2. First General Meeting! The Pre-Health Society’s Monday September 19th
Do you plan on attending Medical School?
Dental School? Veterinary School?
Or any other Pre-Health Career?
Then you should attend…
The Pre-Health Society’s
First General Meeting!
Come to network, learn about the Pre-Health Society, and eat snacks!
Monday September 19th
4:30pm
The Space

3. Chemistry 250-02 Organic Chemistry I Fall, 2016 Day 8 & 9
Organic Chemistry I
Fall, 2016
Day 8 & 9
Wed 9/14/16 & Fri 9/16/16
Chapter 4
Acyclic Alkanes and CycloAlkanes Conformational Analysis & Stereochemistry
Chem Act 6A, 7A & 7B

4. How many H’s are on this molecule?12 14 16 17 18 20
Other
Countdown 10

5. How many H’s are on this molecule?12 14 16 17 18 20
Other
Countdown 10

6. How many units (degrees) of unsaturation?3 4 5 6 7 8 9
Countdown 10

7. How many units (degrees) of unsaturation?3 4 5 6 7 8 9
Countdown 10

8. What are the numbers of primary, secondary, tertiary and quaternary carbons in this molecule?
2, 3, 3, 2
3, 4, 2, 1
3, 3, 3, 1
3, 4, 3, 0

9. What are the numbers of primary, secondary, tertiary and quaternary carbons in this molecule?
2, 3, 3, 2
3, 4, 2, 1
3, 3, 3, 1
3, 4, 3, 0

10. What are the numbers of primary, secondary, tertiary and quaternary hydrogens in this molecule?
6, 6, 2, 1
9, 8, 2, 1
9, 8, 3, 1
9, 8, 3, 0

11. What are the numbers of primary, secondary, tertiary and quaternary hydrogens in this molecule?
6, 6, 2, 1
9, 8, 2, 1
9, 8, 3, 1
9, 8, 3, 0

12. Acyclic Alkanes are non-rigid
≈ 1 kcal/mol

13. Cyclic Alkanes are “rigid” cis and trans isomers

14. The Dance of Ethane Conformational Isomers
Chem Act 6A Models 1-5 complete CTQ 1-12
= 3 kcal/mol
1 kcal/mol each

15. Which statement about bond rotation around the C-C bonds in ethane and ethene is correct? H3C-CH3 H2C=CH2
Rotation around a σ bond is easy because the orbital overlap does not change with rotation.
Rotation around a π bond is easy because there are p orbitals available in all directions of space.
Rotation around a σ bond is hard because the electron pairs from the adjacent bonds must pass by each other.
Rotation around a π bond is hard because the electrons are delocalized.
Rotation around σ and π bonds is equally facile.

16. Which statement about bond rotation around the C-C bonds in ethane and ethene is correct? H3C-CH3 H2C=CH2
Rotation around a σ bond is easy because the orbital overlap does not change with rotation.
Rotation around a π bond is easy because there are p orbitals available in all directions of space.
Rotation around a σ bond is hard because the electron pairs from the adjacent bonds must pass by each other.
Rotation around a π bond is hard because the electrons are delocalized.
Rotation around σ and π bonds is equally facile.

17. The Dance of Propane
1.4 kcal
1 kcal

18. The Dance of Butane Conformational Isomers

19. Melvin Newman Projections (1952)

20. Non-Bonded Intramolecular Interactions Draw low and high energy Newman conformations of 2-methylbutane

21. Which of the above represents a Newman projection of 2-bromo-3-chlorobutane?d e

22. Which of the above represents a Newman projection of 2-bromo-3-chlorobutane?d e

23. Some Cyclic Natural Products

24. Tamiflu

25. Some Cyclic Hydrocarbons CnH2n vs CnH2n+2

26. Chem Activity 7A Cis and Trans Rings (p. 98)
Read Model 1 and complete CTQ 1-4.
If you finish, continue to Model 2.
Note for CTQ 7: We are skipping alkenes (E/Z isomers) for now. Ignore those!

27. Cycloalkanes - Physical Properties

28. Cyclopropane C3H6

29. Cyclopropane Stereoisomers

30. Cyclobutane C4H8

31. Cyclopentane C5H10

32. Some Natural Cyclopentanes The Prostaglandins

33. Are these two molecules the same?
No; one is cis and one is trans.
No; the methyl groups are not on the same side of the ring.
Yes; they have the same #s of C’s and H’s.
Yes; they can be interconverted without breaking bonds.
Yes; they have the same stereochemistry

34. Which of these 4 molecules are the same?
A & B and C & D
A & C and B & D
A & D and B & C
None are the same.
All are the same.

35. CnH2n + 2nO2 = nCO2 + 2nH2O

36. What kind of strain is there and Which cycloalkane is most strain free ?

37. Nomenclature with rings

38. Problems

41. Cyclohexane and its Stereochemistry
Organic Chemistry I
Fall, 2016
Day 9
Fri 9/16/16
Chapter 4
Cyclohexane and its Stereochemistry
Chem Act 7A, 7B - Today

42. Cyclohexane C6H12 and Analogs

43. Visualizing Cyclohexane The Chair – Chem Act 7B Model 3

45. What kind of strain is there and Which cycloalkane is most strain free ?
Chem Act 7B Model 4

46. CnH2n + 2nO2 = nCO2 + 2nH2O

47. Axial and Equatorial Chem Act 7B Model 5
Axial and Equatorial Chem Act 7B Model 5

48. What happens to an axial hydrogen in a chair conformation of cyclohexane when all bonds “rotate” in a synchronized fashion?
nothing, it stays where it was as an axial H
it “flips” to the equatorial position on the same carbon
it “flips” to the equatorial position on the next carbon
the carbon to which the hydrogen is attached changes hybridization
it moves from a cis to a trans position

49. Strain in Substituted Cyclohexanes
ΔG = - RT ln K
ΔG (in kcal/mole) = log K
K log K ΔG
Why so large ?
Why so small ?

50. Substituted Cyclohexanes

51. What happens to a substituent in a chair conformation of cyclohexane when all bonds “rotate” in a synchronized fashion?
nothing, it stays where it was in an axial position
it “flips” to the equatorial position on the same carbon
it moves to the next carbon
the carbon to which the substituent is attached changes hybridization
it moves from a cis to a trans position

52. Which of these 4 molecules have the same relative stereochemistry ?
A & B and C & D
A & C and B & D
A & D and B & C
None have the same.
All have the same.

53. What is the relationship between A and B (or C and D) ?
Constitutional isomers
Conformational isomers
Configurational isomers
They have different molecular weights.
All are the same.

54. 1,2-Dimethylcyclohexane

55. What is the energy difference between the two chair conformations of trans-1,2-dimethylcyclohexane?
zero
one gauche interaction vs two CH3-H diaxial interactions
one gauche interaction vs four CH3-H diaxial interactions
two gauche interactions vs four CH3-H diaxial interactions
one gauche interaction vs two gauche interactions

56. Problem 4.18 Draw the most stable chair conformation of
a) trans-1-Chloro-3-methylcyclohexane
b) cis-1-Ethyl-2-methylcyclohexane
c) cis-1-Bromo-4-ethylcyclohexane
d) cis-1-tert-Butyl-4-ethylcyclohexane

57. Which of the above molecules represents the most stable conformation of trans-1,3-dimethylcyclohexane? a b c d e

58. Which of the above molecules will have the highest energy after the chair flip?d e

59. Which of the above structures represents the most stable (lowest PE) conformation of tert-butyl-3,5-dimethylcyclohexane? a b c d e

60. Which of the above structures represents the least stable (highest PE) conformation of tert-butyl-3,5-dimethylcyclohexane? a b c d e

63. What are the relative geometries of ring fusions (starting from the left) for the steroid shown below?
cis, cis, cis
cis, cis, trans
cis, trans, trans
trans. cis, cis
trans, trans, cis

64. Substituted Cyclohexanes

65. Decalin C10H18

66. Reactions of Alkanes