Abstract Three tertiary β-nitroalkyl peroxynitrates 2a, 2b and 2c were prepared by reaction of N 2 O 4 and excess O 2 with isobutene (la), 2, 3, 3-trimethyl-2-butene (1b) and 2, 3-dimethyl- 2-butene (1c), respectively. These compounds are rather unstable and at 23 slow decomposition occurs. It seems likely that this decomposition starts by OO bond fission yielding an NO 3 radical and a β-nitroalkoxy radical. In the case of 2a this alkoxy radical ...