How to Draw Bond-Line Drawings

Now we can understand why we save so much time by using bond-hne drawings. Of course, we save time by not drawing every C and H. But, there is an even larger benefit to using these drawings. Not only are they easier to draw, but they are easier to read as well. Take the following reaction for example  

It is somewhat difficult to see what is happening in the reaction. You need to stare at it for a while to see the change that took place. However, when we redraw the reaction using bond-line drawings, the reaction becomes very easy to read immediately  

Now that we know how to read these drawings, we need to learn how to draw them. Take the following molecule as an example  

To draw this as a bond-line drawing, we focus on the carbon skeleton, making sure to draw any atoms other than C and H. All atoms other than carbon and hydrogen must be drawn. So the example above would look like this  

Don t forget that carbon atoms in a straight chain are drawn in a zigzag format H H H H 

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It is difficult to know exactly how to draw the bonding in metal complexes and there are often several different acceptable representations. There is no problem when the metal forms a a bond to atoms such as Cl or C as the simple line we normally use for covalent bonds means exactly what it says. The problems arise with ligands that... 

How To Write and Interpret Structural Formulas 15 How To Draw Bond-Line Formulas 18 1.8A The Use of Curved Arrows How To Write Resonance Structures 24... 

When drawing triple bonds, be sure to draw them in a straight line rather than zigzag, because triple bonds are linear (there wiU be more about this in the chapter on geometry). This can be quite confusing at first, because it can get hard to see just how many carbon atoms are in a triple bond, so let s make it clear ... 

Now that we know how to count carbon atoms, we must learn how to count the hydrogen atoms in a bond-line drawing of a molecule. Most hydrogen atoms are not shown, so bond-line drawings can be drawn very quickly. Hydrogen atoms connected to atoms other carbon (such as nitrogen or oxygen) must be drawn ... 

First, open your textbook and flip through the pages in the second half. Choose any bond-line drawing and make sure that you can say with confidence how many carbon atoms you see and how many hydrogen atoms are attached to each of those carbon atoms. 

Now that we have established that formal charges must always be drawn and that lone pairs are usually not drawn, we need to get practice in how to see the lone pairs when they are not drawn. This is not much different from training yourself to see all the hydrogen atoms in a bond-line drawing even though they are not drawn. If you know how to count, then you should be able to figure out how many lone pairs are on an atom where the lone pairs are not drawn. 

Before we can talk about drawing Newman projections, we need to first review one aspect of drawing bond-line stractures that we did not cover in Chapter 1. To show how groups are positioned in 3D space, we often use wedges and dashes ... 

Note how we have resorted to another form of representation of the ethane, ethylene, and acetylene molecules here, representations that are probably familiar to you (see Section 1.1). These line drawings are simpler, much easier to draw, and clearly show how the atoms are bonded - we use a line to indicate the bonding molecular orbital. They do not show the difference between a and rr bonds, however. We also introduce here the way in which we can represent the tetrahedral array of bonds around carbon in a two-dimensional drawing. This is to use wedges and dots for bonds instead of lines. By convention, the wedge means the bond is coming towards you, out of the plane of the paper. The dotted bond means it is going away from you, behind the plane of the paper. We shall discuss stereochemical representations in more detail later (see Section 3.1). 

A fourth of many possible drawings, 3.19, is a different reaction, with the dashed line on the left at the back indicating that the upper lobe on C-2 is turning downwards to overlap with the lower lobe on C-3. This is not what happens—if it were to happen, it would produce a trans double bond in the cyclohexene product. Not only is that impossible for steric reasons, it is also forbidden, as the sum shows—there are two (4q+2)s components. We see from the three drawings 3.15, 3.17, and 3.18 that there is considerable latitude in how to place the dashed lines to identify developing overlap, but they must identify the overlap that is actually developing, just as all three... 

Resonance theory (Sections 2.4-2.5) accounts for the stability and properties of benzene by describing it as a resonance hybrid of two equivalea forms. Neither form is correct by itself the true structure of benzene is somewhere in between the two resonance forms but is impossible to draw with our usual conventions. Many chemists therefore represent benzene by drawing it with a circle inside to indicate the equivalence of the carbon-carbon bonds. This kind of representation has to be used carefully, however, because it doesn t indicate the number of w electrons in the ring. (How many electrons does a circle represent ) In this book, benzene and other aromatic compounds will be represented by a single line-bond structure. We ll be able to keep count of jr electrons this way, but we must be aware of the limii tions of the drawing. . 

The above principles when modified proportionately extend to silane or other <7 complexes. Thus a stretched Si-H bond (2.10 A) is known that roughly corresponds to a 4HH of 1.05 A (see Chapter 11). No matter how much analysis is undertaken, the point at which to draw broken or unbroken lines representing partial versus full bonds and even categorizations such as a complexes, stretched a complexes, and so forth will always be debatable, as it must be for continuum-like behavior. As will be shown below, elongated a complexes present unique dynamical features that further emphasize the extraordinary complexity of a complexes. 

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