1. CHEM 261 SI w/ Wesley Son
10/25/16, 7-8:15, Fernald 11
Email: wson@umass.edu
Concepts Reminders/Advice
- Alkene Reaction Mechanisms - Work on your OWLS!
- E/Z Nomenclature - Exam 2 is on 11/4, keep up with the material!
Alkene Reaction Mechanisms
(Disclaimer: you are NOT responsible for memorizing any of these mechanisms, for the exam you only need to be able to predict
the product. It is good to know them, especially if you like chemistry!)
Acid-Catalyzed Dehydration (Alcohol + Strong Acid -> Alkene)
Mechanism
Predict the product
Alkyl Halide + Strong Base -> Alkene
Mechanism
Predict the product
Alkene + HX (X=Cl, Br, I) -> Alkyl Halide
Mechanism
Predict the product

2. Alkene + X2 -> Dialkyl Halide
Mechanism
Predict the product
Alkene + X2 in H2O -> Alkane w/ OH and X (Halohydrin Formation)
Mechanism
Predict the product
Acid-Catalyzed Hydration (Alkene + H3O+
-> Alcohol)
Mechanism
Predict the product

3. Anti-Markovnikov Addition of Water (Alkene + BH3 -> Alcohol)
Mechanism Don’t worry about it! J
Predict the product
E/Z Nomenclature
Why? When different substituents are attached to a carbon double-bond, there will not always be obvious groups that are cis and
trans to each other. This is why we have E/Z nomenclature.
How to Classify an alkene as being E or Z
E - the higher priority groups are on opposite sides of the double bond.
Z - the higher priority groups are on the same side of the double bond. (The wise Prof. Schnarr once said: “Z -> Zame Zide”
We classify group priority using the Cahn-Ingold Prelog Rules
1. Draw a line perpendicular to the double bond
2. Draw in Hydrogens (if applicable)
3. Look left and right of the line you have drawn and compare the high and low priority groups on each side.
4. Mark the high priority groups
5. If they are on opposite sides, you have an E isomer. If they are on the same side, you have a Z isomer.
Label the following as cis or trans
Label the following as E or Z