ETHERS, EPOXIDES, GLYCOLS, AND THIOETHERS

MftpItlRgNimetilcal) ethers have the general formula R—O—R or Ar—O—Ar mixed (unsymmetrical) Often are R- O—R or Ar—O—Ar7 or Ar—O—R. The derived system names R and Ar as separate words adds die word ether. In the IUPAC system, ethers (ROR) are named as alkoxy- (RO-) substituted aflnwni. cydbc ethers have at least one O in a ring. 

KOMW 14.2 Account for the following, (a) Ethers have significant dipole moments (%1.I8 O). (b) Ethers HW lower Mftg points than isomeric alcohols, (c) The water solubilities of isomeric ethers and alcohols are 

Problem 14.3 Specify and account for your choice of an alkoxide and an alkyl halide to prepare the following ethers by the Williamson reaction (a) C2H5OC(CH3)3, (b) (CH3)2CHOCH2CH=CH2. 4 

The 2° and 3° alkyl halides readily undergo E2 eliminations with strongly basic alkoxides to form alkenes. Hence, to prepare mixed ethers such as (a) and (b) the 1° alkyl groups should come from RX and the 2° and 3° alkyl groups should come from the alkoxide. 

Problem 14.4 Show how dimethyl sulfate, Me0SO2OMe, is used in place of alkyl halides in the Williamson syntheses of methyl ethers. 4 

Alkyl sulfates are conjugate bases of the very strongly acidic alkyl sulfuric acids and are very good leaving groups. Dimethyl sulfate is less expensive than CH3I, the only liquid methyl halide at room temperature. Liquids are easier to use than gases in laboratory syntheses. 

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