Alkenes, Alkynes, and Aromatic Compounds

Hydrocarbons Representative Alkanes, Alkenes, Alkynes, and Aromatic Compounds... 

Alkanes, alkenes, alkynes, and aromatic compounds are members of a family of organic compounds called hydrocarbons, compounds of carbon and hydrogen. These hydrocarbons are the simplest of organic compounds, but are extremely important to our society as fuels and raw materials for chemical industries. We... 

Why did he think this was so One answer is that alkanes are available as raw material for the chemical industry, and new reactions by which they can be converted into functionally substituted organic compounds are likely to be of considerable interest to the industrial chemist. A second answer is that the nature of any interaction between an alkane and a transition metal must be quite different from that of other hydrocarbons (i.e., alkenes, alkynes, and aromatic compounds) having 7r-electrons that can play a dominant role. 

Why are alkenes, alkynes, and aromatic compounds said to be unsaturated ... 

The cyclopropanation of alkenes, alkynes, and aromatic compounds by carbenoids generated in the metal-catalyzed decomposition of diazo ketones has found widespread use as a method for carbon-carbon bond construction for many years, and intramolecular applications of these reactions have provided a useful cyclization strategy. Historically, copper metal, cuprous chloride, cupric sulfate, and other copper salts were used most commonly as catalysts for such reactions however, the superior catalytic activity of rhodium(ll) acetate dimer has recently become well-established.3 This commercially available rhodium salt exhibits high catalytic activity for the decomposition of diazo ketones even at very low catalyst substrate ratios (< 1%) and is less capricious than the old copper catalysts. We recommend the use of rhodium(ll) acetate dimer in preference to copper catalysts in all diazo ketone decomposition reactions. The present synthesis describes a typical cyclization procedure. 

As noted above, hydrocarbon compounds contain only carbon and hydrogen. The major types of hydrocarbons are alkanes, alkenes, alkynes, and aromatic compounds. Examples of each are shown in Figure 1.9. 

All functional groups do not have polar bonds, e.g. alkenes, alkynes, and aromatic compounds have covalent multiple bonds and since space between the multiple bonded carbons is rich in electrons and is therefore nucleophilic. Thus, the nucleophilic centre in these molecules is not a specific atom, but the multiple bond ... 

Dinitro-6-phenyliodonium phenolate (146) is a stable iodonium zwitterion484. It reacts under photolytic conditions with various alkenes, alkynes and aromatic compounds to afford 2,3-dihydrobenzo[ ]furans, benzo[6]furans and 6-aryl-2,4-dinitrophenols. The mechanism involves hypervalent iodine compounds (iodinanes, 147) and is illustrated for the reaction with an aromatic compound (equation 127). Compounds 148 are the major products when ArH = PhH, PhOCH3 or 1,4-dimethoxybenzene. With furan and thiophene, 149 is the principal product. The reaction does not proceed with chlorobenzene and nitrobenzene. 

There are extensive relative rate measurements at temperatures close to ambient for hydrogen transfer reactions of methyl radicals. Their data have been compiled and evaluated by Kerr and Parsonage [49]. The same authors have also evaluated the data on addition reactions of atoms and radicals with alkenes, alkynes and aromatic compounds [69]. 

The physical properties of alkenes, alkynes, and aromatic compounds are very similar to those of alkanes. They are nonpolar. As a result of the "like dissolves like" rule, they are not soluble in water but are very soluble in nonpolar solvents such as other hydrocarbons. They also have relatively low boiling points and melting points. 

HYDROCARBONS REPRESENTATIVE ALKANES, ALKENES, ALKYNES, AND AROMATIC COMPOUNDS... 

Hydrocarbons are compounds composed entirely of carbon and hydrogen atoms bonded to each other by covalent bonds. These molecules are further classified as saturated or unsaturated. Saturated hydrocarbons have only single bonds between carbon atoms. These hydrocarbons are classified as alkanes. Unsaturated hydrocarbons contain a double or triple bond between two carbon atoms and include alkenes, alkynes, and aromatic compounds. These classifications are summarized in Figure 19.3. 

Since Theodor Curtius reported the synthesis of ethyl diazoacetate in 1883, Buchner had investigated its reactions with carbonyl compounds, alkenes, alkynes, and aromatic compounds for more than 30 years.His extensive contributions in this area resulted in two reactions named in his honor the Buchner-Curtius-Schlotterbeck reaction (formation of ketones from aldehydes and aliphatic diazo compounds) and the Buchner reaction. The prototypical example of the latter involves the thermal or photochemical reaction of ethyl diazoacetate with benzene to give (via norcaradiene 7) a mixture of four isomeric cycloheptatrienes 8-11. Initially, Buchner believed that a single norcaradiene product 7 was generated from this reaction, but later, he realized that the hydrolysis of the product afforded a mixture of four isomeric carboxylix acids. The norcaradiene formulation persisted until 1956 when Doering reinvestigated this reaction. ... 

Chapter 5 treats extension of the method to alkenes, alkynes and aromatic compounds by generalizing the force constant matrix. The relationship between bond orders and molecular geometry in conjugated systems is discussed along with VESCF inclusion in MM4. The valence bond description of molecular structure is discussed with special regard to MM4 results for phenanthrene, corranulene, and the C 60 fullerenes along with a general review of aromaticity and electronic spectra. 

Benson S.W., O Neal H.E., "Kinetic Data on Gas Phase Minimolecular Reactions" NSRDS-Nat.Bur.of Standards 21, Washington, 1970 Kerr J.A., Parsonage M.J., "Evaluated Kinetic Data on Gas Phase Hydrogen Transfer Reactions of Methyl Radicals" Butterworth, London, 1976 Kerr J.A., Parsonage M.J., "Reactions of Atoms and Radicals with Alkenes, Alkynes and Aromatic Compounds" Butterworth, London, 1972 (6) Kondratiev V.N., "Rate Constants of Gas Phase Reactions" NSRDS-Nat.Bur.of Standards, Washington, 1972... 

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