Hydrocarbons Organic compounds that aromatic

Thus, transition metal cations in the lower valence state may also act as Lewis bases. Factors that affect the reactions promoted by Lewis acidity are listed in Table I. Lewis acid sites reversibly adsorb water (6s 9, 42), which may thus strongly compete with organic compounds that have weaker Lewis base properties, such as aromatic hydrocarbons. Lewis acidity depends on the degree of hydration and is strongest under desiccating conditions. Examples of reactions that are promoted by Lewis acidity are summarized in Table II. Other examples have been reviewed by Solomon and Howthorne (37). 

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. 

Ionic liquids display good solubility for some organic compounds, typically aromatics, but poor solubility for many saturated hydrocarbons, and solubilities of gases also depend on their properties. It has therefore been possible to run chemical reactions with reactants that are more soluble in the ionic liquids than products. 

The coupling of two mass spectrometer systems has received attention in recent years. This system can be operated in an atmospheric pressure mode by passing the air matrix directly into the ionization source (II). This method minimizes sample contamination and degradation problems. Detection limits are compound-dependent and can vary over more than an order of magnitude for different families of hydrocarbons. For example, an aromatic hydrocarbon such as toluene cannot be detected at levels below 5 ppbv, whereas most aldehydes are detectable at levels as low as 50 pptrv. The tandem MS-MS system has the potential to be a useful detection system for organic compounds that do not store well in collection containers. 

Other organic compounds that have been determined in waste waters include petroleum hydrocarbons, carboxylic acids, aliphatic and aromatic chlorocompounds and phenoxyacetic acid herbicides. See Table 15.14. 

Nearly all the organic compounds that we have studied so far are bases, although very weak ones. Much of the chemistry of alcohols, ethers, esters, and even of alkenes and aromatic hydrocarbons is understandable in terms of the basicity of these compounds. 

Organic compounds that contain benzene rings as part of their structure are called aromatic compounds. The term aromatic was originally used because many of the benzene-related compounds known in the nineteenth century were found in pleasant-smelling oils that came from spices, fruits, and other plant parts. Hydrocarbons such as the alkanes, alkenes, and alkynes are called aliphatic compounds to distinguish them from aromatic compounds. The term aliphatic comes from the Greek word for fat, which is aleiphatos. Early chemists obtained aliphatic compounds by heating animal fats. 

Hydrocarbons are compounds that contain only carbon and hydrogen and are divided into two main classes aliphatic hydrocarbons and aromatic hydrocarbons. This classification dates from the nineteenth century, when organic chemistry was almost exclusively devoted... 

The alkane, alkene, alkyne, and aromatic families are members of a larger grouping referred to as hydrocarbons. Hydrocarbons are organic compounds that contain only carbon and hydrogen. The alkenes, alkynes, and aromatics are unsaturated hydrocarbons since they contain carbon-carbon multiple bonds. The alkanes are referred to as saturated hydrocarbons since they do not contain carbon-carbon multiple bonds, only carbon-carbon single bonds. 

So far all the aromatic compounds you have seen have been hydrocarbons. However, most aromatic systems are heterocyclic—that is, they contain atoms other than just carbon and hydrogen. (In fact the majority of all organic compounds are aromatic heterocycles ) A simple example is pyridine, in which a nitrogen replaces one of the CH groups of benzene. The ring still has three double bonds and thus six tc electrons. 

Aldehydes are organic compounds that have a carbonyl group (-CHO) on the terminal carbon atom of a hydrocarbon chain or attached to an aromatic or heterocyclic ring. The aliphatic aldehydes are useful as chemical intermediates in synthetic chemistry where oxidation produces the corresponding acid and reduction yields the alcohol structure. Condensation reactions of the aldehydes with phenol, urea, or melamine yields useful resinous products. A useful heterocyclic aldehyde, furfural or 2-furaldehyde (the aldehyde group attached to the 2 position on the furan ring), is both a reactant in synthetic chemistry and has several specialized uses as a solvent. 

Structure of Aromatic Hydrocarbons. The term hydrocarbon refers to an organic compound that contains oniy carbon and hydrogen. Aromatics are hydrocarbons characterized by the presence of at least one benzene ring. Aromatics have a graphite-like structure and graphite is often considered as the parent of all these compounds. The structure of benzene is shown below ... 

Aromatic Hydrocarbons A group of organic compounds that contain a benzene ring in their molecules or that have chemical properties similar to benzene. 

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