subsecret - 9-8-2014 at 21:52
Warning: I am simply submitting this procedure to gather advice on whether or not it is feasible. If you are interested in a tested procedure, don't
let me waste your time.
It is known that 2-chloropropane can be produced via an SN1 reaction, when isopropanol and hydrochloric acid are combined. First, the alcohol is
protonated by the HCl, which causes H2O to leave the molecule, leaving a secondary propyl carbocation. Next, the chloride ion attacks the carbocation,
forming 2-chloropropane.
My goal (if the procedure is deemed feasible) is to produce isopropyl chloride via a one-pot distillation.
First Procedure:
1) 100 ml (1.3078 moles) of anhydrous isopropanol are placed into a 500 ml, 2-neck RBF.
2) 152 ml of 31.45% hydrochloric acid (contains 1.3078 moles HCl) is added to the flask, and a distillation apparatus is arranged. A thermometer is
placed into the second neck of the flask.
3) The flask is heated to approximately 36oC, which is enough to allow the 2-chloropropane to distill off as it's formed. Higher
temperatures could be used, but lower ones are favored in order to keep HCl in solution. The 2-chloropropane will not be produced immediately, so the
flask should be kept at 36oC (or slightly above) until distillation begins.
4) Distillation should be continued until the temperature begins to climb to 50oC and beyond, indicating the evaporation of the
isopropanol.
That procedure would be inefficient, however, as significant amounts of water are already brought into the reaction by the HCl solution. It could
still be used by chemists who don't have access to equipment to generate HCl gas. Here's a procedure using HCl gas and anhydrous isopropanol:
Second Procedure:
1) Again, 100 ml of dry isopropanol are placed into 250 ml, 2 neck RBF. A gas generator is assembled, which will produce HCl gas (NaCl + H2SO4). The
output of the HCl generator is connected to a glass tube, which runs to the bottom of the flask containing the isopropanol.
2) As before, a distillation apparatus is assembled from the second neck of the reaction flask.
3) The isopropanol is heated to about 36oC, and HCl gas is slowly fed into the reaction flask. Distillation continues until stillhead
temperature begins to increase significantly.
Both procedures produce somewhat pure 2-chloropropane, which could be dried with CaCl2 and distilled.
[Edited on 10-8-2014 by Awesomeness]
Waffles SS - 9-8-2014 at 22:01
I got better yield when i used Lucas' reagent.Have you ever tried it?
macckone - 9-8-2014 at 23:38
You may want to consider adding zinc chloride as a catalyst.