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Prof. Haynes starts the programme with an examination of the infrared spectrum of cylohexanol at different concentrations. It is apparent that, as the concentration is increased, so the absorption ...produced by the -OH group is progressively replaced by another of higher frequency. This observation is explained in terms of hydrogen bonding. Prof. Haynes then turns to a new topic - the preparation of derivatives. 2.4 Dinitrophenylhydrazones are used to demonstrate what derivatives are and the use chemists make of them. Dr. David Roberts introduces the topics of thin layer and column chromatography. Chromatographic separation on a column is shown using time lapse photography. Prof. Haynes completes the programme by showing the students how to use the thin-layer apparatus supplied in their home kit.
Metadata describing this Open University video programme
Item code: S24-; 05
First transmission date: 11-03-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:25:00
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Producer: Barrie Whatley
Contributors: Len Haynes; David Roberts
Publisher: BBC Open University
Keyword(s): Absorbtion rates; Chromatography techniques; Cylohexanol; Hydrogen bonding; Infra-red spectrum; Preparation of derivatives; Thin-layer chromatography home kit
Footage description: Len Haynes with an -OH infra-red absorption spectrograph. The -OH frequency is lowered as the concentration of alcohol is increased. This intermolecular bonding is shown by an equation on the screen. The spectrograph is shown again. Haynes with five test tubes containing aldehydes and betones. He adds an unknown reagent and gets a precipitate from each. This preparation of chemical derivatives of the compound provides a simple method for determining the chemical structure of a compound. Haynes explains how the reaction works. The unknown reagent is 2,4- dinitrophenylhydrazine and the result of the reactions are 2,4- dinitrophenylhydrazine derivatives. The equations are shown. Haynes demonstrates the technique of re-crystallization. He has a solution of dinitrophenylhydrazine and alcohol at boiling point. The solution is saturated. Haynes filters this solution to get rid of impurities. The solution crystallises in the cold test tube. Haynes explains how the melting point of a compound can be used to identify it. Len Haynes introduces David Roberts. Roberts demonstrates and explains the techniques of thin layer chromatography. The experiment is then shown on speeded up film so that the development process is seen. (The technique is used to separate and identify elements of compounds). Roberts demonstrates and explains a technique for showing up colourless compounds after thin layer chromatography. Roberts next demonstrates and explains the technique of column chromatography. He explains how the apparatus works and then carries on with his demonstration. Speeded up film shows the separation of elements in the column. Roberts explains that column chromatography is useful for separating quite large amounts of a compound while thin layer chromatography only allows small amounts to be separated. Len Haynes explains and demonstrates thin layer chromatography using the home experiment kit. He then shows the results he obtained with the kit for dinitrophenylhydrazine. Haynes sums up.
Master spool number: 6LT/70434
Production number: 00521_2175
Videofinder number: 1722
Available to public: no