Naphthalene picrate

Identification of Aromatic Hydrocarbons. Picric acid combines with many aromatic hydrocarbons, giving addition products of definite m.p. Thus with naphthalene it gives yellow naphthalene picrate, C oHg,(N08)jCeHiOH, m.p. 152°, and with anthracene it gives red anthracene picrate, C 4Hio,(NOj)jCeHjOH, m.p. 138 . For practical details, see p. 394. 

Picrates, Many aromatic hydrocarbons (and other classes of organic compounds) form molecular compounds with picric acid, for example, naphthalene picrate CioHg.CgH2(N02)30H. Some picrates, e.g., anthracene picrate, are so unstable as to be decomposed by many, particularly hydroxylic, solvents they therefore cannot be easily recrystaUised. Their preparation may be accomplished in such non-hydroxylic solvents as chloroform, benzene or ether. The picrates of hydrocarbons can be readily separated into their constituents by warming with dilute ammonia solution and filtering (if the hydrocarbon is a solid) through a moist filter paper. The filtrate contains the picric acid as the ammonium salt, and the hydrocarbon is left on the filter paper. 

The foUowing are typical experimental details for the preparation of naphthalene picrate. Dissolve 0 -1 g. of naphthalene and 0-2 g. of picric acid separately in the minimum volume of hot rectified spirit (about 2 ml.), mix the solutions and allow to cool. FUter and wash with 2 ml. of alcohol. RecrystaUise from hot alcohol, ethyl acetate or ether. 

Dissolve naphthalene in a little spirit, and add an equal quantity of a solution of picric acid in spirit. On cooling, yellow needles of naphthalene picrate separate, C,oHg.CQH20H(NO,)3. Benzene forms colourless crystals, anthracene, scarlet needles, having a similar composition. Sec Appendix, p. 295. 

Naphthalene, 216 Naphthalene picrate, 217 Naphthalene sulphonaie ofsodiiim, 218-/ J-Naphthol, 219 Naphthol yellow, 224 /i Naphthyl acetate, 222 /j-Naphthyl methyl ether, 220 /-Nitracetanilide, 153 w-Nitraniline, 154 /-Nitraniline, 153 Nitric acid (fuming), 22 NitroVienzene, 142 w-Nitrobenzoic acid, 200 Nitrogen, qualitative e rimation, 2 quantitative estimation, 13 Nitrophenol, 183 Nitrosohenzene, 146 /-Nitrosodimethylaniline, 157 Niirosoplienol, 159... 

Naphthalene Picrate. C 0H8+C6H2(N02)3OH golden yel needles forms eutectic mixts with PA mp 149-151.5° explds at 484° (Beil 6, 272,(132) [259])... 

The following are typical experimental details for the preparation of naphthalene picrate. Dissolve 0.1 g of naphthalene in the minimum of hot ethanol and add to 1 ml of a saturated solution of picric acid in ethanol. Warm the mixture and then cool to allow the product to crystallise. 

The magnetic susceptibility of some addition compounds, such as naphthalene picrate, is nearly additive, i.e. equal to the sum of the components (Le Fevre [127], Baddar and Mikhail [128]). This would suggest that the molecules are held by weak electrostatic forces. 

Naphthalene and picric acid form a solid compound which although not a salt is commonly known as naphthalene picrate. If shaken with water it partly decomposes to give solid naphthalene and a solution of picric acid. Bell and Fendley (Trans. Faraday Soc., 1949, 45, 122), measured the e.m.f. at 25 C of the cells ... 

If the cells a and /J are connected back-to-back the chemical process associated with the flow of electricity will be the transference of solid picric acid from a to /9 where with naphthalene it forms naphthalene picrate. Thus, the value E = 0.090 V is the e.m.f. of the cell ... 

Naphthalene picrate. Phenanthrenc picrate. Aeenapthene picrate. 

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