Organic 2 Review Problem 133

Organic 2 Review Problem 133 - the hydrochloric and acetic...

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PREPARATIONS 117 d , i-08: it has a sharp pungent odour resembling that of acetic acid. It is used in organic chemistry chiefly as an acetylating agent, for which purpose it is frequently mixed with acetic acid, sodium acetate, etc .: for examples of such acetylations see pp. 107-112. For reactions of acetic anhydride, see p. 364. Acid Amides. Acid amides may be prepared by the following methods: (1) Dehydration of the corresponding ammonium salt. Thus ammonium acetate on heating loses water giving acetamide. An excess of acetic acid is CH 3 COONH 4 = CH 1 CONH 1 + H t O usually added before heating, in order to suppress thermal dissociation of the ammonium acetate into ammonia and acetic acid. (2) By the action of Concentrated Aqueous Ammonia on: (a) Esters COOC 8 H 5 HNH, CONH 8 I + _> I + 2C 2 H 6 OH CO OC 8 H 5 H NH, CONH 2 Ethyl oxalate Oxamide (b) Add Chlorides C 6 H 5 CO Cl + H NH 2 -> C.H^CONH, + HCl Benzoyl Chloride Benzamide (c) Acid Anhydrides CH 3 CO O-OCCH, + H NH 2 -> CH 8 CONH 2 + CH 8 COOH Acetic anhydride Acetamide In reactions (b) and (c}
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Unformatted text preview: the hydrochloric and acetic acids formed are of course at once neutralised by the excess of ammonia. Method (i) is most frequently used for aliphatic acid amides, while Methods (2a), (26) and (2c) are used most frequently for aromatic acid amides. Of the last three methods, the Acid Chloride Method (26) is the most rapid and certain. The Ester Method (-20) is practicable only when the amide is insoluble in water, and even then is often very slow unless the ester itself is appreciably soluble in the aqueous ammonia solution. For reactions of acid amides, see p. 560. Acetamide. CH 3 CONH 2 . (Method i.) Required: Ammonium carbonate, 15 g.; acetic acid, 50 ml. Add 15 g. of finely powdered ammonium carbonate gradu-ally to 50 ml. of glacial acetic acid contained in a 150 ml. round-bottomed flask, shaking the mixture during the addition to ensure a steady evolution of carbon dioxide. When all the carbonate has...
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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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