Organic Chemistry Laboratory RECRYSTALLIZATION The purpose of this experiment is

Question

Organic Chemistry Laboratory RECRYSTALLIZATION The purpose of this experiment is to enable the student to: 1. Learn about the practical and theoretical aspects of the recrystallization 2. Learn how to purify an impure solid by the simple technique of recrystallization, which involves several steps: (a) selecting the ideal solvent to accomplish such a purification. (b) dissolving the compound in the minimum amount of appropriate solvent while "boiling" hot. (c) filtering insoluble impurities while hot (if any are present) (d) crystallizing the purified compound (e) isolating the pure compound by vacuum filtration. (0 air drying pure compound. Figure 1. General Schematic of Recrystallization Process, After Appropriate Solvent Has Been Selected hot solvent paper clip e hot filter insolubls A SI II of hot solvent a si II hot plate A solid compound SI solid soluble impurity II solid insoluble impurity a dissolved compound si dissolved soluble imparity d) crytsallize compound by cooling solution Buchner fanncl watch glass o aspirator f) dry filter flask vacuam filter to solate crystals Pappus and Goicoechca-Pappas 3-1

Explanation / Answer

The purpose of the crystallization is to get pure compound .

1. The selection of the solvents: The compound should be soluble by heating .

2.Depending up on polarity one can select ethanol with various percentage of ethanol

3. Other solvents used ethyl acetate for medium polar compd.

4.DMF is good solvent for polar compounds

5. Mixture of Acetone: Toluene (3:1) is a good solvent for heterocyclic compounds.

6. For less polar compds. n-hexane , ether , benzene, toluene are the good solvents.

Filtration:

Using vacuum filtration with out disturbing the crystals with better quality of filter paper is essential.

Drying: At a suitable temperature below m.p. point temperature is essential . The water can be

removed at 100-110o C.

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.