Organic Chemistry Liquid Liquid Extraction Experiment

Procedure Weigh a sample of benzoic acid and a sample of 3-aminoacetophenone into a tared 100 mL beaker. Each sample should be approximately 0.5g but be sure to record all decimal places from the balance. Dissolve the mixture of solids in approximately 25 mL of ether or CH2Cl2, whichever is available. Transfer the solution to a separatory funnel and extract with two separate 25-mL portions of 5% sodium hydroxide. Collect the aqueous extracts in one flask and slowly add 1M HCl until the pH is 2 or lower. Add the HCl slowly, but realize that you may need to add as much as 60 mL to get to pH2. Cool the mixture in an ice bath, collect the solid by vacuum filtration, wash with cold water, and dry to constant mass. Transfer the organic layer to a tared filter flask (a filter flask whose mass you have measured) and gently remove the ether solvent by evaporation. Gently warm the flask on a hot plate and swirl to prevent “bumping”. Determine the mass of the flask after the solvent has evaporated (and only the desired compound remains). Using the original mass of each component, calculate your percent recovery for each component. Notes: Once the NaOH solution is added to the separatory funnel, two layers will form since water and organic solvents such as ether and CH2Cl2 are immiscible. The more dense liquid (water or organic solvent) will be the bottom layer.  You must know which layer is on top and which is on the bottom.  Also, you need to know what substance is dissolved in each layer. With this information, you can keep track of the two dissolved components once the layers are separated. Note that most of the aqueous solutions used in lab are dilute enough to have the same density as pure water. A carboxylic acid is often extracted with aqueous sodium bicarbonate NaHCO3 (aq). When bicarbonate reacts with the carboxylic acid, CO2 gas is produced. Take care not to stopper the separatory funnel until the fizzing subsides. Use a stir rod to promote degassing, then stopper and shake gently. A safe operation is to stopper the funnel, invert once then open the stopcock to release pressure. Do this several times until most of the gas is dispelled from the funnel. Then you can vigorously shake the funnel to mix layers thoroughly and separate the layers.

Questions for Data Analysis & Results

1. Calculate the percent recovery for each compound (benzoic acid and 3-aminoacetophenone). Also, comment on any melting point and IR data that you obtained.

Data available:

25ml of NaOH and 25ml of dichloromethane

0.5g benzoic acid and 3-aminoacetophenone

aqueous 0.247

organic 11.136g

HCl (aq)=0.247g

Just tell the method on how to do it