Key Area 1 Flashcards
What is a sigma bond?
The end on overlap of two atomic orbitals
What is a pi bond?
The side on overlap of two atomic orbitals
Why does indigo dye appear blue in daylight?
Light of a complementary colour is absorbed (green/yellow/red)
How does colour arise in dye molecules?
Electrons move from HOMO to LUMO (1 mark)
Light of the complementary colour is seen when light from the visible part of the spectrum is absorbed (1 mark)
What structural feature is responsible for the colour of dye molecules?
The conjugated system
Why would a dye molecule absorb a shorter wavelength of light?
The conjugated system is shorter and so greater energy is absorbed
What is sp² hybridisation?
When an s orbital is mixed with 2 p orbitals
How does geometric isomerism exist in compounds with carbon to carbon double bonds?
When:
-They have 2 different/non-identical groups attached to each carbon atom (in the double bond) (1)
-Restricted rotation around the double bond (1)
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What is meant by the term conjugated system?
An alternating chain of single and double bonded carbons
What type of hybridisation is adopted by atoms in a conjugated system?
sp²
