Salts water soluble compound preparation

Anderson, B. D. Flora, K. P., Preparation of water-soluble compounds through salt formation, in Wermuth, C. G. (ed.), The Practice of Medicinal Chemistry, Academic Press, London, 1996, pp. 739-754. 

The stability, both chemical and physical, of a drug may be enhanced or retarded by salt formation. For example, solid dosage forms of diclofenac contain salt forms rather than the less stable free acid. Although salt formation may result in improved dissolution rate and bioavailability of a poorly water-soluble compound, the preparation of stable salt forms for some drugs may not be feasible and the free acid or base forms may be preferred. For example, the base form of a-pentyl-3-(2-quinolinylmethoxy)benzenemethanol was selected for dosage form design because of the physical instability of its hydrochloride salt. ... 

Preparation of Water-Soluble Compounds Through Salt Formation... 

Sodium fluoroacetate was prepared with the idea of obtaining a stable water-soluble compound containing the CHjF CO group, suitable for feeding experiments. The method of obtaining this salt is described in detail below. It consists essentially in adding cold aqueous sodium hydroxide to methyl fluoro-acetate and evaporating the solution. Subsequent to our initial work, sodium fluoroacetate has been recommended and used as a rodenticide. 

PREPARATION OF WATER-SOLUBLE COMPOUNDS THROUGH SALT FORMATION... 

Preparation of Water-Soluble Compounds Through Salt Formation 611 Table 35.4 Manipulating characteristics of basic drugs by change of salt form... 

The slurry is prepared with the aqueous solution of an acid, base or salt or of an organic, water-soluble compound, instead of with water. 

Its nitrogen readily becomes pentavalent, forming quaternary ammonium salts. Some derivatives of known properties, useful for qualitative identification are the hydrochloride, white crystals melting at 272° with decomposition the nitrate, m.p. 184-185° the picrate, yellow rhombic prisms (from absolute alcohol) melting at 221-222° to a red oiB the />-toluidine, m.p. 150° and the anilide , m.p. 85°. Alkyl iodides readily react with it to form water-soluble compounds. The carboxylic group of nicotinic acid behaves typically, forming salts with alkalies, alkaline earth hydroxides or heavy metals the latter salts are quite insoluble and their preparation is useful to separate nicotinic acid from mixtures. 

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