A. C-C Coupling Pathways, 1 J CC Properties in 1-5, and Experimental Strategy. The calculated dependencies of 1 J C1,C2 in 1 c -5 c on q 2 are shown in Figure , and the calculated dependencies of 1 J C5,C6 on w in 1 c and 2 c are shown in Figure . As the C1-C2-O2-H torsion angle q 2 is rotated through 360 o , 1 J C1,C2 assumes values of ~45 Hz to ~53 Hz (~8 Hz dynamic range). 1 J C1,C2 values of ~47 Hz are observed at q 2 of 60 o and -60 o , whereas a value of ~53 Hz is observed at q 2 = 180 o . This behavior is caused by the effects of O2 lone-pair orbitals on C1-C2 bond length, with the two C2-O2 rotamers orienting one of the lone-pair orbitals anti to the C1-C2 bond (q 2 = 60 o and -60 o ) associated with smaller 1 J C1,C2 values (longer C1-C2 bond) compared to the third rotamer (q 2 = 180 o ) in which the O2-H bond anti to the C1-C2 bond results in a shorter C1-C2 bond and larger 1 J C1,C2 . This explanation is consistent with plots of r C1,C2