13: Unsaturated and Aromatic Hydrocarbons
- Page ID
- 15932
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Our modern society is based to a large degree on the chemicals we discuss in this chapter. Most are made from petroleum. Alkanes—saturated hydrocarbons—have relatively few important chemical properties other than that they undergo combustion and react with halogens. Unsaturated hydrocarbons—hydrocarbons with double or triple bonds—on the other hand, are quite reactive. In fact, they serve as building blocks for many familiar plastics—polyethylene, vinyl plastics, acrylics—and other important synthetic materials (e.g., alcohols, antifreeze, and detergents). Aromatic hydrocarbons have formulas that can be drawn as cyclic alkenes, making them appear unsaturated, but their structure and properties are generally quite different, so they are not considered to be alkenes. Aromatic compounds serve as the basis for many drugs, antiseptics, explosives, solvents, and plastics (e.g., polyesters and polystyrene). The two simplest unsaturated compounds—ethylene (ethene) and acetylene (ethyne)—were once used as anesthetics and were introduced to the medical field in 1924. However, it was discovered that acetylene forms explosive mixtures with air, so its medical use was abandoned in 1925. Ethylene was thought to be safer, but it too was implicated in numerous lethal fires and explosions during anesthesia. Even so, it remained an important anesthetic into the 1960s, when it was replaced by nonflammable anesthetics such as halothane (\(\mathrm{CHBrClCF_3}\)).
- 13.0: Prelude to Unsaturated and Aromatic Hydrocarbons
- This page discusses the significant role of petroleum-derived chemicals in modern society. It highlights the reactivities of various hydrocarbons: alkanes undergo combustion, while unsaturated hydrocarbons are crucial for plastics. Aromatic hydrocarbons are foundational for drugs and solvents. It also notes the transition away from ethylene and acetylene anesthetics due to safety concerns, leading to the adoption of safer alternatives by the 1960s.
- 13.1: Alkenes- Structures and Names
- This page covers alkenes, unsaturated hydrocarbons with carbon-to-carbon double bonds. It explains IUPAC naming conventions, emphasizing the longest carbon chain and the lowest numbering for double bonds. Notable alkenes such as ethene and propene are discussed, along with their industrial importance. Additionally, cycloalkenes are introduced, and examples are provided for naming and structure representation of various alkenes.
- 13.2: Cis-Trans Isomers (Geometric Isomers)
- This page explains cis-trans isomerism in alkenes, which arises from restricted rotation around carbon-carbon double bonds and depends on the positions of substituents. It covers how to identify and classify these isomers, providing examples like 1,2-dichloroethene and 2-butene, while noting that not all alkenes exhibit this property.
- 13.3: Physical Properties of Alkenes
- This page discusses the physical properties of alkenes, including their boiling points, solubility, and role in nature. It highlights ethylene's significance in fruit ripening and notes that artificial ripening can alter taste.
- 13.4: Chemical Properties of Alkenes
- This page discusses the significance of alkenes in addition reactions, highlighting how their double bonds facilitate the attachment of new atoms or groups. Key reactions include hydrogenation, halogenation, and hydration, leading to products like alkanes and alcohols while preserving the alkene's carbon skeleton. Mastering the equations for these reactions is crucial for a deeper understanding of alkene chemistry.
- 13.5: Polymers
- This page discusses addition polymerization, detailing how monomers like ethylene transform into polymers through carbon-to-carbon double bond reactions. It highlights the production of polyethylene for plastic bags and various addition polymers, showcasing their applications in everyday products and significant uses in healthcare, including medical devices like artificial joints and heart valves.
- 13.6: Alkynes
- This page discusses alkynes, hydrocarbons featuring carbon-to-carbon triple bonds, with acetylene (C2H2) as the simplest form. Acetylene is mainly used in welding and as a precursor for chemical intermediates in plastics and fibers. It shares properties and naming conventions with alkenes, following the IUPAC system where alkynes usually end in "-yne."
- 13.7: Aromatic Compounds- Benzene
- This page discusses benzene, a key aromatic hydrocarbon (C6H6) known for its unique bonding that prevents it from undergoing typical addition reactions. Despite having a high degree of unsaturation, it remains relatively unreactive. Benzene is vital in manufacturing plastics and chemicals, yet carries health risks such as leukemia and aplastic anemia due to its toxicity. The compound's stability and distinct properties arise from its structure, characterized by delocalized electrons.
- 13.8: Structure and Nomenclature of Aromatic Compounds
- This page covers the identification, naming, and formula writing of aromatic compounds, particularly those with benzene rings. It includes historical insights on their definition by scent, representative compounds, IUPAC naming conventions, and features of disubstituted benzenes. The text introduces polycyclic aromatic hydrocarbons (PAHs) and their cancer risks while also highlighting the importance of benzene-containing compounds in nutrition and medicine.
- 13.E: Unsaturated and Aromatic Hydrocarbons (Exercises)
- This page provides a comprehensive overview of alkenes, alkynes, and aromatic compounds, highlighting their properties, structures, and naming conventions. It differentiates between saturated and unsaturated hydrocarbons and discusses cis-trans isomers, reactivity, polymerization, and benzene bonding.
- 13.S: Unsaturated and Aromatic Hydrocarbons (Summary)
- This page discusses unsaturated hydrocarbons, focusing on alkenes and alkynes, characterized by double and triple bonds, respectively. Alkenes, represented by the formula CnH2n, can exhibit cis-trans isomerism due to varied arrangements around double bonds. Alkynes, with the formula CnH2n−2, are similarly reactive and use the suffix -yne.