Which of the following does NOT describe why a nucleophile will react more quickly with acetic anhydride than with N,N-diisopropylisobutyramide?

Question

Quizplus · Accepted Answer

11ecba2d_1273_b4ac_a3bf_5bd0b00f72a0_MD0008_00 Induction is an electronic property in which electrons are donated through sigma bonds. Electronegative atoms or electron withdrawing substituents pull electrons away from an adjacent atom toward themselves, creating a dipole with a partial negative charge on the electronegative atom and a partial positive charge on the adjacent atom. The closer the electron withdrawing group to an atom, the greater the inductive effect that atom experiences. Electron withdrawing groups also make good leaving groups because they can stabilize the negative charge acquired after being eliminated. Acetic anhydride and N,N-diisopropylisobutyramide both have two electronegative atoms bonded to each carbonyl carbon. The anhydride carbonyl carbons are bound to two oxygen atoms whereas the amide carbonyl carbon is bound to an oxygen and a nitrogen. Because oxygen is more electronegative than nitrogen, it draws more electron density away from the carbonyl carbon than nitrogen does, creating a larger dipole on the anhydride than on the amide, as well as a more electrophilic carbonyl carbon on the anhydride (Choice B). Therefore, an anhydride, such as acetic anhydride, has a greater inductive effect than an amide, such as N,N-diisopropylisobutyramide. (Choice C) The bulky isopropyl groups on the nitrogen and adjacent to the carbonyl in N,N-diisopropylisobutyramide provide more steric hindrance than the methyl groups on acetic anhydride, making it more difficult for a nucleophile to attack the amide carbonyl. (Choice D) The leaving group of N,N-diisopropylisobutyramide is the amino group, and the leaving group of acetic anhydride is the carboxyl group. Carboxyl groups are better leaving groups than amines because they are stabilized by resonance delocalization of the negative charge. Educational objective: The inductive effect is an electronic property in which the electrons are donated through sigma bonds. Electronegative atoms or electron withdrawing groups tend to create greater dipoles, partial charges, and better leaving groups, and to have greater inductive effects than less electronegative atoms.

Which of the Following Does NOT Describe Why a Nucleophile