Naming compounds cyclic alkanes

Name each of the following cyclic alkanes, and indicate the formula of the compound. 

Substituted benzene compounds are named in the same way cyclic alkanes are. For example, ethylbenzene has a 2-carbon ethyl group attached, and 1,4-dimethylbenzene, also known as para-xylene, has methyl groups attached at positions 1 and 4. 

Cyclic aikenes are named in much the same way as cyclic alkanes however, carbon number 1 must be one of the carbons connected by the double bond. In Figure 21.12b, note the numbering in the compound. The name of this compound is 1,3-dimethylcyclopentene. 

Cyclic alkenes are known compounds. As with cyclic alkanes, the parent name for cyclic alkenes is based on the number of carbon atoms in the ring derived from the analogous linear alkene, but the prefix cyclo is added to the name. The six-carbon cyclic molecule that contains a C=C unit is called cyclohexene (4). Substituents are named in the usual manner, and one carbon of the C=C unit must be Cl. The choice of which C=C carbon becomes Cl is dictated by giving the substituents the lowest number. Compound 5 is a cycloheptene, but the substituents can be numbered 6-ethyl-3,6-dimethyl- or 4-ethyl-4,7-di-methyl. The smaller numbers dictates the priority, which also give the ethyl group the lower number, and 5 is 4-ethyl-4,7-dimethylcycloheptene. Note that the 1-heptene is unnecessary in the name... 

Cyclic compounds that have a ring of carbon atoms, which are not aromatic, are named using the prefix cyclo. For example, cyclobutane is a cyclic alkane with four carbon atoms. The atoms in the ring are numbered so that the smallest numbers indicate the position of substituents. 

The chain and branched chain saturated hydrocarbons make up a family called the alkanes. Some saturated hydrocarbons with five carbon atoms are shown in Figure 18-11. The first example, containing no branches, is called normal-pentane or, briefly, n-pentane. The second example has a single branch at the end of the chain. Such a structural type is commonly identified by the prefix iso- . Hence this isomer is called /50-pentane. The third example in Figure 18-11 also contains five carbon atoms but it contains the distinctive feature of a cyclic carbon structure. Such a compound is identified by the prefix cyclo in its name—in the case shown, cyclopentane. 

In Method 2, described by Rule A-31, the saturated cyclic parent is named as a polycyclo-[.. jalkane. The alkane name identifies the total number of carbon atoms in the ring system. The names bicyclo, tricyclo, tetracyclo, etc. identify parent compounds of two, three, four, etc. rings. Double bonds in the ring are identified by names such as w-alkenc, ,/w-alkadicne, where the n and m give the position of the double bond. Substituents consist of alkyl, cycloalkyl, phenyl, etc. radicals. 

When the suffixes a7nea.nd -eneshow up in a compound name like decane or decene they are usually consistent with the alkane and alkene definitions, but not always. Benzene is a cyclic aromatic hydrocarbon, not a straight chain molecule naphthenes are cyclic compounds. 

These are alkanes in which the carbon atoms form a ring. The prefix cyclo- is used in the names of these compounds to indicate their cyclic nature. 

If the C atoms in an alkane are bonded in a row with a formula of the form CH3(CH2)mCH3, the compound, called an unbranched alkane, is named according to the number of C atoms present. All are named with a stem name and the suffix -ane. A cyclic (ring) alkane has the general formula (CH2)m and is designated by the prefix cyclo-. 

Acyclic nitriles are named by adding -nitrile as a suffix to the alkane name that includes the carbon atom of the nitrile. The carbon atom of the nitrile is C-1. Cyclic compounds with the —CN group bonded to the ring are named using the suffix -carbonitrile. The ring carbon bearing the cyano group is C-1, but that number is not included in the name. 

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