Bromonaphthalenes

Picrates. Some halogen derivatives of the higher aromatic hydrocarbons form picrates (for experimental details, see under Aromatic Hydrocarbons, Section IV,9, 1), for example, a-chloronaphthalene (m.p. 137°), a-bromonaphthalene (m.p. 134°), and p-bromonaphthalene (m.p. 86°). 

Method 1. a-Naphthonitrile. Place 80 g. (54 ml.) of redistilled a-bromonaphthalene (Section IV.20), 43 g. of dry powdered cuprous cyanide (Section II,50,J) and 36 g. (37 ml.) of dry pure pyridine (1) (Section 11,47.22) in a 250 ml. round-bottomed flask fitted with a ground-in reflux condenser carrying a calcium chloride (or cotton wool) guard tube, and heat the mixture in a metal bath at 215-225° for... 

Method 2. Equip a 1 htre thre necked flask with a double surface reflux condenser, a mechanical stirrer and a separatory funnel, and place 12 -2 g. of dry magnesium turnings, a crystal of iodine, 50 ml. of sodium-dried ether and 7-5 g. (5 ml.) of a-bromonaphthalene (Section IV,20) in the flask. If the reaction does not start immediately, reflux gently on a water bath until it does remove the water bath. Stir the mixture, and add a solution of 96 g. (65 ml.) of a-bromonaphthalene in 250 ml. of anhydrous ether from the separatory funnel at such a rate that the reaction is vmder control (1 -5-2 hours). Place a water bath under the flask and continue the stirring and refluxing for a further 30 minutes. The Grignard reagent collects as a heavy oil in the bottom of the flask ... 

By heating halogenated benzenes or naphthalenes with cuprous cyanide, for example, a-naphthonitrile from a-bromonaphthalene and cuprous cyanide (Section IV,163). 

Chapter IV. a-Chloromethylnaphthalene (IV,23) benzylamine (Gabriel synthesis) (IV,39) i r.N -dialkylanilines (from amines and trialkyl orthophosphates) (IV,42) a-naphthaldehyde (Sommelet reaction) (IV,120) a-phenyl-cinnamic acid (Perkin reaction using triethylamine) (IV,124) p-nitrostyrene (IV,129) p-bromonaphthalene and p naphthoic acid (from 2 naphthylamine-1 -sulphonic acid) (IV,62 and IV,164) diphenic acid (from phenanthrene) (IV,165). 

Bromonaphthalene [90-11-9] M 207.1, b 118 /6mm, d 1.489. Purified by passage through activated alumina, and three vacuum distns. 

Bromonaphthalene [580-13-2] M 207.1, m 59 . Purified by fractional elution from a chromatographic column. Crystd from EtOH. 

Thus apolar probe liquids of sufficiently high surface tension to yield finite contact angles against many surfaces are especially valuable for this purpose. Popular examples of these include diiodomethane, with a surface tension of 50.8 mN/m at 23°C, and a-bromonaphthalene, with a surface tension of 44.4 mN/m at the same temperature. One should be cautioned, however, that both are sufficiently volatile that the 7re-effects may not be negligible with their use. 

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