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c) The compound on the right is the stronger acid because the conjugate base produced by the removal of a proton from the CH₃ group is stabilized by resonance. There is no such stabilization in butane. d) The compound on the right is the stronger acid because the CF₃ group is a strong electron-withdrawing group. The CH₃ group is weakly electron donating and destabilizes the conjugate base. e) The compound on the right is more acidic because the nitrogen in this molecule is sp² hybridized. The unshared pair of electrons of the conjugate base will more stable in a sp² hybridized orbital. 4.30 a) The anion on the left is a stronger base because the nitro group of the anion on the right provides additional resonance delocalization of the basic electrons. b) The nitrogen compound is a stronger base than the phosphorus compound because acid strength increases (and base strength decreases) down a column of the periodic table. c) The anion on the left is a stronger base because CI is a stronger electron withdrawing group than Br as a result of its higher electronegativity. d) The anion on the right is a stronger base because is more electronegative than N. 4.31 The acidic hydrogen is the one bonded to the oxygen for each compound. Compound B is a stronger acid than A because of resonance stabilization of its conjugate base. Compound C is a stronger acid than B because of the inductive electron withdrawing effect of the CN group. Compound D is a stronger acid than C because of the additional resonance stabilization of the conjugate base when the CN is attached to the para position. OH OH OH CH₃OH V V V CN CN A B C D 56