Drawing shorthand

The commercial 2D structure editor. Chemistry 4D-Draw, from Chemlnnovativc Software Inc., includes two additional special modules besides conventional chemical drawing tools. NamExpert provides the interpretation ofa compound name according to the lUPAC nomenclature to create the corresponding chemical structure. The latter can be represented in three different styles the shorthand. Kckulc. or semi-structural formula. In contrast to NamExpert, the Nomenclature module assigns lUPAC names to drawn structures. 

Both of these structures satisfy the formal valence rules for carbon, but each has a serious fault. Each structure shows three of the carbon-carbon bonds as double bonds, and three are shown as single bonds. There is a wealth of experimental evidence to indicate that this is not true. Any one of the six carbon-carbon bonds in benzene is. the same as any other. Apparently the fourth bond of each carbon atom is shared equally with each adjacent carbon. This makes it difficult to represent the bonding in benzene by our usual line drawings. Benzene seems to be best represented as the superposition or average of the two structures. For simplicity, chemists use either one of the structures shown in (30) usually expressed in a shorthand form (SI) omitting the hydrogen atoms ... 

Since carbon has four bonds to fill, and because hydrogen is the most likely atom to be attached to carbon in an organic molecule, chemists invented a shorthand notation that is easier to read and draw. 

The positions of the nuclei must be the same in all the structures. This means that when we draw the various canonical forms, all we are doing is putting in the electrons in different ways. For this reason, shorthand ways of representing resonance are easy to devise ... 

Write the shorthand electron configuration and draw the ground-state orbital energy level diagram for the valence electrons in a sulfur atom. 

It is important to discuss cell notation and conventions. Instead of drawing a complete diagram to present electrochemical cells, it is convenient to specify a cell in line formula form or, as may be said, shorthand form. The Cu-Zn cell is thus presented as ... 

Because there are numerous silicates whose structures are made up of repeating patterns based on the Si04 tetrahedron, a type of shorthand notation has been developed for drawing the structures. For example, the Si04 unit can be shown as follows. 

But drawing is laborious, so we generally employ a more sensible alternative we write a cell schematic, which is a convenient abbreviation of a cell. It can be read as though it was a cross-section, showing each interface and phase. It is, therefore, simply a shorthand way of saying which components are incorporated in the cell as cathode, anode, electrolyte, etc., and where they reside. 

A useful technique in specifying a large component is to draw a state chart that focuses on all the elements of a particular type within a larger model—for example, showing what happens to the shapes in a drawing editor for each of the editors operations, select(self) is a shorthand for select(s) [s=self]. It s important to realize that this is really a state chart for the editor, in which the states are defined in terms of the states of its shapes. 

There are many ways of representing an electrochemical cell the simplest, but most laborious, is simply to draw it. A more sensible alternative is to write a cell schematic. Such a schematic is simply a shorthand method of saying what is present, and which part of the cell is die positive, negative, electrolyte, etc. 

It is important to note that pin names do not specify net names or connectivity. In other words, commonly named pins are not automatically connected, and the net to which they are connected is not named the same as the pin names. Thus, as shown above, none of the blocks are connected. To connect the blocks, we need to wire them together. The schematic shown below shows the blocks wired together. Note that some wires are labeled with the text Vcc and Vee. This was done using net aliases as described in section l.H. Note also the wire fragments used for Vee. These wires are all given the same net name (Vee) and thus are connected. This is a shorthand method for connecting components without drawing wires all over your schematic ... 

We can see the different structural features of n-pentane, Ao-pentane, and neo-pentane more clearly by drawing the molecules in two dimensions, as shown in the middle row of Figure 12.1. Alternatively, we can represent them by the stick structures shown in the bottom row. A stick structure is a commonly used, shorthand notation for representing an organic molecule. Each line (stick)... 

A standard shorthand notation is used to describe the construction of galvanic cells and avoid the necessity of drawing pictures. It is based on the convention that the negative electrode is shown at the left. The notation for the galvanic cell shown in Figure 17-1 is... 

Although the anode half-cell always appears on the left in the shorthand notation, its location in a cell drawing is arbitrary. This means that you can t infer which electrode is the anode and which is the cathode from the location of the electrodes in a cell drawing. You must identify the electrodes based on whether each electrode half-reaction is an oxidation or a reduction. 

Using the shorthand notation of Figure 19.5 (page 829), draw the structure of the silicate anion in ... 

Three of these tangent lines are drawn on the curve in Figure 2.1. You can see qualitatively how to draw them, but you cannot tell by inspection exactly what slope to use. This slope can be found by looking at two points Xo and xq + Ax, where Ax (the separation between the two points, pronounced delta x ) is small. We then determine the amount Ay = f(xr> + Ax ) — f(x) that the height of the curve changes between those two points. The ratio Ay/ Ax approaches the slope of the tangent line, in the limit that Ax is very small, and is called the derivative dy/dx. Another common shorthand is to write the derivative of /(x) as fix). 

Draw structures using any of the methods we have seen. You should also be able to examine a shorthand representation for a molecule and recognize all of its features. (Problems 2.17 and 2.18)... 

Several kinds of formulas are used by organic chemists to represent organic compounds. Some of these formulas involve a shorthand notation that requires some explanation. Structural formulas actually show which atoms are bonded to which. There are two types of structural formulas, complete Lewis structures and condensed structural formulas. In addition, there are several ways of drawing condensed structural formulas. As we have seen, a Lewis structure symbolizes a bonding pair of electrons as a pair of dots or as a dash (—). Lone pairs of electrons are shown as pairs of dots. 

In such shorthand structures, each point where lines meet represents a carbon atom, and most H atoms are not shown. Draw the complete structure, showing all carbon and hydrogen atoms. (There will be four bonds to each carbon atom.) Indicate which carbon atoms use sp2 or sp3 hybrid orbitals. Are all carbon atoms in the same plane, as implied by the structure ... 

Because more complicated organic compounds contain many carbon atoms, organic chemists have devised a shorthand to draw them. Keep in mind the following when examining these structures ... 

To understand the structure of palytoxin we need to know more shorthand for drawing chains of organic molecules. The following conventions are often used. 

Important topics in Chapter 1 include drawing Lewis structures, predicting the shap)e of molecules, determining what orbitals are used to form bonds, and how electronegativity affects bond polarity. Equally important is Section 1.7 on drawing organic molecules, both shorthand methods routinely used for simple and complex compounds, as well as three-dimensional representations that allow us to more clearly visualize them. 

Drawing organic molecules presents a special challenge. Because they often contain many atoms, we need shorthand methods to simplify their structures. The two main types of shorthand representations used for organic compounds are condensed structures and skeletal structures. 

Draw each polymer in Problem 30.27 using the shorthand representation shown in Figure 30.2. 

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