CHEM 242- Final Exam Guide - Comprehensive Notes for the exam ( 147 pages long!)
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14-8: cleavage of ethers by hbr and hi (pg 638-640) *hydrohalic acids ranked in order of their reactivity toward the cleavage of ethers: hi > hbr >> hcl. *note for phenyl ethers, phenols do not react further to give halides: *hydrogen peroxide / acetic acid combination is a good oxidant for sulfides. Unlike ethers (which are weak nucleophiles), sulfides are relatively strong nucleophiles: Sulfide attack on unhindered alkyl halides gives sulfonium salts, which can then become strong alkylating agents: Silyl ethers are often used as protecting groups. For example, if we wanted to add a grignard reagent to the carbonyl group of a keto-alcohol, the alcohol group would protonate the grignard reagent and the reaction would fail: We could use ethers as protecting group for hydroxide, but it can be difficult to remove: Five-, six-, and seven-membered (and occasionally four-membered) cyclic ethers are formed in the following way: 14-12: acid-catalyzed ring opening of epoxides (pg 649)
