Hydroxide guanidinium

A series of alkali-amylose complexes can be obtained during the solid-state deacetylation of amylose triacetate, as first described by Senti and Witnauer (32). The unit cells of the individual members of the series of LiOH-, K0H-, NH3OH-, CsOH and guanidinium hydroxide-adducts of amylose appeared to fit an iso-morphous series based on the space group P212 2i> and a tentative crystal structure was proposed (32). The detailed structure of the KOH-amylose complex has now been determined (ll) and the overall structure is similar to that proposed earlier. It is, therefore, likely that all members of the series are isomorphous. 

Aqueous solutions of guanidine cause a structural change in cellulose midway between that produced by aliphatic amines and by alkali hydroxides. The lattice change to a cellulose II structure, which occurs with aqueous alkali hydroxide above a certain concentration, does not occur with guanidine. This was attributed to N-H—O bridges, with the participation of guanidinium ions. 

PAES has been functionalized with quaternary guanidinium groups for use in polymeric hydroxide exchange membranes. The quaternized polymers could be synthesized by the chloromethylation of PAES, followed by the reaction with pentamethyl-guanidine, c.f.. Figure 7.15 [113]. 

A 6-coordinated structure is suggested for the complex anion formed between catechol and silica, reported by Rosenheim, Raibmann. and Schendel (196). The ammonium salt, crystallized from, alcohol, has the composition (NH4)2Si(C H402)3 and dissolves in water without decomposition of the anion. The compound is prepared by boiling freshly precipitated silica in an ammoniacal solution of pyrocatechol out of contact with air. Since silica is not soluble in ammonium hydroxide (because silica does not form silicate ions below about pH 10.8), it is evident that the combined action of ammonia and catechol converts silica to some soluble form other than a simple silicate ion. The corresponding potassium, barium, guanidinium, and pyridinium salts were prepared. 

Ansyln and coworkers designed 79 which contains a Zn(II) center within a cleft containing two guanidinium scaffolds. The guanidinium groups are properly positioned to hydrogen-bond to the Zn(II) bound phosphate ester and stabilize the anionic transition state formed upon nucleophilic attach of hydroxide on the phosphoryl group. 

Guanidine, is almost as basic as hydroxide ion. Its conjugate acid, guanidinium ion 13.6), is a weaker acid than almost any other protonated amine. 

Wang JH, Li SH, Zhang SB (2010) Novel hydroxide-conducting polyelectrolyte composed of a poly(arylene ether sulfone) containing pendant quaternary guanidinium groups for alkaline fuel cell applications. Macromolecules 43 3890-3896... 

Ansyin and coworkers have explored the stoichiometric hydrolysis reactivity of zinc complexes of terpyridyl-type ligand having guanidinium or ammonium appendages (Fig. 8.24) using the RNA dimer adenylyl (3 -> 5 )phosphoadenine (ApA) [119]. The hydrolysis of this substrate yields adenosine 3 -monophos-phate, adenosine 2 -monophosphate, adenosine 2, 3 -cAMP, and adenosine. The optimal rate of reaction of Zn(II)-4 with ApA is found at pH 7.5, which is near the pK value of a zinc-coordinated water molecule in this system (pJCa=7.3 determined independently by potentiometric titration). This suggests the involvement of a zinc hydroxide species as the active complex for ApA hydrolysis. 

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