FLUORINATED DIOLS FROM THE MERCURY-PHOTOSENSITIZED DEHYDRODIMERIZATION OF FLUORINATED ALCOHOLS IN THE VAPOR-PHASE

Several fluorinated diols were synthesized from commercially available fluorinated alcohols via mercury-photosensitized dehydrodimerization in the vapour phase. In almost all cases, the corresponding di-and mes o-diols were obtained in a 50 : 50 ratio. Field-ionization (FI) and fi eld-desorption (FD) mass spectrometry proved effective as an analytica l method for these diols. The nuclear magnetic resonance (NMR) charact eristics of the symmetrically substituted diols depend strongly on the ir stereochemical nature (dl-and meso-diastereoisomers) and substituen ts. The presence of the -CF2H end group, as in 1,1,4,4-tetrafluoro-2,3 -butanediol and 1,1,2,2,5,5,6,6-octafluoro-3,4-hexanediol, causes an a dditional inequivalence in the meso-form due to molecular asymmetry. T he H-1 and F-19 NMR spectra of 1,1,4,4-tetrafluoro-2,3-butanediol and the F-19 NMR spectrum of 1,1,2,2,5,5,6,6-octafluoro-3,4-hexanediol hav e been fully interpreted. (C) 1997 Elsevier Science S.A.