AbstractAbsolute rate constants for H‐atom abstraction by OH radicals from cyclopropane, cyclopentane, and cycloheptane have been determined in the gas phase at 298 K. Hydroxyl radicals were generated by flash photolysis of H2O vapor in the vacuum UV, and monitored by time‐resolved resonance absorption at 308.2 nm [OH(A2Σ+→X2Π)]. The rate constants in units of cm3mol−1s−1at the 95% confidence limits were as follows:k(cC3H6) = (3.74 ± 0.83) × 1010,k(cC5H10) = (3.12 ± 0.23) × 1012,k(cC7H14) = (7.88 ± 1.38) × 1012. A linear correlation was found to exist between the logarithm of the rate constant per CH bond and the corresponding bond dissociation energy for several classes of organic compounds with equivalent CH bonds. The correlation favors a value of D(cC