Benzene nomenclature

Such an acid is 4-methylbenzenesulfonic acid (51 commonly known as p-tol-uenesulfonic acid, tosic acid, or p-TsOH this benzene nomenclature system is discussed in Chapter 21, Section 21.2). Another commercially available sulfonic acid is methanesulfonic acid (52), commonly abbreviated as MsOH, where Ms = mesyl. Tosic acid is a crystalline sohd that is cheap, readily available, and soluble in most organic solvents. Throughout most of this book, the acid catalyst is simply referred to as H+, but the actual acid is usually sulfuric acid or tosic acid. 

It IS hard to find a class of compounds in which the common names of its members have influenced organic nomenclature more than carboxylic acids Not only are the common names of carboxylic acids themselves abundant and widely used but the names of many other compounds are derived from them Benzene took its name from benzoic acid and propane from propionic acid not the other way around The name butane comes from butyric acid present m rancid butter The common names of most aldehydes are derived from the common names of carboxylic acids—valeraldehyde from valeric acid for exam pie Many carboxylic acids are better known by common names than by their systematic ones and the framers of the lUPAC rules have taken a liberal view toward accepting these common names as permissible alternatives to the systematic ones Table 19 1 lists both common and systematic names for a number of important carboxylic acids... 

When applying this principle to replacement names generated from fusion nomenclature, it is essential to keep in mind that fusion names for hydrocarbons ending in -cycloalkene are for fully unsaturated skeletons the -ene ending implies whatever number of double bonds may be necessary, without a multiplier. Thus (117) has six double bonds in the twelve-membered ring, and one must add ten hydrogens to saturate it to the stage of a simple benzene derivative, compound (118). 

The nomenclature used to describe the fused benzene-pyrrole-pyridine system of the compounds under discussion has been repeatedly modified, and the compounds have been numbered in an astonishing variety of ways since Perkin and Robinson introduced the name carboline for the ring system, which was encountered for the first time in the harmala alkaloids. In the earliest version of carboline nomenclature, the parent compound of the series, whose trivial name was norharman, was referred to as 4-carboline and numbered as in 1. Harmine (2) then became ll-methoxy-3-methyl-4-carboline. 

Benzene derivatives. Tbe nomenclature is a combination of the lUPAC system and traditional names. Many of the derivatives are named by the substituent group appearing as the prefbt. These may be considered a subclass of the aliphatic-aromatic hydrocarbon family, which contains both aliphatic and aromatic units in its structures. Thus, alkylbenzenes are made up of a benzene ring and alkane units alkenylbenzenes are Composed of a benzene ring and alkene units and alkynylbenzenes comprise a benzene ring and alkyne units. Examples of alkylbenzenes include... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Structures and nomenclature for the most important five-membered monocycles with one or more heteroatoms are depicted in Scheme 1. The aromaticity scale in five-membered heterocycles has been long debated.97-101 The decreasing order of aromaticity based on various criteria is (DRE values in kcal/ mol) benzene (22.6) > thiophene (6.5) > selenophene > pyrrole (5.3) > tellurophene > fur an (4.3). Pyrrole and furan have comparable ring strains (Scheme 38). The aromaticity of furan is still controversial 100 the NMR shielding by ring current estimated it at about 60% of the aromaticity of benzene, and other methods reviewed earlier102 estimated it at less than 20%. 

Over the years, many people contributed to the development of the field of organic chemistry. To better understand how this science provides so many useful items for our daily use, it is necessary to be familiar with some of the nomenclature of organic chemistry. There are two basic types of hydrocarbon substances, namely, aliphatic and aromatic. There are three basic types of aliphatic hydrocarbon molecules defined by the number of bonds involved in straight linear-chained molecules. If the basic structure of a hydrocarbon molecule is a ring instead of a straight chain, they are known as aromatic hydrocarbons, typified by the benzene ring. 

Both purine and pteridine are parent heterocycles for nomenclature purposes. The systematic procedure for naming fused heterocycles is an extension of that we saw in Section 11.8 where we considered a benzene ring fused to a heterocycle. The main difference is that we have to identify bonds in two... 

A further aid in the location of the solvents and their exact specification is the Chemical Abstracts (CAS) Registry Number, shown in the second column. The Chemical Abstracts name may be the same as the commonly used one or may differ from it considerably, so that it is not always easy to find the solvents in these Chemical Substance Indexes of the Chemical Abstracts. Eor instance, benzene, methyl is a fairly transparent name for toluene, and methanol, phenyl a slightly less one for benzyl alcohol, but one has to become familiar with the systematics of Chemical Abstracts nomenclature in order to search for diethyl ether or any other more complicated compound. It is expected that with all this information available in table Al the solvents listed are definitely specified and readily found in the Abstracts and other compilation of information and data. 

In indole, benzimidazole, and their derivatives, all symmetry restrictions on the IPA and 2PA allowedness of transitions are lifted. In these molecules. La and Lb transitions are not formally defined. However, bands in the low-energy portion of the IPA and 2PA spectra can be assigned to transitions which have similar characteristics to the La and Lb transitions of benzene (although they are red-shifted with respect to benzene or toluene), so the nomenclature is often extended to these systems. 

The benzene rings in the helicenes are indexed by letters as shown. Sometimes helicenes are indicated by short nomenclature symbols, via the number of the con-... 

In the early 1970 s, the American Chemical Society authorized an alternative system for naming fully fluorinated compounds or groups in which the symbol F conveys the sense of perfluoro . This system, which has its roots in phi-nomenclature (e.g., (/(-heptane is 1) proposed in the 1940s, has not been used widely enough to warrant adopting it in this book. According to -nomenclature, for example, 2 is F-ncopcntanc, 3 is F-propene, 4 is F-pro-panal, 5 is bromo-F-benzene, and 6 is ethyl F-ethyl ether. 

In nomenclature, the prefixes a and /3 are used to distinguish between the two structures a indicates that the substituent is attached to the benzene ring which is linked to divalent nitrogen... 

In spectroscopic convention, the upper energy state is written first followed by the lower energy state between which the transition is taking place. For absorption, the arrow points from left to right, e.g. for the lowest energy transition in benzene at 260 nm, in absorption 1B2u - 1A,t and in emission ih - Mw. Other nomenclatures are given in the Table 3.4. 

With respect to unsaturated hydrocarbons we should note that compounds exhibiting one or several double bonds are often called alkenes or olefins. Finally, we need to add a brief note concerning the nomenclature in aromatic systems, particularly, in six-numbered rings such as benzene. Here the terms ortho-, meta-, and ara-substi-tution are often used to express the relative position of two substituents in a given ring system. Identically, we could refer to those isomers as 1,2-(ortho), 1,3-(meta), 1,4-(para) disubstituted compounds (see margin). 

---