Chapter 16 Conjugation

Question 1

What constitutes conjugation?

Answer 1

3 or more atoms adjacent to each other with p orbitals that are parallel and interact

Question 2

What are characteristics of a conjugated molecule?

Answer 2

Lower heat of hydrogenation, Central single bond

Question 3

What is the molecular orbital theory?

Answer 3

Atomic orbitals = # Molecular orbitals

Question 4

What is HOMO?

Answer 4

Highest occupied molecular orbital

Question 5

What is LUMO?

Answer 5

Lowest occupied molecular orbital

Question 6

What happens when UV light is shined onto a molecule?

Answer 6

One electron (1 arrow), from HOMO gets promoted one spot, to LUMO

excited state

Question 7

How does the length of conjugation affect the HOMO-LUMO gap and lambda?

Answer 7

Larger Conjugation: smaller Homo/Lumo gap, longer wavelength (lambda)= less energy

Shorter Conjugation: larger Homo/Lumo gap, shorter wavelength= higher energy

Question 8

and which one is more stable?

Answer 8

Question 9

Answer 9

don’t pay attention to second one, not right- should have two double bonds though

Question 10

Answer 10

Question 11

What is the general rule for Diel-Alder reaction?

Answer 11

Diene + Alkene (dienophile) = one double bond made

Diene + Alkyne (dienophile) = two double bonds formed

Question 12

Describe the two types of bicyclic products that can result

Answer 12

Endo: Electron withdrawing groups on opposite side of pi bridge

Exo: EWG on same side of pi bridge