These types of steric interactions are commonly known as 1,3 diaxial interactions. This makes it very crowded when bulky substituents are oriented in the axial position. This is because substituents in the axial position are relatively close to two other axial substituents. It is known that axial bonds are more hindered than the corresponding equatorial bonds. One can use steric hindrances to determine the propensity of a substituent to reside in the axial or equatorial plane. Steric effects play a major role in the assignment of configurations in cyclohexanes. This difference in steric effects can be used to help predict reactivity in chemical reactions. Because the A-value of tert-butyl is higher, tert-butyl has a larger steric effect than methyl. A methyl group has an A-value of 1.74 while tert-butyl group has an A-value of ~5. In general, the larger a substituent's A-value, the larger the steric effect of that substituent. A-values can help predict the steric effect of a substituent. The utility of A-values can be generalized for use outside of cyclohexane conformations. Thumb|600px|center|A methyl substituent has a significantly smaller A-value than a tert-butyl substituent therefore the most stable conformation has the tert-butyl in the equatorial position. When multiple substituents are taken into consideration, the conformation where the substituent with the largest A-value is equatorial is favored. The most stable conformation will be the one which has the substituent or substituents equatorial. 4.2 Approximating intramolecular force strength using A-ValuesĪ-values help predict the conformation of cyclohexane rings.