Bonding ethane

Peptides built from y-amino acids with L-amino acid-derived chirahty centers form a right-handed (P)-2.6i4 hehx of ca. 5 A pitch with both ethane bonds in a -y)-synclinal conformation (mean values for dihedral angles 9 and 82 of central residues 2-5 in compounds 141 are 72.5 and 64.3°, respectively Fig. 2.36 A and B Tab. 2.8). 

The principle of the method involves the assumption that it is not the ethane bond which is weakened (made unstable) but rather that the free radicals formed upon dissociation are stabilized by resonance to such a degree as to permit them an appreciable existence in equilibrium with the undissociated ethane, in some cases, as we have seen, to such an extent that no ethane is present. We may illustrate by considering the case of hexaphenylethane ... 

For 2,2,3-trimethylbutane (pentamethylethane 32), there is presumably a sixfold rotational potential with six equivalent conformations skewed on either side of perfect staggering. There is a barrier of 6.9kcalmol" to rotation about the central ethane bond . Pentaalkylethanes can also be analysed as trialkylmethanes, remembering... 

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