10/3/24

Question 1

why are allylic carbocations stable

Answer 1

because they are capable of resonance and can share electron density throughout which makes it lower in energy

Question 2

what is more stable, a substituted (allylic carbocation) or a tertiary carbocation

Answer 2

substituted allylic

Question 3

what is more stable, a tertiary carbocation or a primary allylic carbocation

Answer 3

tertiary carbocation

Question 4

what is more stable, a secondary carbocation or a primary allylic carbocation

Answer 4

allylic carbocation

Question 5

what is a real form of the allylic radical

Answer 5

the resonance hybrid

Question 6

how many pi electrons are in a double bond

Answer 6

2

Question 7

how many pi electrons in 1,3-butadiene

Answer 7

4

Question 8

What is HOMO? What happens to this orbital when it is in the ground state? What happens when it is in the excited state?

Answer 8

it is the highest occupied molecular orbital

In the ground state, this orbital remains occupied with two electrons

in the excited state, an electron in this orbital can be promoted to LUMO through an absorption of UV light

Question 9

what is LUMO, when is it occupied? When is it unoccupied?

Answer 9

it is the lowest unoccupied molecular orbital in ground states

it is occupied when an electron from the HOMO is promoted in its excited state with an absorption of light

it is unoccupied in the ground state, when both pi electrons are in the HOMO

Question 10

what is true about the energy in antibonding orbitals versus bonding orbitals

Answer 10

antibonding orbitals are higher in energy, bonding orbitals are lower in energy

Question 11

what does the ∆E between the HOMO and LUMO orbitals correspond to?

Answer 11

the wavelength of U-VIS light that will be absorbed upon excitation

Question 12

what is the absorption of UV-Vis radiation caused by

Answer 12

the transfer of energy from the radiation beam to the electrons that can be excited to higher energy orbitals

Question 13

why are alkenes and nonconjugated systems U-V inactive

Answer 13

they have a larger ∆E than conjugated systems and have an absorption maxima that is below 200nm which is below the UV spectra

Question 14

how does the energy gap between non-conjugated anti-bonding orbitals and conjugated orbitals compare

Answer 14

the energy gap between non-conjugated systems is larger so it absorbs at a higher frequency and falls out of the UV spectrum

Question 15

if you have a higher frequency, what type of wavelength and energy do you have

Answer 15

you have a short wavelength and high energy

Question 16

if you have a lower frequency, what type of wavelength and energy do you have

Answer 16

a longer wavelength and lower energy

Question 17

if you have more conjugated bonds, how will the absorption maxma change

Answer 17

it will have a longer wavelength past 200nm

Question 18

what color do we see

Answer 18

the complimentary color of what is absorbed

Question 19

what is 1,2 addition of a diene with HBr

Answer 19

the hydrogen and bromine add to carbons 1 and 2

Question 20

what is 1,4 addition of a diene with HBr

Answer 20

the hydrogen and bromine add to carbons 1 and 4

Question 21

what is the thermodynamic product

Answer 21

it is the product that is favored at higher temperatures and is most stable (has lower energy on coordinate diagram)

Question 22

what is the kinetic product

Answer 22

it is favored at lower temperatures and it is the pathway that has the smallest activation energy

Question 23

what is an adduct

Answer 23

it is the product of a diels alder reaction

Question 24

what is a diene

Answer 24

a 4 pi electron system

Question 25

what is a dienophile

Answer 25

a 2 pi electron system

Question 26

what is the general reaction of a diels alder

Answer 26

you form two sigma bonds at the expense of 2 pi bonds to form a six membered ring