1. ICE 2 (covering lectures 5 and 6) review session
Marty and Aaron
September 27, 2014

2. Arrow pushing is a narrative that describes how electrons move as bonds are made and broken
Redraw the molecule to explicitly show all atoms and electrons
Number the atoms
Find the beginning of the story (first arrow)
Each arrow represents the moving of a pair of electrons from one spot to another
Follow the narrative until the end and apply the octet rule throughout

3. Arrow Pushing Example 1:
Step 1: Redraw the molecule to show all lone pair electrons and all atoms. Number the carbons.
Question: What is the product given this mechanism: =

4. Arrow Pushing Example 1:
Step 2: Identify the beginning of your narrative (orange electrons and arrow indicate the O making a bond to C8
Question: What is the product given this mechanism:

5. Arrow Pushing Example 1:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

6. Arrow Pushing Example 1:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

7. Arrow Pushing Example 1:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

8. Arrow Pushing Example 1:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

9. Arrow Pushing Example 1:
Step 4: Take stock of the bonds that have been made and broken. Check your answer.
Answer:
Question: What is the product given this mechanism:

10. Arrow Pushing Example 2:
Step 1: Redraw the molecule to show all lone pair electrons and all atoms. Number the carbons.
Question: What is the product given this mechanism: =

11. Arrow Pushing Example 2:
Step 2: Identify the beginning of your narrative (orange electrons and arrow indicate the O making a bond to C8
Question: What is the product given this mechanism:

12. Arrow Pushing Example 2:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

13. Arrow Pushing Example 2:
Step 3: Follow the narrative of the electrons moving from one spot to the next, from beginning to end, always keeping the octet rule in mind
Question: What is the product given this mechanism:

14. Arrow Pushing Example 2:
Step 4: Take stock of the bonds that have been made and broken
Question: What is the product given this mechanism:

15. Arrow Pushing Example 2:
Step 4: Take stock of the bonds that have been made and broken. Check your answer.
Answer:
Question: What is the product given this mechanism:

16. Example 3: Try this for yourselves
What is the product given this reaction mechanism

17. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!

18. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Start by redrawing the reactants, but keep an eraser handy!

19. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Look for bonds that are breaking. [hint: they are bonds from which arrows originate!]

20. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Look for bonds that are breaking. [hint: they are bonds from which arrows originate!]

21. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Now erase them!

22. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Let’s replace them with dotted lines.

23. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Let’s replace them with dotted lines.

24. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Let’s identify the bonds that are forming.

25. Drawing transition states from a mechanism
Draw the transition state:
These atoms are forming a bond
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Let’s identify the bonds that are forming.

26. Drawing transition states from a mechanism
Draw the transition state:
These atoms are forming a bond
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Let’s identify the bonds that are forming… then draw them as dotted lines.

27. Drawing transition states from a mechanism
Draw the transition state:
Another bond is forming… but which one? OR

28. Drawing transition states from a mechanism
Draw the transition state:
Another bond is forming… but which one? OR

29. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Hint: In the transition state, there will be a continuous stretch of dotted lines that show bonds that are alternating between being formed and broken.
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!

30. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
If something is charged in the reactant, but not the product, it will be partially charged in the transition state.
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!

31. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
If something is charged in the reactant, but not the product, it will be partially charged in the transition state.
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!

32. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
If something is charged in the reactant, but not the product, it will be partially charged in the transition state.
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!

33. Drawing transition states from a mechanism
Draw the transition state:
What do I do?
Draw everything that isn’t changing.
Draw the bonds that are breaking using dotted lines.
Draw the bonds that are forming using dotted lines.
Fill in partial charges.
Brackets and double dagger!
Don’t forget this step! Seriously, we will take off points.

34. Drawing arrows given a transition state
What do I do?
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

35. Drawing arrows given a transition state
What do I do?
Which is correct?
Breaking/Forming
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

36. Drawing arrows given a transition state
What do I do?
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!
Breaking/Forming

37. Drawing arrows given a transition state
Breaking/Forming
What do I do?
Your transition state will contain a continuous dotted line – look at either end of this line to figure out where the electrons originated.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

38. Drawing arrows given a transition state
Breaking/Forming
Lone pair
What do I do?
Your transition state will contain a continuous dotted line – look at either end of this line to figure out where the electrons originated.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

39. Drawing arrows given a transition state
Breaking/Forming
What do I do?
Start drawing arrows from the original source of the electrons—the lone pair on nitrogen.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

40. Drawing arrows given a transition state
Breaking/Forming
What do I do?
We know the first thing to do is form the N-C double bond. Do this using an arrow point from the lone pair to the bond that already exists between N and C.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

41. Drawing arrows given a transition state
Breaking/Forming
What do I do?
Next, we know that the C-S bond breaks, and with those electrons, sulfur forms a new bond to another carbon.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

42. Drawing arrows given a transition state
Breaking/Forming
What do I do?
Next, we know that the C-O double bond breaks, and the electrons from that bond form a new O-H bond.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

43. Drawing arrows given a transition state
Breaking/Forming
What do I do?
Finally, the O-H bond in hydronium breaks, leaving a lone pair on oxygen.
Figure out which bonds are breaking and which are forming.
Start from the beginning – find the original source of the electrons (either a lone pair or a bond).
Draw in the arrows!

44. Want extra practice? Answers will be posted online with these slides!
Draw the transition state:
Draw the mechanism arrows that lead to the transition state:

45. Answers: Draw the transition state:
Draw the mechanism arrows that lead to the transition state: