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Chapter Alcohol and Ether Nomenclature of Ethers The functional group of ether is an oxygen atom bonded to two carbon atoms R—O—R ◦ The simplest ether is dimethyl ether, CH3OCH3 ◦ The most common ether is diethyl ether CH3CH2OCH2CH3 Although ethers can be named according to the IUPAC system, chemists almost invariably use common names for low-molecular-weight ethers. ◦ ◦ E.g Common names are derived by listing the alkyl groups bonded to oxygen in alphabetical order and adding the word "ether”. Alternatively, name one of the groups on oxygen as an alkoxy group (RO- ). Name the following molecule E.g Use bond-line to draw Isopropyl methyl ether 4-ethoxy-2-methyl-1-hexene CHM 201 Dang 1 Substitution of Alcohols (ROH RX) CH3Cl + CH3OH + - OH CH3OH Cl- CH3Cl + + Cl- OH - Must convert into a weaker base, in the protonated form ( ROH + NaCl NR (no LG) ROH + HCl RCl + H2O ROH + HBr RBr + H2O ROH + HI RI + H2O OH is strongly basic, unstable, not a good LG ) Explain why (S)-2-butanol forms a racemic mixture when it is heated in aqueous sulfuric acid? CHM 201 Dang 2 E.g Predict the product and provide a mechanism Elimination reactions of Alcohols Aka dehydration of alcohol lost of H2O Required strong acid catalyst Formation of alkene follows Zaitsev’s rule: More substituted alkene is the major product More stable carbocation will be formed faster Benzylic/allylic/3o ROH > 2oROH >> 1oROH CHM 201 Dang 3 Ether is also obtained; it is the product of a competing SN2 reaction E.g Give the major product formed when each of the following alcohols is heated in presence of H2SO4 CHM 201 Dang 4 Oxidation of Alcohols Oxidation: increases # C-O bonds and decreases the # of C-H bonds Reduction: decreases # C-O bonds and increases the # C-H bonds Common reagents: chromic acid, chromate salt, dichromate salt, permanganate Oxidation of a 1° alcohol to a carboxylic acid is commonly carried out using potassium dichromate, K2Cr2O7, in aqueous sulfuric acid. Or using pyridium chlorochromate (PCC) as the oxidizing agent in an anhydrous solvent ◦ Oxidation of a 2° alcohol and cyclic alcohol gives a ketone. CHM 201 Dang 5 Tertiary alcohols are resistant to oxidation Consider the following reaction Predict the product(s) CHM 201 Dang 6