Colour by Design 1: Conjugated & Delocolised Systems

Question 1

Definition of conjugated systems

Answer 1

Organic molecules consisting of alternating single and double bonds ( close together )

Question 2

Definition of delocalised system

Answer 2

In conjugated system the electrons in the p orbitals that make up the pi bond are able to spread out over all the atoms in the system

( carbon still arranged in a ring but no alternating single & double bonds

Each carbon donates an electron from its p orbital

P orbitals combine to form a ring a ring of delocalised electrons )

Question 3

What do conjugated dry stems do to energy gap ( between electrons in terms of colour )

Answer 3

Decrease the gap between the ground state and the excited state of electrons

Question 4

What property of a conjugated system determines the size of an energy gap

Answer 4

• the more electrons that are delocalised in a conjugated system the smaller the energy gap

Question 5

Describe how conjugated systems effect colour

Answer 5

• conjugated system decrease energy gap due to amount of delocalisation electrons
• smaller energy gap = absorption of longer wavelengths of light absorbed
• usually delocalised systems with 5 pi bonds are likely to absorb light in the visible spectrum

Question 6

What is required in a delocalised system for it to be able to absorb light in the visible spectrum

Answer 6

At least 5 pi bonds