<P> It was observed that the cis compound underwent oxidation at a much faster rate than the trans compound . The proposition was that the large hydroxyl group in the axial position was disfavored and formed the carbonyl more readily to relieve this strain . The trans compound had rates identical to those found in the monosubstituted cyclohexanol . </P> <P> Using the A-Values of the hydroxyl and isopropyl subunit, the energetic value of a favorable intramolecular hydrogen bond can be calculated . </P> <P> A-Values are measured using a mono - substituted cyclohexane ring, and are an indication of only the sterics a particular substituent imparts on the molecule . This leads to a problem when there are possible stabilizing electronic factors in a different system . The carboxylic acid substituent shown below is axial in the ground state, despite a positive A-Value . From this observation, it is clear that there are other possible electronic interactions that stabilize the axial conformation . </P> <P> It is important to note that A-values do not predict the physical size of a molecule, only the steric effect . For example, the tert - butyl group (A-value = 4.9) has a larger A-value than the trimethylsilyl group (A-value = 2.5), yet the tert - butyl group actually occupies less space . This difference can be attributed to the longer length of the carbon - silicon bond as compared to the carbon - carbon bond of the tert - butyl group . The longer bond allows for less interactions with neighboring substituents, which effectively makes the trimethylsilyl group less sterically hindering, thus, lowering its A-value . This can also be seen when comparing the halogens . Bromine, iodine, and chlorine all have similar A-values even though their atomic radii differ . A-values then, predict the apparent size of a substituent, and the relative apparent sizes determine the differences in steric effects between compounds . Thus, A-values are useful tools in determining compound reactivity in chemical reactions . </P>

Estimate the energy cost of a 1 3-diaxial interaction between a bromine atom and a methyl group