Penultimate effect in radical copolymerization of 2‐trifluoromethylacrylates

Electron‐deficient 2‐trifluoromethylacrylates (TFMA) undergo radical copolymerization with electron‐rich norbornene derivatives, vinyl ethers, and styrene derivatives, which can be described by the penultimate model much better than by the commonly employed terminal model. In an attempt to directly observe the effect of the CF₃ group in the penultimate unit on the radical reactivity, we employed the Giese's mercury method. 4,4,4‐Trifluorobutyl and n‐butyl radicals produced from respective alkylmercuric chlorides were competitively reacted with t‐butyl 2‐trifluoromethylacrylate (TBTFMA) and t‐butyl methacrylate (TBMA) and the products analyzed with gas chromatography. While TBTFMA has been found to be about 24times more reactive than TBMA toward the n‐butyl radical, the former is about 12 times more reactive than the latter toward the 4,4,4‐trifluorobutyl radical. Thus, the reactivity of the propagating radical toward TBTFMA in comparison with TBMA is suppressed by a factor of two when the penultimate unit has the CF₃ group. We observed a sextet electron spin resonance of the TFMA propagating radical with a coupling constant of ca. 25 gauss between the β‐proton and β‐fluorine. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1559–1565, 2008     

Solid-state reactions from isothermal heat conduction microcalorimetry theoretical approach and evaluation via simulated data

Several recent publications from this laboratory have reported developments in the capacity to calculate thermodynamic and kinetic parameters, such as rate constant, enthalpy, order of reaction, from isothermal micro-calorimetric data. To date these developments have all been associated with the calculation of the desired parameters from solution phase reactions. This paper furthers these developments to a theoretical consideration of solid-state reactions and the calculation of the values for the rate coefficient, k, the fitting parameters m and n, the total number of joules released over the lifetime of reaction, Q, and hence either the specific enthalpy or the molar enthalpy of reaction, H. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microcalorimetry in the screening of discovery compounds and in the investigation of novel drug delivery systems

Calorimetry has for some time been proposed as a rapid method for determination of bioactivity. This paper describes the background to this application and describes how it has been extended to the study of bioassay techniques via microcalorimetry in the development of structure activity relationships (SARs). That SARs can be developed indicates that it is possible to guide drug synthetic strategy through the results of microcalorimetric investigations, and this approach is explored here. In an extension of this approach it is argued that microcalorimetry is well suited to the examination of novel drug delivery systems, allowing investigation of the capacity of drug delivery molecules to release the drug in the presence of a target organism.     

Nachweis und Bestimmung der Halogene

Ohne Zusammenfassung     

Unique Solvability of Certain Hybrid Networks from Their Distances

Phylogenetic relationships among taxa have usually been represented by rooted trees in which the leaves correspond to extant taxa and interior vertices correspond to extinct ancestral taxa. Recently, more general graphs than trees have been investigated in order to be able to represent hybridization, lateral gene transfer, and recombination events. A model is presented in which the genome at a vertex is represented by a binary string. In the presence of hybridization and the absence of convergent evolution and homoplasies, the evolution is modeled by an acyclic digraph. It is shown how distances are most naturally related to the vertices rather than to the edges. Indeed, distances are computed in terms of the “originating weights” at vertices. It is shown that some distances may not in fact correspond to the sum of branch lengths on any path in the graph. In typical applications, direct measurements can be made only on the leaves, including the root. A study is made of how to infer the originating weights at interior vertices from such information. Received August 18, 2004