We describe a large number of binding studies in aqueous media designed to provide new insights into noncovalent binding interactions, especially the cation-a interaction. The studies include 7 different hosts, over 70 guests, and over 150 new binding constants. In addition to the now standard NMR methods, circular dichroism has proven to be an especially useful tool for determining aqueous binding constants. We have found that, in addition to the alkyliminium and tetraalkylammonium guests we have studied previously, sulfonium and guanidinium guests also show substantial cation-r effects. Bromination of the host greatly enhances its binding ability in a general fashion, primarily as a result of hydrophobic interactions. Addition of methoxy groups did not enhance binding, apparently as a result of a collapse of the host into a conformation that is not suitable for binding. Replacement of two benzene rings of the host by furans or thiophenes also did not enhance binding. Ab initio calculations provide a rationalization for this effect and suggest a clearer model for the cation-a interaction.

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assistance and protection from the Scientific Advisory Board of the Organisation for the Prohibition of Chemical Weapons: Part 2. On preventing and treating health effects from acute, prolonged, and repeated nerve agent exposure, and the identification of medical countermeasures able to reduce or eliminate the longer term health effects of nerve agents, Toxicology (2018),

The Chemical Weapons Convention (CWC) is an international disarmament treaty that prohibits the development, stockpiling and use of chemical weapons. This treaty has 193 States Parties (nations for which the treaty is binding) and entered into force in 1997. The CWC contains schedules of chemicals that have been associated with chemical warfare programmes. These scheduled chemicals must be declared by the States that possess them and are subject to verification by the Organisation for the Prohibition of Chemical Weapons (OPCW, the implementing body of the CWC). Isotopically labelled and stereoisomeric variants of the scheduled chemicals have presented ambiguities for interpretation of the requirements of treaty implementation, and advice was sought from the OPCW’s Scientific Advisory Board (SAB) in 2016. The SAB recommended that isotopically labelled compounds or stereoisomers related to the parent compound specified in a schedule should be interpreted as belonging to the same schedule. This advice should benefit scientists and diplomats from the CWC’s State Parties to help ensure a consistent approach to their declarations of scheduled chemicals (which in turn supports both the correctness and completeness of declarations under the CWC). Herein, isotopically labelled and stereoisomeric variants of CWC-scheduled chemicals are reviewed, and the impact of the SAB advice in influencing a change to national licensing in one of the State Parties is discussed. This outcome, an update to national licensing governing compliance to an international treaty, serves as an example of the effectiveness of science diplomacy within an international disarmament treaty.

The Chemical Weapons Convention (CWC) is an international disarmament and nonproliferation treaty that mandates a comprehensive ban on chemical weapons. This treaty entered-into-force in 1997 and has a nearly universal membership of world states. The CWC provides definitions for what constitutes a chemical weapon and describes chemicals for which verification measures and regulatory oversight are required. These chemicals, which must be declared to the Organisation for the Prohibition of Chemical Weapons for verification purposes, appear in three Schedules within the CWC. The Schedules list specific chemical substances and families of chemicals defined by molecular structure descriptions that allow a range of specified variable groups. The text of an international treaty provides a basis for laws and regulatory requirements at international and national levels that must be enacted to comply with treaty obligations. These laws and regulations must account for the "chemistry" that is described in the treaty text, which has been negotiated and agreed upon by world governments. In this paper, we look at some of the chemicals described within the CWC and discuss how atoms and molecules, nomenclature, and Chemical Abstracts Service numbers, isomer enumeration, ring strain, and stereochemistry influence the obligations of States to an international treaty. The material draws upon the authors' experiences from an interactive "Science for Diplomats" initiative that has provided a forum for engaging with chemical disarmament decision-makers to aid in their understanding of fundamental concepts in chemistry that have an impact on treaty implementation. We hope this article will spark interest from chemistry students and educators in the provision of science advice for policymakers and provide policymakers with an appreciation of the complexity and importance of understanding the language of chemistry in support of a world free of chemical weapons.