The pain killer ibuprofen lysine is more soluble in water than ibuprofen and can therefore be administered intravenously - VCE - SSCE Chemistry - Question 8 - 2011 - Paper 1

The correct structure for ibuprofen lysine is represented by option C. This structure shows ibuprofen attached to lysine through the appropriate chemical bond, reflecting the reaction that forms ibuprofen lysine.

To elaborate, the ibuprofen molecule comprises a isobutyl group and a carboxylic acid functional group, while lysine has an amine and a carboxylic acid as well. The amine group of lysine reacts with the carboxylic acid of ibuprofen, leading to the formation of a new amide bond, which is represented correctly in structure C.