The rate coefficients of the reactions of three unsaturated cyclic ethers, 2,5-dihydrofuran (2,5-DHF), 2,3-dihydrofuran (2,3-DHF), and 3,4-dihydropyran (3,4-DHP), with the major day-time tropospheric oxidants e OH (k_OH) and O₃ (kO₃), and that of 3,4-DHP with Cl atom (k_Cl) are determined using relative rate method, at 298 K. The values of k_OH are (6.45 ±1.69), (11.95 ± 2.79) and (11.38 ± 2.64) 10^-11 cm³ molecule^-1 s^-1 for 2,5-DHF, 2,3-DHF and 3,4-DHP, respectively and kO₃ are (1.65 ± 0.31), (443.20 ± 79.0) and (31.36 ± 5.80)  10¹⁷ cm³ molecule^-1 s^-1 for 2,5-DHF, 2,3-DHF and 3,4-DHP, respectively. The value of k_Cl for 3,4-DHP is (6.15 0.84) 10^-10cm³ molecule^-1 s^-1 . The dominant pathway of tropospheric degradation of 2,5-DHF is the reaction with OH, whereas that of 2,3-DHF is the reaction with O₃. Reaction with both OH and O₃ are equally important in the case of 3,4-DHP. Under the conditions of marine boundary layer, the reaction with Cl atom is important in the tropospheric degradation of 2,5-DHF and 3,4-DHP, but insignificant in the case of 2,3-DHF (only 1.8%). The estimated tropospheric lifetimes in the day-time are 2.0, 0.08 and 0.62 h for 2,5-DHF, 2,3-DHF and 3,4-DHP respectively. The presence of O atom, unsaturation, conjugation etc. influences the rate coefficients in a complex manner. However, there is a good correlation of k_OH with HOMO energy, which further improves by treating the molecules separately, either as ethers and hydrocarbons, or as cyclic and acyclic molecules. The values of kO₃ of these ethers fit very well with the straight line regression derived for simple alkenes with their HOMO energy, except 2,3- DHF, which has a high strain enthalpy. The values of k_Cl also show a similar trend of increase with HOMO energy, but the correlation is not as good as that of k_OH.