Organic 2 Review Problem 347

Organic 2 Review Problem 347 - REACTIONS AND IDENTIFICATION...

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Unformatted text preview: REACTIONS AND IDENTIFICATION 331 at once fit a bent delivery-tube as shown in F ig . 68, p. 320. Now insert the delivery-tube into another test-tube containing lime-water, so that the end of the delivery-tube just does not touch the surface of the lime-water (if it dips below the surface of the lime-water, intermittent "sucking-back" is liable to occur later). Boil the sodium carbonate gently for 2-3 minutes, and then remove the delivery-tube, close the lime-water tube with the thumb and shake vigorously. A white precipitate indicates that carbon dioxide has been evolved. The following classes of compound yield carbon dioxide when treated in this way. (a) Carboxylic acids, e.g., tartaric acid, benzoic acid (but not most phenols, hence this reaction can be used to distinguish between carboxylic acids and phenols, see p. 347), ( b ) Sulphonic acids, e.g., sulphanilic acid. (c) Salts of weak bases, e.g., aniline hydrochloride, which hydro- lyses in aqueous solution to aniline and free hydrochloric acid.lyses in aqueous solution to aniline and free hydrochloric acid....
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