Water and acetylation

Water is essential, since acetic acid is formed by the reaction between water and acetyl iodide or the Ni-acetyl complex. Acetic acid is also formed via the hydrolysis of any methyl acetate that is formed by methanol attack on acetyl iodide or the Ni-acetyl complex. 

In studying the reaction of oxygen atoms with CH3CHO by using the photochemical method, at a pressure of 100 mm. Hg and with sensitization by mercury, Cvetanovi664 came to another conclusion, namely, that the reaction of oxygen atoms with acetaldehyde yielded mainly hydroxyl and the CH3CO radical. The hydroxyl formed reacted with an acetaldehyde molecule to form water, and acetyl yields diacetyl. The main reaction products were found to be water and biacetyl. 

Diacetylmorphine also loses one acetyl group by boiling it with water, and acetyl dihydroxypyridine is still more unstable. ... 

Acetylation. Boil i g. of salicylic acid with 4 ml. of an acetic anhydride-acetic acid mixture (equal volumes) under reflux for 10 minutes. Pour into water. Filter off the aspirin (p. 111), wash with water and recrystallise from aqueous acetic acid (1 1) m.p. l36 ... 

Action of silver nitrate. Acidify 2 ml. of aqueous AgNOj solution with dil. HNO3 and add the acid chloride drop by drop with shaking. Acetyl chloride and benzoyl chloride give a precipitate of AgCl. Filter, wash with water, and then with methylated spirit to remove any benzoic acid the AgCl remains. 

Acetylation. Proceed as in 2 (p. 373). Pour the final acetylation mixture into 10 ml. of water, and add 10% NaOH solution, with stirring, until no more anilide is precipitated (acetyl-monoethylaniline is very soluble even in dil. acetic acid acetyUdiphenylamine readily separates without the addition of alkali). Filter, wash with water and recrystallise. 

Acetylation. Heat i g. of />-nitrophenol with 5 ml. of an acetic acid-acetic anhydride mixture under reflux for 15 minutes. Pour into water the solid acetate separates. Filter, wash with water and re-crystallise from ethanol m.p. 77 5°. This treatment usually leaves o-nitrophenol unchanged. The addition, however, of about 0 5 ml. of cone. H2SO4 to the acetylating mixture gives the o-derivative, m.p. 40°. 

A) Benzoyl Derivative. Since acetylation and benzoylation do not always proceed smoothly with nitrophenols, it is best to reduce them to the aminophenol as in (3) above. Add an excess of 20% aqueous sodium hydroxide to the reaction mixture after reduction, cool and then add a small excess of benzoyl chloride, and shake in the usual way. The dibenzoyl derivative wiU separate. Filter, wash with water and recrystalUse. (M.ps., p. 551.)... 

The excess of unchanged acetic anhydride is then hydrolysed by the addition of water, and the total free acetic acid estimated by titration with standard NaOH solution. Simultaneously a control experiment is performed identical with the above except that the alcohol is omitted. The difference in the volumes of NaOH solution required in the two experiments is equivalent to the difference in the amount of acetic add formed, i.e., to the acetic acid used in the actual acetylation. If the molecular weight of the alcohol is known, the number of hydroxyl groups can then be calculated. 

Method 1. Use the apparatus depicted iu Fig. Ill, 56, 1, but omit the thermometer also attach a cotton wool (or calcium chloride) tube to the side arm of the filter fiask receiver in order to prevent the entrance of moisture into the apparatus. Mount the reaction fiask in a water bath e.g., a large beaker or other convenient vessel). It is important that all the apparatus be perfectly dry, since both phosphorus trichloride and acetyl chloride are decomposed by water. The set-up should be assembled in the fume eupboard. 

Reflux 1 g. of the sulphonamide with 2-5 ml. of acetyl chloride for 30 minutes if solution is not complete within 5 minutes, add up to 2-5 ml. of glacial acetic acid. Remove the excess of acetyl chloride by distillation on a water bath, and pour the cold reaction mixture into water. Collect the product, wash with water and dissolve it in warm sodium bicarbonate solution. Acidify the Altered solution with glacial acetic acid Alter oflF the precipitated sulphonacetamide and recrystaUise it from aqueous alcohol. 

Acetylation of the amine may also be effected by boiling with 20 ml. of glacial acetic acid and 14 ml. of acetic anhydride for 15-20 minutes, followed by decomposition of the excess of anhydride with water and, after boiling for 5 minutes, poirring with stirring into about 75 ml. of water the product is appreciably coloured. 

Hydrolyse the acetyl-sulphap3Tidine by boiling it with 10 parts of 2N sodium hydroxide for 1 hour, and allow to cool. Precipitate the base by the addition of 50 per cent, acetic acid until the mixture is just acid to litmus (pH about 6 5) avoid a large excess of acid. Filter off the crude sulphapyridine, wash well with water, and dry at 90° to constant weight (about 12 hours any acetate formed will bo decomposed). The yield is 35 g. RecrystaUise from 90 per cent, acetone (5) the recovery of the pure compoimd, m.p. 190-191°, is about 80 per cent. 

Bemoyl chloride may replace acetyl chloride as a class reagent it possesses the advantage that it is only very slowly decomposed by cold water and consequently may be employed for detecting alcohols even in aqueous solution. The reaction is usually carried out in aqueous solution containing sufficient caustic alkali to decompose any excess of benzoyl chloride into the water-soluble alkali benzoate (Schotten - Baumann reaction compare Section IV,52). The benzoyl esters formed are insoluble in water ... 

Acetyl chloride test. In a small, dry test-tube treat 0 -5 ml. of the compound with 0-3-0-4 ml. of redistUled acetyl chloride and note whether reaction occurs. Add 3 ml. of water and neutralise the aqueous layer with solid sodium bicarbonate. Look for a product different from the original alcohol. 

A mixture of 0.30 mol of the tertiairy acetylenic alcohol, 0.35 mol of acetyl chloride (freshly distilled) and 0.35 mol of /V/V-diethylaniline was gradually heated with manual swirling. At 40-50°C an exothermic reaction started and the temperature rose in a few minutes to 120°C. It was kept at that level by occasional cooling. After the exothermic reaction had subsided, the mixture was heated for an additional 10 min at 125-130°C, during which the mixture was swirled by hand so that the salt that had been deposited on the glass wall was redissolved. After cooling to below 50°C a mixture of 5 ml of 36% HCl and 200 ml of ice-water was added and the obtained solution was extracted with small portions of diethyl ether. The ethereal solutions were washed with water and subsequently dried over magnesium sulfate. The solvent was removed by evaporation in a water-pump vacuum... 

Initiation of polymerisation is said to be effected by zinc diethyl-water and aluminium trialkyl-water-acetyl acetone systems to give the structures indicated in Figure 19.12. 

Organic Chlorides/Halides — Several organic compounds also are hydrolyzed (or react with water) to produce corrosive materials. Notable inclusions among these compounds are acetic anhydride ([CH3COJ2O), and acetyl chloride (CH3COCI), both of which produce acetic acid upon reaction with water. Both acetic anhydride and acetyl chloride are corrosive in addition, mixtures of the vapors of acetic anhydride and acetic acid are flammable in air, and acetyl chloride itself is flammable. 

Mesaconitinone on acid hydrolysis loses a molecule of acetic acid to form benzmesaconinone, Cjj H4j OiqN, and when heated at 175/15 mm. in hydrogen loses water and methyl alcohol forming demethanolanhydro-mesaconitinone, CgaHgjOjN, m.p. 194°, [a] ° -)- 26-24° (CHClj), which can be deprived of its acetyl and benzoyl radicals to yield demethanol-mesaconinone, 23 33 8 ni.p. 250—2 (dec.), -f- 76-5. ... 

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