Question

In a lab, we are to draw and carry out a purification scheme for the carboxylic acid product of a Grignard reaction we've performed, in order to then identify the starting material we used using the melting point of our carboxylic acid product.

A flowchart of our purification scheme is required, indicating where all molecules (in their current ionization states) are at each step, ending with the dry carboxylic acid at the end.

Once the dry ice has been thoroughly mixed into the Grignard reagent, add a mixture of 15 g of crushed ice and 5 mL of 6M hydrochloric acid to hydrolyze any unreacted Grignard reagent and protonate the carboxylate product. Isolate the ether layer (which contains your product). At this point it is up to you to devise and carry out a proper purification procedure. SAFETY: NEVER HEAT ETHER DIRECLTY ON A HOT PLATE TO EVAPORATE. Since you will be using the melting point to identify your product, use your Chem 241 lab skills to isolate high-purity product. If your product is wet you should find a way to dry it before taking the melting point.

Answer 1

Answer 2

the best way of purifying carboxylic acid from the reaction mixture is to convert the carboxylic acid into corresponding sodium salt. To do this just add NaHCO3 to the reaction mass , now all carboxylic acid converted to sodium carboxylate(COONa). then add any organic solvent to aqueous layer to remove all other organic impurities. separate the aqueous layer and add conc HCl to protonate COONa to COOH, mostly it will throw out precipitate from aqueous layer filter and dry it to get maximum pure product.