Special topic Conjugated, UV, & Woodward Feiser Flashcards
To pass because I will cry
What happens when electron moves to a higher energy level
the attraction of the nucleus on electrons decreases. the electrons are freer and have more kinetic energy
The _____________ of ultraviolet (UV) light can promote an electron from a lower electronic state to a higher one
absorption
Ultraviolet light has a slightly _____________ wavelength (and, thus, _________frequency) than visible light
shorter,
higher
The most useful region of UV light for this purpose is ________________-.
200–400 nm
When electrons in a lower energy state (_____________) absorb light having the appropriate energy, an electron is promoted to a higher electronic state (_______________).
the ground state,
the excited state
The energy difference between the two states depends on the ________________.
location of the electron
The promotion of electrons in σ bonds and unconjugated π bonds requires light having a wavelength of _______________
LESS THAN 200 nm
< 200 nm
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
shorter
higher
UV
With ____________, however, the energy difference between the ground and excited states ____________, so longer wavelengths of light can be used to promote electrons.
conjugated dienes
decreases
Why can we promote electrons with light which has longer wavelengths?
because with conjugated dienes the energy difference between the ground and excited states decreases
It is referred to as The wavelength of UV light absorbed by a compound.
λmax.
What is λmax.
It is referred to as The wavelength of UV light absorbed by a compound.
What wavelength does 1,3-Butadiene
It absorbs UV light at λmax = 217 nm
What wavelength does 1,3-cyclohexadiene
It absorbs UV light λmax of 256 nm
Which compound absorbs 217 nm and 256 nm? Which has higher energy?
1,3-Butadiene: 217 nm
1,3-cyclohexadiene: 256 nm
1,3-Butadiene has higher energy because it has a shorter wavelength
Arrange all the electromagnetic light in increasing energy.
Radio< Microwave< Infrared< Visible light< Ultra Violet< X-rays< Gamma rays
The shorter the wavelength the higher the energy
___________________ absorb light in the UV region of the electromagnetic spectrum (200–400 nm).
Conjugated dienes and polyenes
What causes the decrease in the energy difference between the ground state and excited state?
The increase of the number of conjugated π bonds.
What is the relationship of Energy and the number of conjugated π bonds?
Inversely proportional
As the number of conjugated π bonds increases, the energy difference between the ground and excited state ___________, shifting the absorption to longer wavelengths.
decreases
The absorption of longer wavelengths was caused by the ___________________.
Increase of the number of conjugated π bonds
and the decrease in energy difference between the ground and excited state
How many conjugated π bonds does a molecule have when the absorption shifts from UV to Visible region?
Eight or more
When it shifts from UV to visible does it absorb?
It does not absorb
What wavelength from the visible region does Lycopene absorbs?
absorbs visible light at λmax = 470 nm
What color does the 470 nm in the visible region falls?
blue-green region
Why lycopene appears as red?
Because it does not absorb light in the red region, lycopene appears bright red.
What does SPF stands for?
Sun Protection Factor
Ultraviolet radiation from the sun is high enough in energy to _____________
cleave bonds
These are formed by the cleaved bonds
radicals
Radicals formed from cleave bonds can _______________.
prematurely age skin and cause skin cancers
The ultraviolet region is often __________, based on the wavelength of UV light.
subdivided
Wavelength range for UV-B
UV-B (290–320 nm)
Wavelength range for UV-A
UV-A (320–400 nm)
Wavelength range for UV-C
UV-C (< 290 nm)
LESS THAN 290 nm
Which has UV variation is more dangerous?
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.
The highest energy UV light (UV-C) is filtered out by the _________.
ozone layer
Only UV light having wavelengths ___________ reaches the skin’s surface.
greater than 290 nm (> 290 nm)
Most of the UV light that reaches our skin are absorbed by ____________.
melanin
What is melanin?
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.
Prolonged exposure to the sun can _______________________ ___________________________.
allow more UV radiation to reach your skin than melanin can absorb.
What is in the commercial sunscreens that offers added protection from the sun?
conjugated compounds that absorb UV light that shields your skin from the harmful effects of UV radiation.
What are the 2 most common conjugated compounds used in sunscreens?
para-aminobenzoic acid (PABA) and padimate O.
Conjugated compounds shield the skin from what variation of UV? UV-A, UV-B, or UV-C?
UV-B
Conjugated compounds have often little effect on __________.
UV-A
It does not burn the skin however it can still cause long-term damage to skin cells.
UV-A
What are unsaturated hydrocarbons?
Unsaturated hydrocarbons are compounds composed of carbon and hydrogen atoms, with one or more carbon carbon double or triple bonds in their chemical structure
What are conjugated compounds?
Conjugated dienes have the two double bonds separated by a single bond.
Conjugated compounds are molecules where alternating single and double bonds occur.
