Drawing organic structures

Benzene can be written with a circle within the ring to show the delocalisation of electrons (see Section 7.1). However, this does not show the six Jl-electrons, which makes drawing reaction mechanisms impossible. A single resonance form, showing the three C=C bonds, is therefore most often used. 

Summary Determining geometry based on the number of groups 

Determine the geometry around all second-row elements in each compound.  

Problem 1.18 Predict the indicated bond angles in each compound. 

Using the principles of VSEPR theory, you can predict the geometry around any atom in any molecule, no matter how complex. Enanthotoxin is a poisonous compound isolated from a common variety of hemlock grown in England. Predict the geometry around the indicated atoms in enanthotoxin. 

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. 

Cyclic compounds containing at least one heteroatom (e.g. O, N or S) are examples of heterocyclic compounds (heterocycles). 

Alkenes like but-2-en-l-ol can exist as two configurational isomers these isomers are named cis- or traits-, or Z- or E- (Section 3.3.1) 

Condensed structures are most often used for compounds having a chain of atoms bonded together, rather than a ring. The following conventions are used  

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This gives us our first guideline for drawing organic structures. 

When we draw organic structures we try to be as realistic as we can be without putting in superfluous detail. Look at these three pictures. 

The alkene with four carbons, however, is a different story. See the two butane structures in Figure 14.15. The two different structures can be drawru They are different because of the location of the double bond. These two structures are isomers, since they have the same molecular formula (C4H8) but a different structure. Remember when drawing organic structures that all carbons must have exactly four bonds. Notice that a number and a hyphen to the left of the name butene indicates the carbon in the chain on which the double bond first appears (counting from the left). The lowest number possible is always used. For example, if we had counted from the right, 1-butene would have been called 3-butene, which is incorrect. 

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