Author Topic: SiCl4 / Ph(COCl)x way to acid chlorides + anhyd.  (Read 5648 times)

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SiCl4 / Ph(COCl)x way to acid chlorides + anhyd.
« on: May 13, 2004, 12:19:00 AM »
J.Am.Chem.Soc 115,2.1993;531
propionyl chloride
A flame dried 50ml 1-neck round-bottom flask charged with 1.03g (10.4mmol) of sodium propionate and 2.1ml (14.5 mmol) of phtaloyl dichloride was connected through a bent glass tube to a 2-neck  receiving flask in a dry ice / acetone bath. The reaction mixture was maintained at 150°C with magnetic stirring for 1.5 h. Propionyl chloride was allowed to distill into the receiving flask as it was formed (87%). The product was used immediately in the next step.

preparation of phtaloyl dichloride

Patent US2051096

(phtalic anhydride + CCl4 or CHCl3, caution: COCl2 forms)

JACS 60.1938;1325
preparation of acetyl / propionyl chloride w/benzoyl chloride
really cool article, too tired to type.

preparation of benzoyl chloride:
Justus Liebigs Ann. Chem.; 109; 1859; 256 - from benzoic acid w/ K2S2O7 / NaCl
Justus Liebigs Ann. Chem.; 118; 1861; 304 - from the anhydride w/ HCl&nbsp
C.R.Hebd.Seances Acad.Sci.; 68; 1869; 1559; CHBEAM; Chem.Ber.; 2; 1869; 80 w/ P2O5 / HCl

JACS - 49.1927;2114
preparation of acetyl chloride
360g (6 mol) of GAA and 672g (6 mol) of toluene are placed in a liter, round-bottomed,Pyrex flask fitted with a rubber stopper through which was passed a dropping funnel and a reflux condenser. The upper portion of the latter is filled with glass beads and the condenser itself is, in turn, connected to an absorption system consisting of two wash bottles containing acetic acid. The mixture is heated to 50°C andat  that temperature 510g (3 mol) of SiCl4 is added from the dropping funnel during a period of 30 min. The same temperature is maintained until the vigorous evolution of HCl almost ceases. The upright condenser is the replaced by a Glinsky or Hempel column carrying a thermometer and attached to a downward condenser, and the product fractionated over a free flame until the thermometer registers 80-85°C. The product on redistillation gives 400g of acetyl chloride, b.p. 50 - 55°C; yield 85%.

The same method was applied to the other acids, the only difference being the us of other diluting media and a somewhat higher temperature, prior to fractionation, to ensure the completeness of the reaction. 148g of propionic acid in 212g xylene with 170g SiCl4 at 50°C gave 93g propionyl chloride, 50%.

This should be tried on TsOH, too !

synthesis of acetic anhydride
The same reagent (SiCl4) can also be used for the preparation of acid anhydrides from the sodium salts of the corresponding acid using a diluent, preferably the anhydride itself. In the following experiment acetic anhydride itself was used as diluent. 130g of anhydrous NaOAc and 300g of 99% Ac2O were warmed to 50°C and, while stirring , 67g of SiCl4 was added during a period of one hour. The temperature rose to 80°C and the heating was continued for three hours at 90°C. The yield was 75% of 96% anhydride. A second experiment carried out in glassware, using benzene as diluent and heating for 5h at 50-60°C, gave a yield of 50%.