Recrystallization: Lab Experiment
Chem 21
Fall 2009
Experiment 9 — Recrystallization
_____________________________________________________________________________ Pre-lab preparation. (1) Read the supplemental material from Zubrick, The Organic Chem Lab Survival Manual. (2) Draw the structure of acetanilide and report relevant physical data. Be sure to cite the source of the data. You should be able to figure out what's relevant by reading the procedure. (3) Find and report the boiling points of the solvents you will be using for this experiment. (4) Outline the steps in the recrystallization of acetanilide.
Recrystallization involves dissolving a solid in a solvent and crystallizing it again, taking the opportunity to discard impurities along the way. One normally chooses a solvent in which the solubility increases significantly with temperature. The solid is dissolved in a minimal amount of hot solvent, and the solution is filtered to remove insoluble impurities. Upon cooling the solution, the desired compound crystallizes, leaving soluble impurities in solution. Alternatively, a mixed solvent system can be used to modify the solubility — the key is to get the compound into solution then get it back out of solution. Ideally, one would …show more content…
Now we're going to purify these by recrystallization. So that we have plenty of material to work with we're going to start by consolidating samples with other groups. Get together with two other groups, and combine your three samples of benzoic acid, (separately!) combine your three samples of benzocaine, and combine your three samples of fluorenone. (If you misread this and mix everything together, no worries, you can just repeat the extraction to separate them again.) Now, one group is going to recrystallize the benzoic acid from water, one group is going to recrystallize the benzocaine from ethanol and water, and one group is going to recrystallize the fluorenone from
Fall 2009
Experiment 9 — Recrystallization
_____________________________________________________________________________ Pre-lab preparation. (1) Read the supplemental material from Zubrick, The Organic Chem Lab Survival Manual. (2) Draw the structure of acetanilide and report relevant physical data. Be sure to cite the source of the data. You should be able to figure out what's relevant by reading the procedure. (3) Find and report the boiling points of the solvents you will be using for this experiment. (4) Outline the steps in the recrystallization of acetanilide.
Recrystallization involves dissolving a solid in a solvent and crystallizing it again, taking the opportunity to discard impurities along the way. One normally chooses a solvent in which the solubility increases significantly with temperature. The solid is dissolved in a minimal amount of hot solvent, and the solution is filtered to remove insoluble impurities. Upon cooling the solution, the desired compound crystallizes, leaving soluble impurities in solution. Alternatively, a mixed solvent system can be used to modify the solubility — the key is to get the compound into solution then get it back out of solution. Ideally, one would …show more content…
Now we're going to purify these by recrystallization. So that we have plenty of material to work with we're going to start by consolidating samples with other groups. Get together with two other groups, and combine your three samples of benzoic acid, (separately!) combine your three samples of benzocaine, and combine your three samples of fluorenone. (If you misread this and mix everything together, no worries, you can just repeat the extraction to separate them again.) Now, one group is going to recrystallize the benzoic acid from water, one group is going to recrystallize the benzocaine from ethanol and water, and one group is going to recrystallize the fluorenone from