Proton exchange proceeds via a phosphonium ( PH 4 + ) ion in acidic solutions and via PH 2 " at high pH, with equilibrium constants " K " b = 4 ?10 " 28 and " K " z = 41.6 ?10 " 29.
32.
Newer developments omit the carbodiimides totally : the active ester is introduced as a uronium or phosphonium salt of a non-nucleophilic anion ( tetrafluoroborate or hexafluorophosphate ) : HBTU, HATU, HCTU, TBTU, PyBOP . Two uronium types of the coupling additive of Oxyma Pure is also available as COMU or TOTU reagent.
33.
The materials required for the production of the nanoshells are the following; Tetraethyl orthosilicate, ammonium hydroxide, hydroxylamine hydrochloride, 3-aminopropyl tris, hydrogentetrachloroaurate ( III ) trihydrate, tetrakis ( hydroxymethyl ) phosphonium chloride, sodium hydroxide, potassium carbonate, ethanol, Ultrapure water and glassware washed in aqua regia and rinsed thoroughly in water . :)
