An Undergraduate Chemistry Experiment Integrating Theoretical and Practical Aspects of Hypervalent Iodine(I) Compounds

A simple reaction sequence has been developed to produce iodine chloride-pyridine (PyICl) and pyridinium dichloroiodate (PyHICl₂), convenient iodinating agents, in a high yield. Our approach is safe and simple to handle, avoiding the use of elemental chlorine or hazardous manipulations. Designed for an upper-level undergraduate hybrid lecture/lab chemistry course, the experiment integrates key concepts from both inorganic and organic chemistry. The pre-experiment lecture explains the connections between molecular structure, reactivity trends, and reaction types. Over three 4 h lab sessions, students carry out a sequence of quantitative transformations and characterize each intermediate and the final product using ESI mass spectrometry, as well as ¹H and ¹³C NMR spectroscopy. They also apply the PyICl adduct for electrophilic iodination of salicylic acid. This experiment reinforces theoretical knowledge while providing hands-on experience in inorganic and organic synthesis and instrumental analysis. This material, along with its educational value, can also be useful to practical benchtop chemists working in the research and development sector.