It is sometimes necessary to prepare isotopically labeled samples of organic substances for probing biological transformations and reaction mechanisms. Various sources of the radioactive mass-14 carbon isotope are available. Describe synthetic procedures by which benzoic acid, labeled with 14C at its carbonyl carbon could be prepared from benzene and the following 14C-labeled precursors. You may use any necessary organic or inorganic reagents. (In the formulas shown, an asterisk indicates 14C.)