Unformatted text preview: CHM 112B Review Session – February 2nd and 6th Topics: Electrophilic Aromatic Substitution; Chemistry of aryl halides, vinylic halides, and phenols (beginning) GSI – Jessica Kisunzu 1. Complete the general equation for an electrophilic aromatic substitution (EAS) reaction: H
E 2. Most EAS reactions proceed via a general 3‐step mechanism. What are these steps? • Generate ________________________________________ • Attack_________________________ and form _____________________ (_______‐complex) • Lose ______________________________________________ 3. Show the mechanism of the following bromination and label each step of the EAS: Br
Br , FeBr
2 3 4. Provide a set of conditions and the reactive electrophile the following reactions: Nitration – Chlorination – Sulfonation – 5. Draw an energy diagram for an electrophilic aromatic substitution reaction: What is the rate‐determining step? _________________________________________________ _________________________________________________ 6. Draw the expected product(s) and mechanism for the following reactions: a) Cl , FeCl3 What is this reaction called? _______________________________________ Is the FeCl3 stoichiometric or catalytic? ___________________________ b) Cl
FeCl3 c) From: Bai, W.‐J.; Green, J. C.; Pettus, T. R. R. J. Org. Chem. 2012, 77 (1), pp 379‐387. MeO O
OMe Cl AlCl3,
0 °C What is the name of this reaction?_________________________________________________ What is the name of the reactive electrophile?________________________________________ Is the AlCl3 stoichiometric or catalytic and why?_________________________________________ 7. Label each substituent as an ortho/para director or a meta director (make sure you have a reason why): O
NO2 Cl O SO3H 8. Select the correct term in the following sentence: In general, activating substituents direct (ortho/para OR meta) and deactivating substituents direct (ortho/para OR meta). Which substituents are the exceptions? ________________________ 9. Label the substituents in question 7 as either activating or deactivating. 10. a) Give all resonance forms for the sigma‐complex that would lead to the formation of product A in the following reaction and circle the most important one. OMe
Me Cl Cl
A B Why is that structure the most important?_________________________________________________ b) Give all resonance forms of the sigma‐complex that would lead to the formation of product B. c) Which point of substitution is favored and why (explain using the resonance information)?________________________________________________________________________________________ _________________________________________________________________________________________________________
_ d) What named statement helps us to make this analysis and why? ______________________________________________________________________________________________________ ______________________________________________________________________________________________________ 11. Give an example of a meta‐directing group on a benzene ring and show all relevant resonance forms to show why meta is favored. 12. Rank the following compounds from least reactive (1) to most reactive (5) in EAS. Br
OMe 13. Give an explanation for why halogens are deactivating substituents: 14. Fill in reagents in the order that would make the following compounds: a) 1. SO3H 2.
Cl b) O 1. 2. O2N 15. Label each of the following compounds as an allyl, benzyl, vinyl, or aryl bromide: Br Br Br Br ...
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