Table 3. BDE and BDFE Values for the Pertinent C–H Bonds of Substrates 1–56.

^aTaken from ref (31), recommended values (where available).

^bCalculated using the (RO)CBS-QB3 approach (see text).

^cAverage of the recommended values for the C–H bonds at C-2 and C-3 (99.2 and 99.1 kcal mol^–1, respectively).

^dBDE and BDFE values for the C–H bonds that are α to the HBD OH group in intramolecular hydrogen-bonded structures (see text).

^eIn Figure 1, BDEs for 31 and 32 were taken to be the same as the value for 30;³¹ the BDE for 33 was assumed to be the same as the value for 34.³¹

^fBecause the calculations lead to slightly different BDEs and BDFEs for the C–H bonds of this substrate that are cis and trans to the carbonyl group (BDE = 92.6 and 92.3 kcal mol^–1, BDFE = 84.2 and 83.9 kcal mol^–1 respectively), the given values are an average of the BDEs and BDFEs for the two C–H bond couples.

^gIn Figure 1, the BDEs for 51 and 54 were from ref (47) ; see text.