Topic 2: Conjugated Unsaturated Systems

Question 1

Do atomic orbitals describe the location of electrons around a nucleus in an atom?

Answer 1

Yes

Question 2

Number of ____ = number of _____

Answer 2

Molecular orbitals
Atomic orbitals

Question 3

What does additive combination lead to?

Answer 3

Bonding molecular orbitals

Question 4

What does subtractive combination lead to?

Answer 4

Antibonding molecular orbitals

Question 5

Are bonding MOs in higher or lower energy than the atomic orbitals they were derived from?

Answer 5

Lower

Question 6

Are antibonding MOs in higher or lower energy than the atomic orbitals they were derived from?

Answer 6

Higher

Question 7

The [HOMO or LUMO] of the nucleophile attacks the [HOMO or LUMO] of the electrophile

Answer 7

HOMO
LUMO

Question 8

Is there a horizontal plane of symmetry for very MO?

Answer 8

No, there’s a vertical plane of symmetry

Question 9

The greater the extent of conjugation the _____ the energy of molecular orbitals

Answer 9

Lower

Question 10

Hydrocarbons with more than one double or triple bond are referred to as…

Answer 10

Polyunsaturated molecules

Question 11

What is it called when there are multiple bonds that are separated by one or more saturated carbon atoms?

Answer 11

Isolated

Question 12

What is called when there are 2 or more double bonds connected by a common carbon atom, pi bonds are perpendicular to each other?

Answer 12

Cumulated double bonds

Question 13

What is the system of connected p-orbitals that are aligned to allow delocalization of electrons?

Answer 13

Conjugated

Question 14

Conjugated systems must possess what?

Answer 14

At least one atom with a p-orbital next to at least one pi-bond

Question 15

Resonance structures only differ in the distribution of their…

Answer 15

Pi bonds and/or non bonding electrons

Question 16

Does more covalent bonds make a structure more stable?

Answer 16

Yes!

Question 17

UV-Vis electromagnetic radiation ______ electronic transitions in molecules

Answer 17

Promotes

Question 18

The absorbances in UV-Vis are a result of the excitation of electrons from _____ to ______ molecular orbitals

Answer 18

1. HOMO
2. LUMO

Question 19

Is a smaller gap between HOMO and LUMO a result of an increase in conjugation?

Answer 19

Yes

Question 20

More substitution _____ stability

Answer 20

Increases

Question 21

Will high or low temperatures lead to the most stable product?

Answer 21

High, because there is enough energy to achieve the higher energy transition state. It can also be reversible

Question 22

A reaction in which the movement of electrons flows through a ring like transition state, they can only proceed if the symmetry of interactions molecular orbitals match

Answer 22

Pericyclic reaction

Question 23

Dienophile acts as a…

Answer 23

Electrophile

Question 24

In Diels-Alder reaction the diene acts as a…

Answer 24

Nucleophile

Question 25

Are the steps in Diels-Alder concerted?

Answer 25

Yes

Question 26

The diene must adopt a s-___ configuration to bring the two terminal carbons close to the dienophile

Answer 26

Cis

Question 27

Electron donating groups on the diene will ____ the energy of the HOMO

Answer 27

Raise

Question 28

Electron withdrawing groups on the dienophile will ______ the energy of the LUMO

Answer 28

Lower

Question 29

When the dienophile approaches the diene in a manner where the EWG is orientated outside and away from the diene it is what type of product?

Answer 29

Exo

Question 30

When the dienophile approaches the diene in a manner where the EWG is orientated inside and towards from the diene it is what type of product?

Answer 30

Endo

Question 31

ENDO products are favoured because of the _______ interactions

Answer 31

Constructive

Question 32

A racemic mixture

Answer 32

A product mixture with equal amounts of 2 enantiomers