A - acetamide

Figure 4. Stick diagrams representing C-13 spectra at 22.63 MHz (22) of chon-droitins A, B, and C (4a, 4b and 4c, respectively). The vertical, light lines relate resonances for analogous C-13 nuclei in the three different polymers. Not included are sigrwls caused by the acetamido CH, and C==0 carbons, and the carboxyl carbons (U-6). Minor signals that demonstrate the presence of chon-droitin A in C, and of C in A, are found in Figure 1 of Ref. 22. A = acetamide-oxyhexose, U = uronic acid.

Amin (vgl. a. Acetamid, u.s.w.) (4-Athoxycarbonyl-phenyl)-bcnzyliden- 227 Athyl- 41 3... 

Dihydroxypyrrolidinones, which can be considered as cyclic GABA derivatives, are potential nootropic drug candidates. All four possible diastereomers 794—797, as shown in Scheme 174, can be prepared from tartaric acid. Treating L-tartaric acid sequentially with acetyl chloride, methyl glycinate, and then acetyl chloride provides in 81% overall yield the C2-symmetric succinimide 790. In order not to reduce the methyl ester, the very mild treatment with sodium borohydride at —40 °C is employed to prepare the cw-hydroxylactam 791 in an 80% isolated yield. Esterification of 791 with trifiuoroacetic anhydride followed by triethylsilane reduction yields to the extent of 79% the pyrrolidinone 792. This is deprotected with sodium methoxide to provide in 97% yield (3i ,45)-3,4-dihydroxy-A -methoxy-carbonylmethyl-2-pyrrolidinone (793). Ammonolysis of 793 affords (3i ,4 S)-3,4-dihydroxy-2-oxopyrrolidine-A -acetamide (794) in 60% yield. Subsequent modifications to 793 allow for the preparation of (35, 4S)-3,4-dihydroxy-2-oxopyrrolidine-A/-acetamide (795), (3R,4R)-3,4-dihydroxy-2-oxopyrrolidine-A -acetamide (796) and (35, 47 )-3,4-dihydroxy-2-oxopyrrolidine-7V-acetamide (797) [234]. 

Although the conformational studies in Figs. 5 and 6 relate to mechanistic issues, the product of the hydrolyses also drew our attention. Thus, the a-acetamide 54 (n = 1 or 2) was the major product from hydrolyses of the restrained precursors 50 (a/P) and 51 (a/p) shown in Fig. 5, and reproduced in Scheme 9a [70]. Such compounds result from a Ritter reaction [71, 72] to give a nitrilium intermediate, e.g., 53, which rapidly scavenges water. 

However, in spite of these observations, the a-orientation of the reactive intermediates 53 and 57 (Scheme 9) was purely fortuitous [76], and so torsional restraint was not essential for the observed a-acetamide formation. 

Figure 25.4 Conversion obtained in the transesteiification reaction between ethyl valerate and 1-butanol in eight DESs as compared to that obtained in toluene, catalyzed by three hpases Candida antarctica hpase B (CALB), C. antarctica hpase A (CALA), and Pseudomonas cepacia hpase (PCL). ChCl, chohne chloride EAC, ethylammonium chloride A, acetamide G, glycerol EG, ethylene glycol U, urea MA, malonic acid. This figure is drawn by using the data taken from Gorke et al. [8].

Electrostatic potential maps of (a) acetamide and Cb) methylamine are shown. Which has the more basic nitrogen atom Which has the more acidic hydrogen atoms ... 

J-Pyran-2-acetamid, Ai-[[6-(2,3-dimethoxypropyl)tetrahydro-4-hydroxy-5,5-dimethyl-2H-pyran-2-yl]rriethoxymethyl]tetrahydro-a-hydroxy-2-methoxy-5,6-dimethyl-4-rTiethylene]-... 

Acetamide is thus obtained as a colourless crystalline solid, which has a characteristic odour of mice, stated to be due to the presence of small quantities of methylacetamide, CH3CONHCH3. The acetamide can be purified and rendered odourless by re-crystallisation from acetone, and then has m.p. 82°, b.p. 223°. If this recrystallisation is contemplated, the distilled material should be collected directly into a small weighed beaker or conical flask, so that the solidified acetamide can be readily broken up and removed. 

The crude acetonitrile contains as impurity chiefly acetic acid, arising from the action of phosphoric acid on the acetamide. Therefore add to the nitrile about half its volume of water, and then add powdered dry potassium carbonate until the well-shaken mixture is saturated. The potassium carbonate neutralises any acetic acid present, and at the same time salts out the otherwise water-soluble nitrile as a separate upper layer. Allow to stand for 20 minutes with further occasional shaking. Now decant the mixed liquids into a separating-funnel, run off the lower carbonate layer as completely as possible, and then pour off the acetonitrile into a 25 ml, distilling-flask into which about 3-4 g. of phosphorus pentoxide have been placed immediately before. Fit a thermometer and water-condenser to the flask and distil the acetonitrile slowly, collecting the fraction of b.p. 79-82°. Yield 9 5 g. (12 ml.). 

Acetonitrile is a colourless liquid, of b.p. 82° and [Pg.122]

A certain amount of hydrolysis of the original acetamide to acid and ammonia always occurs, and the final amine always contains traces of ammonia. This is separated by extracting the mixed anhydrous hydrochlorides with absolute ethanol, which dissolves the amine hydrochloride but not the ammonium chloride filtration of the hot ethanolic extract removes the ammonium chloride, whilst the amine hydrochloride crystallises readily from the filtrate on cooling. 

Dissolve 36 g. of sodium hydroxide in 160 ml. of water contained in a 500 ml. conical flask, and chill the stirred solution to 0-5° in ice-water. Now add io-8 ml. (32-4 g.) of bromine slowly to the stirred solution exercise care in manipulating liquid bromine ) during this addition the temperature rises slightly, and it should again be reduced to 0-5°. Add a solution of 12 g. of acetamide in 20 ml. of water, in small portions, to the stirred hypobromite solution so that the temperature of the mixture does not exceed 20° the sodium acet-bromoamide is thus obtained in the alkaline solution. Now remove the flask from the ice-water, and set it aside at room temperature for 30 minutes. 

Solutions of solids in liquids can sometimes be separated by distilling off the liquid and leaving a residue of the solid, e.g., acetone and acetamide. 

Acetamide and acetonitrile, unless specially purified, possess a mouse-like odour. 

By the action of concentrate aqueous ammonia solution upon esters. This process is spoken of as ammonolysls of the ester, by analogy with hydrolysis applied to a similar reaction with water. If the amide is soluble in water, e.g., acetamide, it may be isolated by distillation, for example ... 

The acetamide often contains a minute amount of impurity having an odour resembling mice excrement this can be removed by washing with a small volume of a 10 per cent, solution of ethyl alcohol in ether or by recrystallLsation. Dissolve 5 g. of impure acetamide in a mixture of 5 ml. of benzene and 1 5 ml. of dry ethyl acetate warm on a water bath until all is dissolved and cool rapidly in ice or cold water. Filter oflF the crystals, press between Alter paper and dry in a desiccator. The unpleasant odour is absent and the pure acetamide melts at 81°. Beautiful large crystals may be obtained by dissolving the acetamide (5 g.) in warm methyl alcohol (4 ml.), adding ether (40 ml.) and allowing to stand. 

If the acetamide crystallises in the condenser, it may be melted by the cautious application of a flame. 

The functions of the potassium carbonate are (a) to neutralise the acetic acid arising from the action of the phosphoric acid upon the acetamide, and (6) to salt out the otherwise soluble methyl cyanide as an upper layer. 

Place 25 g. of dry acetamide in a 350 ml. conical or flat-bottomed flask, and add 69 g. (23 ml.) of bromine (CAUTION ) a deep red liquid is produced. Cool the flask in ice water and add 10 per cent, sodium hydroxide solution (about 210 ml.) in small portions and with vigorous shaking until the solution acquires a pale yellow colour. At this stage the bromoacetamlde is present in the alkaline solution. If any solid should crystallise out, add a little water. 

Place 45 g. of benzamide (Section IV, 188) and 80 g. of phosphorus pentoxide in a 250 ml. Claisen flask (for exact experimeutal details on the handling and weighing out of phosphoric oxide, see under Acetamide, Section 111,111). Mix well. Arrange for distillation (Fig.//, 29, 1 or Fig. II, 20, 1) under reduced pressure use a water pump with an air leak in the system so that a pressure of about 100 mm. is attained. Heat the flask with a free flame until no more liquid distils the nitrile will pass over at 126-130°/100 mm. Wash the distillate with a little sodium carbonate solution, then with water, and dry over anhydrous calcium chloride or magnesium sulphate. Distil under normal pressure (Fig. II, 13, 2 or II, 13, 6) from a 50 ml. flask the benzonitrile passes over as a colourless liquid at 188-189° (compare Section IV,66). The yield is 28 g. 

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