Hydrocarbon functional groups alkenes

This chapter will build on principles introduced in previous chapters and show applications to common chemical reactions of two important hydrocarbon functional groups alkenes and alkynes. The chapter will also introduce several new chemical reagents (compounds that react with an alkene or alkyne to give a new molecule), as well as several new types of reactions. The theme of acid-base chemistry will be used as a basis for understanding each chemical transformation where it is appropriate. Mechanisms that are the step-by-step processes by which one molecule is transformed into another by tracking the intermediates will also be discussed. The concept of mechanism was introduced in Chapter 7 (Section 7.8). 

In our study of the simple hydrocarbons, there are only two functional groups. One is a carbon-to-carbon double bond. Hydrocarbons that contain a carbon-to-carbon double bond are alkenes. The other hydrocarbon functional group is a carbon-to-carbon triple bond. Hydrocarbons that contain a triple bond are alkynes. These functional groups are the reactive sites in the alkenes and alkynes. The result is that alkenes and alkynes are more reactive than the alkanes. 

Alkenes (olefins) are unsaturated hydrocarbons that contain carbon-carbon double bonds. A double bond consists of a cr bond and a tt bond. A tt bond is weaker than a a bond, and this makes tt bonds more reactive than cr bonds. Thus, it bond is considered to be a functional group. Alkenes form a homologous series with general molecular formula C H2 . The simplest members of the series are ethene (C2H4), propene (CsHg), butene (C4Hg) and pentene (CsHjo)-... 

Hydrocarbons contain only hydrogen and carbon. The hydrocarbon functional groups include alkanes, alkenes, alkynes, and arenes (aromatic compounds). Simple hydrocarbons have few medicinal applications, but are the feedstock of the petrochemical industry to produce plastics, dyes, solvents, detergents, and adhesives (to name just a few). Therefore, hydrocarbons are essential to the medical field. Additionally, all hydrocarbons are flammable and, therefore, find application as fuels. For example, gasoline is a mixture of hydrocarbons. 

O aikene an unsaturated hydrocarbon that contains at least one double bond between two of the carbon atoms in the chain the simplest aikene is ethene, CjH4 O homologous series a family of organic compounds with similar chemical properties as they contain the same functional group alkenes, alcohols, for instance O isomers molecules with the same molecular formula but different stnictural formulae O substitution reaction a reaction in which one or more hydrogen atoms in a hydrocarbon are replaced by atoms of another element... 

When certain atoms are collected into discrete units, they have special physical and/or chemical properties. Such units are known as functional groups. The C=C unit of alkenes and the C=C unit of alkynes are examples of hydrocarbon functional groups. The C-C unit of an alkane is not considered to be a functional group because it is the backbone of virtually all organic molecules. Functional groups can include atoms other than carbon or hydrogen and the presence of these other atoms (call them heteroatoms) leads to new functional groups. 

Hydrocarbons that contain a carbon-carbon triple bond are called alkynes Non cyclic alkynes have the molecular formula C H2 -2 Acetylene (HC=CH) is the simplest alkyne We call compounds that have their triple bond at the end of a carbon chain (RC=CH) monosubstituted or terminal alkynes Disubstituted alkynes (RC=CR ) have internal triple bonds You will see m this chapter that a carbon-carbon triple bond is a functional group reacting with many of the same reagents that react with the double bonds of alkenes... 

Just as the alkanes and alkenes had general formulas, the carbon derivatives all have general formulas. The hydrocarbon backbone provides a portion of the general formula, and the functional group provides the other part. In each case, the hydrocarbon derivative is represented by the formula R-, and the hydrocarbon backbone has its own specific formula. The term substituted hydrocarbon is another name for hydrocarbon derivative, because the functional group is substituted for one or more hydrogen atoms in the chemical reaction. 

Alkenes are hydrocarbons that contain a carbon-carbon double bond. A carbon-carbon double bond is both an important structural unit and an important functional group in organic chemistry. The shape of an organic molecule is influenced by the presence of this bond, and the double bond is the site of most of the chemical reactions that alkenes undergo. Some representative alkenes include isobutylene (an industrial chemical), a-pinene (a fragrant liquid obtained from pine trees), and famesene (a naturally occuning alkene with three double bonds). 

As with several other functional groups considered earlier, epoxides are most commonly found in alkaloid metabolites rather than the original compound. These epoxides may arise via oxidation of alkenes or aromatic hydrocarbons. Epoxide hydrolase catalyzes hydrolysis of epoxides to the more hydrophilic diol. As seen in Scheme 6, this is usually a stereospecific reaction that always yields a... 

Functional Groups Defining Alkenes, Alkynes, and Aromatic Hydrocarbons... 

You first should decide what type of compound it is. The decision usually is straightforward for hydrocarbons, which will fall in one or the other of the categories alkanes, alkenes, alkynes, arenes, cycloalkanes, and so on. But when the compound has more than one functional group it is not always obvious which is the parent function. For example, Compound 1 could be named as an alkene (because of the double-bond function) or as an alcohol (because of the OH function) ... 

There are no simple rules to follow that dictate which is the parent function, and we suggest that the order of precedence of functional groups set by Chemical Abstracts be used whenever possible (see Table 7-1). By this system, the OH group takes precedence over hydrocarbons, and Compound 1 therefore is named as an alcohol, not as an alkene. 

It is convenient to consider the indifferent or neutral oxygen derivatives of the hydrocarbons - (a) aldehydes and ketones, (b) esters and anhydrides, (c) alcohols and ethers - together. All of these, with the exception of the water-soluble members of low molecular weight, are soluble only in concentrated sulphuric acid, as are alkenes and readily sulphonated arenes. The above classes of compounds must be tested for in the order in which they are listed, otherwise erroneous conclusions may be drawn from the reactions for the functional group about to be described. 

Osmium-catalysed dihydroxylation of olefins is a powerful route towards enantioselective introduction of chiral centers into organic substrates [82]. Its importance is remarkable because of its common use in organic and natural product synthesis, due to its ability to introduce two vicinal functional groups into hydrocarbons with no functional groups [83]. Prof. Sharpless received the 2001 Nobel Prize in chemistry for his development of asymmetric catalytic oxidation reactions of alkenes, including his outstanding achievements in the osmium asymmetric dihydroxylation of olefins. 

Under the same conditions, several types of hydrocarbon are also converted to fully deuterated compounds. The results are summarized in Table 1. Cydooctene was also transformed into fully deuterated cydooctene without a skeletal rearrangement. As shown in entries 2 and 3, saturated hydrocarbons have also been transformed into fully deuterated compounds. As described above, an interaction between allylic C-H bonds and palladium hydride induces the H-D exchange reaction for alkenes. H-D exchange in alkanes, however, cannot be explained in this way. Direct C-H activation without assistance from any functional group may be a route to the formation of fully deuterated alkanes. 

The occurrence of hydrocarbons (usually mono- and di-alkenes) with an epoxide function group have been reported usually as sex attractants. The sex attractant of the female gypsy moth, Lymantria dispar, was identified as the C18 2-methyl alkane derivative cis-7,S-epoxy-2-methyloctadecane (Bierl et al 1972). For the housefly, M. domestica, a major sex pheromone component is the C23 -alkane epoxide d.v-9,1O-cpoxytricosane (Uebel et al 1978) with a lesser quantity of 9,10-epoxyheptacosane (Mpuru et al., 2001). 

In the tables on the following pages, the symbols R and R represent hydrocarbons in covalent linkage to the functional group. Many derivatives are named in a similar manner to alkenes and alkynes, but the location and suffix of the functional group is used in place of -ene and -yne. 

Halides are second only to carboxylic acids in their versatility in organic synthesis. Functional group transformations into alkenes, alkynes, amines, aldehydes, alcohols, ethers, hydrocarbons, ketones and other groups may be performed with ease in high yield. However, the major synthetic importance of halides arises from the ease by which compounds that contain this functionality may be used in carbon-carbon bond-forming reactions and in the preparation of heterocyclic compounds. 

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