PROCEDURE TO DO Weigh benzoic acid and biphenyl isolated from last day and recor

Question

PROCEDURE TO DO Weigh benzoic acid and biphenyl isolated from last day and record the masses in the raw data from last day Determine experimental melting points of benzoic acid and biphenyl samples and record the melting points in the raw data from last day Dispose of benzoic acid and biphenyl samples in appropriate dump bottles . Caution: The next three experiments make use of concentrated sulfuric acid (18 molL), which is one of the more dangerous concentrated acids. All concentrated acids, particularly conc. sulfuric acid, will burn the skin. Handle them carefully (wear gloves) and wash up immediately if you spill any on your hands. NOTE: Wash the graduated cylinder used to obtain the acid (with cold water) to remove all traces of sulfuric acid. Place 60 mL of absolute ethanol (density 0.789 gmL) in a dry Erlenmeyer flask and add carefully, with stirring, 4 mL of concentrated (18 m suluric acid. Place 3.2 g of 4-aminobenzoic acid into a dry 250 mL round-bottom flask. Add the solution of ethanol and sulfuric acid to the RBF along with boiling stones and a magnetic stir bar. Clamp the RBF over a heating mantle on top of a magnetic stir plate. Attach a reflux condenser (see the figure in the apparatus appendix) and reflux (at ~90 %) until the last of the solid has dissolved. Convert the reflux apparatus into a distillation stones and distil receiving flask. Add new boiling apparatus using a 50 mL round bottom flask as the approximately 40 mL of ethanol from the mixture into a 50 mL round bottom flask. Cool the round bottom flask containing the residue in cold water and pour it into a 1 L beaker containing about 40 mL of cold water. Rinse the flask with 100 mL of cold water and add the washings to the 1 L beaker. Remove the stir bar from the sample and returm it to the front. Neutralize the solution in the beaker with 2 mol-L sodium carbonate solution and check the pH with full range pH paper. Add the sodium carbonate cautiously to avoid excessive foaming, and stir well before checking the pH especially near neutral pH (It is necessary to stir vigorously before attempting to determine the pH of the solution in order to get an accurate determination of pH). Do not add an excess of sodium carbonate; if you do, consult an instructor immediately, otherwise product loss may result. Collect the crude product by suction filtration. Cold water may be used to rinse the product from the beaker and to

Explanation / Answer

1. The above reaction would not had been successful if 95% ethanol was used instead of absolute ethanol because the product formed would not have recrystallized out of the solution due to excessive dilution with water of the system. Also the solubility of the starting material would have been affected in the first step. Overall reducing the yield of the reaction.

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