Deprotonation, multiple

The structure of the deprotonated ethylenediamine complex [Os(en-H)2en]-Br2 has been confirmed (Figure 1.58) the Os=NH bonds (2.11-2.19 A) indicating clear multiple bond character. It can be used as a source of conventional ethylenediamine complexes. 

One element of database generation that is a key consideration is whether to expand the representative compounds to include alternative tautomers, protonated and deprotonated forms of the molecule, and also to enumerate stereochemistry fully if not specified in the input. Depending on the molecules in question and the options considered, these can lead to a 10-fold increase in the size of the database to be explored. However, such an expansion is necessary if methods are used that are sensitive to such chemical precision (e.g., docking). For 3D similarity searching, it is sometimes more efficient to consider various modifications to the query, leading to multiple searches against a smaller database. 

Thus, the pKa value equals pH if the concentrations of protonated and deprotonated states are identical. For this reason, pKa is also called p/fi/2- Equation (10-4) can be rearranged and written in a generalized form in the presence of multiple titration sites,... 

A characteristic feature of ESMS is the detection of multiply charged analytes. Macromolecules, such as proteins have multiple sites where protonation or deprotonation (the two most common charge inducing mechanisms in electrospray—other routes to charge induction include, ionization through adduct formation, through gas-phase reactions, and through electrochemical oxidation or reduction) occur. These are desorbed effectively in ESMS and... 

Figure 47 The structure of a inverse crown with multiple deprotonated ferrocenes 96.

Cumene is generated following a deprotonation step [85]. One of the undesired reactions is multiple alkylahon with propylene. Oligomerization of propylene is also undesired. Beta zeolite is a typical catalyst for this reaction. A series of Beta zeolites synthesized with Si/Af rahos ranging from 20 to 350 were evaluated for the alkylation of benzene with propylene at 423°K and 3 MPa in the presence of benzene alkene molar raho of 7.0. The benzene alkene molar ratio was kept high in order to minimize the undesired reactions. The selectivity to the mono-alkylate product was 92-93% in every case with the balance being the dialkylated product. The activity decreased with increase in Si/Al2 but the selectivity was independent of the Si/A12 ratio [86]. 

Ferrocene is best deprotonated by f-BuLi/f-BuOK in THF at 0 since BuLi alone will not lithiate ferrocene in the absence of TMEDA and leads to multiple lithiation in the presence of TMEDA. In the example in Scheme 134, a sulphur electrophile and a Kagan-Sharpless epoxidation lead to the enantiomerically pure sulphinyl ferrocene 278. The sulphinyl group directs stereoselective ortholithiation (see Section I.B.2), allowing the formation of products such as 279. Nucleophilic attack at sulphur is avoided by using triisopropylphenyllithium for this lithiation. 

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