Week 5-July 26

Week 5-July 26 - Week 5 July 26, 2011 Acidity of Carbonyl...

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Week 5 July 26, 2011 Acidity of Carbonyl Compounds What will result if you treat acetone with 1 mole of a very strong base? The resulting species, called an enolate , can be a base or a nucleophile . It is known as an ambident nucleophile . Show the two products that can result from the protonation of this enolate. Do you recognize these products? Show the enolate that will result from the deprotonation of the most acidic proton in each of the following species: O O H O O H O Reading : Section 22.1 79
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Week 5 July 26, 2011 pKa ! s of Carbonyl Compounds Explain the trends in pK a values for the following carbonyl compounds: R OR O O H H RO OR O O H H R CH 2 R O RO CH 2 R O N C CH 2 R Compound pKa 11 13 20 25 31 Conjugate Base Each of these compounds is treated with the base NaOEt. What will the predominant species be at equilibrium in each case? R OR O O H H RO OR O O H H R CH 2 R O RO CH 2 R O N C CH 2 R + EtO + EtO + EtO + EtO + EtO Reading : Section 22.1 80
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Week 5 July 26, 2011 Enols and Enolates All carbonyl compounds are in equilibrium with their enol forms; in addition, depending on the pH, they may be in equilibrium with protonated or deprotonated (enolate) forms: O OH OH O carbonyl compound enol enolate protonated carbonyl Acidic Solution Basic Solution very slow + H + fast + H + fast – H + fast – H
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Week 5-July 26 - Week 5 July 26, 2011 Acidity of Carbonyl...

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