Fractional Distillation

Source: Laboratory of Dr. Nicholas Leadbeater — University of Connecticut

Distillation is perhaps the most common laboratory technique employed by chemists for the purification of organic liquids. Compounds in a mixture with different boiling points separate into individual components when the mixture is carefully distilled. The two main types of distillation are "simple distillation" and "fractional distillation", and both are widely used in organic chemistry laboratories.

Simple distillation is used when the liquid is (a) relatively pure (containing no more than 10% liquid contaminants), (b) has a non-volatile component, such as a solid contaminant, or (c) is mixed with another liquid with a boiling point that differs by at least 25 °C. Fractional distillation is used when separating mixtures of liquids whose boiling points are more similar (separated by less than 25 °C).

This video will detail the fractional distillation of a mixture of two common organic solvents, cyclohexane and toluene.

1. Set-up of Fractional Distillation Apparatus

Fractional Distillation of a Cyclohexane-Toluene Mixture

The purity of the distillate can be assessed by a number of techniques. One of the best is NMR spectroscopy. The ¹H-NMR spectrum of the initial mixture prior to distillation is shown in Figure 6. Signals for both toluene and cyclohexane are clearly visible. ¹HNMR spectra of the pure cyclohexane and pure toluene distil

Distillation accounts for about 95 % of all current industrial separation processes. The main difference between distillations performed on the laboratory-scale and those performed industrially is that the former are usually run in a batch-wise manner, whereas the latter are often run continuously. In continuous distillation, the starting mixture, vapors, and distillate are kept at a constant composition by carefully replenishing the staring material and removing fractions from both vapor and liquid in the system. The mo

Transcript

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Fractional Distillation Apparatus	Quantity
Retort stands (ring stands)	2
Screw jack	1
Clamps	4
Keck clamps	4
Magnetic stir bar