Aryl-Bound Trifluoromethyl Groups

TABLE 5.4. MF Chemical Shifts for CF3 Groups in Disubstituted Benzenes 

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An oxygen bound to a trifluoromethyl group has much less effect upon its chemical shift than a chlorine substituent. Thus, the fluorines of trifluoromethyl ethers (—58 ppm) are not as deshielded as those of CF3C1 (—28 ppm). Those of CF3 sulfides and selenides are deshielded still further (—42 and -37 ppm, respectively). Also, aryl and alkyl trifluoromethyl ethers have similar fluorine chemical shifts, as do aryl and alkyl trifluoromethyl sulfides. 

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