Kinetic isotope effects (KIEs) provide a powerful tool to interrogate transition states of both enzymic and non-enzymic reactions, provided that one can measure the intrinsic KIE on the chemical step of interest, that is, the isotope effect undiminished by other isotope-insensitive steps that may contribute to the overall rate of reaction. For small molecules reacting in solution the KIE measur...

In plants and algae, photosystem II uses light energy to oxidize water to oxygen at a metalloradical site that comprises a tetranuclear manganese cluster and a tyrosyl radical. A model is proposed whereby the tyrosyl radical functions by abstracting hydrogen atoms from substrate water bound as terminal ligands to two of the four manganese ions. Molecular oxygen is produced in the final step in ...

The title compound, C(11)H(14)ClNO(3), was prepared by the condensation of equimolar quanti-ties of 5-chloro-salicyl-aldehyde and 2-amino-2-methyl-propane-1,3-diol in methanol. In the crystal, it exists in the zwitterionic form, with nominal proton transfer from the phenol group to the imine N atom. This results in the formation of an intra-molecular N-H⋯O hydrogen bond, which generates an S(6)...

Based on ab initio calculated results, a new mechanism is proposed that intramolecular hydrogen atom transfer may occur Ž . during the photodissociation of o-chlorotoluene at 266 nm. This mechanism is different from the general suggestion, i.e. 1 Ž . Ž . Ž . Ž . o-chlorotoluene S TMo-chlorotoluene T TMClqo-tolylTMbenzylqCl. Our suggestion is 2 o-chlorotoluene S TMo1 1 1 Ž . Ž . Ž . chlorotoluen...

the microstructure and thermal properties of the synthesized block copolymers and terpolymers via atom transfer radical polymerization (atrp) were studied. the mole fraction of the blocks and chain length of the pvac-b-pma block copolymers were estimated with 1h nmr spectroscopy.differential scanning calorimety measurement shows two different transitions at 36°c and 8°c assigned to pvac and pma...