Could you explain “highest occupied molecular orbital” (HOMO) (It is the highest in energy orbital with electrons; usually responsible for donating electrons - GS) and “lowest unoccupied molecular orbital” (LUMO)? (It is the lowest in energy empty orbital; usually responsible for withdrawing electrons - GS).

Do acid catalyzed (No, the configuration is usually lost because of the intermediacy of a carbocation - GS). and base catalyzed (Yes - GS). opening of epoxide rings result in inversion of configuration?

Will the deprotonated acetoacetic ester attack the less substituted side of the epoxide? (Yes, it will, because it is an SN2 reaction. - GS).

Could we go over how E2 and SN2 reactions compete and how you decide which reaction will proceed? There is a portion about it from our reading homework, but I am having difficulty understanding the concept (SN2 is sensitive to nucleophilicity (+) and steric hindrance (-). E2 is favored by basicity, temperature, and stability of the C=C bond. - GS).

Professor Sereda I have a question regarding stereochemistry of acid catalyzed hydration of epoxides. I know a carbocation is formed in the make-up intermediate and they are planar; however would the nucleophile add anti the the already present OH group? Or could attack from both sides since it is planar? (It can attack from either side, which is why the second step of anti-dihydroxylation should be performed in the absence of acids.  - GS).

During Hydrogenation, will alkynes react faster than an alkene would- due to the shorter bond length of the alkyne? (Yes. The shorter carbon-carbon triple bond fits better to the length of H-H bond - GS).

Why is the hydroboration-oxidation based on steric hindrance instead of markovnikov’s rule? (Hydroboration as any other reaction proceeds by the only rule: through a lower in energy transition state. Because for the mechanism of hydroboration, Markovnikov rule does not apply to the final product of hydration - GS).