Abstract: Process, and resulting product, for improved hydroperoxidation of branched alkanes of at least 4 carbon atoms, especially useful in preparation of isoprene from isopentane; comprising the substantial elimination of acetic acid and similar by-products in the hydroperoxidation reaction which are harmful to the yield of the desired hydroperoxides; all of which is achieved by at least one washing between at least two successive oxidizing reactors. The wash solution may be just water or advantageously a pre-saturated aqueous solution containing the oxidation products which are desired not to be extracted from the organic phase of the reaction medium.