Wedge projection

Most carbon-containing molecules are three-dimensional. In methane, the bonds of C make equal angles of 109.5° with each other, and each of the four H s is at a vertex of a regular tetrahedron whose center is occupied by the C atom. The spatial relationship is indicated as in Fig. l-2(a) (Newman projeetion) or in Fig. l-2(ft) ( wedge projection). Except for ethene, which is planar, and ethyne, which is linear, the structures in Fig. 1-1 are all three-dimensional. 

In such diagrams, either (i) the flat ring is perpendicular to the plane of the paper, with the bond(s) facing the viewer drawn heavy and with the substituents in the plane of the paper and projecting up and down, or (ii) the flat ring is in the plane of the paper, with wedges projecting toward the viewer and dots away from the viewer. 

Know the meaning of conformation, staggered, eclipsed, dash-wedge projection, Newman projection, sawhorse projection, rotational isomers, rotamers. 

Wedge projection, 2, 51, 71 Williamson synthesis, 279, 295, 435 Wittig reaction, 319 Wolff-Kishner reduction, 311 Woodward-Hoffmann rules, 177... 

FIGURE 1.8 A wedge-and-dash drawing of the structure of methane. A solid wedge projects from the plane of the paper toward you a dashed wedge projects away from you. A bond represented by a line drawn in the customary way lies in the plane of the paper. 

In the erythro-diisotactic configuration (eit), the substituents R and R all lie on the same side in a Fischer projection, whereas in a flying wedge projection, all the R substituents are found on one side, but the R substituents on the other side of the plane of the paper. In the Newman projection of the eclipsed conformation, R lies above R and H above H in the eit configuration. The characteristic features of the three other configurations can be seen in Figure 3-7. 

Bold and hashed wedges are commonly used in complex molecules, but an additional convention is required. For example, in the representation of paclitaxel (4), ° it cannot be true that all of the bold wedges project toward the viewer to the same plane in space, nor can it be true that all of the dashed wedges project to the same plane behind the page. Rather, each wedge is a local descriptor only, and the sense of depth of the viewer is to be reset at the origin of each wedge. 

These elements can accommodate more than eight electrons in their valence shells and therefore can form more than four covalent bonds. Examples are compounds such as PCI5 and SFe. Bonds written as (dashed wedges) project behind the plane of the paper. Bonds written as (solid wedges) project in front of the paper. 

Solid wedges project out toward you (H in C- H is in front of the plane). 

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