, an orange-red solution is obtained, and sometimes a yellow-white precipitate (all of which are enol salts) is precipitated.
3. Acidification. Add 50% acetic acid until the reaction solution is weakly acidic (solid dissolved).
4. Dispense. The reaction solution is transferred into a dispensing funnel, an equal volume of saturated sodium chloride solution is added, shaken, and left to stand.
5. Dry. The ethyl acetate layer is separated and dried with anhydrous sodium sulfate.
6. Distillation. The water bath distills ethyl acetate, the residue is moved to a 25 ml g distillation bottle, distilled under reduced pressure, and the fractions are collected.
Experimental considerations:
1． This experiment requires anhydrous operation. Pay attention to the safe use of sodium.
2． Playing sodium beads is very critical, sodium beads play well (small), which can not only improve yield, but also shorten the reaction time. The sodium beads must not be stopped during the production process, and should be shaken back and forth, not rotated.
3． When converting ethyl acetate sodium salt with acetate, when the solution has become weakly acidic and there is still a small amount of solids that have not been completely dissolved, a small amount of water can be added to dissolve it. Care should be taken to avoid adding excessive amounts of acetic acid, otherwise it will increase the solubility of the ester in the aqueous layer and reduce the yield. In addition, when the acid is too high, it will promote the production of the by-product "dehydrated acetic acid", thereby reducing the yield.