In synthesis of tetraphenylcyclopentadienone, I need those two blued questions !

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In synthesis of tetraphenylcyclopentadienone,

I need those two blued questions !

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Combine the purified benzil (IV-02. 300 mg) obtained from the previous step with 1,3- diphenylacetone (300 mg) and ethylene glycol (1.5 mL) in a 10 mL round bottom flask containing a stir bar. Attach an air condenser and heat the reaction at 135-145 °C for 10 minutes, in which the added benzil should dissolve. Once a homogenous solution is obtained, the heat is removed and the reaction allowed to cool to 80-100°C When recording the details of your experiment, which important feature of the temperatures should be noted? While the reaction mixture is still hot, 300 L of a 40% benzyltrimethylammonium hydroxide solution in methanol (Triton B) is cautiously added with stirring. Allow the reaction mixture to cool to room temperature. While the reaction mixture is cooled, dark purple crystals of tetraphenylcyclopentadienone (IV-03) should be formed. Cooling the reaction flask with water could also facilitate the formation of the crystals. Although in general, color is not a good analytical tool, in this case the product is colored deep p?rple and is indicative of the desired material. Explain why the reaction produces a colored product from colorless starting materials

Explanation / Answer

1) Initially, the reaction mixture is heated to 135-145oC and then cooled to 80-100oC. So the cooling has to be monitored as temperature should not go below 80oC. Also, it is a range between we need to keep the reaction mixture's temperature.

2) In the product the alpha-beta-unsaturated ketone (in fact it is a cyclopentadienone!) there is a chromophore present and further addition of excess conjugation with 4 phenyl rings makes the product absorb in the shorter wavelength with strong absorption. This is not the case in both starting material hence product formed is colored while starting materials are colorless.

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