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Chemical and spectroscopic properties of benzenoid compounds examined.
Metadata describing this Open University video programme
Item code: S24-; 08
First transmission date: 29-04-1972
Published: 1972
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Duration: 00:23:45
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Producer: Barrie Whatley
Contributors: Len Haynes; Roger Hill
Publisher: BBC Open University
Keyword(s): Anthracene; Benzenoid ring; Infra-red spectra; Properties of benzene and cyclohexene; Reactions of cyclohexanol and phenol; Saturated/unsaturated carbon; Ultra-violet spectra
Footage description: Len Haynes introduces the programme. R.R. Hill compares cyclohexene with benzene in a series of simple experiments. Hill puts a few drops of each on dishes and sets light to them. Hill next adds a few drops of each to identical solutions of potassium permanganate. Hill then adds a few drops of the cyclohexene and benzene to identical solutions of bromine in water. Haynes with an electron contour map of benzene. He shows that the six carbons form a regular hexagon with carbon bonds all the same length. This suggests that benzene is not a typical alkene. R. R. Hill examines the infra-red spectra of cyclohexane, cyclohexene, cyclohexa 1.3 diene and toluene. Hill points out their characteristics. Haynes sums up by explaining that infra-red spectroscopy can show not only the presence of a benzoid ring but also the way in which that ring is linked into the structure. Haynes poses the question - will the phenyl group affect the properties ot the functional group attached to it? Hill with samples of cyclohexanol and phenol. He first reacts them with sodium. Hill then adds sodium hydroxide to both phenol and cyclohezanol, (these have been dissolved in water) The chemical equations for both are shown on the screen. Hill with samples of cyclohexanol and phenol dissolved in alcohol. He adds a few drops of ferric chloride to each. A deep violet colour is given to the phenol solution but not the cyclohexanol. Hill demonstrates that not only the reaction with ferric chloride but most of the properties of X in Ph-X which differ from those in say, CH3-X, are not due to any special influence of an aromatic ring, but merely to the fact that X is bound to unsaturated carbon in one case and saturated carbon in the other. X-C=C is likely to react in a similar fashion as PhX. Hill uses a solution of ethyl acetoacetate to react with ferric chloride for his demonstration. Haynes sums up so far. Shots of the ultra violet spectrum of cyclohexane. Hill points out the characteristics. U-V spectrum of cyclohexene is superimposed. Hill points out the absorption characteristics. U-V spectrum for a conjugated (?) shown. Hill points out the absorption characteristics. U-V spectrum for benzene. Hill points out the absorption characteristics. These differ considerably in form from typical alkene absorption. Hill shows the ultra-violet spectra for benzines which have been modified by the addition of other groups. Hill explains how the addition of a double bond increases the polarisability of benzene. The resulting spectra are shown U-V spectrum of anthracene shown. Haynes with a sample of anthracene. He places it under an ultra-violet light to demonstrate the property of fluorescence common to many polycyclic hydrocarbons.
Master spool number: 6LT/70384
Production number: 00521_2173
Videofinder number: 1725
Available to public: no