Chemical Reactions of Hydrocarbons

An alkyl halide is an alkane in which a halogen atom has been substituted for a hydrogen atom viewed in another way, an alkyl halide is an alkyl group bonded to a halogen. The molecule is attacked with base in the presence of an alcohol  

Acetylene is the only alkyne produced commercially in large quantities. It is manufactured in a two-step process in which calcium oxide reacts with coke (carbon) at high temperatures to produce calcium carbide and carbon monoxide  

Calcium carbide then reacts with water to produce acetylene  

13 Given the reactants in an addition or substitution reaction between (a) an alkane, alkene, alkyne, or benzene and (b) a hydrogen or halogen molecule, predict the products of the reaction. 

The combustibility—ability to burn in air—of the hydrocarbons is probably the chemical reaction most important to modern society (Fig. 21.14). As components of liquid 

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The basic equation for the chemical reaction of hydrocarbon molecules in ideal combustion is provided by the following ... 

Ozone is produced as a result of chemical reactions of hydrocarbons and nitrogen oxides in the air in the presence of sunlight. It is a pungent-smelling, faintly bluish gas. Ozone can irritate the respiratory system and impair lung function. Other oxidants that accompany ozone are strong eye irritants. 

The important hydrocarbon classes are alkanes, alkenes, aromatics, and oxygenates. The first three classes are generally released to the atmosphere, whereas the fourth class, the oxygenates, is generally formed in the atmosphere. Propene will be used to illustrate the types of reactions that take place with alkenes. Propene reactions are initiated by a chemical reaction of OH or O3 with the carbon-carbon double bond. The chemical steps that follow result in the formation of free radicals of several different types which can undergo reaction with O2, NO, SO2, and NO2 to promote the formation of photochemical smog products. 

The saturated hydrocarbons are relatively inert except at high temperatures. For example, sodium metal is usually stored immersed in an alkane such as kerosene (8 to 14 carbon atoms) to protect it from reaction with water or oxygen. Combustion is almost the only important chemical reaction of the alkanes. That reaction, however, makes the hydrocarbons one of the most important energy sources of our modern technology. 

Square brackets around a molecular species indicate atmospheric concentration. The rate constants k times the reactant concentration product refers to the rates of the chemical reactions of the indicated number. The photolytic flux term /l4 refers to the photodissociation rate of N02 in Reaction R14, its value is proportional to solar intensity.]. RO2 stands for an organic peroxyl radical (R is an organic group) that is capable of oxidizing NO to NO2. Hydrocarbons oxidize to form a very large number of different RO2 species the simplest of the family is methylperoxyl radical involved in R5, R6 and R8. 

This overview is organized into several major sections. The first is a description of the cluster source, reactor, and the general mechanisms used to describe the reaction kinetics that will be studied. The next two sections describe the relatively simple reactions of hydrogen, nitrogen, methane, carbon monoxide, and oxygen reactions with a variety of metal clusters, followed by the more complicated dehydrogenation reactions of hydrocarbons with platinum clusters. The last section develops a model to rationalize the observed chemical behavior and describes several predictions that can be made from the model. 

The term prompt NO derives from the fact that the nitrogen in air can form small quantities of CN compounds in the flame zone. In contrast, thermal NO forms in the high-temperature post-flame zone. These CN compounds subsequently react to form NO. The stable compound HCN has been found in the flame zone and is a product in very fuel-rich flames. Chemical models of hydrocarbon reaction processes reveal that, early in the reaction, O atom concentrations can reach superequilibrium proportions and, indeed, if temperatures are high enough, these high concentrations could lead to early formation of NO by the same mechanisms that describe thermal NO formation. 

Reaction stoichiometry and mechanism. This process, which selectively produces linear alcohols ranging fhom to about C ,is based on the chemical reactions of Table IT. Main reactions (fa,b) produce alcohols and their related unavoidable by-products, CO and H O, the former being favored at low H /CO ratios due to side or consecutive shift reaction (c). Secondary reactions produce light hydrocarbons (d,e). The reactions stoichiometry (H /CO) varies between 0.6 and 3, depending on the nature of the products and the number of carbon atoms involved. Most of these reactions are strongly exothermic. 

Chemicals can be labeled as either a primary air pollutant or secondary air pollutant. Primary air pollutants are those such as carbon monoxide and sulfur dioxide that enter the atmosphere directly as a result of human or natural events. Carbon monoxide s primary source in the atmosphere is the incomplete combustion of gasoline. Hundreds of different chemicals are present in gasoline. The combustion of octane, C Hj, can be used to represent the general reaction of hydrocarbons in an automobile engine to produce energy ... 

To obtain the first clue to the reaction mechanism, two hydrocarbons may be considered (1) 1-hexadecene (cetene), representing group I, and (2) isopropylbenzene (cumene), representing group II. What common property of the catalyst will explain the cracking patterns of both, in conformity with what is known of the chemical reactions of carbon compounds ... 

For reviews of double-bond migrations, see Pines Stalick Base-Catalyzed Reactions of Hydrocarbons and Related Compounds Academic Press New York. 1977, pp, 25-123 DeWolfe, in Bamford Tipper Comprehensive Chemical Kinetics, vol. 9 Elsevier, New York, 1973, pp. 437-449 Yanovskaya Shakhidayatov Russ. Chem. Rev. 1970,39, 859-874 Hubert Reimlinger Synthesis 1969, 97-112,1970, 405-430 Mackenzie, in The Chemistry of Alkenes. vol. 1, Patai, Ed., pp. 416-436, vol. 2, Zabicky, Ed., pp. 132-148 Wiley New York, 1964, 1970 Broaddus, Acc. Chem. Res. 1968, I, 231-238 Cram, Ref. 25, pp. 175-210. 

Initially, we will be concerned with the physical properties of alkanes and how these properties can be correlated by the important concept of homology. This will be followed by a brief survey of the occurrence and uses of hydrocarbons, with special reference to the petroleum industry. Chemical reactions of alkanes then will be discussed, with special emphasis on combustion and substitution reactions. These reactions are employed to illustrate how we can predict and use energy changes — particularly AH, the heat evolved or absorbed by a reacting system, which often can be estimated from bond energies. Then we consider some of the problems involved in predicting reaction rates in the context of a specific reaction, the chlorination of methane. The example is complex, but it has the virtue that we are able to break the overall reaction into quite simple steps. 

R. L. Burwell, Jr., "Deuterium as a Tracer in Reactions of Hydrocarbons on Metallic Catalysts, Accounts of Chemical Research 2, 289 (1969). 

The chemical properties of hydrocarbons can be understood in terms of the mechanisms of their reactions, the details of the steps that turn one compound into another. Once the mechanism of a reaction is known, we may be able to use the knowledge to create new substances in a rational way, rather than just by trial and error. 

Selective oxidation of small abundant hydrocarbons is the most important type of reaction in organic chemicals production. For example, essentially all building blocks for the manufacture of plastics and synthetic fibers are produced by oxidation of hydrocarbons [129], Among these, oxidations by molecular oxygen play a particularly important role [130,131], A key problem is the product specificity in the reactions of hydrocarbon with 02 here, photoassisted processes hold special promise. Photoinitiated reactions of 02 furnish access to products that in many cases cannot be obtained by a dark reaction of 02. Moreover, photochemical reactions can be conducted at or around ambient temperature, thus minimizing the chance for loss of product specificity due to secondary thermal chemistry of the initial products. 

Kopinke, F.-D., Georgi, A., Mackenzie, K., and Kumke, M. U. (2000). Sorption and chemical reactions of polycyclic aromatic hydrocarbons with dissolved refractory organic subtances and related model compounds. In Refractory Organic Substances (ROS) in the Environment, Frimmel, F. H., Abbt-Braun, G., Heumann, K. G., Hock, B., Ludemann, H.-D., and Spiteller, M., eds., Wiley-VCH, Weinheim, pp. 475-515. 

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