Special topic Conjugated, UV, & Woodward Feiser

Question 1

What happens when electron moves to a higher energy level

Answer 1

the attraction of the nucleus on electrons decreases. the electrons are freer and have more kinetic energy

Question 2

The _____________ of ultraviolet (UV) light can promote an electron from a lower electronic state to a higher one

Answer 2

absorption

Question 3

Ultraviolet light has a slightly _____________ wavelength (and, thus, _________frequency) than visible light

Answer 3

shorter,
higher

Question 4

The most useful region of UV light for this purpose is ________________-.

Answer 4

200–400 nm

Question 5

When electrons in a lower energy state (_____________) absorb light having the appropriate energy, an electron is promoted to a higher electronic state (_______________).

Answer 5

the ground state,
the excited state

Question 6

The energy difference between the two states depends on the ________________.

Answer 6

location of the electron

Question 7

The promotion of electrons in σ bonds and unconjugated π bonds requires light having a wavelength of _______________

Answer 7

LESS THAN 200 nm
< 200 nm

Question 8

The light that is required for the promotion σ bonds and unconjugated π bonds has a less than 200 nm wavelength which means that, it has a _______ wavelength and ________ energy than light in the _______ region of the electro magnetic spectrum

Answer 8

shorter
higher
UV

Question 9

With ____________, however, the energy difference between the ground and excited states ____________, so longer wavelengths of light can be used to promote electrons.

Answer 9

conjugated dienes
decreases

Question 10

Why can we promote electrons with light which has longer wavelengths?

Answer 10

because with conjugated dienes the energy difference between the ground and excited states decreases

Question 11

It is referred to as The wavelength of UV light absorbed by a compound.

Answer 11

λmax.

Question 12

What is λmax.

Answer 12

It is referred to as The wavelength of UV light absorbed by a compound.

Question 13

What wavelength does 1,3-Butadiene

Answer 13

It absorbs UV light at λmax = 217 nm

Question 14

What wavelength does 1,3-cyclohexadiene

Answer 14

It absorbs UV light λmax of 256 nm

Question 15

Which compound absorbs 217 nm and 256 nm? Which has higher energy?

Answer 15

1,3-Butadiene: 217 nm

1,3-cyclohexadiene: 256 nm

1,3-Butadiene has higher energy because it has a shorter wavelength

Question 16

Arrange all the electromagnetic light in increasing energy.

Answer 16

Radio< Microwave< Infrared< Visible light< Ultra Violet< X-rays< Gamma rays

The shorter the wavelength the higher the energy

Question 17

___________________ absorb light in the UV region of the electromagnetic spectrum (200–400 nm).

Answer 17

Conjugated dienes and polyenes

Question 18

What causes the decrease in the energy difference between the ground state and excited state?

Answer 18

The increase of the number of conjugated π bonds.

Question 19

What is the relationship of Energy and the number of conjugated π bonds?

Answer 19

Inversely proportional

Question 20

As the number of conjugated π bonds increases, the energy difference between the ground and excited state ___________, shifting the absorption to longer wavelengths.

Answer 20

decreases

Question 21

The absorption of longer wavelengths was caused by the ___________________.

Answer 21

Increase of the number of conjugated π bonds

and the decrease in energy difference between the ground and excited state

Question 22

How many conjugated π bonds does a molecule have when the absorption shifts from UV to Visible region?

Answer 22

Eight or more

Question 23

When it shifts from UV to visible does it absorb?

Answer 23

It does not absorb

Question 24

What wavelength from the visible region does Lycopene absorbs?

Answer 24

absorbs visible light at λmax = 470 nm

Question 25

What color does the 470 nm in the visible region falls?

Answer 25

blue-green region

Question 26

Why lycopene appears as red?

Answer 26

Because it does not absorb light in the red region, lycopene appears bright red.

Question 27

What does SPF stands for?

Answer 27

Sun Protection Factor

Question 28

Ultraviolet radiation from the sun is high enough in energy to _____________

Answer 28

cleave bonds

Question 29

These are formed by the cleaved bonds

Answer 29

radicals

Question 30

Radicals formed from cleave bonds can _______________.

Answer 30

prematurely age skin and cause skin cancers

Question 31

The ultraviolet region is often __________, based on the wavelength of UV light.

Answer 31

subdivided

Question 32

Wavelength range for UV-B

Answer 32

UV-B (290–320 nm)

Question 33

Wavelength range for UV-A

Answer 33

UV-A (320–400 nm)

Question 34

Wavelength range for UV-C

Answer 34

UV-C (< 290 nm)
LESS THAN 290 nm

Question 35

Which has UV variation is more dangerous?

Answer 35

UV-C because it’s wavelength is < 290 nm. It has the smallest wavelength among the 3 and because of its short wavelength, it has a higher energy compared to others.

Question 36

The highest energy UV light (UV-C) is filtered out by the _________.

Answer 36

ozone layer

Question 37

Only UV light having wavelengths ___________ reaches the skin’s surface.

Answer 37

greater than 290 nm (> 290 nm)

Question 38

Most of the UV light that reaches our skin are absorbed by ____________.

Answer 38

melanin

Question 39

What is melanin?

Answer 39

It is the highly conjugated colored pigment in the skin that serves as the body’s natural protection against the harmful effects of UV radiation.

Question 40

Prolonged exposure to the sun can _______________________ ___________________________.

Answer 40

allow more UV radiation to reach your skin than melanin can absorb.

Question 41

What is in the commercial sunscreens that offers added protection from the sun?

Answer 41

conjugated compounds that absorb UV light that shields your skin from the harmful effects of UV radiation.

Question 42

What are the 2 most common conjugated compounds used in sunscreens?

Answer 42

para-aminobenzoic acid (PABA) and padimate O.

Question 43

Conjugated compounds shield the skin from what variation of UV? UV-A, UV-B, or UV-C?

Answer 43

UV-B

Question 44

Conjugated compounds have often little effect on __________.

Answer 44

UV-A

Question 45

It does not burn the skin however it can still cause long-term damage to skin cells.

Answer 45

UV-A

Question 46

What are unsaturated hydrocarbons?

Answer 46

Unsaturated hydrocarbons are compounds composed of carbon and hydrogen atoms, with one or more carbon carbon double or triple bonds in their chemical structure

Question 47

What are conjugated compounds?

Answer 47

Conjugated dienes have the two double bonds separated by a single bond.

Conjugated compounds are molecules where alternating single and double bonds occur.