Alkyne series

The unsaturated open-chain hydrocarbons include the alkene or olefin series, the diene series, and the alkyne series. The alkene series is made up of chain hydrocarbons in which a double bond exists between two carbon atoms. The general formula for the series is CnH2n, where n is the number of carbon atoms. As in the paraffin series, the lower members are gases, intermediate compounds are liquids, and the higher members of the series are solids. The alkene series compounds are more active chemically than the saturated compounds. They react easily with substances such as halogens by adding atoms at the double bonds. 

They are not found to any extent in natural products, but are produced in the destructive distillation of complex natural substances, such as coal, and are formed in large amounts in petroleum refining, particularly in the cracking process. The first member of the series is ethylene, C2H4. The dienes contain two double bonds between pairs of carbon atoms in the molecule. They are related to the complex hydrocarbons in natural rubber and are important in the manufacture of synthetic rubber and plastics. The most important members of this series are butadiene, C4H5 and isoprene, CsHg. 

The members of the alkyne series contain a triple bond between two carbon atoms in the molecule. They are very active chemically and are not found free in nature. They form a series analogous to the alkene series. The first and most important member of the series is acetylene, C2H2. 

The simplest of the saturated cyclic hydrocarbons, or cycloalkanes, is cyclopropane, C3Hg, the molecules of which are made up of three carbon atoms to each of which two hydrogen atoms are attached. Cyclopropane is somewhat more reactive than the corresponding open-chain alkane, propane, C3Hg. Other cycloalkanes make up a part of ordinary gasoline. 

Several unsaturated cyclic hydrocarbons, having the general formula C]qHj5, occur in certain fragrant natural oils that are distilled from plant materials. These hydrocarbons are called terpenes and include pinene (in turpentine) and limonene (in lemon and orange oils). 

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Compounds consisting of only carbon and hydrogen have the simplest compositions of all organic compounds. These compounds are called hydrocarbons. It is possible to classify the hydrocarbons into four series, based on the characteristic structures of the molecules in each series. These series are known as (1) the alkane series, (2) the alkene series, (3) the alkyne series, and (4) the aromatic series. There are many subdivisions of each series, and it is also possible to have molecules that could be classified as belonging to more than one series. 

The alkyne series of hydrocarbons is characterized by having molecules with one triple bond each. They have the general formula C H2 2. Like other unsaturated hydrocarbons, the alkynes are quite... 

Alkynes are similar to both alkanes and alkenes because they form a homologous series. Alkynes have the general formula of CnH2n-2- So, for example, the first member of the alkyne series, ethyne, has the formula C2H2. (You may know this compound by its common name acetylene.) The next member, propyne, has the formula C3H4. 

It is the first member of the alkyne series which is one of the major chemicals used in industry. ... 

The alkyne series of hydrocarbons is characterized by having molecules with one triple bond each. They have the general formula C H2 2 and the name ending -yne. Like other unsaturated hydrocarbons, the alkynes are quite reactive. Ethyne is commonly known as acetylene. It is the most important member of the series commercially, being widely used as a fuel in acetylene torches and also as a raw material in the manufacture of synthetic rubber and other industrial chemicals. 

For the structural formula, we will start by laying down the two carbon atoms and connecting them with a triple bond. How do we know that the carbon atoms are joined by a triple bond Remember The suffix -yne indicates the alkyne series, which contain a triple bond. The triple bond can t be between a carbon and hydrogen atom, because hydrogen atoms only have... 

The alkyne series is characterized by molecules with one triple bond each. They are quite reactive. Ethyne is commonly known as acetylene, a commercially important fuel and raw material in the manufacture of rubber and other industrial chemicals. 

In the alkyne series (50,61) methyl- and ethylacetylene are reduced, but not dimethylacetylene. Allene is also reduced by N2ase, possibly via isomerization to methylacetylene (Figure 7). 

In addition to the lUPAC rules, it is important to learn a few common names. For example, the simplest members of the alkene and alkyne series are frequently referred to by their older common names, ethylene, acetylene, and propylene. 

Acetylene, C2H2, is the first member of the alkyne series (Fig. 21.9). Despite its -ene ending, acetylene is an alkyne, not an alkene. The lUPAC system is used for all alkynes except acetylene. So, for the alkynes with three and four carbon atoms, the lUPAC names are propyne and butyne, respectively. 

Recently, the structure and chemistry of materials of the type (SiH2) and (SiH) have been investigated and reviewed. However, these compounds cannot be considered analogous to the alkene or alkyne series in carbon chemistry because of their polymeric nature. The inability of silicon to form multiple bonds with itself or other elements is well known, but perhaps not easily explained. It might be pointed out that none of the elements below the second period in the periodic table appears to form stable double bonds with themselves. For example, the compounds phosphobenzene and arsenobenzene, supposedly analogs of azobenzene, are better described as tetraphenylcyclotetraphosphine and hexaphenylcyclohexa-arsine, respectively. Also, sulfur, under ordinary conditions, exists as a cyclic octamer. 

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