assignment 4 answers - CHM 1321 Assignment 4 Answers 1) For...

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1 CHM 1321 Assignment 4 Answers 1) For the following pairs of compounds, predict which one will be the strongest acid and justify your choice. NH 2 OH OH O OH a) b) vs vs c) CBr 3 CO 2 H vs CH 3 CO 2 H R NH 2 R NH + H (1) R OH R O + H (2) look at the conjugate bases: -in equation 2 the atom bearing the negative charge is more electronegative than the atom holding the negative charge in equation 1. Therefore the negative charge will be more stabilized in the conjugate base of equation 2 -this means that this conjugate base will be more stable and a weaker base than the conjugate base in equation 1 - since the conjugate base in equation 2 is weaker, the corresponding acid will be stronger So is the stronger acid OH (2) RO H + H O H O + H (1) The conjugate base in equation 2 is stabilized by resonance. O O this conjugate base is more stabilized than that in equation 1, therefore this is the weaker conjugate base and O H is the stronger acid O O H Br Br Br O O Br Br Br H + O O H H H H O O H H H H + (1) (2) The bromines in equation 1 are more electronegative than the corresponding hydrogens in equation 2. The stronger electron withdrawing power of the bromines stabilize the conjugate base in (1) by the inductive effect. Since the conjugate base in (1) is more stable than in (2) it is a weaker base and therefore the acid in equation (1) is the stronger acid
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2 R SH NMe MeN O SH S O O O H R OH NMe MeN O SH R S R O O H NMe MeN O OH H H d) vs e) vs + (1) + (2) -in equation 1 the atom bearing the negative charge is larger (lower in the periodic table) than the atom holding the negative charge in equation 2. Therefore the negative charge will be more dispersed in the conjugate base of equation 1 -the dispersion of negative charge in the conjugate base in equation 1 results in better stabilization of the negative charge, therefore this conjugate base will be more stable and a weaker base than the conjugate base in equation 2 - since the conjugate base in equation 1 is weaker, the corresponding acid will be stronger So is the stronger acid R S O O O H R S O O O +H RO H (1) (2) The conjugate base in equation 1 is stabilized by resonance R S O O O R S O O O R S O O O this stabilizes this conjugate base more than that in equation 2, therefore this is the weaker conjugate base and is the stronger acid R S O O OH
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3 OH CF 3 OH CF 3 OH CH 3 OH CH 3 O CF 3 O CH 3 H H f) vs + + (1) (2) The flourines in equation 1 are more electronegative than the corresponding hydrogens in equation 2. The stronger electron withdrawing power of the flourines stabilize the conjugate base in (1) by the inductive effect. Since the conjugate base in (1) is more stable than in (2) it is a weaker base and therefore the acid in equation (1) is the stronger acid 2) Write equations for the following reactions using arrow notation. Predict whether the reaction will favor the starting materials or products and justify your choice.
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This note was uploaded on 10/24/2010 for the course SCIENCE 2776 taught by Professor Dr.alisonflynn during the Fall '10 term at University of Ottawa.

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assignment 4 answers - CHM 1321 Assignment 4 Answers 1) For...

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