EXPERIMENTS
All experiments must be conducted in a well equipped laboratory and supervised by a qualified chemist.Preparative organic chemistry generally follows the scheme
- Reaction
- Removing inorganic chemicals present. If acid or base is used, first neutralise the system and wash with water.
- Isolation. Extraction or distillation.
- Drying if water is present. This is normally done with anhydrous calcium sulphate, anhydrous magnesium sulphate, or molecular sieve. The wet organic liquid is turbid while the dry organic liquid is clear.
- Purification. Distillation if it is liquid and recrystalisation if it is a solid.
- Weigh to determine the yield.
- Determine the boiling point if it is a liquid and the melting point if it is a solid.
The last three steps will be known here as PWD (purify, weight, determine boiling or melting point) in this write up. DWD is for − distill, weight, determine boiling or melting point − in this write up. These terms are not used anywhere else. Note that the weight and volume measurement for the reagents and products need not be precise in preparative chemistry, as they do not help in understanding the chemistry. A rough balance and a measuring cylinder can be used. The only measurement that must be precise is the determination of melting or boiling point as this will indicate the compound prepared and its purity.
ALL ORGANIC CHEMICALS MUST BE CLEARLY LABELED AND KEPT AT THE CORRECT TEMPERATURE AND IN A WELL VENTILATED ROOM. STRICTLY NO SMOKING PLEASE.
DO NOT DISCARD ANY WASTES INTO THE SINK. PLACE THE WASTE IN THE CORRECT BOTTLE AND LABELED IT - ACID, BASE, ORGANIC, INORGANIC. FOR THE ORGANICS AND INORGANICS SEPARATE THE "CAT FROM THE MICE".
THE WASTES MUST BE DISPOSED OFF IN THE PROPER MANNER. THE FIRST CONSIDERATION IS TO RECYCLE THEM, ESPECIALLY THE SOLVENT WASTES. SO HAVE INDIVIDUAL BOTTLE FOR MAJOR SOLVENTS USED IN THE LAB, AND RECOVER THEM.
OPEN A BOTTLE OF CHEMICAL IN A FUMEHOOD. THERE WILL ALWAYS BE A BUILT−UP OF VAPOUR AND IT CAN HIT YOU RIGHT IN THE FACE. CARELESS CHEMIST WILL NOT LIVE LONG TO TELL THE STORY.
CHECK THE LAB FOR "BOMBS" (CHEMICALS NO LONGER NEEDED) AFTER EVERY REACTION. RETURN THEM TO THE STORE FOR SAFE KEEPING.
All experiments posted here are general outlines to help chemistry teachers improve the teaching of chemistry. It is too vague for students to attempt to do the experiments by themselves. Chemistry experiments are hazardous if not conducted with sufficient understanding. They are many hidden factors only a well trained chemist can appreciate.
