No abstract

The method of continuous variation is applied to the reaction between barium chloride and diammonium hydrogen phosphate in neutral, acidic, and basic conditions. Depending on the medium, barium dihydrogen phosphate, barium hydrogen phosphate, or barium phosphate is precipitated. The precipitates are washed, dried, and weighed. Construction of a continuous variation plot for each condition leads to the deduction of the molecular formula of the phosphate precipitated. This experiment demonstrates the concept of stoichiometric relationships between ions in the formation of compounds and serves to give students practice in calculations involving limiting reagents.

Through-space (19) F-(15) N couplings revealed the configuration of flubenzimine, with the CF3 group on N4 pointing towards the lone pair of N5. The (19) F-(15) N coupling constants were measured at natural abundance using a spin-state selective indirect-detection pulse sequence. As (15) N-labelled proteins are routinely synthesized for NMR studies, through-space (19) F-(15) N couplings have the potential to probe the stereochemistry of these proteins by (19) F labelling of some amino acids or can reveal the site of docking of fluorine-containing drugs. Copyright © 2016 John Wiley & Sons, Ltd.