0- ethyl bromide

The lARC has determined that there is sufficient evidence for the carcinogenicity of ethyl benzene in animals and inadequate evidence in humans. Overall, it is considered possibly carcinogenic to humans. ° 

Ethyl benzene is not mutagenic in most test systems, but it has caused a mutagenic effect in mouse lymphoma cells and has induced a marginal yet significant increase in sister chromatid exchanges in human lymphocytes at toxic doses.  

Two drops of the liquid in the eyes of a rabbit caused slight conjunctival irritation but no corneal injury. The liquid in contact with the skin of a rabbit caused erythema, exfoliation, and vesiculation.  

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for ethyl benzene is lOOppm (434mg/m ) with a shortterm excursion limit (TLV-STEL) of 125 ppm (543 mg/m ). 

Yant WP, Schrenk HH, Waite CP, Patty FA Acute response of guinea pigs to vapors of some new commercial organic compounds. Public Health Rep 45 1241-1250, 1930 

In the preparation of hydrobromic acid for the manufacture of ethyl bromide, particular care must be taken to avoid the presence of any excess of sulfur dioxide gas. The evolution of gas during the distillation of the ethyl bromide will invariably result in a large loss of this volatile product (b. p. 38-39°). 

A hydrobromic acid solution is prepared in a 5-I. round-bottom flask by the reduction of 1000 g. of bromine in the presence of 1100 g. of cracked ice. Experimental details have been given under (A) Hydrobromic Acid. A mixture of 2075 g. of aqueous (48 per cent) hydrobromic acid and 600 g. of concentrated sulfuric add may be used in place of the above reduction mixture. After the addition of 500 g. of ordinary 92 per cent ethyl alcohol, the flask is attached to a long condenser set ready for distillation and 1000 g. of concentrated sulfuric acid are slowly added through a separatory funnel. Because of the volatility of ethyl bromide, the mixture is not heated under reflux, but is subjected instead to slow distillation. The end of the condenser is provided with an adapter tube, and the distillate Is collected in a flask containing ice water. The crude 

and c) Methyl iodide is much more reactive than the other alkyl iodides. Reactions analogous to those illustrated in the above experiments take place with the higher iodides, but much more slowly. The bromides are less reactive than the iodides the chlorides are, in most cases, very stable. Tertiary halides are much more reactive than the halides derived from secondary and primary alcohols. 

Ethyl bromide boils at 38.4° and has the specific gravity 1.47 at 13°. The yield in this preparation should be about 80 per cent of the theoretical. 

—The ethyl bromide prepared in this way contains a small amount of ether, from which it cannot be separated readily by distillation, since ether boils at 35° and ethyl bromide at 38.4°. In separating the two substances advantage is taken of the fact that ether is soluble in cold concentrated sulphuric acid, while ethyl bromide is not soluble. The bromide prepared by the method given above can be purified by adding it slowly with constant shaking, to an equal volume of concentrated sulphuric acid kept cold by immersion in ice-water. After this treatment the liquids are separated and the ethyl bromide shaken with water, dried, and distilled. 

Solubilities of ethyl bromide.—Using about 1 cc. in each test, determine whether ethyl bromide dissolves in the following 

—(a) Some tertiary halides are decomposed when treated with concentrated sulphuric acid. 

Fit up the apparatus as shown in Fig. 43. The distilling -flask should have a capacity of not less than i litre, and is attached to a long condenser. An adapter is fixed to the end of the condenser, dipping into a conical flask (250 c.c.), which serves as receiver. The alcohol and sulphuric acid are mixed in the distilling flask and cooled to the ordinary tempeiatuie under the tap. The potassium biomide, coarsely pou dered, is then added. The flask, which is closed with a cork, is fixed to the condenser and heated on the sand-bath. A sufficient quantity of water is poured into the receiver to close the end of the adapter. After a short tune the liquid in the flask begins to boil and froth up, and the ethyl bromide, in the form of heavy 

Determination of Specific Gravity.—A simple method for determining the specific gravity of liquids is as follows I. pyknometer, or small glass bottle, is used of about 20 to 30 c.c. capacity, with narrow neck, upon which a mark is etched and which is closed by a ground glass stopper (Fig. 45). 

The bottle is thoroughly cleaned and dried by warming and aspirating air through it, after which it is allowed to cool and weighed. It is then filled with the liquid, which is poured in 

A very delicate and useful piece of apparatus, which is leadily made with the blow-pipe, is Perkins modification of Sprengel s pyknometer. It is especially adapted for small quantities of liquid and for the moie volatile ones. The apparatus (Fig. 46) consists of a U l ube to hold from 2 to 10 c.c., drawm out at each end into a fine capillary. The one capillaiy limb, a, is bent outwards and is furnished with a small bulb the other, b, is bent at a right angle with the first. On the limb a, between the bulb and the top of the U-tnbe a mark is etched. The 

Exavifile—An experiment with ethyl bromide gave the fol-low ing result — 

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Figure Bl.22.2. RAIRS data from molecular ethyl bromide adsorbed on a Pt(l 11) surface at 100 K. The two traces shown, which correspond to coverages of 20% and 100% saturation, illustrate the use of the RAIRS surface selection nde for the detemiination of adsorption geometries. Only one peak, but a different one, is observed in each case while the signal detected at low coverages is due to the asymmetric defomiation of the...

Ethylene can be similarly prepared by the action of ethanolic potash on ethyl bromide, but the yield is usually very low. 

Assemble the apparatus shown in Fig. 6o. A is a 500 ml. bolt-head flask connected by a knee-tube B to a water-condenser C, to the lower end of which is fitted the adaptor D. In view of the low boiling-point of the ethyl bromide, it is essential that the various portions of the apparatus are connected together by well-bored, tightly fitting corks. (For this reason, the apparatus shown in Fig. 23(0), p. 45, is preferable.)... 

Ethyl bromide soon distils over, and collects as heavy oily drops under the water in the receiving flask, evaporation of the very volatile distillate being thus prevented. If the mixture in the flask A froths badly, moderate the heating of the sand-bath. When no more oily drops of ethyl bromide come over, pour the contents of the receiving flask into a separating-funnel, and carefully run oflF the heavy lower layer of ethyl bromide. Discard the upper aqueous layer, and return the ethyl bromide to the funnel. Add an equal volume of 10% sodium carbonate solution, cork the funnel securely and shake cautiously. Owing to the presence of hydrobromic and sulphurous acids in the crude ethyl bromide, a brisk evolution of carbon dioxide occurs therefore release the... 

Ethyl bromide is a colourless liquid, of b.p. 38° and [Pg.102]

Hydrolysis of Ethyl Bromide. Add -a few drops of pure freshly distilled ethyl bromide to 2-3 ml. of aqueous silver nitrate solution in a test-tube and shake. Only a faint opalescence of silver bromide should be formed. -Now carefully warm the mixture in a small Bunsen flame, with gentle shaking silver bromide soon appears as a white suspension which rapidly increases in quantity and becomes a heavy precipitate. The ethyl bromide is thus moderately stable in cold water, but rapidly hydrolysed by hot water. 

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. 

The Alkyl Halides. Ethyl bromide and iodide (see below) are typical alkyl halides. Compounds of this class are of very great importance in synthetic work, owing to the reactivity of the halogen atom. This is illustrated by the following reactions ... 

Ethyl iodide is a heavy liquid, of b.p. 72° and of d, 1 94 insoluble in water, When freshly distilled it is colourless, but on prolonged exposure to light it darkens in colour owing to the liberation of free iodine. Its chemical properties are almost identical with those of ethyl bromide given on pp. 102 and 103. 

Dissolve 3-8 g. of sodium in 75 mi. of rectified spirit, using otherwise the same conditions as in the preparation of anisole. Then add 15 g. of phenol, and to the clear solution add 13 2 ml. (19-1 g., n mois.) of ethyl bromide. Continue precisely as in the preparation of anisole, shaking the ethereal extract with sodium hydroxide solution as before in order to eliminate any unchanged phenol. Finally collect the fraction boiling at 168-172°. Yield, 14 g. 

This reaction is precisely parallel to the Wurtz Reaction in the aliphatic series, by which, for instance, n-butane can be obtained by the action of sodium on ethyl bromide. 

Methyl iodide, ethyl bromide and iodide, higher alpihatic halides chloroform, iodoform, carbon tetrachloride chlorobenzene, bromobenzene, iodobenzene benzyl chloride. 

Physical Properties. All heavier than, and insoluble in water. All liquids, except iodoform, CHI3, which is a yellow crystalline solid with a characteristic odour. The remainder are colourless liquids when pure ethyl iodide, CjHjI, and iodobenzene, CjHgl, are, however, usually yellow or even brown in colour. Methyl iodide, CH3I, ethyl bromide, CgH Br, ethyl iodide, chloroform, CHCI3, and carbon tetrachloride, CCI4, have sweetish odours, that of chloroform being particularly characteristic. 

Ethyl bromide and ethyl iodide behave similarly. Benzyl chloride gives a faint precipitate in the cold, but the precipitation is complete on gentle warming. 

Similar results are obtained with methyl iodide, ethyl bromide, ethyl iodide, iodoform, carbon tetrachloride, and benzyl chloride. 

Methyl iodide, ethyl bromide and ethyl iodide also evolve small amounts of ethylene when treated as above. If this is suspected, a small quantity of the substance should be heated with alcoholic NaOH solution in a small flask, fitted with a knee delivery-tube. Pass the gas evolved through a very dilute solution of KMn04 which has been made alkaline with aqueous NagCOj solution. If ethylene has been formed, a brown precipitate of MnOj will be produced (a transient green colour may appear). 

Ethyl Bromide. Fit a 1-litre round-bottomed flask with a two holed cork carrying a separatory funnel and a wide (6-8 mm.) bent tube connected to a long efficient condenser set for downward distillation (Fig. 111,35,1) alternatively, Fig. Ill, 35, 1. a two-way addition tube (Fig. 11, 1, 8)... 

Add 4 0 g. (4 0 ml.) of pure anihne dropwise to a cold solution of ethyl magnesium bromide (or iodide) prepared from 1 Og. of magnesium, 5 0 g. (3-5 ml.) of ethyl bromide (or the equivalent quantity of ethyl iodide), and 30 ml. of pure, sodium-dried ether. When the vigorous evolution of ethane has ceased, introduce 0 02 mol of the ester in 10 ml. of anhydrous ether, and warm the mixture on a water bath for 10 minutes cool. Add dilute hydrochloric acid to dissolve the magnesium compounds and excess of aniline. Separate the ethereal layer, dry it with anhydrous magnesium sulphate and evaporate the ether. Recrystallise the residual anihde, which is obtained in almost quantitative yield, from dilute alcohol or other suitable solvent. 

Note on the laboratory preparation of monoethylaniline. Although the laboratory preparation of monomethyl- or monoethyl-aniline is hardly worth whUe, the following experimental details may be useful to those who wish to prepare pure monoethylaniline directly from amline. In a flask, fitted with a double surface reflux condenser, place 50 g. (49 ml.) of aniline and 65 g. of ethyl bromide, and boU gently for 2 hours or until the mixture has almost entirely sohdified. Dissolve it in water and boil off the small quantity of unreacted ethyl bromide. Render the mixture alkaUne with concentrated sodium hydroxide solution, extract the precipitated bases with three 50 ml. portions of ether, and distil off the ether. The residual oil contains anihne, mono- and di-ethylaniline. Dissolve it in excess of dilute hydrochloric acid (say, 100 ml. of concentrated acid and 400 ml. of water), cool in ice, and add with stirring a solution of 37 g. of sodium nitrite in 100 ml. of water do not allow the temperature to rise above 10°. Tnis leads to the formation of a solution of phenyl diazonium chloride, of N-nitrosoethylaniline and of p-nitrosodiethylaniline. The nitrosoethylaniline separates as a dark coloured oil. Extract the oil with ether, distil off the ether, and reduce the nitrosoamine with tin and hydrochloric acid (see above). The yield of ethylaniline is 20 g. 

Alkylbenzenes are also obtained (but in somewhat lower yield) from phenyl-sodium and alkyl bromides. Thus ethylbenzene is produced from phenyl-sodium and ethyl bromide ... 

Ethylbenzene. Prepare a suspension of phenyl-sodium from 23 g. of sodium wire, 200 ml. of light petroleum (b.p. 40-60°) and 56 3 g. (50 9 ml.) of chlorobenzene as described above for p-Toluic acid. Add 43 -5 g. (30 ml.) of ethyl bromide during 30-45 minutes at 30° and stir the mixture for a further hour. Add water slowly to decompose the excess of sodium and work up the product as detailed for n-Butylbenzene. The yield of ethylbenzene, b.p. 135-136°, is 23 g. 

In the flask were placed 800 ml (note 1) of dry diethyl ether. Twenty grams of lithium (note 2) were flattened (thickness about 1 mm) with a hammer (note 3) and cut into small pieces (about 10 x 2 1 mm ), which were introduced at the same time into the flask. The contents of the flask were cooled to -30°C, after the air in the flask had been replaced with nitrogen. From the dropping funnel, which contained 1.12 mol of ethyl bromide, were added 10-15 g of ethyl bromide. 

It took 5-10 min before the reaction started this was visible by the appearance of turbidity of the diethyl ether and later by the appearance of a gloss on the pieces of lithium and a distinct increase in temperature. Care was taken that the temperature did not rise above -20°C (note 4). When the reaction had subsided, the addition of ethyl bromide was continued, now dropwise (note 5). The temperature was kept between -20 and -30 C (note 6). After the addition, which was carried out in 30-40 min, stirring was continued for about a further 1 h. The temperature was allowed to rise gradually to -10°C. When the gloss on the piece of lithium had disappeared, the solution was poured into another flask through... 

At higher temperatures the reaction between ethyl bromide and ethyl-lithium ("Wurz coupling") becomes significant. 

In some experiments the presence of hexane is undesirable in view of the volatility of the products. In these cases one can use butyllithium in pentane (prepared from butyllithium in hexane, by replacing the hexane with pentane see Exp. 10) or ethyllithium in diethyl ether, prepared from ethyl bromide and 11thiurn (see Exp. 1). 

To a solution of ethylnagnesium bromide in 350 ml of THF, prepared from 0.5 mol of ethyl bromide (see Chapter 11, Exp. 6) was added in 10 min at 10°C 0.47 mol of 1-hexyne (Exp. 62) and at 0°C 0.47 mol of trimethylsilylacetylene (Exp. 31) or a solution of 0.60 mol of propyne in 70 ml of THF (cooled below -20°C). With trimethyl si lylacetylene an exothermic reaction started almost immediately, so that efficient cooling in a bath of dry-ice and acetone was necessary in order to keep the temperature between 10 and 15°C. When the exothermic reaction had subsided, the mixture was warmed to 20°C and was kept at that temperature for 1 h. With 1-hexyne the cooling bath was removed directly after the addition and the temperature was allowed to rise to 40-45°C and was maintained at that level for 1 h. 

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