課程名稱︰化學鍵
課程性質︰選修
課程教師︰彭旭明/王瑜
開課系所︰化學系
考試時間︰2005/06/23
試題 :
1. Work out the π-orbitals of C5H5 express their orbital shapes and relative
energys. How many π electrons there are ? Compare the stabilities of this
molecule withe those of C5H5+ and C5H5 . Explain why C5H5 is used quite
often as a ligand in the transition metal complexes ?
2. Work out the MOs of formaldehyde , H2CO ; describe all the orbitals
concerning C-O. Give the frontier orbitals (HOMO and LUMO). What is the
bond order of C-O ? What happens when the molecule undergoes photo-
excitation ?
3. Illustrate the Walsh (orbital correlation) diagram of AH2 as it bends away
from the linear geometry using only s and p orvitals for A. Based on this ,
predict and explain the geometries of BeH2 ; AlH2 ; SiH2 ; PH2 ; Ch2+ ;
AlH2+ ; SiH2+ ; Ph2 2+ .
4. Construct the Walsh diagram for the MOs of H4 in square planar and
rectangular geometries . Predict which geometry is more stable and why ?
Based on this , will you predict the geometry of the cyclobutadiene ?
5. Construct the molecular geometry of methylene cyclopropene using
fragmentation of two C-C double bonds ; analyze the interactions between
the fragment MOs . Draw all possible Lewis structures of this molecule .
Predict whether this molecule has a dipole moment , if so in which
dirention ?
6. Considering the benzyl cation , C7H7+ , in a planar geometry using the
interaction of fragmentation orbitals of C6H5 and CH2+ . Discuss the
changes in geometry in comparison with that of benzene .
7. Ditermine whether the cyclization of 1,3-cis-buta-diene is thermally
allowed of forbidden ?
8. What is Markovnikov's rule ? Explain the addition reaction of CH2CHCH3
(propene) + HBr and give the reaction profiles of this reaction for two
modes (α and β positions) of attack of H+ on propene .
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