Isotopic exchange studies, water structure

Although the exact mechanism for iodobenzene formation from the diazonium cation is unclear, the phenyl cation is not an impossible intermediate, it is still considered to be the best candidate for the intermediate in phenol formation from arenediazonium salts and hot water (Section 22-4). In addition, it is known that diazonium cations exchange their bonded N2 with gaseous N2 (detected in isotope studies), direct evidence that reversible dissociation of N2 to leave behind a phenyl cation can take place. This system is an example of how a seemingly simple structure can exhibit a lot of complexity in its behavior. 

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