Previous Chapter - 1.7 Locating Reagents (PLANNING)

 

2. REACTION

2.1 General approach

2.1.1 Step by Step

  1. Locate a clean, dry flask, a stir bar, a septum and any other apparatus necessary for the procedure. Calculate the total mL of solution, and use a flask with at least twice that capacity.
  2. If the reaction is moisture or air sensitive, oven- or flame-dry the flask and prepare to run the experiment under an inert atmosphere.
  3. Purify your reagents and solvents, if necessary.
  4. Locate syringes and needles of appropriate size, if necessary.
  5. Weigh your reactants, into your reaction flask, onto weighing paper, or into a separate flask (a pointy flask is useful for reagents that will be added in solvent). Consult your procedure to see what is necessary. Do not mix anything yet, and do not weigh sensitive reagents until just before use.

2.1.2 Rookie Mistakes

2.1.3 Tips

General:

Stirring:

If stirring stops during a reaction, all bets are off. It is very important to stir continuously throughout an experiment. If your reaction is heterogeneous, it must be stirred very vigorously to ensure efficient mixing.

Stir Bars:

Overhead Stirring:

When a stirbar simply does not do the job, mechanical stirring is necessary. An overhead stirring apparatus is typically employed. Situations when overhead stirring may be required: high viscosity solutions, large scale reactions, or in heterogeneous reactions when a stirbar becomes mired in gunky, gooey, or otherwise insoluble material.

2.1.4 Notes

Temperature Control: Resources

Synthetic organic experiments are conducted at temperatures ranging from -90 degrees to 200 degrees Celsius. It is important to know how to achieve and maintain the correct temperature for a reaction, especially over long time periods. Temperature should be monitored with a low-temperature alcohol thermometer.

Low Temperature Cooling Baths

High Temperature Reactions

 

Next - 2.2 Setting up the reaction