- Role of the kinetic template effect in the preparation of an original copper complex
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Reaction of diethylenetriamine with phenol derivatives possessing a phenyl ester function yields a ligand corresponding to the monocondensation of diethylenetriamine with the phenol derivative. In a following step, its coordination to copper ions gives a neutral complex that is able to react with orthovanillin in order to yield an original complex made of a non symmetric ligand possessing three nitrogen, amide, imine and secondary amine, and four oxygen, amide, phenol (2) and methoxy donor atoms, thanks to the kinetic template effect. In our example, the copper center brings the three reactive functions (first primary amine and aldehyde, then amide) in close vicinity so that the formation of an imine function and the protonation of the amide function can occur. The structural determination of the resulting complex confirms an unexpected copper coordination.
- Costes, Jean-Pierre,Duhayon, Carine,Vendier, Laure
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- Proximity effect on the general base catalysed hydrolysis of amide linkage: The role of cationic surfactant, CTABr
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The bis phenoxide forms of (1,2) bis(2-hydroxybenzamido) ethane(I) , (1,5) bis(2-hydroxybenzamido) 3-azapentane(II) , (1,3) bis(2-hydroxybenzamido) propane(III) , and (1,8) bis(2-hydroxybenzamido) 3,6- diazaoctane(IV) undergo facile hydrolysis of one of the amide groups (0.02 ≤ [OH?]T (mol dm? 3) ≤ 0.5, 10% MeOH (v/v) + H2O medium) without exhibiting [OH?] dependence. The reactivity trend follows I ~ II >> III ~ IV with low activation enthalpy {25.7±2.8 ≤ δH≠ (kJ mol?1) ≤ 64.8±7.0}. The high negative and comparable values of activation entropy{?234 ±8 ≤ δS≠ (J K?1 mol? 1) ≤ ?127 ± 20} are consistent with closely similar, and ordered transition states which can be assembled by favourably oriented phenoxide groups. The solvent kinetic isotope effect for I, κ H2O/κ D2O+H2O ~ 1 (20 and 50 volume% D2O) , indicates that proton transfer is not involved as a part of the rate controlling process. The observed slowing down of the rate of this reaction for I in the micellar pseudo phase of CTABr also supports the proposed mechanism. Under premicellar conditions, however, rate acceleration is observed, a consequence believed to be associated with the capping effect of the hydrophobic tail of the surfactant cation forming the reactive ion-pair, CTA+, (I-2H) 2? exclusively in the aqueous pseudo phase. Indian Academy of Sciences.
- Dash, Sarat C.,Dash, Anadi C.
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experimental part
p. 497 - 507
(2012/03/26)
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