Trivial names alkanes

Alkanes. The saturated open-chain (acyclic) hydrocarbons (C H2 +2) have names ending in -ane. The first four members have the trivial names methane (CH4), ethane (CH3CH3 or C2H5), propane (C3H8), and butane (C4Hjo). For the remainder of the alkanes, the first portion of the name... 

These names are called common or trivial names. As the size of the alkane increases, the number of isomers increases dramatically. It would be very cumbersome to continue this process of providing different prefixes for each isomer of a larger alkane. 

There are two ways of naming alkyl halides. The systematic (IUPAC) nomenclature treats an alkyl halide as an alkane with a halo- substituent Fluorine is fluoro-, chlorine is chloro-, bromine is bromo-, and iodine is iodo-. The result is a systematic haloalkane name, as in 1-chlorobutane or 2-bromopropane. Common or trivial names are constructed by naming the alkyl group and then the halide, as in isopropyl bromide. This is the origin of the term alkyl halide. Common names are useful only for simple alkyl halides, such as the following ... 

The nomenclature of FA reflects the long history of their smdy and description. Most FA were originally described under trivial names prior to the adoption of the international molecular nomenclature rules in 1892 (Table 3.1). Even after adopting the International Union of Pure and Applied Chemistry (lUPAC) system for nomenclature (lUPAC-IUB, 1977), the habit of assigning trivial names to FA continues. The basis of the systematic nomenclature system is an extension of that accepted for hydrocarbon (alkane/alkene) naming. Hence, the descriptive name is based on the number of carbon atoms contained in the molecule, with the suffix -e replaced with -oic acid. However, in most instances, FA are referred to by their formula notations. As is the case with systematic and trivial names, there exists an lUPAC accepted formula notation nomenclature and several earher versions (Table 3.2). Each system... 

It is also important to remember that configurational isomers are common and that these (Z)- and ( )-isomers have important geometric constraints, including such obvious features as the inability to introduce a strain-free (E) double bond into a ring with fewer than eight carbons. As was the case for alkanes, trivial names also intrude for substituted alkenes. Thus, the ethenyl oup (CH2=CH-) is commonly called vinyl and the 2-propenyl group (CH2=CH-CH2-) is called allyl. 

The naming convention for alkanes is introduced. There are several common or trivial names that are often used and which, therefore, must be learned. 

After we developed a structure for ethane (p. 68), we examined substituted alkanes. Here we do the same thing for ethene, and discover a new kind of isomerism. There is but one ethylene (or ethene, if you insist). We can make derivatives of this molecule by mentally replacing a hydrogen with some X group. Figure 3.16 shows a few such compounds. These are not called ethenyl or even ethylenyl compounds but instead bear the delightfiilly trivial name, so far untampered with, of vinyl. 

There is little difference in physical properties between the alkenes and their saturated relatives, the alkanes. The odors of the alkenes are a bit more pungent and perhaps justify being called evU-smelling. Tn fact, the old trivial name for alkenes, olefins, readily evokes the sense of smell. Tables 3.2 and 3.3 list some data for alkenes and cycloalkenes. 

Aliphatic framework molecules most common in organic acids include alkanes (saturated hydrocarbons) and alkenes (unsaturated hydrocarbons). These saturated and unsaturated aliphatic carboxylic acids may be acyclic (straight or branched chains) or alicyclic (aliphatic rings). Acyclic aliphatic monocarboxylic acids are also referred to as fatty acids (Table 1). The first five saturated acids (formic to valeric) of this type are sometimes referred to as short-chain, low-molecular-weight, or volatile fatty acids. Although a nomenclature for these acids has been established by the International Union of Pure and Applied Chemistry (lUPAC), the convention of using the trivial names for the first five saturated acids has remained. Similarly, trivial names are used for the aliphatic dicarboxylic acids (Table 2) that are saturated with two to four carbon atoms (C2-C4) and unsaturated with four carbon atoms (C4). Alicyclic carboxylic acids contain one or more saturated or partially unsaturated rings. These acids most commonly occur... 

Saturated hydrocarbons are classified by the parent name alkanes substituent groups derived from them are called alkyl (or alkanyl, see below) groups. The naming system is based on the unbranched members of the homologous series C H2 +1 of which only the first four are designated by trivial names. 

The root for the name of each alkene is derived from the alkane having the same number of C atoms as the longest chain containing the double bond. In the trivial (common) system of nomenclature, the suffix -ylene is added to the characteristic root. In systematic (TUPAC) nomenclature, the suffix -ene is added to the characteristic root. 

When only a relatively few organic compounds were known, chemists gave them what are today called trivial or common names, such as methane, ethane, propane, and butane. The names for the larger alkanes were derived from the Greek prefixes that indicate the number of carbon atoms in the molecule. Thus, pentane contains five carbons, hexane has six, heptane has seven, and so forth, as shown in k Table 1.4. 

Hydrocarbon chains with free valences at each terminal C atom are frequently still called trimethylene-, tetramethylene-, etc. instead of alkane-l-n>-diyl groups, the systematically correct designation. Unsaturated substituent groups of this kind are named by replacing the terminal syllable. .. ene with. .. enylene. The trivial terms ethylene for -CH2-CH2-, propylene for H3C-CH-CH2-, and vinylene for -CH=CH- are still frequently... 

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