Types of Chemical Bonds
The attractive force which has the ability of holding various constituent elements like atoms, ions, molecules, etc. together in different chemical species is termed as a chemical bond. Chemical compounds are dependent on the strength of chemical bonds between its constituents. Stronger the chemical bond, more will be the stability in the chemical compounds. Hence, it can be said that bonding defines the stability of chemical compounds.
Polarizability In Organic Chemistry
Polarizability refers to the ability of an atom/molecule to distort the electron cloud of neighboring species towards itself and the process of distortion of electron cloud is known as polarization.
Coordinate Covalent Bonds
A coordinate covalent bond is also known as a dative bond, which is a type of covalent bond. It is formed between two atoms, where the two electrons required to form the bond come from the same atom resulting in a semi-polar bond. The study of coordinate covalent bond or dative bond is important to know about the special type of bonding that leads to different properties. Since covalent compounds are non-polar whereas coordinate bonds results always in polar compounds due to charge separation.
A. Propane Measurements:
C1–C2–C3 bond angle |
1. |
H–C2–H bond angle |
2. |
H–C1–C2 bond angle |
3. |
H–C1–H bond angle |
4. |
C–C bond length in propane |
5. |
B. 2,2-Dimethylbutane Measurements: Carbon numbering here refers to IUPAC numberings.
C2–C3–C4 bond angle |
6. |
anti-C1–C2–C3 bond angle |
7. |
gauche-C1–C2–C3 bond angle |
8. |
C2–C3 bond length |
9. |
C. Butane Measurements:
Strain energy—anti conformation |
10. |
C1–C2–C3 bond angle—anti |
11. |
H–C1–C2 bond angle—anti |
12. |
DAtA & AnALYSiS Molecular Modeling I 75
C1–C2–C3–H dihedral angle—anti |
13. |
Strain energy—gauche conformation |
14. |
C1–C2–C3 bond angle—gauche |
15. |
C1–C2–C3–C4 dihedral angle—gauche |
16. |
C1–C4 H–H distance—gauche |
17. |
H–C1–C2–C3 dihedral angle—gauche |
18. |
PART II. BOND ROTATION IN BUTANE (STRUCTURES AND ENERGIES)
Dihedral angle—eclipsed conformation |
19. |
Relative energy—eclipsed |
20. |
C1–C2–C3 bond angle—eclipsed |
21. |
C1–C4 H–H distance—eclipsed |
22. |
C2–C3 bond distance—eclipsed |
23. |
C1–C2 bond distance—eclipsed |
24. |
Dihedral angle—second eclipsed conformation |
25. |
Relative energy—second eclipsed |
26. |
C1–C2–C3 bond angle—second eclipsed |
27. |
C2–C3 bond distance—second eclipsed |
28. |
76
WRITE-UP
PART III. CONFORMATIONAL ANALYSIS OF SUBSTITUTED CYCLOHEXANES
Strain energy—diaxial 1,2-dimethylcyclohexane |
29. |
Me–C–C–Me dihedral angle—diaxial |
30. |
Strain energy—diequatorial 1,2-dimethylcyclohexane |
31. |
Me–C–C–Me dihedral angle—diequatorial |
32. |
Strain energy—axial-equatorial 1,2-dimethylcyclohexane |
33. |
Me–C–C–Me dihedral angle— axial-equatorial |
34. |
PART IV. COMPARISON OF AXIAL AND EQUATORIAL STRAIN ENERGIES FOR TRIMETHYL-X SUBSTITUENTS A. t-Butylcyclohexane:
Strain energy— |
35. |
H–C–C–CMe3 dihedral angle— axial t-butylcyclohexane |
36. |
Symmetrical? |
|
C–CMe3 bond length— axial t-butylcyclohexane |
37. |
Closest C–C bond length (Methyl over ring) |
38 |
Strain energy— |
39. |
C–CMe3 bond length— equatorial t-butylcyclohexane |
40. |
Symmetrical? |
Draw your assigned substituent on the two structures below and record the calculated strain energy for each structure.
Axial: X(CH3)3 |
Equatorial: X(CH3)3 |
Calculated axial strain energy: 41. |
Calculated equatorial strain energy: 44. |
C–X bond length—axial isomer: 42. |
|
Closest C–C bond distance (methyl over ring): 43. |
Calculated energies for other –X(CH3)3 groups from other students’ calculations:
Substituent: |
Calculations by: |
Axial strain energy: |
Equatorial strain energy: |
C–X bond length—axial isomer: |
|
Closest C–C bond distance (methyl over ring): |
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