Wedge-shaped bond

A note on good practice Dashed and solid wedge-shaped bonds are commonly used when displaying organic structures to convey a sense of the three-dimensional shapes. The dashed wedge-shaped bonds go into the page and the solid wedge-shaped bonds come toward us. The thin lines are in the plane of the paper. 

Adrenaline can exist as two enantiomers that are mirror images of each other (Fig. 2.3) and are thus non-superimposible. In Figure 2.3 the wedge-shaped bonds indicate bonds above the plane of the paper, the dotted bonds indicate bonds pointing... 

FIGURE 3-3 Stereoisomerism in n-amino acids, (a) The two stereoisomers of alanine, l- and o-alanine, are nonsuperimposable mirror images of each other (enantiomers), (b, c) Two different conventions for showing the configurations in space of stereoisomers. In perspective formulas (b) the solid wedge-shaped bonds project out of the plane of the paper, the dashed bonds behind it. In projection formulas (c) the horizontal bonds are assumed to project out of the plane of the paper, the vertical bonds behind. However, projection formulas are often used casually and are not always intended to portray a specific stereochemical configuration. 

FIGURE 7-2 Three ways to represent the two stereoisomers of glyc-eraldehyde. The stereoisomers are mirror images of each other. Ball-and-stick models show the actual configuration of molecules. By convention, in Fischer projection formulas, horizontal bonds project out of the plane of the paper, toward the reader vertical bonds project behind the plane of the paper, away from the reader. Recall (see Fig. 1-17) that in perspective formulas, solid wedge-shaped bonds point toward the reader, dashed wedges point away. 

Fig. 7.29 The enantiomers of a-hexachlorocyclohexane (a-HCH). Bold wedge shaped bonds represent bonds rising from the plane of the page toward the viewer, and bonds represented by dashed lines are receding from the plane of the page away from the viewer. See also Box 7.3.

A reminder solid wedge-shaped bonds are coming towards us out of the paper while cross-hatched bonds are going back into the page away from us. 

The wedge-shaped bond symbols stand for electron pairs which tend to stay more on the side of the broad end of the wedge thus imparting an excess charge on that side. 

Dehydrogenation of a primary alcohol (or oxidation by removal of hydrogen) also can be seen to be a removal of electrons (formulas below). It should be noted that the initial step, the dissociation of a proton with formation of the alcoholate ion, does not involve a change in oxidation level. In the second step, the molecule becomes even more polarized, as symbolized by the wedge-shaped bond, and finally the binding pair of electrons comes off together with the proton. 

The three-dimensional structure of ethane, C2H6, has the shape of two tetrahedra joined together. Each carbon atom is sp3 hybridized, with four sigma bonds formed by the four sp3 hybrid orbitals. Dashed lines represent bonds that go away from the viewer, wedges represent bonds that come out toward the viewer, and other bond lines are in the plane of the page. All the bond angles are close to 109.5°. 

Supramolecular organization of dendrons can lead to columnar or spherical superstructures, depending on directional and attractive interactions between such wedge-shaped molecules as well as size and shape. For instance, hydrogen-bonding... 

One of the most unexpected results obtained was for Pg, where the much-studied cubic (0 ) form corresponds to a shallow local minimum in the energy surface. Simulated annealing led, however, to the Czv structure (Fig. 4b), which is much (ca. 1.7 eV) more stable. This wedge structure, which may be viewed as a (distorted) cube with one bond rotated through 90°, is a structural unit in violet (monoclinic, Hittorf) phosphorus [48]. A second isomer of Pg ( >21, Fig. 4a) is also much more stable than the cubic form. There is a striking analogy between the structures of the Pg-isomers and those of the valence isoelectronic hydrocarbons (CH)g. The cubic form of the latter (cubane) has been prepared by Eaton and Cole [49], and can be converted catalytically to the wedge-shaped form (cuneane) [50]. 

---