Alkanes—An Introduction

Minute amounts elicit an activity such as mating, aggregation, or defense. Because pheromones are biodegradable and highly specific, they can be used in some cases to control insect populations (Section 20.10). 

Recall from Section 3.2 that alkanes are aliphatic hydrocarbons having only C - C and C - H 

Structures for the two simplest acyclic alkanes were given in Chapter 1. Methane, CH4, has a single carbon atom, and ethane, CH3CH3, has two. All C atoms in an alkane are surrounded by four groups, making them sp hybridized and tetrahedral, and all bond angles are 109.5°. 

The three-carbon alkane CH3CH2CH3, called propane, has molecular formula C3H8. Each carbon in the three-dimensional drawing has two bonds in the plane (solid lines), one bond in front (on a wedge), and one bond behind the plane (on a dashed line). 

To draw the structure of an alkane, join the carbon atoms together with single bonds, and add enough H atoms to make each C tetravalent. 

Recall from Section 3.2 that alkanes are aliphatic hydrocarbons having only C-C and C-Hct bonds. Because their carbon atoms can be joined together in chains or rings, they can be categorized as acyclic or cyclic. 

Cyclohexane is one component of the mango, the most widely consumed fmit in the world. 

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Sources and Uses of Alkanes An Introduction to Polymers (section 4.5)... 

Alkanes Nomenclature, Conformational Analysis, and an Introduction to synthesis... 

Abstract An overview of the gas-phase reactions responsible for the photooxidation of air pollutants is provided. Starting with an introduction to the field of atmospheric chemistry we proceed to discuss the concept, and utility, of atmospheric lifetime. The processes responsible for the degradation of alkanes, alkenes, aromatics, NO, SO, CFCs and their replacements are discussed in turn. Areas of uncertainty are highlighted. Finally, the research needs are discussed. 

The combustion of alkanes, the concentration of atmospheric carbon dioxide, and global warming (Section 4.14B) An introduction to lipids, biomolecules whose properties can be explained by understanding alkane chemistry cholesterol in the cell membrane (Section 4.15)... 

Oxidatirai constitutes one of the key steps for the introduction of functional groups into the raw materials of organic synthesis which are almost invariably an alkane, an alkene, or an aromatic molecule.Traditional methodology is plagued by several drawbacks, that is... 

Chapter 6, Ionic and Molecular Compounds, describes how atoms form ionic and covalent bonds. Chemical formulas are written, and ionic compounds— including those with polyatomic ions—and molecular compounds are named. An introduction to the three-dimensional shape of carbon molecules provides a basis for the shape of organic and biochemical compounds. Organic chemistry is introduced with the properties of inorganic and organic compounds and condensed structural formulas of alkanes. Section 6.1 is now tilled Ions Transfer of Electrons, 6.2 is titled Writing Formulas for Ionic Compounds, 6.3 is... 

Alcohol (Chapter 17 introduction) A compound with an -OH group bonded to a saturated, alkane-like carbon, ROH. 

The Lead-Off Reaction Addition of HBr to Alkenes Students usually attach great-importance to a text s lead-off reaction because it is the first reaction they see and is discussed in such detail. 1 use the addition of HBr to an alkene as the lead-off to illustrate general principles of organic chemistry for several reasons the reaction is relatively straightforward it involves a common but important functional group no prior knowledge of stereochemistry or kinetics in needed to understand it and, most important, it is a polar reaction. As such, 1 believe that electrophilic addition reactions represent a much more useful and realistic introduction to functional-group chemistry than a lead-off such as radical alkane chlorination. 

Radical addition of dibromodifluoromethane to alkenes followed by sodium borohydride reduction is a convenient two-step method for the introduction of the difluoromethyl group.5 Either one or both carbon-bromine bonds in the intermediate dibromides may be reduced, depending on the reaction conditions. In the case of acyclic dibromodifluoromethane-alkene adducts, the reduction occurs regioselectively to yield the relatively inaccessible bromodifluoromethyl-substituted alkanes. The latter are potential building blocks for other fluorinated compounds. For example, they may be dehydrohalogenated to 1,1-difluoroalkenes an example of this methodology is illustrated in this synthesis of (3,3-difluoroallyl)trimethylsilane. 

Free electron pairs are a good source for an electron which is to be ejected and therefore, the IE of ethanol and dimethylether is lower than that of ethane. It has been shown that the IE of a poly-substituted alkane is almost the same as the IE of the structurally identical mono-substituted alkane which has the lowest value. [27] The other substituent, provided it is separated by at least two carbon atoms, exerts a very small effect upon the IE, e.g., the IE of dimethylsulfide, CH3SCH3, 8.7 eV, is almost the same as that of methionine, CH3SCH2CH2CH(NH2)COOH. Introduction of an oxygen decreases the IE less than nitrogen, sulfur or even selenium do, since these elements have lower electronegativities and thus, are even better sources of an electron. 

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