Lewis acids and bases factors, in addition to electron configuration factors, play a role in determining the strength of the interaction between the bulky di-"t"-butylpyridine and tiny proton. Lewis acids and bases A Lewis acid is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH is a Lewis
Chemical safety assessment Restriction of Chemical substances) in which hazard and exposure data are considered together to assess the risk of a substance. Chemical safety assessment Chemical safety assessment (CSA) "has to be performed by registrants for substances manufactured and imported in quantities starting at 10 tonnes per year and by downstream users if their uses are not addressed by their supplier," according to REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) legislation. The CSA includes the evaluation of all available relevant information in order to assess risks arising from the manufacture and/or use of a substance. The process needs to be documented