Podcast
Questions and Answers
Which of the following compounds is an example of a compound with sufficient conjugation that absorbs in the visible region?
Which of the following compounds is an example of a compound with sufficient conjugation that absorbs in the visible region?
What effect does the length of the conjugated system generally have on the values of λmax?
What effect does the length of the conjugated system generally have on the values of λmax?
What is an auxochrome?
What is an auxochrome?
Which of the following is NOT an example of an auxochrome group?
Which of the following is NOT an example of an auxochrome group?
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What is the general effect of bathochromic groups on wavelength?
What is the general effect of bathochromic groups on wavelength?
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What does ΔE = hν= hc/λ represent?
What does ΔE = hν= hc/λ represent?
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What type of transitions do chromophores with both π and non-bonding electrons undergo?
What type of transitions do chromophores with both π and non-bonding electrons undergo?
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What is the role of chromophores in relation to the color of compounds?
What is the role of chromophores in relation to the color of compounds?
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What happens to the absorption maximum when two or more conjugated chromophore groups are present?
What happens to the absorption maximum when two or more conjugated chromophore groups are present?
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Which compound shows a lower energy transition, 1,3-butadiene or ethylene?
Which compound shows a lower energy transition, 1,3-butadiene or ethylene?
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What type of molecular orbitals are formed in conjugated dienes, from the separate alkene groups?
What type of molecular orbitals are formed in conjugated dienes, from the separate alkene groups?
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Which compound shows a higher absorption maximum, ethylene or 1,3-butadiene?
Which compound shows a higher absorption maximum, ethylene or 1,3-butadiene?
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Study Notes
Conjugation and Absorption
- Compounds with sufficient conjugation absorb in the visible region.
- The length of the conjugated system generally increases the values of λmax.
Auxochrome Groups
- An auxochrome is a group that increases the intensity of color by extending the conjugation of a chromophore.
- The -OH group is not an example of an auxochrome group.
Bathochromic Groups
- Bathochromic groups shift the absorption maximum to a longer wavelength.
Energy Transitions
- ΔE = hν = hc/λ represents the energy of a transition.
Chromophores and Transitions
- Chromophores with both π and non-bonding electrons undergo n → π* and π → π* transitions.
- The role of chromophores is to determine the color of compounds by absorbing specific wavelengths of light.
Multiple Chromophore Groups
- When two or more conjugated chromophore groups are present, the absorption maximum increases.
Comparing Compounds
- 1,3-butadiene shows a lower energy transition than ethylene.
- 1,3-butadiene shows a higher absorption maximum than ethylene.
Molecular Orbitals
- In conjugated dienes, separate alkene groups form molecular orbitals that are delocalized and extended.
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Description
Test your knowledge on chromophores and their role in the absorption of light. Explore the factors affecting the wavelength and intensity of absorption in compounds containing chromophores.
