Water picrates from

Place a mixture of 0-5 g. of finely powdered thiourea, 0-5 g. of the alkyl halide and 5 ml. of alcohol in a test-tube or small flask equipped with a reflux condenser. Reflux the mixture for a j)eriod depending upon the nature of the halide primary alkyl bromides and iodides, 10-20 minutes (according to the molecular weight) secondary alkyl bromides or iodides, 2-3 hours alkyl chlorides, 3-5 hours polymethy lene dibromides or di-iodides, 20-50 minutes. Then add 0 5 g. of picric acid, boil until a clear solution is obtained, and cool. If no precipitate is obtained, add a few drops of water. RecrystaUise the resulting S-alkyl-iso-thiuronium picrate from alcohol. 

Table 1. Extraction (%) of alkali metal picrates from the aqueous into the organic phase by 3a-d 3a-d 10 2 M (in dichloromethane), alkaline metal picrates 10 1 M (in water), picric acid 7xl0 5 M (in water).

In the tetra-bridged phosphocavitands containing four donor P(0)R groups, the P=0 bonds can adopt the inward (f) or outward (o) orientations relatively to the molecular cavity. Only the ini isomer with the four P=0 groups oriented inwards can benefit from both cooperativity of P=0 binding and r-in-teractions with the aromatic cavity of the resorc[4]arene framework [19, 63]. The complexation properties of new iiii tetra-phosphonatocavitands 12b-12d and 12g towards metal ions were characterized by extraction of the metal picrate from water to chloroform solution containing the host compound (Fig. 4). 

Extraction Percentages (% ) of Alkali Picrates from Water into Dichloromethane... 

Early results with these systems were encouraging. A comparison of 2-(I) and 4-(methoxyphenoxy)methyl (II) (CH3-0-C6H4-0-CH2-) derivatives of 15-crown-5 (III) with the latter compound proved instructive. Liotta (8) reported that the cyclization yield for 15-crown-5 was 29%. We found that when the methoxy group was para and too remote to interact with a ring-bound cation, the cyclization yield was 30%. When the methoxy group was ortho, the cyclization yield more than doubled (ca. 70%). Two-phase extraction constant studies (9) also proved encouraging. The method involves extraction of sodium picrate from water into a nonpolar solvent like chloroform or dichloromethane. The picrate anion is highly colored and its... 

Trichocereine is a colorless basic oil it distils in vacuo without decomposition and is soluble in water, alcohol, ether, and chloroform. The salts crystallize well hydrochloride (from alcohol), m.p. 205 picrate (from acetone), yellow needles, m.p. 171-172 picrolonate (from alcohol-acetone), yellow prisms, m.p. 166°. If the melted salt is heated again, it melts at 175 . The platinichloride crystallizes from water and melts at 184-185° aurichloride, m.p. 136-139 (with decomp.) methio-dide, m.p. 226-228° picrate of the quaternary iV-methyl trichocereine (from water), m.p. 165°. 

In order to further assess the ability of the crown-polymers and 12 and of PEG to act under liquid-liquid conditions as PTC s, we determined the extent of transfer of sodium and potassiima picrate from water into methylene chloride in the presence of these phase transfer agents (PTA s). The polymers were essentially Identically effective, transferring approximately 5% of sodium picrate and 20% of potassium picrate into the methylene chloride (0.181 g/100 mL of solvent and 0.0954 mM and 0.085 mM in potassium and sodium picrate, resoectively). Interestingly, PEG 1000 was comparable to PEG 6800 for sodium complexation (3.9% vs. 3.6% transferred) but not for potassium complexation (14.5% vs. 19.2% transferred) when compared on a equal-mass basis. The preference for potassium over sodium is surprising, and has been noted by Yamazaki and coworkers. 

Mix together 1 0 g. of pure p-naphthol and the theoretical quantity of 50 per cent, potassium hydroxide solution, add 0-5 g. of the halide, followed by sufficient rectified spirit to produce a clear solution. For alkyl chlorides, the addition of a little potassium iodide is recommended. Heat the mixture under reflux for 15 minutes, and dissolve any potassium halide by the addition of a few drops of water. The p-naphthyl ether usually crystallises out on cooling if it does not, dilute the solution with 10 per cent, sodium hydroxide solution untU precipitation occurs. Dissolve the p-naphthyl ether in the minimum volume of hot alcohol and add the calculated quantity of picric acid dissolved in hot alcohol. The picrate separates out on cooling. Recrystallise it from rectified spirit. 

If the amine is soluble in water, mix it with a slight excess (about 25 per cent.) of a saturated solution of picric acid in water (the solubility in cold water is about 1 per cent.). If the amine is insoluble in water, dissolve it by the addition of 2-3 drops of dilute hydrochloric acid (1 1) for each 2-3 ml. of water, then add a sUght excess of the reagent. If a heavy precipitate does not form immediately after the addition of the picric acid solution, allow the mixture to stand for some time and then shake vigorously. Filter off the precipitated picrate and recrystaUise it from boiling water, alcohol or dilute alcohol, boiUng 10 per cent, acetic acid, chloroform or, best, benzene. 

The most versatile derivative from which the free base can be readily recovered is the picrate. This is very satisfactory for primary and secondary aliphatic amines and aromatic amines and is particularly so for heterocyclic bases. The amine, dissolv in water or alcohol, is treated with excess of a saturated solution of picric acid in water or alcohol, respectively, until separation of the picrate is complete. If separation does not occur, the solution is stirred vigorously and warmed for a few minutes, or diluted with a solvent in which the picrate is insoluble. Thus, a solution of the amine and picric acid in ethanol can be treated with petroleum ether to precipitate the picrate. Alternatively, the amine can be dissolved in alcohol and aqueous picric acid added. The picrate is filtered off, washed with water or ethanol and recrystallised from boiling water, ethanol, methanol, aqueous ethanol, methanol or chloroform. The solubility of picric acid in water and ethanol is 1.4 and 6.23 % respectively at 20°. 

Other purification procedures include the formation of the picrate, prepared in benzene soln and crystd to constant melting point, then decomposed with warm 10% NaOH and extracted into ether the extract was washed with water, and distd under reduced pressure. The oxalate has also been used. The base has been fractionally crystd by partial freezing and also from aq 80% EtOH then from absolute EtOH. It has been distd from zinc dust, under nitrogen. 

Tetraethylammonium picrate [741-03-7] M 342.1, m >300 (dec). Purified by successive crystns from water or 95% EtOH followed by drying in vacuum at 70°. 

Potassium picrate [573-83-1] M 267.2. Crystd from water or 95% EtOH, and dried at room temperature in vacuum. It is soluble in 200 parts of cold water and 4 parts of boiling water. THE DRY SOLID EXPLODES WHEN STRUCK OR HEATED. 

B. HAUCI4, separates as an oil, but solidifies on standing and may be recrystallised from water containing hydrochloric acid. The crystals melt at 137-9° or below 100° when heated under water. This salt and the picrate, rectangular plates, m.p. 175-6°, are well adapted for the identification of the alkaloid. The methobromide, m.p. 223-5°, and the inethonitrate, m.p. 166-8°, are now both used in medicine. 

Tropacocaine (Benzoyl-ili-tropeine), CuHj gOgN, was discovered by Giesel in Java coca leaves and has since been found in Peruvian coca. Its preparation from the former source has been described by Hara and Sakamoto, It crystallises in needles, m.p. 49°, is insoluble in water, but soluble in alcohol, ether or dilute ammonia and is generally prepared by benzoylating /t-tropine, and purified as the hydrochloride. Its alcoholic solution is alkaline and optically inactive. The hydrochloride forms needles, m.p. 271° (dec.), and the hydrobromide leaflets. The aurichloride separates in minute yellow needles, m.p. 208°, from hot aqueous solutions the picrate has m.p. 238-9°. When heated with hydrochloric acid or baryta water the alkaloid is hydrolysed to benzoic acid and -tropine. ... 

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