We present a simple, mild, and highly effective method for the direct conversion of primary alcohols to carboxylic acids. TPAP serves as the catalyst, and NMO center dot H(2)O plays a dual role, acting as the co-oxidant and as a reagent for aldehyde hydrate stabilization. This previously unknown stabilizing effect of geminal diols by N-oxides is the key for the efficiency of the overall transformation.