CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides 16.3 PHYSICAL PROPERTIES OF ETHERS It is instructive to compare the physical properties of ethers with alkanes and With respect to boiling point, ethers resemble alkanes more than alcohols. With to solubility in water the reverse is true: ethers resemble alcohols more than CH3, CH3 CH3 CH, CH,CH2 CH3 CH3 CH,CH2CH,OH g point: 117°C ability in water: 7.5 g/100 mL Insoluble 9g/100mL In general, the boiling points of alcohols are unusually high because of hydrogen bonding(Section 4.5). Attractive forces in the liquid phases of ethers and alkanes, which ack -OH groups and cannot form intermolecular hydrogen bonds, are much weaker, and their boiling points lower. As shown in Figure 16.1, however, the presence of an oxygen atom permits ethers to participate in hydrogen bonds to water molecules. These attractive forces cause ethers to dissolve in water to approximately the same extent as comparably constituted alco- hols. Alkanes cannot engage in hydrogen bonding to water. PROBLEM 16. 3 Ethers tend to dissolve in alcohols and vice versa. Represent the hydrogen-bonding interaction between an alcohol molecule and an ether molecule 16. 4 CROWN ETHERS Ro:+M- R,O-M Ether Metal Ether-metal ion FIGURE 16.1 Hydro- gen bonding between di- and water. th attractive force betw een the neaa ed of diethyl ether and one of drogens of water. The ele trostatic potential surfaces illustrate the complementary interaction between the electron-rich (red) region o diethyl ether and the elec tron-poor (blue) region of Back Forward Main MenuToc Study Guide ToC Student o MHHE Website16.3 PHYSICAL PROPERTIES OF ETHERS It is instructive to compare the physical properties of ethers with alkanes and alcohols. With respect to boiling point, ethers resemble alkanes more than alcohols. With respect to solubility in water the reverse is true; ethers resemble alcohols more than alkanes. Why? In general, the boiling points of alcohols are unusually high because of hydrogen bonding (Section 4.5). Attractive forces in the liquid phases of ethers and alkanes, which lack ±OH groups and cannot form intermolecular hydrogen bonds, are much weaker, and their boiling points lower. As shown in Figure 16.1, however, the presence of an oxygen atom permits ethers to participate in hydrogen bonds to water molecules. These attractive forces cause ethers to dissolve in water to approximately the same extent as comparably constituted alco￾hols. Alkanes cannot engage in hydrogen bonding to water. PROBLEM 16.3 Ethers tend to dissolve in alcohols and vice versa. Represent the hydrogen-bonding interaction between an alcohol molecule and an ether molecule. 16.4 CROWN ETHERS Their polar carbon–oxygen bonds and the presence of unshared electron pairs at oxygen contribute to the ability of ethers to form Lewis acid-Lewis base complexes with metal ions. R2O Ether (Lewis base) M Metal ion (Lewis acid) R2O M Ether–metal ion complex CH3CH2OCH2CH3 Diethyl ether 35°C 7.5 g/100 mL Boiling point: Solubility in water: CH3CH2CH2CH2CH3 Pentane 36°C Insoluble CH3CH2CH2CH2OH 1-Butanol 117°C 9 g/100 mL 622 CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides   FIGURE 16.1 Hydro￾gen bonding between di￾ethyl ether and water. The dashed line represents the attractive force between the negatively polarized oxygen of diethyl ether and one of the positively polarized hy￾drogens of water. The elec￾trostatic potential surfaces illustrate the complementary interaction between the electron-rich (red) region of diethyl ether and the elec￾tron-poor (blue) region of water. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website