Preparative organic work with small quantities

The preparation and purification of chlorine were described on page 103 together with methods for other halogens. 

The preparation and purification of hydrogen chloride, bromide, and iodide were reported on pages 119-121. 

Ethylene, supplied in steel bottles, is purified by cold sulfuric acid and dried by phosphoric oxide. It can be prepared in the laboratory as follows  

Preparation of ethylene from ethanol and phosphoric acid 58 Syrupy phosphoric acid (50-60 ml) is warmed in a round-bottomed flask to 200-230° and anhydrous ethanol is dropped in from a dropping funnel. The rate of addition determines the rate of evolution of the ethylene. The product is washed with potassium hydroxide solution contained in two wash-bottles at 0° and with concentrated sulfuric acid. 

Ethylene can also be obtained by removing the bromine from ethylene dibromide by means of zinc.59 

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Preparative organic work with small quantities... 

Preparative hplc is now becoming widely used in organic chemistry for separating compounds with very similar polarity (see Chapter 11 for more details). Before committing all your material to a preparative column it is always best to run a small quantity of the sample on an analytical column, in order to work out the best conditions. Indeed, columns are produced in various sizes which are directly comparable with one another. 

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