Refluxing

Refluxing is the technique used to apply energy to a reaction over an extended period of time. Typically during refluxing, vapors of the reactants will be given off. A reflux condenser is used to condense these vapors back into liquid. This drips back into the reaction flask.

 

What equipment to use and how to use it:

In order to properly reflux something, you must obtain the proper equipment to do this effectively.

What you'll need:

 

Heat source and oil bath. The milk jug with the rubber hoses coming out of it is my water source. The milk jug is a resovior and there is a water pump inside it. 3-neck flask with 2 stoppers (You only need one open hole for refluxing, so a 1-neck flask can be used) Reflux Con-Denser

The glycerin used to lubricate the ground glass joints.

 

How to reflux a reaction:

First you must set up your hot plate, ringstand, and metal pot as shown in the picture below

Now fill your pot 3/4ths full of oil (or with water if the reaction doesn't need to get above 90C). Take your flask and suspend it above the oil bath as shown and fill it with the reactants that you want to reflux

If you are using a 3-neck flask, lubricate the two stoppers with glycerin and stopper up the holes on the sides of the flask

Submerge the flask in the oil bath so that the surface of the reactants is below the surface of the oil (if possible), but do not let the flask touch the bottom of the pot.

Take your reflux column and lubricate the male joint with a layer of glycerin. This is how you should lubricate all ground glass joints.

Before Lubrication
After Lubrication

Insert the lubricated male joint into the female joint that has not been covered with a stopper (if using a 3-neck flask), on the flask

Take another clamp and clamp the reflux column, 75% of the way up, to the ringstand to make sure it stays there

Attach the water inlet tube onto the connection at the bottom of the reflux column

Attach the water outlet or water return tube to the top of the column in the same manner as the water inlet tube. You are now ready to begin refluxing.

To begin refluxing, turn on the water so that there is cold water flowing through the coils or the jacket and then turn the heat on high (it will take a while for the oil bath to warm up)

 

For reactions that tell you how long to reflux it for, you must start the timer after you see the first drop drip back into the mixture (after it has become a vapor and then was condensed). The majority of the condensation should happen within the first 1/3rd of the column. If it is not, your water is either not cold enough or the heat on the hotplate is too high. If you use a water resovior like I do, you'll need some sort of external cooling for the resovior (I just use ice cubes). The water will stay cool enough to efficiently condense water vapors for about 45minutes before more ice should be added (this is all depending on the flow of your pump, lenghth of the column, and size of the resovior).

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