Chemistry 110a Exam 5 Review Sheet
Review Session: Wednesday November 18, 7:00 PM, SN Auditorium.
Exam 5: Friday, November 20, 7:50 AM, SN Auditorium
Chapter 10 Radical Reactions
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You should know the difference between bond heterolysis and bond homolysis (important for
radical generation).
Radical structure and trends in stability. Remember, radical stability plays a role in analyzing
transition states, which can often allow us to predict product ratios (most reactions climb the
shortest hill).
You should be able to write down and identify the key stages of a radical chain reaction, e.g., the
halogenation of methane [initiation, propagation, termination].
You should be comfortable with the fact that the bromine radical is a less reactive, yet more
selective radical compared to the chlorine radical. We examined the transition states of a key step
of the radical chain (H abstraction), one exothermic, one endothermic, and invoked the Hammond
Postulate to rationalize the resulting product ratios. We learned that free-radical bromination is a
synthetically useful process for say, adding bromine to a tertiary position.
Stereochemical implications of radical chemistry. Planar radical structure invites racemization.
What is an octane number? How are CFCs destroying the ozone layer, and why should we care
about the ozone layer? Who was Thomas Midgley?
HBr/peroxides addition to alkenes as an anti-Markovnikov reaction. Reaction mechanism. BHT
as an antioxidant—how does it work as a preservative?
Chapter 11: Alcohols and Ethers
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Nomenclature of alcohols and ethers.
Activation of hydroxyl groups in order to change them into other functional groups or into leaving
groups. (a) Sulfonate ester preparation (mesylates, tosylates). These are good leaving groups-why? (b) Conversion of R-OH to R-Cl (1° or 2°) using SOCl2, thionyl chloride. Mechanism of
reaction reveals why 3° alcohols are not useful substrates. (c) Conversion of R-OH to R-Br using
PBr3, phosphorous tribromide. Mechanism of reaction reveals why 3° alcohols are not useful
substrates. (d) Alkyl halides from HX treatment of R-OH. Mechanism reveals potential
problems with this method.
The Williamson ether synthesis. (You've seen this before!)
Tert-butyl ethers and silicon ethers as protecting groups. Why would you want to use a protecting
group?
Epoxides: synthesis from alkenes using peracids: mechanism of reaction. Reactions of epoxides
under basic or acidic conditions (outcomes are different). Anti dihydroxylation of alkenes.
Compare this method with other dihydroxylation agents, e.g., OsO 4 or KMnO4 (cold, basic).
The Sharpless asymmetric epoxidation as an example of an enantioselective reaction.
Crown ethers. What are these substances used for? Phase-transfer catalysis, artifical ion channels,
relevance to natural products such as antibiotics.
You should be able to utilize these reactions in combination with earlier reactions we have studied
for the evaluation and/or design of synthetic proposals that start with cheap and readily available
starting materials.