所屬科目：研究所、轉學考(插大)◆有機化學及無機化學
1.Explain why H-C-H (119.9°) of ethene (H₂C=CH2) is larger than that of 116.5° for formaldehyde (H₂CO) (6%).
2. Based on VSEPR (Valence-Shell Electron-Pair Repulsion) theory, explain why an ion, , adopts a geometric shape as a regular octahedron, rather than a distorted octahedron (6%).
3. Explain why NiCl₄²⁻ is a square-planar ion, whereas Ni(CO)₄ is a tetrahedral molecule (6%).
4.Which kinds of the symmetry elements can make a molecule achiral? (6%)
5. Explain why a bridging carbonyl group of a dinuclear metal carbonyl compound (for example, Mn₂(CO)₁₀) displays a smaller νco frequency (in cm⁻¹) than a terminal carbonyl group (6%).
6. Explain why a neutral molecule, C₂, has a shorter bond length than a cationic molecule, C₂⁺,whereas the reverse is true for O₂ and O₂⁺ (8%).
7. A student tried to use ZnO as an oxidization reagent to prepare n-octane from n-BuLi. However,he did not obtain n-octane from the reaction. Instead, what he obtained is ZnBu₂. Explain why he obtained such an unexpected result (6%).
8. A student wants to produce (η⁵-C₅H₅)Mo(CO)₃(CF₃) from K⁺ (η⁵-C₅H₅)Mo(CO)₃. Suggest a suitable electrophilic reagent for him (4%) and write a reasonable reaction route, leading to the desired product (4%).
9. Although a singlet signal is observed at room temperature in the ¹⁹F NMR spectrum of CIF₃, the signal becomes complicated at - 60 °C. Draw a possible NMR pattern for the ¹⁹F NMR multiplet at the temperature (¹⁹F at 100% natural abundance with I = 1/2) (6%).
10. Transition-metal d-d transition is Laporte (orbitally) forbidden and a transition-metal complex is usually lightly colored in solution. Explain why KMnO₄ dissolves in water and becomes a deep blue solution (6%).
11. The reaction of CrCl₃ with PhLi is complicated. One neutral product contains one chromium atom and four Ph groups. Based on the 18-electron rule, draw a possible structure and give your reason (6%).
12. Write an IUPAC name for K₂[Fe(en)₂(CN)₂] (4%), write the electron configuration in a crystal field and calculate the related crystal field stabilization energy in Dq values (6%).
13. One student found that the reaction of Fe(CO)₅ with Me₃NO produced Fe(CO)₄(NMe₃) and CO₂. Propose a detailed mechanism (8%).
(a) The oxidative addition of [Co(dppe)₂]⁺ or [Ir(dppe)₂]⁺ with H₂ (6%).
(b) The migratory insertion of [CpMo(CO)₃Me] or [CpMo(CO)₃(CF₃)] with PPh₃ (6%).
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, adopts a geometric shape as a regular octahedron, rather than a distorted octahedron (6%).