CHAPTER TWO Alkanes to the study of materials from natural sources, and terms were coined that reflected a sub- stance's origin. Two sources were fats and oils, and the word aliphatic was derived from the greek word aleiphar (fat). Aromatic hydrocarbons, irrespective of their own odor, were typically obtained by chemical treatment of pleasant-smelling plant extracts Aliphatic hydrocarbons include three major groups: alkanes, alkenes, and alkynes Alkanes are hydrocarbons in which all the bonds are single bonds, alkenes contain a carbon-carbon double bond, and alkynes contain a carbon-carbon triple bond. Exam ples of the three classes of aliphatic hydrocarbons are the two-carbon compounds ethane, ethylene, and acetylene. Bonding in ethane, ethylene, H d acetylene was discussed in Sections 1. 16-1.18 Ethane Ethy lene Acetylene (alkane) (alkene) Another name for aromatic hydrocarbons is arenes. Arenes have properties that are much different from alkanes, alkenes, and alkynes. The most important aromatic hydrocarbon nzene Bonding in benzene will discussed in Section 11.5 Benzene Many of the principles of organic chemistry can be developed by examining the series of hydrocarbons in the order: alkanes, alkenes, alkynes, and arenes. Alkanes are introduced in this chapter, alkenes in Chapters 5 and 6, alkynes in Chapter 9, and arenes in Chapters ll and 12. 2.2 REACTIVE SITES IN HYDROCARBONS A functional group is the structural unit responsible for a given molecule's reactivity under a particular set of conditions. It can be as small as a single hydrogen atom, or it can encompass several atoms. The functional group of an alkane is any one of its hydro- gen substituents. A reaction that we shall discuss in Chapter 4 is one in which an alkane reacts with chlorine. For example CH3CH3 CI CH3,CI+ hlorine Chloroethane Hydrogen chloride One of the hydrogen atoms of ethane is replaced by chlorine. This replacement of hydro- gen by chlorine is a characteristic reaction of all alkanes and can be represented for the R一H+ Alkyl chloride Hydrogen chloride Back Forward Main MenuToc Study Guide ToC Student o MHHE Websiteto the study of materials from natural sources, and terms were coined that reflected a sub￾stance’s origin. Two sources were fats and oils, and the word aliphatic was derived from the Greek word aleiphar (“fat”). Aromatic hydrocarbons, irrespective of their own odor, were typically obtained by chemical treatment of pleasant-smelling plant extracts. Aliphatic hydrocarbons include three major groups: alkanes, alkenes, and alkynes. Alkanes are hydrocarbons in which all the bonds are single bonds, alkenes contain a carbon–carbon double bond, and alkynes contain a carbon–carbon triple bond. Exam￾ples of the three classes of aliphatic hydrocarbons are the two-carbon compounds ethane, ethylene, and acetylene. Another name for aromatic hydrocarbons is arenes. Arenes have properties that are much different from alkanes, alkenes, and alkynes. The most important aromatic hydrocarbon is benzene. Many of the principles of organic chemistry can be developed by examining the series of hydrocarbons in the order: alkanes, alkenes, alkynes, and arenes. Alkanes are introduced in this chapter, alkenes in Chapters 5 and 6, alkynes in Chapter 9, and arenes in Chapters 11 and 12. 2.2 REACTIVE SITES IN HYDROCARBONS A functional group is the structural unit responsible for a given molecule’s reactivity under a particular set of conditions. It can be as small as a single hydrogen atom, or it can encompass several atoms. The functional group of an alkane is any one of its hydro￾gen substituents. A reaction that we shall discuss in Chapter 4 is one in which an alkane reacts with chlorine. For example: One of the hydrogen atoms of ethane is replaced by chlorine. This replacement of hydro￾gen by chlorine is a characteristic reaction of all alkanes and can be represented for the general case by the equation: R±H Alkane Cl2 Chlorine R±Cl Alkyl chloride HCl Hydrogen chloride CH3CH3 Ethane Cl2 Chlorine CH3CH2Cl Chloroethane HCl Hydrogen chloride C C C C C C H H H H H H Benzene (arene) Ethane (alkane) H C H H C H H H Ethylene (alkene) H H H H C C Acetylene (alkyne) H C C H 54 CHAPTER TWO Alkanes Bonding in ethane, ethylene, and acetylene was discussed in Sections 1.16–1.18. Bonding in benzene will be discussed in Section 11.5. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website