2-Bromotoluene

A mixture of 63 g. (0.25 mole) of crystallized cupric sulfate, 20 g. (0.31 mole) of copper turnings, 154 g. (1.1 moles) of sodium bromide, 30 g. (0.28 mole) of concentrated sulfuric acid (sp. gr. 1.84), and 11. of water is refluxed over a flame for three to four hours until the color becomes yellowish (Note 1). 

When the hydrobromic acid-cuprous bromide solution is ready for use, the diazonium solution is prepared. A solution of 107 g. (1 mole) of / -toluidine and 196 g. (1.9 moles) of concentrated sulfuric acid (sp. gr. 1.84) in 1 1. of water is cooled below 200 and diazotized with a solution of 70 g. (1 mole) of sodium nitrite in 125 cc. of water. This requires about twenty to thirty minutes when the temperature is maintained between 150 and 200 by means of an ice bath. 

round-bottom flask containing the hydrobromic acid-cuprous bromide solution, is arranged for steam distillation. After the copper solution is heated to boiling, the diazonium solution is gradually added from a separatory funnel and a vigorous current of steam is passed through the reaction mixture at the same time. This procedure requires about two hours. 

The aqueous distillate is made alkaline with sodium hydroxide solution and the -bromotoluene is separated from the water layer (Note 2). The crude product weighs 131-137 g. For purification the crude product is washed once with concentrated sulfuric acid (Note 3) and then with water. It is dried over a little calcium chloride, filtered, and distilled. The yield of pure product amounts to 120-126 g. (70-73 per cent of the theoretical amount) boiling at 183-185° and melting at 25-26°. 

If the color of the solution has not been discharged after heating for three to four hours, a few grams of sodium sulfite may be added to complete the reduction. 

3-Bromo-4-aminotoluene hydrochloride. Transfer the partially dried 3-bromo-4-acetaminotoluene to a 1 5-litre round-bottomed flask, add 250 ml. of rectified spirit, and reflux on a water bath until the sohd dissolves completely. Introduce through the condenser 250 ml. of concentrated hydrochloric acid to the boihng solution and continue the refluxing for a further 3 hours. During this time crystals of 3-bromo-4-aminotoluene hydrochloride separate. Pour the hot mixture into a 1-Utre beaker and cool thoroughly. Filter the crystals of the hydrochloride at the pump through a Buchner funnel and wash rapidly with two 50 ml. portions of chilled rectified spirit. The yield of the hydrochloride is 150 g. 

3-Bromo-4-aminotoluene, Suspend the hydrochloride in 400 ml, of water in a 1-Utre beaker equipped with a mechanical stirrer. Add a solution of 70 g. of sodium hydroxide in 350 ml. of water. The free base separates as a dark heavy oil. After cooUng to 15-20°, transfer the mixture to a separatory funnel and run off the crude 3-bromo-4-amino-toluene. This weighs 125 g. and can be used directly in the next step (3). 

In a 1 or 1-5 htre round-bottomed flask prepare a solution of 53-5 g. of o-toluidine in 170 ml. of 48 per cent, hydrobromic acid, cool to 5° by immersion in a bath of ice and salt. Diazotise by the gradual addition of a solution of 36 -5 g. of sodium nitrite in 50 ml. of water stopper the flask after each addition and shake until all red fumes are absorbed. Keep the temperature between 5° and 10°. When the diazotisation is complete, add 2 g. of copper powder or copper bronze, attach a reflux condenser to the flask, and heat very cautiously on a water bath. Immediately evolution of gas occurs, cool the flask in crushed ice unless the 

Gattermann s Method.— Accoiding to this method the diazonium bromide is first picparcd and then decomposed by finely divided metallic copper. The 50 grams /-toluidine is dissohed in 200 c.c. liydrobromic acid previously diluted with too c.c. water and diazoliscd in the usual way. To this solution 

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Referring to the numerical example following Eq. 11-18, what would be the surface tension of a liquid of density 1.423 g/crc (2-bromotoluene), the rest of the data being the same ... 

For the preparation of w-bromotoluene, the following sequence of reactions from p-toluidine may be used ... 

An example of this is given in Section IV.63—the conversion of 3-bromo-4-aminotoluene into m-bromotoluene. Another application is to the preparation of. iM.-tribromobenzene (Section IV,72) ... 

Prepare a solution of p-tolyldiazonium chloride from 53 -5 g. of p-tolui-dine using the proportions and experimental conditions given under p-Chlorotoluene (Section IV,61). Add the diazonium chloride solution to the boiling cuprous bromide solution, and proceed as in Method 1. The yield of pure, colourless p-bromotoluene, b.p, 182-184° (mainly 183°), is 40 g. m.p. 26°,... 

For initial experience in the uae of Uthium, the preparation of either p-toluic acid or of a-napbtboic acid mcay be undertaken. For the former, p-bromotoluene is converted into the lithium derivative and the latter carbonated with soUd carbon dioxide ... 

By the reaction of bromotoluene with ethylene under pressure, p-methylsty-rene and stilbene (45) are obtained[44,45]. A polymer 47 is obtained by the reaction of >-bromostyrene (46) with ethylene. The reaction has been applied to polymer synthesis[46]. One example is the reaction of 1,4-divinylbenzcne (48) with 9,10-dibromoanthracene to give the oligo(arylenevinylene)s 49[47]. 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives The reactivity of a particular position in o bromotoluene for example is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene On the basis of the partial rate factor data given here for Fnedel-Crafts acylation predict the major product of the reaction of o bromotoluene with acetyl chlonde and aluminum chloride... 

Three regioisomers (o m and p methylamline) were formed from m bromotoluene CH3 CH3 CH3 CH3... 

The hydrolysis of p bromotoluene with aqueous sodium hydroxide at 300°C yields m methylphenol and p methylphenol in a 5 4 ratio What is the meta—para ratio for the same reac tion carried out on p chlorotoluene" ... 

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