Hydrocarbons functional groups

As each functional group is discussed in future chapters, the spectroscopic properties of that group will be described. For the present, we ll point out some distinguishing features of the hydrocarbon functional groups already studied and briefly preview some other common functional groups. We should also point out, however, that in addition to interpreting absorptions that ore present in an IR spectrum, it s also possible to get structural information by noticing which absorptions are not present. If the spectrum of a compound has no absorptions at 3300 and 2150 cm-1, the compound is not a terminal alkyne if the spectrum has no absorption near 3400 cm -, the compound Is not an alcohol and so on. 

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. 

The principal saturated hydrocarbon functional groups of concern are methyl, methylene and methyne (—CH3, —CH2—, = CH—). The spectra of typical hydrocarbon mixtures (for example as in gas oil and gasoline) are dominated by two pairs of strong bands in the first overtone and combination regions (5900-5500 cm-1 and 4350-4250 cm-1). These are predominantly methylene (—CH2—). The methyl end groups typically show up as a weaker higher-frequency shoulder to these methylene doublets. 

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. 

Pinto, A. Near-infrared spectroscopy of hydrocarbon functional groups. Spectrochim. Acta 28A, 585-597 (1972). 

Reactions of Hydrocarbons. Several types of reactive hydrocarbon functional groups can be used to polymerize and cross-Unk monomers and ohgomers into thermoset plastics. These include addition polymerization of acetylene-terminated molecules and ring-opening polymerization of strained carbon rings. They also include Friedel-Crafts condensation to form hydrocarbon polymers. 

R stands for any hydrocarbon functional groups. The reason we include is to... 

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. 

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). 

Tosi, C. and A. Pinto, Near-Infrared Spectroscopy of Hydrocarbon Functional Groups. Spectrochim. 

Now let us examine the aromatic hydrocarbons (Figure 14.20). Again, the benzene ring is the structural feature that identifyies a hydrocarbon as aromatic (i.e., it is the aromatic hydrocarbon functional group). The benzene... 

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