SYNTHESIS OF TRIETHYL ORTHOFORMATE (Triethoxymethane)

CAUTION: This experiment should be conducted in an efficient fume cupboard.

• Fit a 1500-ml round-bottomed flask with a large double surface reflux condenser. 

• Make sure that the apparatus is thoroughly dry. 

• Place 750 ml of super-dry ethanol and 123 g (82 ml, 1.03 mol) of dry chloroform (CAUTION) in the flask. 

• Add 52 g (2.25 mol) of clean sodium, cut into small pieces, through the condenser in the course of 30 minutes; when the reaction becomes vigorous, cool the outside of the flask by running water from the condenser outlet. 

• When all the sodium has reacted and the mixture has attained room temperature, filter off the sodium chloride through a sintered glass funnel. 

• The filtration apparatus must be thoroughly dry, and a drying tube, filled with granular calcium chloride, should be placed between the filter flask and the pump. 

• Wash the solid on the filter with 50 ml of absolute ethanol and allow the washings to run into the main filtrate. 

• Distil the solution from a water bath through an efficient fractionating column in order to recover the excess of chloroform and most of the alcohol; collect the distillate (about 500 g) (A) in a filter flask protected by a drying tube. 

• Decant the liquid remaining in the flask from a little salt which has separated, and distil it through an all-glass Dufton (or Widmer) column. 

• A fraction (B) of low boiling point passes over first, followed by the triethyl orthoformate at 144-146 °C. The yield is 35 g (23%) but depends somewhat upon the efficiency of the fractionation.

• Carry out a second run with the recovered chloroform-alcohol mixture (A): add 100 g of dry chloroform and sufficient super-dry ethanol (200-250 ml) to give a total volume of 750 ml. 

• Add 52 g of sodium as before. 

• Remove the excess of chloroform and alcohol as before on a water bath through a fractionating column, add the intermediate fraction (B) from the first run, and fractionate again. The yield of product, b.p. 144-146 °C is 45 g (29%), p.m.r. spectrum (CC1 4 , TMS) S 1. 1 9 (t, 9H), 3.52 (q, 6H) and 5.00 (<5, 1 H).