Vicinal fluorine-fluorine coupling constants in perfluoropropyl groups

The geminal fluorines in XCF(2)-CF(2)Y groups are magnetically inequivalent. The fluorines comprise an AA'XX' spin which should show non-first-order NMR spectra, but usually appear deceptively simple with little indication of vicinal coupling. Detailed analysis of the spectra of perfluorobutyric acid (1) and 2,2,3,3,4,4,4-heptafluorobutanol (2) are reported. The (3)J(AX) and (3)J(AX') range between 4 and 9 Hz and are of opposite sign. (C) 2009 Elsevier B.V. All rights reserved.