CHAPTER FOUR Alcohols and Alkyl Halides R R O:+H-A O—H Acid kyloxonium ion Conjugate base We shall see that several important reactions of alcohols involve strong acids either as reagents or as catalysts to increase the rate of reaction. In all these reactions the first step is formation of an alkyloxonium ion by proton transfer from the acid to the oxygen of the alcohol PROBLEM 4.9 Write an equation transfer from hydrogen chloride to tert-butyl alcohol. Use curved arro k electron movement, and identify the acid, base, conjugate acid, and PROBLEM 4.10 Is the equilibrium constant for proton transfer from hydrogen chloride to tert-butyl alcohol greater than 1 or less than 1? Alkyl halides are neither very acidic nor very basic and are absent from Table 4.2 In general, compounds, including alkyl halides, in which all the protons are bonded to carbon are exceedingly weak acids--too weak to be included in the table 4.7 ACID-BASE REACTIONS: A MECHANISM FOR PROTON TRANSFER Potential energy diagrams of the type used in Chapter 3 to describe conformational processes can also help us understand more about chemical reactions. Consider the trans fer of a proton from hydrogen bromide to water Br-H+:0:、:Br:+H-O: A potential energy diagram for this reaction is shown in Figure 4.6. Because the transfer of a proton from hydrogen bromide to water is exothermic, the products are placed lower in energy than the reactants. The diagram depicts the reaction as occurring in a single elementary step. An elementary step is one that involves only one transition state. A reaction can proceed by way of a single elementary step, in which case it is described as a concerted reaction, or by a series of elementary steps. In the case of pro- ton transfer from hydrogen bromide to water, breaking of the H-Br bond and making of the H2o-H bond occur "in concert with each other. The species present at the transition state is not a stable structure and cannot be isolated or examined directly. Its structure is assumed to be one in which the proton being transferred is partially bonded to both bromine and oxygen simultaneously, although not necessarily to the same extent. ate structures represe partial bonds, that is, bond in the process of being made or broke Back Forward Main Menu Study Guide ToC Student OLC MHHE WebsiteWe shall see that several important reactions of alcohols involve strong acids either as reagents or as catalysts to increase the rate of reaction. In all these reactions the first step is formation of an alkyloxonium ion by proton transfer from the acid to the oxygen of the alcohol. PROBLEM 4.9 Write an equation for proton transfer from hydrogen chloride to tert-butyl alcohol. Use curved arrows to track electron movement, and identify the acid, base, conjugate acid, and conjugate base. PROBLEM 4.10 Is the equilibrium constant for proton transfer from hydrogen chloride to tert-butyl alcohol greater than 1 or less than 1? Alkyl halides are neither very acidic nor very basic and are absent from Table 4.2. In general, compounds, including alkyl halides, in which all the protons are bonded to carbon are exceedingly weak acids—too weak to be included in the table. 4.7 ACID–BASE REACTIONS: A MECHANISM FOR PROTON TRANSFER Potential energy diagrams of the type used in Chapter 3 to describe conformational processes can also help us understand more about chemical reactions. Consider the trans￾fer of a proton from hydrogen bromide to water: A potential energy diagram for this reaction is shown in Figure 4.6. Because the transfer of a proton from hydrogen bromide to water is exothermic, the products are placed lower in energy than the reactants. The diagram depicts the reaction as occurring in a single elementary step. An elementary step is one that involves only one transition state. A reaction can proceed by way of a single elementary step, in which case it is described as a concerted reaction, or by a series of elementary steps. In the case of pro￾ton transfer from hydrogen bromide to water, breaking of the H±Br bond and making of the H2O ±H bond occur “in concert” with each other. The species present at the transition state is not a stable structure and cannot be isolated or examined directly. Its structure is assumed to be one in which the proton being transferred is partially bonded to both bromine and oxygen simultaneously, although not necessarily to the same extent. Br H O H H  Br  H H H O H H H Br O R H O Alcohol H A Acid A Alkyloxonium ion Conjugate base R H O H 136 CHAPTER FOUR Alcohols and Alkyl Halides Dashed lines in transition￾state structures represent partial bonds, that is, bonds in the process of being made or broken. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website