A convenient and clean route to transform, in aqueous medium, various alkanes to carboxylic acids via single-pot carboxylation with CO and water, under mild conditions, has been achieved, proceeding efficiently and selectively even without any metal catalyst and any acid additive, at low temperatures; the relevant hydroxylating role of H(2)O and radical mechanisms are disclosed by radical-trap, H(2)(18)O and DFT studies.