Deprotonation grade

Structures for vanadyl complexes of citric acid.P l The formulae for the citrato complexes [(VO)2(Hcit)(H2cit)] and [(VO)2(Hcit)2] have been modified to account for the deprotonation grade of the coordinated citrate. Note, in the structurally characterised complex [(VO)2(cit)(Hcit)] , the differing coordination modes of the two Hcit. ... 

Wild-type PYP was prepared as described in [10]. Samples of PYP in native conformation were prepared in 10 mM phosphate buffer (pH = 7.5), using HPLC grade water. Denaturation of PYP was achieved by adding solid guanidinium chloride to 7 M final concentration. After denaturation, the pH was set to 9.6 with KOH, in order to deprotonate the chromophore. The absorbance of each sample was adjusted to 1 per mm at the absorption maximum. 

Trans-pCA was purchased from Sigma. Thms-pCM and trans-pCT have been synthesized for this study [10]. Deprotonation of pCA and pCM was achieved by adding 0.05 M of KOH in HPLC grade water. Samples of deprotonated pCT were prepared in a borate Britton-Robinson buffer at pH 10.2 [10]. The absorbance was adjusted to 1 per mm at the absorption maximum. 

Taking H3BO3 for example, which is a very weak acid in aqueous solutions (i.e., its grade of deprotonation is very low) becomes strongly deprotonated in liquid ammonia and is acting in reactions accordingly in such media. On the other hand, strong bases will loose... 

Because of the basic conditions of the reaction it is difficult to extend the use to enoUzable aldehydes. Another limiting factor is the possibility of a [2,3]-sigmatro-pic shift if allyl halides are used (Scheme 7.55). This problem can be overcome with two strategies (a) the design of a sulfide that favours a-deprotonation, and/or (b) introduction of a higher grade of hindrance in the a -positions, so that the alternative deprotonation in this position has a kinetic disadvantage [201],... 

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