Meta-, disubstituted benzenes prefixes

Disubstituted benzenes are named using one of the prefixes ortho- (o), meta- (in), or para- (p). An ortho-disubstituted benzene has its two substituents in a 1,2 relationship on the ring, a meta-disubstituted benzene has its two substituents in a 1,3 relationship, and a para-disubstituted benzene has its substituents in a 1,4 relationship. 

The prefix ortho signifies a 1 2 disubstituted benzene ring meta signifies 1 3 disubstitu tion and para signifies 1 4 disubstitution The prefixes o m and p can be used when a substance is named as a benzene derivative or when a specific base name (such as ace tophenone) is used For example... 

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

Benzene molecules bearing alkyl substituents are called alkylbenzenes. The simplest of these is methylbenzene (common name, toluene), shown in Figure 27-1 Ic. The dimethyl-benzenes are called xylenes. Three different compounds (Table 27-6) have the formula CgH4(CH3)2 (see margin). These three xylenes are constitutional isomers. In naming these (as well as other disubstituted benzenes), we use prefixes ortho- (abbreviated o-), meta- m-), or para- (p-) to refer to relative positions of substituents on the benzene ring. The ortho- prefix refers to two substituents located on adjacent carbon atoms for example, 1,2-dimethylbenzene is o-xylene. The meta- prefix identifies substituents on C atoms 1 and 3, so 1,3-dimethylbenzene is 7w-xylene. The para- prefix refers to substituents on C atoms 1 and 4, so 1,4-dimethylbenzene is p-xylene. 

Meta- (m-) Common-name prefix for 1,3-disubstituted benzenes. 

Merrifield solid-state peptide synthesis Automated synthesis using polystyrene to anchor a peptide chain. Meso compound A compound with at least two stereocenters yet superimposable on its mirror image. Meta- (m-) Common-name prefix for 1.3-disubstituted benzenes. 

Note the use of the prefixes, 0- for ortho-, m- for meta-, and p- for para-, to indicate the 1,2-, 1,3-, and 1,4-disubstituted benzene, respectively. There are many aromatic hydrocarbons with fused benzene rings—rings with 2 C atoms in common —as in naphthalene, CioHg, a white solid (m.p. SOX) used as a moth repellent ... 

There are three possible arrangements of disubstituted benzenes. These arrangements are designated by the prefixes 1,2- (ortho, or o-) for adjacent substituents, 1,3 (meta-, or m-) for 1,3-disubstitution, and 1,4 (para-, orp-) for 1,4-disubstimtion. The substituents are listed in alphabetical order. 

In Summary Simple monosubstituted benzenes are named by placing the substituent name before the word benzene. For more highly substituted systems, 1,2-, 1,3-, and 1,4- (or ortho-, meta-, and para-) prefixes indicate the positions of disubstitution. Alternatively, the ring is numbered, and substituents labeled with these numbers are named in alphabetical order. Many simple substituted benzenes have common names. 

Substituted benzenes are named by adding prefixes or suffixes to the word benzene. Disubstituted systems are labeled as 1,2-, 1,3-, and 1,4- or ortho, meta, and para, depending on the location of the substituents. Many benzene derivatives have common names, sometimes used as bases for naming their substituted analogs. As a substituent, an aromatic system is called aryl the parent aryl substituent, CsHs, is called phenyl its homolog C6H5CH2 is named phenylmethyl (benzyl). 

To name a benzene ring with one substituent, name the substituent and add the word benzene. To name a disubstituted ring, select the correct prefix (ortho = 1,2 meta = 1,3 para= 1,4) and alphabetize the substituents. Use a common name if it is a derivative of that monosubstituted benzene. 

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