CHAPTER THREE Conformations of Alkanes and Cycloalkanes In this chapter we'll examine the conformations of various alkanes and cycloal kanes. focusing most of our attention on three of them: ethane, butane and cyclohexane. ng A detailed study of even these three will take us a long way toward understand bond in hydrogen peroxide main ideas of conformational analysis. The conformation of a molecule affects many of its properties. Conformational analysis is a tool used not only by chemists but also by researchers in the life sciences as they attempt to develop a clearer picture of how molecules--as simple as hydrogen peroxide or as complicated as DNA--behave in biological processes 3.1 CONFORMATIONAL ANALYSIS OF ETHANE Ethane is the simplest hydrocarbon that can have distinct conformations. Two, the staggered conformation and the eclipsed conformation, deserve special attention and are illustrated in Figure 3. 1. The C-H bonds in the staggered conformation are arranged so that each one bisects the angle made by a pair of C-H bonds on the adjacent car- bon. In the eclipsed conformation each C-H bond is aligned with a C-H bond on the adjacent carbon. The staggered and eclipsed conformations interconvert by rotation around the carbon-carbon bond. Different conformations of the same molecule are some times called conformers or rotamers Among the various ways in which the staggered and eclipsed forms are portrayed wedge-and-dash, sawhorse, and Newman projection drawings are especially usefuL. These are shown for the staggered conformation of ethane in Figure 3.2 and for the eclipsed conformation in Figure 3.3 We used wedge-and-dash drawings in earlier chapters, and so Figures 3. 2a and 3.3a are familiar to us. A sawhorse drawing( Figures 3.2b and 3.3b) shows the conformation of a molecule without having to resort to different styles of bonds. In a devised by Professor Melvin Newman projection(Figures 3.2c and 3.3c), we sight down the C-C bond, and repre- Newman of Ohio State sent the front carbon by a point and the back carbon by a circle. Each carbon has three University in the 1950s. substituents that are placed symmetrically around it. Eclipsed conformation of ethane FIGURE 3.1 The stag ered and eclipsed conf mations of ethane shown as ball-and-spoke models (left) and as space-filling models (right) Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteIn this chapter we’ll examine the conformations of various alkanes and cycloal￾kanes, focusing most of our attention on three of them: ethane, butane, and cyclohexane. A detailed study of even these three will take us a long way toward understanding the main ideas of conformational analysis. The conformation of a molecule affects many of its properties. Conformational analysis is a tool used not only by chemists but also by researchers in the life sciences as they attempt to develop a clearer picture of how molecules—as simple as hydrogen peroxide or as complicated as DNA—behave in biological processes. 3.1 CONFORMATIONAL ANALYSIS OF ETHANE Ethane is the simplest hydrocarbon that can have distinct conformations. Two, the staggered conformation and the eclipsed conformation, deserve special attention and are illustrated in Figure 3.1. The C±H bonds in the staggered conformation are arranged so that each one bisects the angle made by a pair of C±H bonds on the adjacent car￾bon. In the eclipsed conformation each C±H bond is aligned with a C±H bond on the adjacent carbon. The staggered and eclipsed conformations interconvert by rotation around the carbon–carbon bond. Different conformations of the same molecule are some￾times called conformers or rotamers. Among the various ways in which the staggered and eclipsed forms are portrayed, wedge-and-dash, sawhorse, and Newman projection drawings are especially useful. These are shown for the staggered conformation of ethane in Figure 3.2 and for the eclipsed conformation in Figure 3.3. We used wedge-and-dash drawings in earlier chapters, and so Figures 3.2a and 3.3a are familiar to us. A sawhorse drawing (Figures 3.2b and 3.3b) shows the conformation of a molecule without having to resort to different styles of bonds. In a Newman projection (Figures 3.2c and 3.3c), we sight down the C±C bond, and repre￾sent the front carbon by a point and the back carbon by a circle. Each carbon has three substituents that are placed symmetrically around it. 90 CHAPTER THREE Conformations of Alkanes and Cycloalkanes Eclipsed conformation of ethane Staggered conformation of ethane FIGURE 3.1 The stag￾gered and eclipsed confor￾mations of ethane shown as ball-and-spoke models (left) and as space-filling models (right). Newman projections were devised by Professor Melvin S. Newman of Ohio State University in the 1950s. Learning By Modeling contains an animation showing the rotation about the O±O bond in hydrogen peroxide. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website