Methylbenzene, naming

The procedure has been extended to symmetric methylbenzenes, namely p-xylene, 1,3,5-trimethylbenzene (mesitylene) and 1,2,4,5-tetramethylbenzene (durene) [52]. The steric hindrance causes no major limitation to the reaction and a dean monoarylation rather than a polysubstitution is obtained. For instance, a variety of ArX under irradiation in the presence of mesitylene affords the bulky biaryl compounds in satisfactory yields (>50%) (Scheme 10.36) [52],... 

The skeletal rearrangement of various strained cyclic compounds is carried out with a catalytic amount of soluble complexes of PdCl2. Namely, the rearrangements of bulvalene (67) to bicyclo[4.2.2]deca-2,4,7,9-tetraene (68)[54], cubane (69) to cuneane (70)[55], hexamethyl Dewar benzene (71) to hexa-methylbenzene (72)[56], and 3-oxaquadricyclanes[57] and quadricyclane (73) to norbornadiene[58-60] take place mostly at room temperature. Reaction of iodocubane (74) with a terminal alkyne catalyzed by Pd(0) and CuBr unexpectedly affords an alkynylcyclooctatetraene 75, without giving the desired cubylalkyne 76. Probably the rearrangement is a Pd-catalyzed reaction[61]. 

Monosubstitution can occur at any one of the six equivalent carbons of the ring. Most of the monosubstituted benzenes have common names such as toluene (methylbenzene), phenol (hydroxybenzene), and aniline (aminobenzene). 

Aromatic substances, more than any other class of organic compounds, have acquired a large number of nonsystematic names. The use of such names is discouraged, but 1UPAC rules allow for some of the more widely used ones to be retained (Table 15.1). Thus, methylbenzene is known commonly as toluene hydroxybenzene, as phenol ami nobenzene, as aniline and so on. 

Use of hyphens single- and multiple-word names. The general rule is to determine whether the parent is itself an element or compound. If so, then the name is written as a single word if not, then the name is written as multiple words. Methylbenzene is written as one word, for instance, because the parent—benzene—is itself a compound. Diethyl ether, however, is written as two words because the parent—ether—is a class name rather than a compound name. Some further examples follow ... 

Trinitrotoluene, TNT, is a well-known explosive, (a) Using the structure available on the Web site, determine the systematic name for TNT. (b) TNT is made by nitrating toluene (methylbenzene) with a... 

When the two groups in disubstituted benzenes are different, the same three isomers are possible that are possible when the substituents are the same. Compounds with two different substituents are usually named as positional derivatives of a monosubstituted (parent) compound. Above, the common (and commercial) name for methylbenzene is toluene, and the chlorinated derivatives are named as shown above. However, the same two chlorinated derivatives can also be properly named 2-chloromethylbenzene and 4-chloromethylbenzene. In this case, for naming, the parent compound is methylbenzene and it is understood that the methyl group is in the 1-position. The terms ortho- (1,2-), meta- (1,3-), and para- (1,4-) are also sometimes used for example, 2-chlorotoluene can be called ortho-c Aoioio -uene. This can be very confusing, but in the chemical industry, outside of the research labs, the common names for the parent compounds are almost always used. 

With trisubstitution by the same or different substituents, the three positional isomers shown above are possible. When the substituent groups are the same, the positional numbers are given followed by the suffix tri-. For example, if the three groups are chlorine, the first isomer above is named 1,2,3-trichlorobenzene. The compound above with different substituents is named as a derivative of the parent compound toluene (methylbenzene) where it is understood that the methyl group is in the 1-position. 

Common Name 1-Ethyl-2-methylbenzene Synonym 2-ethyltoluene, o-ethyltoluene... 

Chemical Name 1-ethyl-2-methylbenzene, l-methyl-2-ethylbenzene... 

Common Name l-Ethyl-3-methylbenzene Synonym 3-ethyltoluene, m-ethyl toluene... 

Chemical Name l-ethyl-3-methylbenzene, l-methyl-3-ethylbenzene... 

When the parent molecules connected by the azo group are different, azo is placed between the complete names of the parent molecules, substituted or unsubstituted. Locants are placed between the affix azo and the names of the molecules to which each refers. Preference is given to the more complex parent molecule for citation as the first component, e.g., 2-aminonaphthalene-l-azo-(4 -chloro-2 -methylbenzene). 

The common name for methylbenzene is toluene. Toluene is used to produce explosives, such as trinitrotoluene (TNT). Phenylethene, with the common name styrene, is an important ingredient in the production of plastics and rubber. 

There are many other aromatic hydrocarbons, i.e. compounds like benzene, which contain rings of six carbon atoms stabilised by electron delocalisation. For example, if one of the hydrogen atoms in benzene is replaced by a methyl group, then a hydrocarbon called methylbenzene (or toluene) is formed. It has the structural formulae shown. Methylbenzene can be regarded as a substituted alkane. One of the hydrogen atoms in methane has been substituted by a or —group, which is known as a phenyl group. So an alternative name for methylbenzene is phenylmethane. Other examples of aromatic hydrocarbons include naphthalene and anthracene. 

Toluene is a clear, flammable, aromatic hydrocarbon liquid with a smell similar to benzene. It is also called methylbenzene, indicating that a methyl group has been added to one of benzenes carbon atoms. Toluene was first isolated by Pierre-Joseph Pelletier (1788—1842) and Philippe Walter (1810—1847) in 1837. The name toluene comes from the South American tree Toluifera balsamum. Henri-Etienne Sainte-Claire Deville (1818—1881) isolated toluene from the tree s gum, Tolu balsam, in 1841. 

Experimental work using a pulse-quench catalytic reactor650 to probe transition between induction reactions and hydrocarbon synthesis on a working H-ZSM-5 catalyst has resulted in the suggestion that stable cyclopentenyl cations are formed during the induction period from small amounts of olefins formed in an induction reaction 647 One study reports a surprising observation, namely, enhanced aromatic formation over the physical mixture of Ga203 and H-ZSM-5 (1 1) (18.2% of benzene and methylbenzenes).651... 

Substituted aromatic compounds are named using the suffix -benzene. Thus, C6H5Br is bromobenzene, C6H5CH3 is methylbenzene (also called toluene), C6H5N02 is nitrobenzene, and so on. Disubstituted aromatic compounds are named using one of the prefixes ortho-, meta-, or para-. An ortho- or o-disubstituted benzene has its two substituents in a 1,2 relationship on the ring a meta- or m-disubstituted benzene has its two substituents in a 1,3 relationship and a para- or p-disubstituted benzene has its substituents in a 1,4 relationship. When the benzene ring itself is a substituent, the name phenyl (pronounced fen-nil) is used. 

Common Name 2, 4-Dichlorotoluene Synonym 2, 4-dichloro-l-methylbenzene Chemical Name 2, 4-dichlorotoluene CAS Registry No 95-73-8 Molecular Formula C7H6C12 Molecular Weight 161.029 Melting Point (°C) ... 

Common Name 3, 4-Dichlorotoluene Synonym 3, 4-dichloro-l-methylbenzene Chemical Name ... 

Chemical Name 2-Bromo-N-ethyl-N,N-dimethylbenzenemethanaminium 4-methylbenzene sulfonate... 

Chemical Name 3-aminotoluene, m-amino-methylbenzene, m-methylaniline, m-toluidine... 

Toluene, the common name for methylbenzene, can be combined (both chemically and in making names for compounds ) with three nitro groups to give the famous explosive trinitrotoluene or TNT. 

Some benzene derivatives have special names. Methylbenzene is usually called toluene, hydroxybenzene is known as phenol and aminobenzene is almost always called aniline. 

Synonyms and trade names methacide, methylbenzene, phenyhnethane, toluol, toluene (dissolved)... 

Synonyms and trade names toluene-2,4-diisocyanate, 2,4-diisocyanato-l-methylbenzene, diiso-cyanatotoluene, TDI, creorcinol diisocyanate, m-tol-uene diisocyanate, 4-methyl-l,3-phenylene diisocyanate. 

Nomenclature chaos in organic chemistry will not be ordered until a one-one correspondence between structure and name is restored. It was with this object specifically in view that a notational system (5) was devised which will generate a unique systematic name in every case. This does not, of course, mean (as some have supposed) that the sole and exclusive use of systematic names for organic substances is advocated. It would be pedantic to talk of hydroxybenzene or 4-hydroxy-l-methylbenzene when phenol or p-cresol is meant. But there must be an agreed, unique systematic or fiducial name for... 

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. 

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