Reaction pocket

In the b positional state, The Rieske cluster can interact with quinone bound in the reaction pocket, but the distance to heme Ci is too large (>30 A) to allow fast electron transfer. 

The transesterification reaction can be attributed to the perturbation of the ester carbonyl group in the [CDc/o5e< -substrate] complex. The possibility of this side reaction was predicted by earlier quantum-chemical calculations [18]. These results indicated that the reaction pocket in methyl pyruvate for the nucleophilic attack is situated between the two carbonyl groups, i.e. both carbonyl groups can be perturbed by a nucleophile provided both carbonyl groups have the right "directionality". However, the right "directionality" for both carbonyl groups can be obtained if they are in syn position. 

The reaction mechanism for the heterogeneous and homogeneous acid-catalysed esterification were reported to be similar (17). However, there is a major difference concerning the snrface hydrophobicity. Reaction pockets are created inside a hydrophobic environment, where the fatty acid molecules can be absorbed and react further. Water molecules are unlikely to be absorbed on sites enclosed in hydrophobic areas. 

Figure 3.17 Schematic drawing and 3D structure of Ni[P(Ph)3]4, also showing the reaction pocket created by the dissociation of one of the triphenylphosphine ligands.

Cyclodextrins provide a hydrophobic micromedium in an aqueous phase. This characteristic is analogous to the reaction pockets of enzymes. Enzymes provide size-selective hydrophobic cavities and catalyze the reactions of bound substrates. As one might therefore expect, artificial enzymes based on cy-... 

Leaving the reaction pocket by the products, because they do not have enough space in the pocket (Fig. 13.23b3). 

Based on the concept of monosubstitution of the NHC backbone, complex 19 was developed in 2011 by the same group (Scheme 3.7) [26]. This special architecture allows the creation of a rigid reaction pocket, which has a significant impact on enantioselectivity. Hence, this new catalyst was Investigated m AROCM metathesis showing very good results in terms of reactivity and enantioselectivity. However, the E/Z selectivity was only moderate. 

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