Special topic Conjugated, UV, & Woodward Feiser Flashcards
To pass because I will cry (47 cards)
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
