Question

Suppose that you are a colour chemist and had been asked to intensify the colour of a dye without changing the type of compound, and that the dye in question was a polyene. Would you choose to lengthen or to shorten the chain? Would the modification to the length shift the apparent colour of the dye towards the red or the blue? What does lengthening or shortening the chain do?
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Answer 1

Explanation:

Conjugated systems having increasing length have a larger absorption intensity. Therefore in order to intensify the color of the dye without changing the type of the compound, we would like to increase the length of the dye (polyene here). Also, as the length of a molecular chain is increased, the separation between energy levels decrease as an analogy with the...