End ene

Open chain hydrocarbons which are undersaturated, i.e. having at least one carbon-carbon double bond are part of the olefin series, and have the ending -ene . Those with one carbon-carbon double bond are called mono-olefins or alkenes, for example ethylene CH2 = CH2. 

Bivalent radicals derived from unbranched alkenes, alkadienes, and alkynes by removing a hydrogen atom from each of the terminal carbon atoms are named by replacing the endings -ene, -diene, and -yne by -enylene, -dienylene, and -ynylene, respectively. Positions of double and triple bonds are indicated by numbers when necessary. The name vinylene instead of ethenylene is retained for —CH=CH—. 

The ending ene is adopted for straight-chain monounsaturated hydrocarbons. Thus, butenes refer to 1-butene and 2-butene. The en.6m. jlene denotes a monounsaturated hydrocarbon that consists of the same number of carbons as expressed by the name ie, butylenes are 1-butene, 2-butene, and isobutylene (methylpropene). The generic names alkenes and olefins refer to monounsaturated hydrocarbons. 

The following prefixes are used to represent monocyclic hydrocarbon components other than benzene cyclopropa-, cyclobuta-, cyclopenta-, cyclohepta-, etc. When a monocyclic hydrocarbon is the base component, it carries the ending ene , signifying the maximum number of non-cumulative double bonds (examples 33 and 34). 

When both double and triple bonds occur in the same molecule, the lUPAC system recommends the use of both endings -ene, and -y ne, with the former always preceding the latter in the name. Common alkynyl groups are... 

The alkene series of hydrocarbons is characterized by having one double bond in the carbon chain. The characteristic formula for members of the series is C H2 . Since there must be at least two carbon atoms present to have a carbon-to-carbon double bond, the first member of this series is ethene, C2H4, also known as ethylene. Propene (propylene), C,Hh, and butene (butylene), C4HK, are the next two members of the series. Note that the systematic names of these compounds denote the number of carbon atoms in the chain with the name derived from that of the alkane having the same number of carbon atoms (Table 21-2). Note also that the characteristic ending -ene is part of the name of each of these compounds. 

In the other method, the ending -ane is changed to -ene or -yne to indicate the presence of a double or triple bond. This is used for alkanes and mono- and polycyclic alkane parent hydrides. In alkanes and cycloalkanes, the change of the -ane ending to -ene or -yne indicates the presence of one double or triple bond. Multiplicative prefixes di-, tri-, tetra-, etc. are used to signal the multiplicity of unsaturated bonds. Locants placed immediately in front of the endings -ene and -yne are used as needed. 

S.4.2 Unsaturated and divalent substituents. Unsaturated monovalent substituents are named systematically by attaching the suffixes -yl to the stem of the parent name that carries the ending -ene or -yne. Retained trivial names include vinyl for -CH=CH2, allyl for -CH2-CH=CH2 and isopropenyl for -C(CH3)=CH2, but only when it is unsubstituted. 

The prefixes designating attached components are formed by changing the ending -ene of the name of the component hydrocarbon into -eno e.g., pyreno (from pyrene). When more than one prefix is present, they are arranged in alphabetical order. The following common... 

For monocyclic prefixes other than benzo , the following names are recognized, each to represent the form with the maximum number of non-cumulative double bonds cyclopenta, cyclohepta, cycloocta, cyclo-nona, etc. When the base component is a monocyclic system, the ending -ene signifies the maximum number of non-cumulative double bonds, and thus does not denote one double bond only. 

Univalent radicals derived from ortho-fused or ortho- and peri-fused polycyclic hydrocarbons with names ending in -ene by removal of a hydrogen atom from an aromatic or alicyclic ring are named in principle by changing the ending -ene of the names of the hydrocarbons to -enyl . 

I proposed therefore for this hydrocarbon the ending -ene in order to avoid confusion with the alkaloids. This is necessary since, at least for a long time, the entire art of organic nomenclature will consist in modifications of endings. 

Locate the C atoms in the longest C chain that contains the double bond. Use the base name prefix with the ending -ene. 

Alkynes also undergo the acid-catalyzed addition of water. The product of the reaction is an enol. An enol has a carbon-carbon double bond and an OH group bonded to one of the sp carbons. (The ending ene signifies the double bond, and ol the OH. When the two endings are joined, the final e of ene is dropped to avoid two consecutive vowels, but it is pronounced as if the e were there, ene-oL )... 

Ans. The lUPAC rules for alkynes are exactly the same as those for alkenes except that the ending -ene is changed to -yne. The compound is 4-isopropyl-2-heptyne with the numbering of the carbon chain shown below ... 

Some compounds of alkenes have more than one double bond in the structure. Naming of the prefix for the number of carbons is the same as with the other alkenes. The ending ene is still used to indicate double bonds in the alkene family. There is, however, a prefix used to indicate the number of double bonds in the compound. The prefix di is inserted before the ene in the name to indicate two double bonds. For example, butene with two double bonds is called butadiene. The prefix tri is inserted to indicate three double bonds. Hexene, with three double bonds, is called hexatriene. There must be at least four carbons before two double bonds can... 

The second class of simple hydrocarbons, the alkenes, consists of molecules that contain at least one double-bonded carbon pair. Alkenes follow the same naming convention used for alkanes. A prefix (to describe the number of carbon atoms) is combined with the ending "ene" to denote an alkene. Ethene, for example is the two-carbon molecule that contains one double bond. The chemical formula for the simple alkenes follows the expression Because one of the carbon pairs is double... 

The ending -ene is used to designate a carbon-carbon double bond. When more than one double bond is present, the ending is -diene, -triene, and so on. The ending -yne (rhymes with wine) is used for a triple bond -diyne for two triple bonds and so on). Compounds with a double and a triple bond are -enynes. 

In lUPAC nomenclature, the simpler ending -ene is used instead of -ylene, as in ethene and propene. More complicated systems require adaptations and extensions of the rules for naming alkanes (Section 2-6). 

With the exception of benzo, fusion prefixes for monocyclic systems are treated as exemplified for cyclopenta, cyclohepta etc. It should be noted here that for fused polycyclic systems the ending. ..ene always indicates the maximum number of non-cumulative double bonds, that is, a man-cude system ... 

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