Prefixes cyclic hydrocarbons

Cyclic hydrocarbon systems consisting of three or more rings may be named in accordance with the principles stated in Rule A-31. The appropriate prefix tricyclo- , tetracyclo- , etc., is substituted for bicyclo- before the name of the open-chain hydrocarbon containing the same total number of carbon atoms. Radicals derived from these hydrocarbons are named according to the principles set forth in Rule A-31.4. 

Assemblies of two identical cyclic hydrocarbon systems are named in either of two ways (a) by placing the prefix bi- before the name of the corresponding radical, or (b) for systems joined by a single bond by placing the prefix bi- before the name of the corresponding... 

In replacement nomenclature, the name of a heterocyclic compound is formed by prefixing a terms, such as oxa , thia , aza , etc. to the name of the corresponding cyclic hydrocarbon. As IUPAC Rule B-4 states that the replacement method should be applied to a homocyclic hydrocarbon, we use pentalene for this purpose. The replacement procedure forbids the use of heterocyclic parent structures and for this reason the name thiathiophthene , which is found in the literature, is not in compliance with IUPAC recommendations. Another name which is sometimes found is thiothiophthene , which is even worse because of an incorrect use of the prefix thio . 

One of the reasons that such a variety of organic compounds exists is that carbon atoms can form ring structures. An organic compound that contains a hydrocarbon ring is called a cyclic hydrocarbon. To indicate that a hydrocarbon has a ring structure, the prefix cyclo- is used with the hydrocarbon name. Thus, cyclic hydrocarbons that contain only single bonds are called cycloalkanes. 

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. 

Step 1 Find tbe root Identify the longest chain or ring in the hydrocarbon. If the hydrocarbon is an alkene or an alkyne, make sure that you include any multiple bonds in the main chain. Remember that the chain does not have to be in a straight line. Count the number of carbon atoms in the main chain to obtain the root. If it is a cyclic compound, add the prefix -cyclo- before the root. 

Ketones. Acyclic ketones are named (1) by adding the suffix -one to the name of the hydrocarbon forming the principal chain or (2) by citing the names of the radicals R1 and R2 followed by the word ketone. In addition to the preceding nomenclature, acyclic monoacyl derivatives of cyclic compounds may be named (3) by prefixing the name of the acyl group to the name of the cyclic compound. For example,... 

Cyclic (or ringed) hydrocarbons are simply named with the prefix cyc/o- followed by an ending that is determined by how many carbon atoms are in the molecule. For example, a ringed hydrocarbon molecule containing five carbon atoms and only single bonds would be named cyclopentane. If the same molecule had a double bond between two carbon atoms in the ring, the name would be cyclopentene. 

The common method of naming aldehydes corresponds very closely to that of the related acids (see Carboxylic acids), in that the term aldehyde is added to the base name of the acid. For example, formaldehyde (qv) comes from formic acid, acetaldehyde (qv) from acetic acid, and butyraldehyde (qv) from butyric acid. If the compound contains more than two aldehyde groups, or is cyclic, the name is formed using carbaldehyde to indicate the functionality. The IUPAC system of aldehyde nomenclature drops the final e from the name of the parent acyclic hydrocarbon and adds al. If two aldehyde functional groups are present, the suffix - dial is used The prefix formyl is used with polyfunctional compounds. Examples of nomenclature types are shown in Table 1. 

The systematic nomenclature of fused-ring thiiranes and thiirenes is based on their parent hydrocarbons, for example, 6-thiabicyclo[3.1.0]hexane 1, 9-thiabicyclo[6.1.0]non-4-ene 2, 3-oxa-6-thiabicyclo[3.1.0]hexane 3, and 9-thiabicy-clo[6.1.0]non-l(8)-ene 6. A different nomenclature, which is frequently used, especially for more complex structures, is based on the name of the parent cyclic olefins and the addition of sulfide or episulfide as a suffix. In this manner, 2 is named cycloocta-l,5-diene monoepisulfide. Alternatively, epithio can be used as a prefix, leading to the name epithio-2,5-dihydrofuran for 3 <1996CHEC-II(1)241>. 

Cyclic aliphatic hydrocarbons are named by prefixing cyclo- to the name of the corresponding open-chain hydrocarbon having the same number of carbon atoms as the ring. For example ... 

Cyclic structures very simply are named as the parent hydrocarbon prefixed by the term cyclo. For example, C4H8... 

The prefixes di, tri, tetra, penta, hexa, etc. indicate how many of each substituent is in the molecule. A cyclic (ring) hydrocarbon is designated by the prefix cyclo. ... 

Cyclic ethers can be named in several ways. One simple way is to use teplacement nomenclature, in which we relate the cyclic ether to the corresponding hydrocarbon ring system and use the prefix oxa- to indicate that an oxygen atom replaces a CH2 group. In another system, a cyclic three-membered ether is named oxirane and a four-membered ether is called oxetane. Several simple cyclic ethers also have common names in the examples below, these common names are given in parentheses. Tetrahydrofuran (THF) and 1,4-dioxane are useful solvents ... 

The idea that carbon atoms can be bound in cyclic structures (besides forming chains and branched chains) appeared during the second half of nineteenth century. When these cyclic structures are saturated hydrocarbons we talk about cycloalkanes. In the nomenclature of this class of compounds the name is formed by adding the prefix cyclo-. 

If three or more identical cyclic systems are joined together the multiplying prefixes ter, quater, quinque, sexi, septi, octi, novi, etc. are attached to the hydrocarbon (but not the group) name. Members of the polyphenyl series are treated as exceptions. 

This nomenclature type uses substractive prefixes to indicate removal of atoms or groups of atoms from a trivially or systematically named parent structure. While additive nomenclature is used above all for hydrogenated cyclic systems, subtractive nomenclature focuses primarily on the opposite phenomenon, i. e. introduction of unsaturation. This has already been dealt with extensively in the discussions relating to hydrocarbon systems, where the terminal syllables. .. ene and. ..yne signify loss of two and four hydrogen atoms with concomitant formation of a double and triple bond, respectively. A more explicit symbolization of dehydrogenation in the guise of a subtractive prefix is particularly recommendable for certain natural products of the steroid and carbohydrate series as well as for dehy-droarenes (less precisely also named arynes) and dehydroannulenes. 

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