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103年 - 103 國立成功大學_碩士班招生考試試題_化學系：無機化學#123766
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4.Which kinds of the symmetry elements can make a molecule achiral? (6%)
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二、英文題Read this article and give us your analysis and comment.
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1.Explain why H-C-H (119.9°) of ethene (H₂C=CH2) is larger than that of 116.5° for formaldehyde (H₂CO) (6%).
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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%).
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3. Explain why NiCl₄²⁻ is a square-planar ion, whereas Ni(CO)₄ is a tetrahedral molecule (6%).
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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%).
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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%).
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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%).
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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%).
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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%).
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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%).
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