There are quite a few words with the ending <on>, where the final syllable is unstressed, but the pronunciation is ɒn rather than ən. Many of these are technical terms, but there are also some everyday words. Here is a list of examples:
argon boron boson colon coupon electron hadron meson micron moron neon neuron neutron nylon photon proton radon rayon
2013_07_20