Problem Set 2

# A b c o o o o o oh ho ho ho h d o o chem 33 kanan

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(a) (b) (c) O O O O O OH HO HO HO H (d) O O Chem 33, Kanan & Stack, 2012 PS 2; pg 5

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9. For each of the following compounds, identify the favored protonation state if the solution was buffered at the indicated pH. First determine the pKas for of the relevant acids for all species considered. For estimates of pK a s use the pKa table on the inside of the back cover of J&F or in class notes. O S O OH HO or or O S O O HO O S O O O pH = 3 CO 2 H or or SH CO 2 - SH CO 2 - S pH = 9 O OH NH 3 + O O NH 3 + O O NH 2 or or O N H CH 3 + or O N CH 3 or pH = 10 pH = 3 pH = 4 pK a s from Monday class 8. The reaction of LiN(CHMe 2 ) 2 and acetone (Me 2 C=O) has a calculated Gibbs free energy of reaction of –23.8 kcal mol -1 . Assuming the p K a of the C–H bond in acetone is 20, what is the p K a of the conjugate acid of LiN(CHMe 2 ) 2 ? CH 3 H 3 C N Li + H 3 C CH 3 + O H 3 C CH 3 CH 3 H 3 C NH H 3 C CH 3 + O H 3 C CH 2 Li + O Li + H 3 C CH 2 acetone resonance stabilized acetone enolate anion or O N CH 3 H O O O O Chem 33, Kanan & Stack, 2012 PS 2; pg 6
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