CH3 5. 3 H3C. HO ČH3 3-isopropyl-5-methylcyclohexanol There are four cis,trans isomers for 3-isopropyl-5-methylcyclohexanol, where the cis,trans designations of the substituents are made relative to the OH group: • up, up, up (cis,cis) • up, up, down (cis,trans) up, down, down (trans,cis) • up, down, up (trans,trans) Consider the most stable chair for each of these isomers, and then draw the most stable and least stable isomer based on a comparison of the best chair for each one. • To simplify matters, consider only axial vs equatorial energies of the groups (i.e. do not worry about the interactions between the groups, which in reality is also • Use the wedge/hash bond tools to indicate stereochemistry where it exists. • You do not have to explicitly draw H atoms. Use "flat" representations of rings, not chairs, in your drawing. Most stable Least stable

2. In the molecular orbital (MO) scheme for frontier orbitals of benzene, answer the following: a) how many of the carbons in benzene are sp²/p hybridized? b) how many p-n electrons does this system have? c) how many T,7* MOs can be constructed from the carbon p-orbitals? d) labeling these yn (n= 1 to ....) increasing in energy, how many vertical nodes do the following MOs have ? Y2,43 ¥4,Y5 e) on the hexagonal skeleton to right, draw the molecular orbital for y3, or y4. Are these MOs bonding, non-bonding or antibonding? Clearly show/tell why. f) in benzene, what orbital(s) is/are the HOMO? yn = g) what is the (value of the) aromatic stabilization energy for benzene? h) is benzene more or less stable than 1,3,5-cyclohexatriene? more less i) in two words, what is the structure of benzene? the LUMO? yn = kJ/mol (circle one)

1. Concept map: For carbon, draw out the orbital energy diagram of sp³, sp², and sp hybridized orbitals, including the leftover unhybridized orbitals, if any.

In cyclooctatetrane, how many electrons are in nonbonding molecular orbitals?