Reactions of the Criegee intermediate (CI, ˙CH₂OO˙) are important in atmospheric ozonolysis models. In this work, we compute the rates for reactions between ˙CH₂OO˙ and HCHO, CH₃CHO and CH₃COCH₃ leading to the formation of secondary ozonides (SOZ) and organic acids. Relative to infinitely separated reactants, the SOZ in all three cases is found to be 48–51 kcal mol⁻¹ lower in energy, formed via 1,3-cycloaddition of ˙CH₂OO˙ across the CO bond. The lowest energy pathway found for SOZ decomposition is intramolecular disproportionation of the singlet biradical intermediate formed from cleavage of the O–O bond to form hydroxyalkyl esters. These hydroxyalkyl esters undergo concerted decomposition providing a low energy pathway from SOZ to acids. Geometries and frequencies of all stationary points were obtained using the B3LYP/MG3S DFT model chemistry, and energies were refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. RRKM calculations were used to obtain microcanonical rate coefficients (k(E)) and the reservoir state method was used to obtain temperature and pressure dependent rate coefficients (k(T, P)) and product branching ratios. At atmospheric pressure, the yield of collisionally stabilized SOZ was found to increase in the order HCHO < CH₃CHO < CH₃COCH₃ (the highest yield being 10⁻⁴ times lower than the initial ˙CH₂OO˙ concentration). At low pressures, chemically activated formation of organic acids (formic acid in the case of HCHO and CH₃COCH₃, formic and acetic acid in the case of CH₃CHO) was found to be the major product channel in agreement with recent direct measurements. Collisional energy transfer parameters and the barrier heights for SOZ reactions were found to be the most sensitive parameters determining SOZ and organic acid yield.