Wedge notation

In Figure 1.4, the diamond lattice was taken to be a low -energy conformation of cyclodecane. Another way to represent this conformation is based on Dale s numerical system describing the number of bonds found between corner atoms. Dale s system is sometimes called wedge notation.Unfortunately, this can be somewhat difficult to calculate, and the method does not seem to be widely used. It is based on the idea that even-membered rings can exist in four quadrangular (four-cornered system) conformations (see 178). (1) All... 

PROBLEM 22.2 Use solid-wedge, dashed-wedge notation to write three-dimensional representations for the following molecules shown in Rscher projection. Label each stereogenic carbon as either R) or (5). 

Figure 2.6 The compound operation /C3 for ethane in the staggered conformation (a) using flying wedge notation (b) in the Newman projection.

The structure at the far right above uses the dash-wedge notation to indicate three dimensions. A solid wedge indicates that a bond projects out of the paper toward the reader. A dashed bond indicates that it projects behind the paper away from the viewer. Ordinary lines represent bonds in the plane of the paper. The dash-wedge notation is an important and widely used tool for depicting the three-dimensional structme of molecules. 

Each of the two carbon atoms is sp hybridized and forms three solid-wedge notation. The tt bond in an alkene places electron density above and below the plane of the atoms bonded to the carbon atoms by [Pg.1300]

Organic molecules are three-dimensional, so showing structures on paper in two dimensions can give a misleading picture of what the molecule actually looks like. This has led to the use of wedged line notation, which provides a simple way of showing organic molecules to Indicate their three-dimensional nature. 

RS Designations for Alanine and Lactate Draw (using wedge-bond notation) and label the (R) and (S) isomers of 2-aminopropanoic acid (alanine) and 2-hydroxypropanoic acid (lactic acid). 

There are two common variations on this notation. Sometimes, at the chiral centre, only three bonds may be shown, two of which are of normal thickness, while the third is either dashed or a solid wedge the fourth bond is to a hydrogen atom, and is not shown for it is assumed to be orientated as necessary to complete the usual geometry of the chiral centre. In the other common variation, three bonds to the chiral centre are represented with lines of normal thickness, and only the fourth uses a solid wedge or dashed line to indicate the stereochemistry. Neither of these variations are as clear as the normal version. 

Using the wedge-and-dash notation, draw the nine stereoisomers of 1,2,3,4,5,6-hexachlorocyclohexane. From the nine stereoisomers, identify one pair of enantiomers. 

Dashed-wedge line notation Molecular repre.sentation using dashed lines for bonds angled below tlic page, wedges for bonds angled above it. 

In order to examine the coexistence of a wedge with a finite contact angle and the thin film, we have to consider the variation of the profile and hence of the local value of what was termed zo (Eqs. (4.54,4.55)) in the plane of the substrate (in the x and y directions). We therefore identify the local value of zo with a profile height, h x) and reserve the notation zo to denote the thickness of the thin film in equilibrium — from the minimization of Eqs. (4.60,4.62). For simplicity, we focus on a one-dimensional variation of the height, h(x), in the... 

Introducing a new piece of notation, let us say that the complex Horn Km, Kn) is homotopy equivalent to a wedge of f m,n) spheres. Let S —,—) denote the Stirling numbers of the second kind, and SFi x) = n>k denote the generating function (in the first variable) for these... 

The three molecules of interest are methane (4A), ammonia (6A), and water (7A), shown first in the Lewis electron dot representations. Using the VSEPR model, these three molecules are drawn again using the wedge-dashed line notation. Methane (CH4, 4B) has no unshared electrons on carbon but there are electrons in the C-H covalent bonds. Assume that repulsion of the electrons in the bonds leads to a tetrahedral arrangement to minimize electronic repulsion. Ammonia (H3N, 6B) has a tetrahedral array around nitrogen if the electron pair is taken into account. If only the atoms are viewed, however, 6B has the pyramidal shape shown. Water (HOH, 7B) has two electron pairs that occupy the corners of a tetrahedral shape, as shown. 

The ability to determine if a molecule and its mirror image are superimposable is key for recognition of enantiomers. Because a model is not always available, the way the molecule is drawn on paper is important. This book uses line notation with wedges and dashes to indicate stereochemistry (see Chapter 1, Section 1.1, and Chapter 4, Section 4.1), as with 4A. Occasionally, other representations are useful. Emil Fischer (Germany 1825-1919 Nobel laureate, 1902) was a remarkable chemist whose work influences chemistry even today. His name is used for a particular method for drawing stereoisomers. 

Hashed and wedged line notation is introduced in Section 3.3.2... 

New wedge-dash notation for tetrahedral structures and trigonal pyramidal structures was added. 

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