(Ch # 07)
Mr. Wayne Xie
1)To purify samples of organic compounds that are solids at room temperature. 2)To dissociate the impure sample in the minimum amount of an appropriate hot solvent
Chemical Index :
Naphthalene; mp 82 *C
1,4-Dichlorobenzene; mp 56 *C
4-Chloroaniline; mp 68 - 71 *C; pKb 4.15
Ethyl 4-Aminobenzoate; mp 90 *C; pKb 4.92
Partition Coefficient of Benzoic Acid
1) Carefully weigh approximately 100 mg of benzoic acid and place it into the centrifuge tube (or test tube). The dichloromethane addition should be carried out in the hood. Using a 10-mL graduated cylinder, add 2 mL of dichloromethane to the centrifuge tube. Mix until the benzoic acid dissolves.
2) Add 2 mL of water to the benzoic acid dissolved in dichloromethane. Cap the centrifuge tube and shake (or use a Vortex mixer) until the two phases have been thoroughly mixed. Vent the vial (by releasing the cap-seal) and then allow the two layers to separate.
3) With a disposable pipet , carefully remove the entire mixture. Allow the two layers to separate in the pipet. Drain the lower layer dichloromethane from the pipet into a test tube. Discard the pipet containing water. Add a rice sized portion of anhydrous sodium sulfate and shake the mixture. With a new disposable pipet transfer the CH2Cl2 layer into a large pre-weight test tube.
4) Under a hood, evaporate the CH2Cl2 layer by warming the test-tube in a water bath (CAUTION: This evaporation must be done in a fume hood). After the solvent has been completely removed, finalize the drying of the benzoic acid by placing the test tube under vacuum and pre-weigh the dry test-tube containing the residual benzoic acid.
5) Calculate the dichloromethane/water partition coefficient for benzoic acid.
Separation of Neutral and Basic Substances
1) the acid +...