Nomenclature of benzene derivatives

Methylbenzene is usually called toluene, hydroxybenzene is almost always called phenol, and aminobenzene is almost always called aniline. These and other examples are indicated here  

2-Dibromobenzene 1,3-Dibromobenzene 1,4-Dibromobenzene (o-dibromobenzene) (m-dibromobenzene) (p-dibromobenzene) ortho meta para 

2-Nitrobenzoic acid 3-Nitrobenzoic acid 4-Nitrobenzoic acid 

2-Dimethyibenzene 1,3-Dimethylbenzene 1,4-Dimethyibenzene (o-xyiene) (m-xylene) (p-xyiene) 

A hydrocarbon composed of one saturated chain and one benzene ring is usually named as a derivative of the larger structural unit. However, if the chain is unsaturated, the 

Benzene derivatives have been isolated and used as industrial reagents for well over 100 years. Many of their names are rooted in the historical traditions of chemistry. The following compounds are usually called by their historical common names, and almost 

Many compounds are named as derivatives of benzene, with their substituents named just as though they were attached to an alkane. 

Disubstituted benzenes are named using the prefixes ortho-, meta-, and para- to specify the substitution patterns. These terms are abbreviated o-, m-, and p-. Numbers can also be used to specify the substitution in disubstituted benzenes. 

With three or more substituents on the benzene ring, numbers are used to indicate their positions. Assign the numbers as you would with a substituted cyclohexane, to give the lowest possible numbers to the substituents. The carbon atom bearing the 

Many disubstituted benzenes (and polysubstituted benzenes) have historical names. Some of these are obscure, with no obvious connection to the structure of the molecule. 

It is estimated that 25% of the world s recoverable coal (coal that can be readily mined) is located in the United States. As such, it is believed that the United States has enough natural resources to meet all of its energy needs for at least 200 years. To provide some additional perspective, consider the fact that these natural resources contain more than double the energy contained in all of the combined oil reserves in the Middle East. 

It is believed that the earth s coal deposits were formed as organic matter from prehistoric plant life was subjected to high pressures and temperatures over long periods of time. The molecular structure of coal involves haphazard arrangements of aromatic moieties (highlighted in orange boxes), connected to each other by nonaromatic links (shown in green boxes)  

Although aromatic compounds can be obtained from coal, the primary source of aromatic compounds is from petroleum, using a prcx ess called reforming (Section 4.5). 

Monosubstituted derivatives of benzene are named systematically using benzene as the parent and listing the substituent as a prefix. Below are several examples. 

The following are some monosubstituted aromatic compounds that have common names accepted by lUPAC. You must commit these names to memory, as they will be used extensively throughout the remaining chapters. 

Each carbon atom in a benzene ring is surrounded by three atoms and no lone pairs of electrons, making it sp hybridized and trigonal planar with all bond angles 120°. Each carbon also has a p orbital with one electron that extends above and below the plane of the molecule. 

Problenn 17.1 Draw all possible resonance structures for biphenyl. 

Problem 17.2 What orbitals are used to form the bonds indicated in each molecule Of the indicated C—C bonds, which is the shortest  

Many organic molecules contain a benzene ring with one or more substituents, so we must leam how to name them. Many common names are recognized by the lUPAC system, however, so this complicates the nomenclature of benzene derivatives somewhat. 

Overlap of six adjacent p orbitals creates two rings of electron density, one above and one below the plane of the benzene ring. 

When there are two substituents, their relative positions must be specified thus, 3.34, 3.35, and 3.36 are named as 1,2-, 1,3-, and 1,4-dimethylbenzene. The common name for dimethyl-benzene is xylene, and given its wide use as an industrial solvent, this name is likely to survive 

FIGURE 3.25 Some common names of monosubstituted benzene derivatives. 

Draw line structures for each of the following molecules  

We can now add the substituents at the appropriate positions. The new one here is amino, which is how we describe the -NHj group as a substituent  

9(b) Remember that meta means that the two substituents are in a 1,3-relationship  

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The nomenclature of benzene derivatives is described in Sec. 4.6. Common names and structures to be memorized include those of toluene, styrene, phenol, aniline, and xylene. Monosubstituted benzenes are named as benzene derivatives (bromobenzene, nitrobenzene, and so on). Disubstituted benzenes are named as ortho- (1,2-), meta- (1,3-), or para- (1,4-), depending on the relative positions of the substituents on the ring. Two important groups are phenyl (C6H5-) and benzyl (C6H5CH2-). 

Polynuclear Aromatic Hydrocarbons 735 16-11 Aromatic Allotropes of Carbon 737 16-12 Fused Heterocyclic Compounds 739 16-13 Nomenclature of Benzene Derivatives 740... 

The nomenclature of benzene derivatives is similar to the nomenclature for saturated ring systems. If there is more than one substituent present, numbers are used to indicate substituent positions. For example, the compound... 

Solution All of these structures are derivatives of benzene. Hence, a consideration of the nomenclature of benzene derivations will aid in the drawing of these compounds. ... 

The Discovery of Benzene 627 Nomenclature of Benzene Derivatives 628 Reactions of Benzene 630 The Kekule Structure for Benzene 631 The Thermodynamic Stability of Benzene 632 Modern Theories of the Structure of Benzene 634 Huckel s Rule The 4n +2 tt Electron Rule 637 Other Aromatic Compounds 645... 

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