1. a common way to understand if a mechanism is correct is to use deuterium (d = 2h) in place of hydrogen in a reaction (the method is called isotopic labeling). if dcl in d2o replaced hcl and d2so4 replaced h2so4 and so on for all solvents in this reaction, for which mechanisms would would expect deuterium to be present in the double bond of fumaric acid? explain how your arrived at your prediction using the mechanisms provided.