[AWK]

The extent of elimination depends on temperature. For ether synthesis you should use a quite specified temperature within range 10 C. When you incerease temperature by 30 C, only elimination of water take place.

[xc]

Hi AWK

Concerning the temperature, I don't know if you are talking about the Williamson's synthesis (S_N2 substitution with an alcoxide) or the acid-catalyzed condensation. In this last case, the temperature is usually high (130 - 150 ºC) without significant elimination. Over 150 ºC elimination starts to be significant.

I've just discovered this is not the first time that this reaction is discussed here!http://www.chemicalforums.com/index.php?board=3;action=display;threadid=1460

[evil_lurker_reloaded]

Ether is a rather easy chemical to synth.

Take a 3 neck 1000ml flask, rig up for fractional distillation. On one of the side necks, put a thermometer adapter, on the other a 500ml or so addition funnel.

Now charge the funnel with 250ml of everclear pure grain alcohol and slowly add it to 250ml 98% H2SO4 (careful, it gets very hot). Fill the funnel up again to 500ml.

Ok, now start heating and magnetic stirring. At around 115ºC, ether will begin form and will start to come over. Don't worry about the temp at the top of the distillation three way adapter, the Et2O has an insane partial vapor pressure and will physically push itself over even though it is below its boiling point.

Start dripping in the EtOH at this point (on the surface), as fast as you can without the top of the very top 3" or so of the column becoming too warm to comfortably handle. The EtOH will reflux back down into the flask where it is again subject to dehydration. It helps a lot speedwise to put a fan on the column, and to use a longer column (say 400-500mm in length).

When the production starts to slack off, crank up the heat a little bit, say for every 100ml added about 5ºC.

The trick is to keep the top of the column cool enough so that the alcohol will reflux back down... the proper drip rate is 1-2 drops per second or thereabouts. Sounds complicated but after one does a run or two its fairly easy.. try and keep the amount of alcohol going in the same as the ether going out.

Yields average around 500ml of isolated either per 750ml bottle in 4-6 hours depending on the skill of the operator and the efficiancy of the cooling equipment in preventing the ether from re-evaporating out of the recieving flask's vacuum adapter.

Wash with a little NaOH (to remove sulfur compounds)followed by another wash of saturated CaCl solution (to remove any alcohol... CaCl forms the addition product), and finally dry with CaCl and redistill.