Disclosed herein are 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene compositions for use in refrigeration and air conditioning systems, particularly in centrifugal compressor systems. Also disclosed are 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene in combination with at least one bromofluorocarbon, ketones, alcohols, chlorocarbons, ethers, esters, 4-chloro-1,1,2,3,3,4-hexafluorobutene, N-(difluoromethyl)-N,N-dimethylamine, or mixtures thereof, which are azeotropic or near azeotropic.