Alkyl halides ammonolysis

Good yields of 1° amines are obtained by using large excess of ammonia. The ammonolysis proceeds best by using primary alkyl halides. The tertiary alkyl halides tend to form alkenes due to the dominance of the competing elimination reaction. 

Delepine reaction org chem Slow ammonolysis of alkyl halides in acid to primary amines in the presence of hexamethylenetetramine. del-3,pTn re,ak-sh3n deliquescence phys chem The absorption of atmospheric water vapor by a crystalline solid until the crystal eventually dissolves into a saturated solution. del-3 kwes-3ns ... 

Reductive amination, the catalytic or chemical reduction of aldehydes (RCHO) and ketones (R2CO) in the presence of ammonia or an amine, accomplishes much the same purpose as the reaction of halides. It too can be used to prepare any class of amine, and has certain advantages over the halide reaction. The formation of mixtures is more readily controlled in reductive amination than in ammonolysis of halides. Reductive amination of ketones yields amines containing a ec-alkyl group these amines are difficult to prepare by ammonolysis because of the tendency of jec-alkyl halides to undergo elimination rather than substitution. 

Like these other nucleophilic substitution reactions, ammonolysis is limited chiefly to alkyl halides or substituted alkyl halides. As with other reactions of this kind, elimination tends to compete (Sec. 14.23) with substitution ammonia can attack... 

Reductive amination of ketones yields amines containing a sec-a ky group such amines are difficult to obtain by ammonolysis because of the tendency for jec-alkyl halides to undergo elimination. For example, cyclohexanone is converted into cyclohexylamine in good yield, whereas ammonolysis of bromocyclohexane yields only cyclohexene. 

C) Ammonolysis of Alkyl Halides. Place 20 ml of a saturated alcoholic solution of ammonia in methanol (90 per cent) in each of two test tubes. To the first add 2 g of n-amyl bromide, and to the second 2 g of amyl bromide. Cork, shake, label, and set aside until the following laboratory period. Add to each reaction mixture 20 ml of water, and separate the upper layer of amine (and imchanged halide). Test two drops of each product for amy-lene by shaking with 2 ml of 0.1% potassium permanganate or bromine water. Record the observations. Place the sample of amine in the proper bottle provided by the instructor for future study. 

If secondary and tertiary amines are desired, only 2 to 3 moles of ammonia are used. Aqueous ammonia does not react to any extent at room temperature, owing to the immiscibility of halide and water. Industrially, aqueous ammonia is used and heated in an autoclave under pressure. Tertiary halides, as, for example, tert-butyl and tert- m.y bromides, do not yield amines, but yield olefines almost exclusively. The object of the present experiment is to illustrate the ammonolysis of alkyl halides. The ammonolysis of aryl halides cannot be easily accomplished in the laboratory, as it involves the use of high pressure, and temperatures of about 200°. Industrially the method is practical. 

More generally, ammonolysis or aminolysis of alkyl halides, and particularly primary alkyl halides, is likely to give rise to mixtures of the primary, secondary and tertiary amines (reactions 19, 20 and 21). The proportions of the three possible amines in such a mixture may be varied by alterations in the relative proportions of the reactants. Where, for example, the primary amine is the desired product, the use of liquid ammonia (to ensure high concentration of ammonia), and also of sodamide (one mole per mole of alkyl halide) in liquid ammonia have been recommended, though some dehydrohalogena-tion of the alkyl halide may occur when sodamide is used (reaction 42). 

In the reaction of ammonia with the alkyl halide, secondary and tertiary amine formation become more important as the concentration of ammonia is reduced. In favourable cases, e.g. the mono-, di- and trioctylamines firom ammonolysis of n-octyl chloride , the amines may be separable by distillation. In other cases, chemical methods... 

You have read (Unit 10, Class Xll) that the carbon - halogen bond In alkyl or benzyl haUdes can be easily cleaved by a nucleophile. Hence, an allqrl or ben l haUde on reaction with an ethanollc solution of ammonia undergoes nucleophilic substitution reaction m which the halogen atom Is replaced by an amino (-NHJ group. This process of cleavage of the C-X bond by ammonia molecule Is known as ammonolysis. The reaction Is carried out In a sealed tube at 373 K. The primary amine thus obtained behaves as a nucleophile and can further react with allqrl halide to form secondary and tertiary amines, and finally quaternary ammonium salt. 

We have already encountered alkylation of amines as a side reaction in the preparation of primary amines by the ammonolysis of halides (Sec. 22.10), and as a method of synthesis of secondary and tertiary amines (Sec. 22.13). Let us look at one further aspect of this reaction, the formation of quaternary ammonium salts. 

The ammonolysis of the alkyl monohalides suffers from the difficulties involved in the separation of the mixture of amines. The reaction is best carried out by adding the halide to a saturated (15-20%) alcoholic solution of ammonia. If a greater proportion of primary amine is desired, 9-10 moles of ammonia and one mole of halide are allowed to stand at room temperature for several days, or ammonium nitrate is added and the amomit of ammonia is reduced. The addition of salt reduces the solubility of the halide... 

Acylfurans, ammonolysis, 665 frcm acylation of furans, 665 2-fnroyl halides, 665 used in synthesis of 2-alkyl (aryl)-3-pyridinols, 665 N-acylpyridones, rearrangement, 776... 

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