Alkyne An unsaturated hydrocarbon

Alkyne. An unsaturated hydrocarbon having one triple bond, CnH2n-2-... 

Alkene an unsaturated hydrocarbon containing a carbon-carbon double bond. The general formula is C H2 . (22.2) Alkyne an unsaturated hydrocarbon containing a triple carbon-carbon bond. The general formula is C H2 2. (22.2) Alloy a substance that contains a mixture of elements and has metallic properties. (16.4)... 

Alkyne an unsaturated hydrocarbon containing a carbon-carbon triple bond. The general formula is C H2 2-... 

Alkyne An unsaturated hydrocarbon that contains a carbon-carbon triple bond. 

Alkynes An unsaturated hydrocarbon that contains one or more triple bonds between carbon atoms is called an alkyne. Alkynes with one triple bond have the general formula C H2 2. The simplest alkyne is ethyne (C2H2), which is commonly called acetylene. The next simplest alkyne is propyne (C3H4). Their condensed structural formulas are shown below. 

Nickel-catalyzed cyclizations, couplings, and cycloadditions involving three reactive components have been an active area of research for the past decade [39,40]. Central to these reactions is the involvement of a low-valent nickel capable of facilitating oxidative coupling of an unsaturated hydrocarbon (such as an alkyne, allene, or alkene) and a carbonyl substrate (such as an aldehyde or ketone). The use of NHCs as ligands has been evaluated for couplings of aldehydes. Such reactions typically afford O-protected allylic alcohols in good yields. 

Both double and triple bonds are multiple bonds. Therefore alkynes are unsaturated hydrocarbons, just as alkenes are. To name alkynes and draw their structures, you follow the same rules that you used for alkenes. The only difference is the suffix -yne, which you need to use when naming alkyne compounds. Also, remember to count the number of bonds for each carbon. An alkyne bond counts as three bonds. 

The rules for naming an unsaturated hydrocarbon with fewer than four carbon atoms are similar to those for naming alkanes. A two-carbon alkene is named ethene, with the suffix -ene indicating that the molecule is an alkene. A three-carbon alkyne is named propyne, with the suffix -yne indicating that the molecule is an alkyne. 

Key point. Alkenes and alkynes are unsaturated hydrocarbons, which possess a C=C double bond and a C=C triple bond, respectively. As (weak) re-bonds are more reactive than (strong) o-bonds, alkenes and alkynes are more reactive than alkanes. The electron-rich double or triple bond can act as a nucleophile, and most reactions of alkenes/ alkynes involve electrophilic addition reactions. In these reactions, the re-bond attacks an electrophile to generate a carbocation, which then reacts with a nucleophile. Overall, these reactions lead to the addition of two new substituents at the expense of the re-bond. 

Alkenes and alkynes are unsaturated hydrocarbons. The characteristic functional group of an alkene is the carbon-carbon double bond. The functional group that... 

Two procedures are available for the dichlorophosphonation of alkenes and alkynes. The first of these, namely the use of PCI3 and oxygen, has already been mentioned briefly in connection with reactions which involved phenylethene. The second procedure involves the interaction of an unsaturated hydrocarbon with PCI5 and this, too, has been discussed to some extent in connection with those reactions which particularly involve arylethenes (Chapter 2, Sections III.A and VI.D). 

Alkynes are unsaturated hydrocarbons that contain a carbon-carbon triple bond, i.e., two adjacent carbon atoms are joined by three bonds. Alkynes have the general formula C H2 2 where n is an integer greater than 1. The simplest member of the alkyne family is C2H2 (lUPAC name ethyne common name acetylene) ... 

Alkynes are unsaturated hydrocarbons containing one or more C bonds. The simplest alkyne is acetylene (C2H2), a highly reactive molecule. When acetylene is burned in a stream of oxygen in an oxyacetylene torch, the flame reaches about 3200 K. Because alkynes in general are highly reactive, they are not as widely distributed in nature as alkenes alkynes, however, are important intermediates in many industrial processes. 

Indicate whether each statement is true or false, (a) Alkanes do not contain any carbon-carbon multiple bonds, (b) Cyclobutane contains a four-membered ring, (c) Alkenes contain carbon-carbon triple bonds, (d) Alkynes contain carbon-carbon double bonds, (e) Pentane is a saturated hydrocarbon but 1-pentene is an unsaturated hydrocarbon, (f) Cyclohexane is an aromatic hydrocarbon, (g) The methyl group contains one less hydrogen atom than methane. 

A hydrocarbon that contains one or more carbon-carbon double bonds, triple bonds, or benzene rings is classified as an unsaturated hydrocarbon. We study alkanes (saturated hydrocarbons) in this chapter. We study alkenes and alkynes (both unsaturated hydrocarbons) in Chapters 4 and 5, and arenes (also unsaturated hydrocarbons) in Chapters. 

IN THIS CHAPTER, we begin our study of unsaturated hydrocarbons. An unsaturated hydrocarbon is a hydrocarbon that has fewer hydrogens bonded to carbon than an alkane has. There are three classes of unsaturated hydrocarbons alkenes, alkynes, and arenas. Alkenes contain one or more carbon-carbon double bonds, and alkynes contain one or more carbon-carbon triple bonds. Ethene (ethylene) is the simplest alkene, and ethyne (acetylene) is the simplest alkyne ... 

An unsaturated hydrocarbon contains one or more carbon-carbon double or triple bonds. The term unsaturation indicates that fewer hydrogens are bonded to carbon than in an alkane, C 2n+i- three most important classes of unsaturated hydrocarbons are alkenes, alkynes, and arenes. Alkenes contain a carbon-carbon double bond and, with one double bond and no rings, have the general formula C 2n- Alkynes contain a carbon-carbon triple bond and, with one triple bond and no rings, have the general formula CJi2 2- The simplest alkene is ethylene, and the simplest alkyne is acetylene. 

Alkenes and alkynes are unsaturated hydrocarbons because they contain double and triple bonds, respectively. An alkene contains at least one double bond between carbons. The double bond forms when two adjacent carbon atoms share two pairs of valence electrons. The simplest alkene is ethene, C2H4, which is often called by its conunon name, ethylene. In ethene, each carbon atom is attached to two H atoms and the other carbon atom in the double bond. The resulting molecule has a flat geometry because the carbon and hydrogen atoms all lie in the same plane (see Figure 17.2). In an alkyne, a triple bond occurs when two carbon atoms share three pairs of valence electrons. 

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. 

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