{"id":2323,"date":"2017-01-29T12:56:19","date_gmt":"2017-01-29T20:56:19","guid":{"rendered":"http:\/\/www.wou.edu\/chemistry\/?page_id=2323"},"modified":"2017-04-17T11:26:08","modified_gmt":"2017-04-17T18:26:08","slug":"ch105-chapter-7","status":"publish","type":"page","link":"https:\/\/wou.edu\/chemistry\/courses\/online-chemistry-textbooks\/ch105-consumer-chemistry\/ch105-chapter-7\/","title":{"rendered":"CH105: Chapter 7 – Alkanes and Halogenated Hydrocarbons"},"content":{"rendered":"

Chapter 7: Alkanes and Halogenated Hydrocarbons<\/strong><\/span><\/h2>\n

This text is published under creative commons licensing, for referencing and adaptation, please click<\/span> here. <\/em><\/strong><\/a><\/span><\/p>\n

Opening Essay<\/strong><\/span><\/a><\/h4>\n

7.1<\/span> Recognition of Organic Structures<\/span><\/strong><\/a><\/h3>\n

7.2<\/span> Introduction to Alkanes<\/span><\/strong><\/a><\/h3>\n

Straight Chain Alkanes<\/strong><\/span><\/a><\/h4>\n

Branched Chain Alkanes<\/strong><\/span><\/a><\/h4>\n

Cycloalkanes<\/strong><\/span><\/a><\/h4>\n

Classification of Carbon Bonds<\/strong><\/span><\/a><\/h4>\n

7.3 <\/span>Properties of\u00a0Alkanes<\/strong><\/span><\/a><\/h3>\n

Melting Points and Boiling Points<\/strong><\/span><\/a><\/h4>\n

Solubility<\/span><\/strong><\/a><\/h4>\n

Alkane Properties and Environmental Hazards: A Closer Look<\/span><\/strong><\/a><\/h4>\n

7.4 Chemical Reactivity of Alkanes<\/span><\/strong><\/a><\/h3>\n

Combustion Reactions<\/strong><\/span><\/a><\/h4>\n

Halogenation Reactions (Substitution Type)<\/strong><\/span><\/a><\/h4>\n

Cracking Alkanes<\/strong><\/span><\/a><\/h4>\n

7.5 Chapter Summary<\/strong><\/span><\/a><\/h3>\n

7.6 End-of-Chapter Exercises<\/strong><\/span><\/a><\/h3>\n

7.7 References<\/strong><\/span><\/a><\/h3>\n

 <\/p>\n

\n
\n

Opening Essay<\/span><\/strong><\/h4>\n

Hydrocarbons are the simplest organic compounds, but they have interesting physiological effects. These effects depend on the size of the hydrocarbon molecules and where on or in the body they are applied. Alkanes of low molar mass\u2014those with from 1 to approximately 10 or so carbon atoms\u2014are gases or light liquids that act as anesthetics. Inhaling (\u201csniffing\u201d) these hydrocarbons in gasoline or aerosol propellants for their intoxicating effect is a major health problem that can lead to liver, kidney, or brain damage or to immediate death by asphyxiation by excluding oxygen.\u00a0\u00a0Pressurized canisters of propane and butane gas, both of which are intended for use as fuels, are\u00a0abused as inhalants.<\/span><\/p>\n

\"\"<\/a><\/p>\n

Figure 7.1. A range of petroleum-based products that can be abused as inhalants<\/strong>. Photo By:<\/span> Lance Cpl. Matthew K. Hacker<\/a><\/p>\n

\n

Swallowed, liquid alkanes do little harm while in the stomach. In the lungs, however, they cause \u201cchemical\u201d pneumonia by dissolving fatlike molecules from cell membranes in the tiny air sacs (alveoli). The lungs become unable to expel fluids, just as in pneumonia caused by bacteria or viruses. People who swallow gasoline or other liquid alkane mixtures should not be made to vomit, as this would increase the chance of getting alkanes into the lungs. (There is no home-treatment antidote for gasoline poisoning; call a poison control center.)<\/span><\/p>\n

Liquid alkanes with approximately 5\u201316 carbon atoms per molecule wash away natural skin oils and cause drying and chapping of the skin, while heavier liquid alkanes (those with approximately 17 or more carbon atoms per molecule) act as emollients (skin softeners). Such alkane mixtures as mineral oil and petroleum jelly can be applied as a protective film. Water and aqueous solutions such as urine will not dissolve such a film, which explains why petroleum jelly protects a baby\u2019s tender skin from diaper rash.<\/span><\/p>\n<\/div>\n

In this chapter we will investigate\u00a0the alkanes, compounds containing only two elements, carbon and hydrogen, and having only single bonds. We will also investigate alkanes that have halogens incorporated into their structure.\u00a0\u00a0Recall that halogens\u00a0are the elements in Family 7A on the periodic table and contain representative elements such as chlorine, fluorine, iodine, and bromine. There are several other kinds of hydrocarbons, distinguished by the types of bonding between carbon atoms and by the properties that result from that bonding. In Chapter\u00a08 we will examine hydrocarbons with double bonds, with triple bonds, and with a special kind of bonding called aromaticity<\/em>. Then in Chapter\u00a09, we will study some compounds considered to be derived from hydrocarbons by replacing one or more hydrogen atoms with an oxygen-containing group. Chapter 10 focuses on organic acids and bases.<\/span><\/p>\n

(Back to the Top)<\/strong><\/em><\/span><\/a><\/h5>\n
\n
\n

7.1<\/span> Recognition of Organic Structures<\/strong><\/span><\/h3>\n
\n

Learning Objective<\/span><\/strong><\/h4>\n
    \n
  1. To be able to recognize the composition and properties typical of organic and inorganic compounds.<\/span><\/li>\n<\/ol>\n<\/div>\n

    Scientists of the 18th and early 19th centuries studied compounds obtained from plants and animals and labeled them organic<\/em> because they were isolated from \u201corganized\u201d (living) systems. Compounds isolated from nonliving systems, such as rocks and ores, the atmosphere, and the oceans, were labeled inorganic<\/em>. For many years, scientists thought organic compounds could be made by only living organisms because they possessed a vital force found only in living systems. The vital force theory began to decline in 1828, when the German chemist Friedrich W\u00f6hler synthesized urea from inorganic starting materials. He reacted silver cyanate (AgOCN) and ammonium chloride (NH4<\/span><\/sub>Cl), expecting to get ammonium cyanate (NH4<\/span><\/sub>OCN). What he expected is described by the following equation.<\/span><\/p>\n

    AgOCN + NH4<\/sub>Cl \u2192 AgCl + NH4<\/sub>OCN<\/span><\/span><\/p>\n

    Instead, he found the product to be urea (NH2<\/span><\/sub>CONH2<\/span><\/sub>), a well-known organic material readily isolated from urine. This result led to a series of experiments in which a wide variety of organic compounds were made from inorganic starting materials. The vital force theory gradually went away as chemists learned that they could make many organic compounds in the laboratory.<\/span><\/p>\n

    Today organic chemistry<\/strong><\/em> has been reclassified as<\/span> the study of compounds that contain carbon, and inorganic chemistry <\/span>is the study of the chemistry of all other elements. It may seem strange that we divide chemistry into two branches\u2014one that considers compounds of only one element and one that covers the 100-plus remaining elements. However, this division seems more reasonable when we consider that of tens of millions of compounds that have been characterized, the overwhelming majority are carbon compounds.<\/span><\/p>\n

    \n

    Note<\/strong><\/span><\/h4>\n

    The word organic<\/em> has different meanings. Organic fertilizer, such as cow manure, is organic in the original sense; it is derived from living organisms. Organic foods generally are foods grown without synthetic pesticides or fertilizers. Organic chemistry is the chemistry of compounds of carbon. <\/span>Carbon is unique among the other elements in that its atoms can form stable covalent bonds with each other and with atoms of other elements in a multitude of variations. The resulting molecules can contain from one to millions of carbon atoms. <\/span><\/p>\n<\/div>\n

    Organic compounds, like inorganic compounds, obey all the natural laws. Often there is no clear distinction in the chemical or physical properties among organic and inorganic molecules. Nevertheless, it is useful to compare typical members of each class, as in Table\u00a07.1 (Keep in mind, however, that there are exceptions to every category in this table.) To further illustrate typical differences among organic and inorganic compounds, Table\u00a07.1 also lists properties of the inorganic compound sodium chloride (common table salt, NaCl) and the organic compound hexane (C6<\/span><\/sub>H14<\/span><\/sub>), a solvent that is used to extract soybean oil from soybeans (among other uses). Many compounds can be classified as organic or inorganic by the presence or absence of certain typical properties, as illustrated in Table 7.1.<\/span><\/p>\n

    \n

    Table 7.1<\/span> General Contrasting Properties and Examples of Organic and Inorganic Compounds<\/span><\/strong><\/p>\n

    \"\"<\/a><\/p>\n

    Concept Review Exercises:\u00a0 Click to Complete the Questions<\/a><\/strong><\/span><\/strong><\/em><\/span><\/p>\n

    Key Takeaway<\/strong><\/em><\/span><\/h5>\n<\/div>\n
    \n