N -butyl bromide

The preparation of -butyl bromide as an example of ester formation by Method 1 (p. 95) has certain advantages over the above preparation of ethyl bromide. -Butanol is free from Excise restrictions, and the -butyl bromide is of course less volatile. and therefore more readily manipulated without loss than ethyl bromide furthermore, the n-butyl bromide boils ca. 40° below -butyl ether, and traces of the latter formed in the reaction can therefore be readily eliminated by fractional distillation. 

Run off the lower layer of bromide, dry it with calcium chloride (as in the above preparation of ethyl bromide) and finally distil the filtered bromide from a small flask, preferably through a short column. Collect the n-butyl bromide as a colourless liquid of b.p. 99-102°. Yield, 30 g. 

This acid mixture may be prepared (compare Section 11,49, 1) by placing 120 g. (37-5 ml.) of bromine and 130 g. of crushed ice in a 500 ml. flask, cooling the latter in ice, and passing sulphur dioxide (from a siphon of the liquefied gas) into the bromine layer at such a rate that the gas is completely absorb. The flask is shaken occasionally, and the flow of gas is stopped inunediately the red colour due to free bromine has disappeared the mixture will then have a yellow colour. The resulting acid mixture is equivalent to 260 g. of 48 per cent, hydrobromio acid to which 75 g. of concentrated sulphuric acid have been added it need not be dis. tilled for the preparation of n-butyl bromide. 

Filter the dried product through a fluted filter paper or a small cotton wool plug supported in a funnel into a dry 50 ml. distilling flask, and distil on a wire gauze or from an air bath (Fig. 11, 5, 3). Collect the fraction, b.p. 100-103°. The yield of n-butyl bromide is 18-19 g. 

In a 200 ml. distilling flask place 64 g. (50 ml.) of dry n-butyl bromide and 80 g. of dry silver nitrite (1). Insert a reflux condenser, carrying a cotton wool (or calcium chloride) guard tube, into the mouth of the flask and close the side arm with a small stopper. Allow the mixture to stand for 2 hours heat on a steam bath for 4 hours (some brown fumes are evolved), followed by 8 hours in an oil bath at 110°. Distil the mixture and collect the fraction of b.p. 149-151° as pure 1-nitro-n-butane (18 g.). A further small quantity may be obtained by distilling the fractions of low boihng point from a Widmer flask. 

Into a 1500 ml. round-bottomed flask place 97-5 g. of finely-powdered sodium cyanide (1), 125 ml. of water, and a few chips of porous porcelain. Attach a reflux condenser and warm on a water bath until all the sodium cyanide dissolves. Introduce a solution of 250 g. (196 ml.) of n-butyl bromide (Sections 111,35 and 111,37) in 290 ml. of pure methyl alcohol, and reflux gently on a water bath for 28-30 hours. Cool to room temperature and remove the sodium bromide which has separated by filtration through a sintered glass funnel at the pump wash the crystals with about 100 ml. of methyl alcohol. Transfer the filtrate and washings to From n caproamide by SOClj method. 

The fact that n-butylbenzene can be prepared in reasonable yield by the action of sodium upon a mixture of bromohenzene and n-butyl bromide can be partly explained on the assumption that n-butyl bromide reacts with phenyl-sodium more rapidly than does bromobenzene. It is interesting to note that n-butylbenzene can be prepared either from benzylsodium and n-propyl bromide or from phenylsodium and n-butyl bromide (Section VI,29). 

Addition of n butyl bromide then gives M-butylacetylene (1-hexyne) ... 

Linder an atmosphere of argon, a solution of n-butyl bromide (137 g, 1 moll in anhydrous ether (500 ml) is added with stirring to small chips of lithium containing 1-2% of sodium (15.5 g, 2.2 g-atom) in ether (150 mL). The... 

Neopentyl (2,2-dimethylpropyl) systems are resistant to nucleo diilic substitution reactions. They are primary and do not form caibocation intermediates, but the /-butyl substituent efiTectively hinders back-side attack. The rate of reaction of neopent>i bromide with iodide ion is 470 times slower than that of n-butyl bromide. Usually, tiie ner rentyl system reacts with rearrangement to the /-pentyl system, aldiough use of good nucleophiles in polar aprotic solvents permits direct displacement to occur. Entry 2 shows that such a reaction with azide ion as the nucleophile proceeds with complete inversion of configuration. The primary beiuyl system in entry 3 exhibits high, but not complete, inversiotL This is attributed to racemization of the reactant by ionization and internal return. 

Halogen-metal interconversion between bromothiophenes and n-butyllithium, leading to thienyllithium derivatives and n-butyl bromide, occurs almost instantaneously and in very high yield even at... 

The most thoroughly investigated compounds are the alkyl-pyridines. Coleman and Fuoss compared the reactions of pyridine, 4-picoline, and 4-isopropylpyridine with n-butyl bromide and found a steady increase in the rate in the order given the activation energies are 16.0,15.95, and 15.6 kcal per mole, respectively. Brown and Cahn carried out a detailed study of the reactions of 2-, 3-, and 4-alkyl-pyridines with methyl, ethyl, and isopropyl iodides in nitrobenzene the results are given in Table II. These data show the higher activation... 

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