39. Which amine would you expect to form the least stable adducts with BMe₃? (A) NEt₃ (B) NH₂Me₂ (C) NHMe₂ (D) NH₃ (E) Quinuclidine (on the right)

4. Both ZnS and CaF₂ have a face-centered cubic unit cell where the S²⁻ and Ca²⁺ ions are closest packed in each structure. Which of the following is true? (A) There are 4 tetrahedral holes empty in each structure. (B) In both compounds, one-half of the tetrahedral holes are filled. (C) In both compounds, all the tetrahedral holes are filled. (D) There are 8 Zn²⁺ ions and 4 F⁻ ions in the unit cell. (E) In ZnS, one-half of the tetrahedral holes are filled by Zn²⁺ ions, whereas in CaF₂ all the tetrahedral holes are filled with F⁻ ions.

39. Which amine would you expect to form the least stable adducts with BMe₃?

(A) NEt₃
(B) NH₂Me₂
(C) NHMe₂
(D) NH₃
(E) Quinuclidine (on the right)

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