Practical techniques

Refluxing is a techniques used in organic synthesis to produce carboxylic acid and ketones. 

1. Clamp the flask upright by its neck.

2. Add bumping granules to the reaction mixture so it will boil smoothly.

3- Apply grease to to the ground glass joint on the condenser and attach the flask to the joint.

4- Heat the flask.

5- Pass water through the rubber tubing and the condenser.

Notes-

Do not put the stopper on the top of the condenser as pressure will increase in the system possible causing an appertus explosion.

Clamp the condenser gently as the condenser is fragile and could break.

Distillation is used to produce aldehydes from primary alcohols.

1. Flask is clamped by its neck and the still head is connected to a flask. The still head adaptor has two ground glass joints, one to fit to the condenser.

2. The receiver is also clamped at the point where it attaches to the condenser.

3. Rubber tubing is connected to the tap and condenser inlet and the other is attached to an inlet and the outlet rests in the sink to pass water into.

4.The flask is heated and the mixture will boil. Different liquids in mixtures will have different boiling points.

5. Liquids with the lowest boiling point is the most volitle and will boil off first.

6. Vapour moves out of the flask and condenses in the condenser to liquid which drips into the collecting flask.

This technique is used separate different organic liquids.

1. Ensure the top of the separating funnel is closed.

2. Pour the mixture of liquids into the separating funnel. Place a stopper in the top of the funnel and invert to mix the contents.

3.Let the layers settle and add water to see which layer increases in volume ( aqeous layer).

4. Place a conical flask under the separating funnel and remove the stopper and open the tap until the whole lower layr has left the funnel.

5.Collect the other fluid in another conical flask.

6. Label the flasks so that you do not confuse them.

Drying agents are used to take up water to become hydrated.

1. Add organic liquid to the conical flask.

2. Add  a drying agent to the liquid and swirl the contents to mix together.

3. Place stopper on the flask to prevent the product from evapourating wave and leave for 10 minutes.

4. If the solid has stuck together in a lump there is still some water present. Add more drying agent until the solid is disperesed in a solution as fine powder.

5. Decant the liquid from the solid into another flask. If the liquid id dry it should be clear.

This technique is used to separate a solid from a liquid reaction mixture.

1- using pressure tubing connect one end of the tube to the vacuum outlet and attach the other end to the rubber tubing of the buchner flask.

2- Using a rubber bung to attach the pressure tubing to ensure that it makes a tight seal.

3- Switch on the vacuum pump and place a piece of filter paper inside the buchner flask and wet it with the same solvent that you used in the reaction mixture.

4-  Pour the mixture containing a solid and liquid into a buchner funnel containing filter paper.

5- The reduced pressure in the flask forces the liquid through the funnel, leaving the solid on the filter paper.

6- Rinse the crytals in the funnel with the solvent and let it dry still under reduced pressure.

This technique is used to purify a solid product.

1- Dissolve the solid in the minimum amount of hot solvent.

2- Filter through fluted filter paper to remove insoluable impurities.

3- Allow it to cool slowly and form crystals the soluble impurities stay in solution.

4- Filter it under reduced pressure to remove soluble impurities

5- Wash the crytals with ice cold solvent and allow to dry

The solvent must be carefully chosen so that the solid is very soluable when the solvent is hot but nearly insoluable when its cold..

This is used to ascertain the purity of a sample ( impurites lower the melting point and increases the temperature range over which a solid melts).

1- Seal over one end of the capillary tube and add the powder sample to the none sealed end.

2- Place the sample into the melting point apperatus and slowly raise the temperature.

3- Record the temperature when the solid starts to melt and when its completely melted.

4-  Compare the temperature range to a range in the  a reference book.

Alternatively a oil bath or thiele tube can be used which involves inserting a thermometer through a cork  and using a micro burner slowly heat the side arm of the thiele tube to record a range of temperatures.