Alcohols and Ethers: Key Terms and Reactions
Terms for Chapter 11: Alcohols & Ethers
Alcohol (Sec 2.6, 4.3F, 11.1): A molecule containing a hydroxyl group, -OH, bound to an sp3 hybridized carbon atom, with the general formula ROH.
Ether (Sec 2.7, 11.1): A molecule containing an oxygen atom bonded to two alkyl or aryl groups, with the general formula ROR’.
Alkoxy group (Sec 11.2): The RO- group; obtained by removing a hydrogen atom from an alcohol, ROH.
Acid-catalyzed hydration of alkenes (Sec 8.5 – 8.10, 11.4): The addition of the components of water, H-OH, to the C=C group of an alkene, which forms an alcohol according to Markovnikov’s rule; the acid catalyst adds H+ to form the more stable carbocation (which may undergo rearrangements), then water adds to the carbocation to produce the more substituted alcohol, as a mixture of syn and anti addition products.
Rearrangement reaction (Sec 3.1, 7.8, 11.4): A reaction in which the carbon skeleton of a molecule is rearranged to produce a different isomer of the original molecule.
Oxymercuration-demercuration of alkenes (Sec 8.6, 11.4): A two-step method that converts an alkene into an alcohol, with Markovnikov regiochemistry, and usually no rearrangements. The first step is oxymercuration that reacts the alkene with water and mercuric acetate, Hg(OOCCH3)2, which adds a hydroxyl group, -OH, and an acetoxymercury group, -HgOOCCH3, to adjacent carbons of the double bond. The second step is demercuration that reduces the first product with sodium borohydride, NaBH4, which removes the acetoxymercury group and replaces it with hydrogen, to produce the more substituted alcohol as a mixture of syn and anti addition products.
Hydroboration-oxidation of alkenes (Sec 8.7, 8.8, 11.4): A two-step method that converts an alkene into an alcohol, with anti-Markovnikov regiochemistry, syn stereochemistry, and usually no rearrangements. The first step adds boron hydride, BH3, to the C=C group of an alkene. The second step oxidizes the first product with basic hydrogen peroxide, H2O2, which produces the less substituted alcohol.
Amphoteric: A compound that can function as either an acid or a base. Also called amphiprotic.
Alkyloxonium ion (Sec 3.13, 7.7, 11.5): A protonated alcohol, RO+H2, with a positive charge on the oxygen atom, which is the conjugate acid of an alcohol, ROH.
Dialkyloxonium ion (Sec 3.12, 11.5, 11.12): A protonated ether, RO+(H)R’, with a positive charge on the oxygen atom, which is the conjugate acid of an ether, ROR’.
Alkoxide ion (Sec 3.15, 6.15B, 11.6): A deprotonated alcohol, RO–, with a negative charge on the oxygen atom, which is the conjugate base of an alcohol, ROH.
Sulfonate ester (Sec 11.10): An alcohol derivative with the formula RSO2OR’, containing one carbon atom bound to sulfur, and another carbon bound to an oxygen atom; the most common sulfonate esters are mesylates, tosylates, and triflates.
Mesylate (Sec 11.10): A methanesulfonate ester (ester of an alcohol with methanesulfonic acid); the mesylate group is an excellent leaving group.
Tosylate (Sec 11.10): A p-toluenesulfonate ester (ester of an alcohol with para-toluenesulfonic acid); the tosylate group is an excellent leaving group.
Triflate (Sec 11.10): A trifluoromethanesulfonate ester (ester of an alcohol with trifluoromethanesulfonic acid); the triflate group is an excellent leaving group.
Dehydration (Sec 7.7, 7.8, 11.11A): Removal of -OH and -H substituents from nearby atoms; commonly employed in the preparation of alkenes and ethers by heating alcohols in the presence of an acid catalyst.
Williamson synthesis (Sec 11.11B, 21.6): Synthesis of an unsymmetrical ether by alkylation of an alkoxide anion, RO–, with a primary alkyl halide, R’X (or alkyl sulfate or alkyl sulfonate), which reacts by an SN2 mechanism: RO– + R’X → ROR’ + X–
Sulfate ester (Sec 11.11): An alcohol derivative with the formula ROSO2OR’, in which alkyl groups replace both of the hydrogen atoms in sulfuric acid, HOSO2OH.
Protecting group (Sec 11.11, 12.9, 15.14A, 16.7C): A group that is introduced into a molecule to protect a sensitive group, while the reaction is carried out at some other location in the molecule; the protecting group is later removed in a subsequent reaction.
Epoxide (Sec 11.13, 11.14): A cyclic ether with a three-membered ring, containing one oxygen and two carbon atoms. Also called an oxirane.
Peroxy acid (Sec 11.13A): An acid with the general formula RCO3H, that contains a carbon-oxygen double bond and an oxygen-oxygen single bond. Also called a peracid.
Epoxidation (Sec 11.13A): Reaction of an alkene with a peroxy acid, RCO3H, to form an epoxide; common peroxy acids are MCPBA (meta-chloroperoxybenzoic acid) and MMPP (magnesium monoperoxyphthalate).
Acid-catalyzed ring opening of an epoxide (Sec 11.14): In acidic solution, a nucleophile attacks an unsymmetrical epoxide primarily at the more substituted carbon of the epoxide by an SN1 like mechanism.
Base-catalyzed ring opening of an epoxide (Sec 11.14): In basic solution, a nucleophile attacks an unsymmetrical epoxide primarily at the less substituted carbon of the epoxide by an SN2 mechanism.
Polyether (Sec 11.14A): A water soluble polymer of repeating ether groups, RO-(RO-)n-ROH; an example is poly(ethylene glycol) or carbowax, which is produced by the anionic polymerization of ethylene oxide with methoxide anion.
Anti 1,2-Dihydroxylation (Sec 11.15): A series of two reactions for the anti addition of two hydroxyl groups, -OH, to opposite sides of adjacent carbons in a C=C group of an alkene; the first reaction is the epoxidation of the alkene with a peroxy acid to give an epoxide, then the second reaction is the acid-catalyzed hydrolysis of the epoxide, which produces a 1,2-diol (glycol); a cyclohexene will be converted into a trans-1,2-diol.
Syn 1,2-Dihydroxylation (Sec 8.16, 11.15): A syn addition reaction in which an oxidizing agent, such as osmium tetroxide, OsO4, adds two hydroxyl groups, -OH, to the same side of adjacent doubly bonded carbon atoms in alkenes to produce 1,2-diols (glycols); cycloalkenes will oxidize into cis-1,2-cycloalkanediols.
Crown ether (Sec 11.16): A cyclic polyether that has the ability to form a complex with a metal cation; crown ethers are named as x-crown-y, where x is the total number of atoms in the ring, and y is the number of oxygen atoms in the ring.
Phase-transfer catalyst (Sec 11.16): A reagent that transports an ion from an aqueous phase into a nonpolar phase where reactions take place more rapidly; common phase-transfer catalysts are crown ethers and quaternary ammonium halides, R4N+X–.
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