Organic II - Conjugation Systems (Chp 15)

Question 1

When does conjugation occur?

Answer 1

Whenever p orbitals can overlap on 3 or more adjacent atoms.

Question 2

Conjugated double bonds are separated by a _________ bond.

Answer 2

single

Question 3

Isolated double bonds are separated by ________________ bonds.

Answer 3

2 or more single

Question 4

Conjugated double bonds are _____ stable than other bonds.

Answer 4

more

Question 5

Conjugated double bonds have extra ______.

Answer 5

stability

Question 6

The more stable the compound, the less heat released during _____________.

Answer 6

hydrogenation

Question 7

How many lobes does each p orbital have with the wave function?

Answer 7

2 lobes

Question 8

How many p orbitals does 1,2-dibutene have?

Answer 8

4 p orbitals (atomic orbitals)

Question 9

When lobes overlap constructively, what is formed?

Answer 9

A pi bonding (p) MO is formed

Question 10

Even number of MOs leads to an…

Answer 10

even number of bonding and antibonding MOs.

Question 11

The number of atomic orbitals equals…

Answer 11

the number of molecular orbitals (MO).

Question 12

Odd number of MOs means there are…

Answer 12

bonding, antibonding and a bonding MO.

Question 13

The maximum number of nodes equals…

Answer 13

n-1 (n = number of atomic orbitals)

Question 14

What creates nodes?

Answer 14

Antibonding

Question 15

Which is more stable, s-trans or s-cis? Why?

Answer 15

s-trans b/c it has no interference b/w protons.

Question 16

Describe an allylic carbon.

Answer 16

The carbon directly attached to an sp2 carbon (double bonded carbon).

Question 17

Which is more stable? s-trans or s-cis?

Answer 17

s-trans

Question 18

Molecules with resonance structures are more ______ than those that don’t.

Answer 18

stable

Question 19

List the order of stability for carbocations.

Answer 19

CH3+ < primary < secondary, primary allylic < tertiary, secondary allylic

Question 20

Which forms faster? Kinetic product or the thermodynamic product?

Answer 20

Kinetic product.

Question 21

List the radical stabilities.

Answer 21

1 < 2 < 3 < 1 allylic

Question 22

NBS provides a low, _________ concentration of ___.

Answer 22

constant; Br2

Question 23

NBS reacting with HBr by-product to produce Br2 to prevent what?

Answer 23

HBr addition across the double bond.

Question 24

Are there any bonding interactions when there are only nodes?

Answer 24

No.

Question 25

Diel-Alder reactions produces a ____.

Answer 25

ring

Question 26

How many steps does diels-alder reactions take?

Answer 26

One.

Question 27

What two reactants are needed in Diel-Alder reactions?

Answer 27

A diene and a dienophile.

Question 28

The diene in Diels-Alder reactions need to be in ___ conformation.

Answer 28

cis

Question 29

Dienes like to react with an ____________ alkene to give cyclohexene or cyclohexadiene rings.

Answer 29

electron-poor

Question 30

Why is a 1,3-cyclopentadiene more stable than 2,3-butadiene?

Answer 30

Because the double bonds are fixed in the cyclic compound and is in cis conformation.

Question 31

For Diels-Alder rxc, diene must be in ____ conformation.

Answer 31

s-cis

Question 32

For Diel-alder reactions, what of kind of products will you always get?

Answer 32

1,2- and 1,4-product

Question 33

What are the steps to finding a diene and dienophile? (3 steps)

Answer 33

1) Find the 6 C ring with double bond 2) Draw the 3 arrows starting from the pi bond 3) Draw the diene and dienophile

Question 34

What does pericyclic reaction mean?

Answer 34

Everything happens in one step.

Question 35

What is an example of a pericyclic reaction?

Answer 35

Diels-Alder reaction

Question 36

MOs must overlap ____________ to stabilize the ____________ state in pericyclic reactions.

Answer 36

constructively; transition

Question 37

An energy gap in ultraviolet spectroscopy is _______ with conjugated dienes than other dienes.

Answer 37

higher

Question 38

The lower the energy, the ________ the wavelength.

Answer 38

longer

Question 39

What does the spectrometer measure?

Answer 39

The intensity of a reference beam through solvent only (Ir) and the intensity of a beam through a solution of the sample (Is)

Question 40

What law does absorbance follow?

Answer 40

Beer's Law

Question 41

Give the formula for absorbance.

Answer 41

A = εcl ε - molar absorptivity c - sampel concentration in moles per liters l - length of light path in cm

Question 42

The more conjugation, the ________ the wavelength, and the ________ the gap between MOs.

Answer 42

longer; smaller

Question 43

To see if a reaction is photochemically produced what must happen?

Answer 43

The HOMO+ of diene and LUMO of dienophile must be bonded on both sides.