A chemist was called to an abandoned aspirin factory to determine the contents of a badly corroded vat. Knowing that two salvage workers had become ill from breathing the fumes, she put on her breathing apparatus as soon as she noticed an overpowering odor like that of vinegar but much more pungent. She entered the building and took a sample of the contents of the vat. The mass spectrum showed a molecular weight of 102, and the NMR spectrum showed only a singlet at 2.15. The IR spectrum shows strong peaks at ~1810, 1760, ~1420,~1380 and~1110 cm^-1, and medium peaks at 1000 and 900 cm^-1. Identify the compound.