Examples include the Cannizzaro reaction, where approximately 50 % of the reactant aldehyde becomes the other oxidation state of the target, the Wittig reaction, where high-mass phosphorus reagents are used but ultimately become waste, and the Gabriel synthesis, which produces a stoichiometric quantity of phthalic acid
12.
In this, it was thought to resemble the classic Cannizzaro reaction mechanism, in which the attack of a hydroxylate on an aldehyde renders it into a tetravalent alcohol anion; this anion donates its hydrogens to a second aldehyde, forming a carboxylic acid and an alcohol . ( In effect, two identical aldehydes reduce and oxidize each other, leaving the net oxidation state the same .)
