Ring-opening rate constant

Values of the Acid Dissociation Constant (K) and Ring-Opening Rate Constant (k2) of [L4Co(02COH)]2 + and the Decarboxylation Rate Constant (k2) of the Corresponding Monodentate Bicarbonato Complexes (at 25.0 °C,... 

These equations are in line with Eq. (30), such that kx denotes the ring-opening rate constant of the protonated carbonato complex and / 2 is the decarboxylation rate constant of the ring-opened bicarbonato complex. Values of these rate constants and the acid dissociation constants of some protonated carbonato complexes of cobalt(TII) (see Table III) reflect the ligand dependence with respect to charge variations, steric constraint, and donor properties of the non-labile ligands. 

The H-n.m.r. parameters of the four D-penturonic acids and of 2-deoxy-D-eo t o-penturonic acid in D2O have been recorded, and aqueous solutions of their l- C-substituted analogues have been studied by C-n.m.r. spectroscopy over a range of pH values, with particular emphasis on the ring-opening reactions of the furanose rings. The rate constants for ring-opening were determined at pH 1.5 for the protonated and at pH 4.5 for the ioiuzed forms. ... 

On neutralization, the ring-opened species slowly ring-closes again. At 20°, for the ring-opened substance from pteridine, the first-order rate constant is about 10 sec. ... 

Rate Constants for the Ring-Opening Reaction OF Hydrated Cations" ... 

Rate constants for ring-opening of dioxolan-2-yl radicals have been measured by Barclay et a/.241 as 103-104 s 1 at 75 °C (Scheme 4.29). There is also evidence that ring-opening is reversible.24 244 Thus, isomerization of the initially formed product to one more thermodynamically favored is possible if propagation is slow. 

The concentration of the lactam in the final product is determined by (3.11). Cyclic dimers can also form, and these also take part in the polymerization12 the reactions are acid catalyzed. The kinetics of this ring-opening polymerization with the three reactions in (3.10)—(3.12) is complex. The reaction rate constants and equilibrium constants have been described by several authors,5 6,8,12 28 and more pragmatic approaches for describing the reaction kinetics have also been given.28,31,33... 

This is less common than rearrangement of carbocations, but it does occur (though not when R = alkyl or hydrogen see Chapter 18). Perhaps the best-known rearrangement is that of cyclopropylcarbinyl radicals to a butenyl radical. The rate constant for this rapid ring opening has been measured in... 

Cyclopropylcarbinyl radicals (5) are alkyl radicals but they undergo rapid ring opening to give butenyl radicals." The rate constant for this process has been measured by picosecond radical kinetic techniques to be in the range of 10 M s for the parent to lO Af s for substituted derivatives. This process has been observed in bicyclo[4.1,0]heptan-4-ones. ... 

In acidic aqueous solution the displacement of 1,1-cyclobutanedicar-boxylate (cbdca2-) from [Pt(cbdca)(NH3)2] (Figure 1) resembles the successive displacements of two monodentate carboxylates [18]. Rate constants of 8 x 10 5 s-1 and 8.0 x 10 4 s-1 (298.2 K) were found for the ring-opening step of nonprotonated and protonated species, respectively. 

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