Click here for a copy of my lecture notes from today's lecture

Click here for the other handouts used in class today

1.There are four different mechanisms possible when a haloalkane reacts with a nucleophile/base. It is important to categorize the nucleophile/base with respect to nucleophile and base strength. Click here for a table of nucleophiles grouped by nucleophile and base strength and a mechanism decision map.

A) SN2 (Substitution, Nucleophilic, Bimolecular) - reaction involves a single step in which nucleophile attacks backside of a carbon-leaving group bond (the electrophile), making a new bond as the leaving group departs. Click here to see a movie of an SN2 reaction. There is an InVERSiON of stereochemistry at the site of an SN2 reaction.

B) E2 (Elimination, Bimolecular) - anti-periplanar - involves a base reacting with the proton that MUST be anti-periplanar to the leaving group (that simultaneously leaves) in a single step to give an alkene. Click here to see the movie.When there is a choice in an E2 reaction, the more stable alkene predominates. This is referred to as Zaitsev's rule.

C) When a weak nucleophile/very weak base is used with a tertiary haloalkane, upon heating, not much happens until a carbocation is produced by spontaneous departure of the halide (slow). The cation then reacts through a combination of SN1 (Substitution, Nucleophilic, Unimolecular) and E1 (Elimination, Unimolecular) pathways in which a nucleophile is added or a proton removed from the carbocation, respectively.

2. It is important to categorize the nucleophile/base with respect to nucleophile and base strength. Click here for a table of nucleophiles grouped by nucleophile and base strength and a mechanism decision map.

A) Methyl and primary haloalkanes react with the SN2 mechasnism for all nucleophiles in the table except for tBuOK. tBuOK is a srong base that is so stereically hindered it cannot undergo an SN2 reaction, so even primary haloalkanes will undergo an E2 reaction with tBuOK.

B). For secondary haloalkanes, the strong bases labeled in the table react predominantly via the E2 mechanism. Most other nucleophiles react via the SN2 mechanism, except for the "very weak bases" listed in the table that react via the SN1/E1 pathway.

C). Tertiary haloalkanes react via E2 (never SN2) except when the "very weak bases" listed in the table are used, then they go SN1/E1.

HOMEWORK:

Read: Sections 9.5 - 9.9.

Take the Daily Quiz 17 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture. Together, they will count as 5% of your final grade.

Finish working on the Gradescope Homework Problem Set 8, due tonight at 10 PM on Wednesday, November 6. Click here to access the Gradescope Homework Problem Set 8.

There is no Aktive learning homework this week.The Gradescope homework is challenging and I would like you to focus on it.

When you are done with Gradescope Homework Problem Set 8, start working on Gradescope Homework Problem Set 9 due Tuesday November 12. Click here to access the Gradescope Homework Problem Set 9. Note there are Aktiv Learning and Gradescope Questions for Problem Set 9, and you MUST DO BOTH.