Tetrapropylammonium perruthenate

Tetrapropylammonium perruthenate (TPAP or TPAPR) is the chemical compound described by the formula N(C₃H₇)₄RuO₄. Sometimes known as the Ley–Griffith reagent, this ruthenium compound is used as a reagent in organic synthesis. This salt consists of the tetrapropylammonium cation and the perruthenate, RuO₄⁻ anion. Ruthenium tetroxide is a highly aggressive oxidant, but its one-electron reduced derivative is a mild oxidizing agent for the conversion of alcohols to aldehydes. This oxidizing agent can also be used to oxidize primary alcohols all the way to the carboxylic acid. Use of a higher catalyst loading, larger amount of the co-oxidant, and addition of two equivalents of water. In this situation, the aldehyde reacts with water to form the geminal-diol hydrate, which is then oxidized again.

The oxidation generates water that can be removed by adding molecular sieves. TPAP is expensive, but it can be used in catalytic amounts. The catalytic cycle is maintained by adding a stoichiometric amount of a co-oxidant such as N-methylmorpholine N-oxide or molecular oxygen.