Thiols are one of the most important classes of chemicals used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. This study is an internally-referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and di-thiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S-H stretching feature relative to an internal reference peak as a function of solution pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curveitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation. Using this Raman titration method, first and second thiol pKa values for 1,2-benzenedithol in water were determined for the first time. This method is convenient to implement and its underlying theory is easy to follow.

No description available.

Hannover, Universiẗat, Diss., 1999.

Universiẗat, Diss., 2002--Tübingen.

No description available.

No description available.

No description available.

This dissertation reports on the recent discovery that calix[4]pyrrole not only functions as an anion receptor, but also has the ability to act as an ion pair receptor. It was discovered that in the solid state large diffuse cations, such as Cs+ and imidazolium, will occupy the electron-rich cone-like cavity that is formed upon anion binding to the NH region of the calix[4]pyrrole core. Also discussed are efforts devoted to improving the anion binding ability of calixpyrroles and fine-tuning their inherent selectivity. This has been probed through a variety of structural modifications. One of the most attractive of the modification strategies currently being explored involves expansion of the central binding cavity by using higher order β-fluorinated calix[n]pyrroles; n = 5, 6, and 8. An advantage of β-fluorinated calix[4]pyrrole is that it shows enhanced anion binding affinities toward several anions compared to the parent calix[4]pyrrole. Fluorinated calixpyrroles have also shown an ability to extract anions from aqueous environments into organic media. An alternative strategy has been to attach “straps” resulting in bicyclic systems, which further define the binding cavity achieving higher affinity and anion selectivity. The binding interactions of calixpyrrole and it derivative have been quantified using analytical techniques, such as nuclear magnetic resonance spectroscopy and isothermal titration calorimetry. The results of these latter studies will be discussed herein. / text

Ions play pivotal roles both biologically and environmentally. The effects felt from the impact of ions, much like their relative charge, can be positive or negative. Ions are responsible for catalyzing and executing precise control over many of the essential processes that occur in our bodies. Ions can also be major contributors as environmental pollutants having catastrophic effects. There is a great deal of interest in better understanding the role and effect of ions in the surrounding environments. The ability to study ions of interest relies on efficient recognition and sensing of these targets. The field of supramolecular chemistry is particularly well suited for this task as it utilizes non-covalent molecular interactions in much the same way natural system involving ions operate. Broadly, this body of research seeks to explore the subtle interactions of various targeted ions with supramolecular receptors. This research is an effort to further understand the nature of these interactions for potential recognition and sensing applications as well as better understanding the highly complex systems found in biology. Chapter I provides a brief overview of various mechanisms of ion coordination in supramolecular chemistry and emphasizes some key examples demonstrating the importance of the various types of coordination as it pertains to the research presented herein. Chapter II highlights a unique class of phosphine oxide-based tripodal ditopic receptors and presents studies on their interactions with alkali metals and halides. Chapter III covers the synthesis and study of anionic binding trends for a series of heteroaromatic-containing urea-based receptors and discusses the influence of anion binding on receptor conformation. Chapter IV provides preliminary results on the application of the bipyridal bisurea-based anion receptor, presented in Chapter III, as ligand for metal salts. Chapter V focuses on a series of pyridal bisurea-based receptors with regard to their ability to serve as chloride sensitive probes in cellular environments. This dissertation contains both previously published and unpublished co-authored material. / 10000-01-01

Generally human titration performance under schedules of reinforcement has not been investigated. In an attempt to examine the variables which control titration, an interlocking progressive-ratio schedule was devised. Under an interlocking progressive-ratio schedule, the number of responses required for reinforcement increases by a constant (the increment value) after every ratio, but during each ratio the response requirement can be lowered (the decrement value) by emitting pauses of a specified duration (the stepdown duration). The first experiment sought to determine if children would titrate when exposed to interlocking progressive-ratio schedules. Although three of the four subjects did not show evidence of titration initially, through a series of manipulations all came under schedule control. Experiment 2 was conducted to determine the effects of a series of increment value manipulations on the level of titration. The series of increment values was tested under large and small decrement conditions. The results showed that increment value was an important determiner of titration level only when the decrement value was small. When the decrement value was large, changes in increment value had no effect upon titration. In Experiment 3 the effects of a series of decrement manipulations on titration level were examined. The decrement manipulations were investigated under two increment values. The results indicated that as the decrement value was decreased the titration level tended to increase under both increment conditions. In all of the experiments, rate of responding, pausing, titration variability, and patterns of responding were examined. Generally rate of responding, pausing, and response patterning were found to be related to changes in increment and decrement values. Titration variability showed no systematic changes across manipulations. Analysis of subjects' behavior in terms of preference indicated that the subjects tended to minimize number of responses rather than maximize reinforcement frequency. Subjects would pause to bring down the response requirement, and thus increase the time between reinforcements, rather than emit responses on a lever, which would have resulted in more reinforcements per unit of time.