Alkali metal starchates

The limited solubility of starch and its modified products may affect the reversibility of many reactions. This may explain several, apparently unusual, reactions reported in starch chemistry. There are, for example, reports of starch esterification with sodium hydrogenphosphates, acylation of starch with acyl amides (which is equivalent to the transformation of an amide into an ester), and the formation of alkali-metal starchates upon treatment of starch with alkali (a reaction which fails for simple alcohols). A specific property of starch is its ability to form surface sorption and helical inclusion-complexes with many inorganic and organic guest molecules.4... 

Other starch varieties chemically bind metal atoms only to the hydroxyl groups, in the same manner as alcoholates. Alkali metal starchates were obtained for the first time by the use of either metal amides in liquid ammonia641 or metals in liquid amines.642 These methods were subsequently used by others.643 Sodium 2-starchate could be prepared by refluxing an alcohol solution of NaOH and dry starch.644 The reaction of dry starch with controlled amount of NaOH in 1-butanol provided either monosodium 2-starchate or disodium 2,3-starchate.645,646 However, complexes of NaOH with starch were also characterized.37,38 Thallation of starch could be performed with thallous hydroxide.647... 

Low density expl contg starchate of alkali metal or ammonia in which the metal is attached through an O atom to a C in the 2 position in the starch mol. Thiochloro, thioammonium or nitro-starches may also be used. E.g NH4 starchate, thiochloro, thioammonium 75 ... 

---