Organic 2 Review Problem 93

Organic 2 Review Problem 93 - regenerating the sulphuric...

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PREPARATIONS 77 solution is allowed to cool slowly (and preferably allowed to stand over- night), a crop of large, well-formed and very beautiful crystals results. In either case, filter off the crystals at the pump, wash rapidly with a small quantity of distilled water, drain thoroughly, and dry in an atmospheric calcium chloride desiccator to avoid dehydration of the crystals. By further evaporation of the filtrate, a second but less pure crop of crystals may be obtained. For reactions of acetic acid and acetates, see p. 347. The Interaction of Ethanol and Sulphuric Acid. Three compounds may be formed by the interaction of ethanol and sulphuric acid, according to the experimental conditions: (1) When concentrated sulphuric acid is added to ethanol, the mixture becomes hot owing to the formation of ethyl hydrogen sulphate, the yield of which is increased if the mixture is then gently boiled under reflux: C 2 H 5 OH + H 2 SO 4 -> C 2 H 5 HSO 4 + H 2 O (2) If the mixture contains an excess of ethanol, and is heated to 140°, the ethyl hydrogen sulphate reacts with the ethanol, giving diethyl ether And
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Unformatted text preview: regenerating the sulphuric acid: C 2 H 5 HSO 4-f HOC 2 H 5-> C 2 H 5 OC 2 H 5 + H 2 SO 4 (3) If the mixture contains a considerable excess of sulphuric acid and is heated to 160-170, the ethyl hydrogen sulphate breaks down, giving ethylene and again regenerating the sulphuric acid. C 2 H 5 HSO 4 = C 1 H 4 + H 2 SO 4 The mechanism of the formation of these three compounds is based on the initial reaction between ethanol and a strong acid such as sulphuric acid, which involves protonation of the ethanolic oxygen to form the ion (I). + CH 3 CH 2 OH r H 2 SO 4-^ CH 3 CH 2-OH [- HSO 4 (I) H This ion (I) can react in three ways, according to the conditions. (a) reaction with the HSO 4 may give ethyl hydrogen sulphate CH 3 CH-OH -f HSO 4- CH 3 CH 2 OSO 3 H - H 2 O H (b) reaction with ethanol gives diethyl ether H- -L-CH 3 CH 2-OH- CH 3 CHoOH-~ CH 3 CH 2 OCH 2 CH n H 2 O -H H (c) dehydration gives ethylene CH 3 CHoOH-CH, -CH, H,() H H...
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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