NAMING OF ALKYNES

The IUPAC names of alkynes are derived from those of the corresponding alkenes by replacing the suffix -ene with -yne. Thus we have... 

Hydrocarbons that contain one or more carbon-to-carbon triple bonds are called alkynes. The names of alkynes end in -yne. Ethyne, commonly known as acetylene, is the simplest alkyne. It consists of two carbon atoms with a triple bond between them, with each carbon also bonded to one hydrogen atom. The chemical formula for ethyne is C2H2. 

Common Names The common names of alkynes describe them as derivatives of acetylene. Most alkynes can be named as a molecule of acetylene with one or two alkyl substituents. This nomenclature is like the common nomenclature for ethers, where we name the two alkyl groups bonded to oxygen. 

Names of compounds containing C=C bonds end with -yne. Again the name of the parent compound is determined by the nnmber of carbon atoms in the longest chain (see Table 24.1 for names of alkane counterparts). As in the case of alkenes, the names of alkynes indicate the position of the carbon-carbon triple bond, as, for example, in... 

The procedure for the naming of alkynes similar to that used for alkenes, except the suffix is -yne. 

Write the lUPAC names of alkynes from their molecular stmctures. (Section 2.5)... 

Write the lUPAC names of alkynes from their molecular structures. 

The naming of alkynes is similar to that of alkenes, with the lowest number possible being used to locate the triple bond. For example, the name of... 

We form lUPAC names of alkynes by changing the -an- infix of the parent alkane to -yn- (Section 3.5). Thus, HC = CH is named efhyne, and CHsC=CH is named propyne. The lUPAC system retains the name acetylene therefore, there are two acceptable names for HC = CH ethynedcnd acetylene. Of these two names, acetylene s used much more frequently. For larger molecules, we number the longest carbon chain that contains the triple bond from the end that gives the triply bonded carbons the lower set of numbers. We indicate the location of the triple bond by the number of the first carbon of the triple bond. 

A similar fifth step is involved in the naming of alkynes as the position of the carbon-carbon triple bond needs to be indicated. The simplest alkyne is ethyne, C2H2, and again the series develops by the addition of a -CH2- group to the chain. The first alkyne molecule that can show isomerism due to a difference in position of the triple bond is butyne in which the triple bond can either be central to the molecule or at the end of the chain. The first alkyne molecule that can show a branched chain isomer must contain five carbon atoms. 

We have already discussed one important chemical property of alkynes the acidity of acetylene and terminal alkynes In the remaining sections of this chapter several other reactions of alkynes will be explored Most of them will be similar to reactions of alkenes Like alkenes alkynes undergo addition reactions We 11 begin with a reaction familiar to us from our study of alkenes namely catalytic hydrogenation... 

Monocyclic Aliphatic Hydrocarbons. Monocyclic aliphatic hydrocarbons (with no side chains) are named by prefixing cyclo- to the name of the corresponding open-chain hydrocarbon having the same number of carbon atoms as the ring. Radicals are formed as with the alkanes, alkenes, and alkynes. Examples ... 

Another analogous series of unsaturated hydrocarbons that contain just one multiple bond, but, instead of being a double bond, it is a triple bond is the alkynes. The names of all the compounds end in -yne. The only compound m this series that is at all common happens to be an extremely hazardous material. It is a highly unstable (to heat, shock, and pressure), highly flammable gas that is the first compound in the series. This two-carbon unsaturated hydrocarbon with a triple bond between its two carbon atoms is called ethyne, and indeed this is its proper name. It is, however, known by its common name, acetylene. 

Two new sections on the protection of phosphates and the alkyne-CH are included. All other sections of the book have been expanded, some more than others. The section on the protection of alcohols has increased substantially, reflecting the trend of the nineties to synthesize acetate- and propionate-derived natural products. An effort was made to include many more enzymatic methods of protection and deprotection. Most of these are associated with the protection of alcohols as esters and the protection of carboxylic acids. Here we have not attempted to be exhaustive, but hopefully, a sufficient number of cases are provided that illustrate the true power of this technology, so that the reader will examine some of the excellent monographs and review articles cited in the references. The Reactivity Charts in Chapter 10 are identical to those in the first edition. The chart number appears beside the name of each protective group when it is first introduced. No attempt was made to update these Charts, not only because of the sheer magnitude of the task, but because it is nearly impossible in... 

A few remarkable, but rather uncommon, transfer hydrogenations also deserve mention within the context of this chapter namely, the reduction of alkynes to alkenes using a chromium catalyst, and the reduction of double bonds using diimines. 

This number indicates the number of the first carbon atom that is part of the double/triple bond. (2) The name of longest carbon chain is formed by taking the alkane name, dropping the -ane suffix and replace it by -ene for an alkene or -yne for an alkyne. 

In this section, you reviewed how to name and draw alkanes, alkenes, and alkynes. You also learned how to name aromatic hydrocarbons. The names of all the other organic compounds you will encounter in this unit are based on the names of hydrocarbons. In the next section, you will learn about organic compounds that have single bonds to halogen atoms, oxygen atoms, and nitrogen atoms. 

A tanden anh-vicinal difunctionalization of alkynes, involving the addition of a lithium organotellurolate to an activated alkyne, with subsequent trapping of the vinyllithium intermediate with electrophiles, was recently reported and named electrotelluration. ... 

Alkenes and alkynes are unsaturated hydrocarbons. Alkenes contain at least one carbon-carbon double bond and alkynes have at least one carbon-carbon triple bond. The names of alkenes and alkynes use the alkane prefixes, but add ene and yne endings, respectively (Table 15.3). 

Another analogous series of unsaturated hydrocarbons that contain just one multiple bond, but, instead of being a double bond, it is a triple bond is the alkynes. The names of all die compounds... 

The IUPAC Rules are exactly the same for naming alkynes as for naming of alkenes except that die suffix -yne replaces -ene. 

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