HWKey (11) - stabilizes the anion. For this reason, the...

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Problem of the Day #10 – Answer Key Deadline : 3:00 p.m., Monday, 6/23/08 LATE WORK WILL NOT BE ACCEPTED OR GRADED!!! This problem is worth a total of 20 raw points. Arrange the compounds in each of the following sets in order of decreasing pK a [1 = highest pK a ; 3 = lowest pK a ]. Then, provide a brief explanation for your answer. The space provided should be adequate for a suitable explanation!!! CH 3 CH 2 OH Cl 2 CHCH 2 OH ClCH 2 CH 2 OH (a) E x p l a n a t i o n : 1 3 2 Incorporation of electronegative chlorine atoms in the molecule stabilizes the resulting conjugate base via an inductive effect. Having two chlorine atoms in the molecule is more stabilizing than having only one. CH 3 CH 2 OH ClCH 2 CH 2 SH (b) E x p l a n a t i o n : CH 3 CH 2 SH 3 1 2 Moving down a column, acidity increases because the negative charge of the conjugate is localized on a larger atom. The negative charge is “spread out” over a larger volume, which
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Unformatted text preview: stabilizes the anion. For this reason, the thiol is more acidic than the alcohol. The thiol that also contains a chlorine substituent is more acidic than the thiol that lacks a chlorine substituent, due to the inductive effect caused by the electronegative chlorine atom. (c) E x p l a n a t i o n : H As(CH 3 ) 2 H As(CH 3 ) 2 H H N(CH 3 ) 2 2 3 1 Considering the same element, positively charged molecules are more acidic than neutral molecules (the conjugate base is a neutral molecule which is more stable than an anion). As stated above, when moving down a column, acidity increases, because localization of the negative charge on a larger atom stabilizes the conjugate base anion....
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