The transients formed during the reactions of oxidizing radicals with 1-naphthol (1) and 2-naphthol (2) in aqueous medium have been investigated by pulse radiolysis with detection by absorption spectroscopy and density functional theory (DFT) calculations. The transient spectra formed on hydroxyl radical (center dot OH) reactions of 1 and 2 exhibited Amax at 340 and 350 nm at neutral pH. The rate constants of the center dot OH reactions of 1 (2) were determined from build-up kinetics at Amax of the transients as (9.63 +/- 0.04) X 109 M-1 s(-1) ((7.31 +/- 0.11) x 10(9) M-1 s(-1)). DFT calculations using the B3LYP/6-31+G(d,p) method have been performed to locate favorable reaction sites in both 1 and 2 and identification of the pertinent transients responsible for experimental results. Calculations demonstrated that 'OH additions can occur mostly at Cl and C4 positions of 1, and at Cl and C8 positions of 2. Among several isomeric center dot OH adducts possible, the Cl adduct was found to be energetically most stable both in 1 and 2. Time-dependent density functional theory (TDDFT) calculations in the solution phase has shown that the experimental spectrum of 1 was mainly attributed by Ia(4) (kinetically driven "OH-adduct) formed via the addition of 'OH at the C4 position which was 0.73 kcal/mol endergonic compared to 1a1 (thermodynamic 'OH adduct), whereas 2a(1) (thermodynamic/kinetic center dot OH-adduct) was mainly responsible for the experimental spectrum of 2. Naphthoxyl radicals of 1 and 2 have been predicted as the transient formed in the reaction of 'OH at basic pH. In addition, the same transient species resulted from the reactions of oxide radical ion (O center dot) at pH 13 and azide radical (N-3 center dot) at pH 7 with 1 and 2. Further, UV photolysis of aqueous solutions of 1 and 2 containing H2O2 (UV/H2O2) were used for the 'OH induced oxidation product formations up on 60% degradations of 1 and 2; profiling of the oxidation products were performed by using an ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) method. According to the UPLC-QTOF-MS analyses, the preliminary oxidation products are limited to dihydroxy naphthalenes and naphthoquinones with N-2-saturation, while some additional products (mainly isomeric monohydroxy-naphthoquinones) have been observed in the degradations of 1 and 2 in the presence of 02. We postulate that dihydroxy naphthalenes are derived explicitly from the most favorable 'OH-adducts speculated (preference is in terms of the kinetic/thermodynamic dominancy of transients) by using theoretical calculations which in turn substantiate the proposed reaction mechanisms. The observations of 'OH-adducts for an aromatic phenol (herein for both 1 and 2 at pH 7) rather than phenoxyl type radical in the pulse radiolysis experiments is a distinct and unique illustration. The present study provides a meaningful basis for the early stages associated with the 'OH initiated advanced oxidation processes of 1- and 2-naphthols.