1 Figure 4.3 Examples of cycloalkane nomenclature Nomenclature

2 Introduction to Cycloalkanes Figure 4.11 Three-dimensional structure of some cycloalkanes

Chapter 83 Addition of HX (1) Protonation of double bond yields the most stable carbocation. Positive charge goes to the carbon that was not protonated. X =>

Chapter 84 Addition of HX (2) =>

Chapter 85 Mechanism for Hydration =>

Chapter 86 Orientation for Hydration Markovnikov product is formed. =>

Chapter 87 Mechanism for Halogenation Pi electrons attack the bromine molecule. A bromide ion splits off. Intermediate is a cyclic bromonium ion. =>

Chapter 88 Mechanism (2) Halide ion approaches from side opposite the three-membered ring. =>

Chapter 89 Predict the Product Predict the product when the given alkene reacts with chlorine in water. =>

Chapter 810 Mechanism One-step concerted reaction. Several bonds break and form simultaneously. =>

Chapter 811 One-Step Reaction To synthesize the glycol without isolating the epoxide, use aqueous peroxyacetic acid or peroxyformic acid. The reaction is stereospecific. =>

Chapter 812 Ozonolysis Example Ozonide DMSO =>

13 Compounds with two hydroxy groups are called diols or glycols. Compounds with three hydroxy groups are called triols. Diols and Triols

14 Epoxides can be named in three different ways— epoxyalkanes, oxiranes, or alkene oxides. To name an epoxide as an epoxyalkane, first name the alkane chain or ring to which the O atom is attached, and use the prefix “epoxy” to name the epoxide as a substituent. Use two numbers to designate the location of the atoms to which the O is bonded. Naming Epoxides

15 Alcohols and ethers are both common products of nucleophilic substitution. The preparation of ethers by the method shown in the last two equations is called the Williamson ether synthesis. Preparation of Alcohols and Ethers

16 An alkoxide salt is needed to make an ether. Alkoxides can be prepared from alcohols by a Brønsted-Lowry acid-base reaction. For example, sodium ethoxide (NaOCH 2 CH 3 ) is prepared by treating ethanol with NaH. NaH is an especially good base for forming alkoxide because the by-product of the reaction, H 2, is a gas that just bubbles out of the reaction mixture. Preparation of Alkoxides

17 Substitution and Elimination Reactions of Alcohols Treatment of alcohols with a strong acid protonates the O converting the bad leaving group ¯OH into H 2 O, a good leaving group. This makes it possible to perform substitution and elimination reactions on alcohols.

18 Typical acids used for alcohol dehydration are H 2 SO 4 or p-toluenesulfonic acid (TsOH). Dehydration Requires Strong Acids Dehydration is typically carried out using H 2 SO 4 and other strong acids, or phosphorus oxychloride (POCl 3 ) in the presence of an amine base.

19 When an alcohol has two or three  carbons, dehydration is regioselective and follows the Zaitsev rule. The more substituted alkene is the major product when a mixture of constitutional isomers is possible. Zaitsev’s Rule

20 2 ° and 3 ° alcohols react by an E1 mechanism, whereas 1 ° alcohols react by an E2 mechanism. Dehydration by E1 Mechanism

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23 Knowing the mechanism allows us to predict the stereochemistry of the products when the reaction occurs at a stereogenic center. Stereochemistry of Reaction of Alcohols with HX

24 When a 1° or 2° alcohol is treated with SOCl 2 and pyridine, an alkyl chloride is formed, with HCl and SO 2 as by-products. The mechanism of this reaction consists of two parts: 1.Conversion of the OH group into a better leaving group. 2.Nucleophilic substitution by Cl¯ via an S N 2 reaction. Conversion of Alcohols to Alkyl Chlorides with SOCl 2

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26 Because alkyl tosylates have good leaving groups, they undergo both nucleophilic substitution and  elimination, exactly as alkyl halides do. Generally, alkyl tosylates are treated with strong nucleophiles and bases, so the mechanism of substitution is S N 2, and the mechanism of elimination is E2. Substitution and Elimination of Tosylates

27 Figure 9.9 Opening an Epoxide Ring with HCl

28 Figure 9.10 Synthesis Using Opening of an Epoxide Ring

29 When polyaromatic hydrocarbons are inhaled or ingested, they are oxidized in the liver to species that often contain a highly reactive epoxide ring. The strained three-membered ring reacts readily with biological nucleophiles such as DNA or enzymes, leading to ring-opened products that often disrupt cell function, causing cancer or cell death. Health Effects of Epoxides