Copyright 2010 Pearson Education, Inc. Chapter Fourteen 1

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1 An alcohol has an OH bonded to an alkyl group; a phenol has an OH bonded directly to an aromatic ring; and an ether has an O bonded to two organic groups. Chapter Fourteen 1

2 Ethyl alcohol, dimethyl ether, and propane have similar molecular weights, yet ethyl alcohol boils more than 100 higher than the other two. The high boiling points of ethyl alcohol and water are due to hydrogen bonding. Alkanes and ethers do not have hydroxyl groups and cannot form hydrogen bonds. As a result, they have lower boiling points. Ethers, in fact, resemble alkanes in many of their properties. Chapter Fourteen 2

3 14.2 Some Common Alcohols Simple alcohols are very common organic chemicals. They are useful as solvents, antifreeze agents, and disinfectants, and they are involved in the metabolic processes of all living organisms. Methyl alcohol is commonly known as wood alcohol because it was once prepared by heating wood in the absence of air. Today it is made in large quantities by reaction of carbon monoxide with hydrogen. Methanol is used to make formaldehyde and methyl tert-butyl ether (MTBE), an octane booster added to gasoline. Methyl alcohol is colorless, miscible with water, and toxic to humans when ingested. Chapter Fourteen 3

4 Ethyl alcohol produced by fermentation is called grain alcohol; with methyl alcohol, camphor, or kerosene added it is called denatured alcohol. Industrially, most ethanol is made by hydration of ethylene. Absolute alcohol is 100% ethyl alcohol. Gasohol is a blend of ethyl alcohol and gasoline. Isopropyl alcohol, or rubbing alcohol, is used for rubdowns, as a solvent, as a sterilant for instruments, and as a skin cleanser before drawing blood or giving injections. Less toxic than methyl alcohol, isopropyl alcohol is more toxic than ethyl alcohol. Chapter Fourteen 4

5 Ethylene glycol, a diol, is: a toxic, colorless liquid, miscible with water and insoluble in nonpolar solvents. Its two major uses are as antifreeze and as a material for making polyester. The triol, glycerol or glycerin, is: a nontoxic, colorless liquid that is miscible with water. Its used as a sweetener, a moisturizer, in plastics manufacture, in antifreeze and shock-absorber fluids, and as a solvent. Chapter Fourteen 5

6 14.3 Naming Alcohols Common names of many alcohols identify the alkyl group and then add the word alcohol. In the IUPAC system: STEP 1: Name the parent compound. Find the longest chain that has the hydroxyl substituent attached, and name the chain by replacing the -e ending of the corresponding alkane with -ol: Chapter Fourteen 6

7 STEP 2: Number the carbon atoms in the main chain. Begin at the end nearer the hydroxyl group, ignoring the location of other substituents: If the compound is a cyclic alcohol, add the -ol ending to the name of the parent cycloalkane. In a cyclic alcohol, begin with the carbon that bears the OH group and proceed in a direction that gives the other substituents the lowest possible numbers. Chapter Fourteen 7

8 STEP 3: Write the name, placing the number that locates the hydroxyl group immediately before the parent compound name. Number the positions of all other substituents, and list them alphabetically. Note that in a cyclic alcohol, it is not necessary to use the number 1 to specify the location of the OH group. Chapter Fourteen 8

9 Dialcohols, or diols, are often called glycols. Ethylene glycol is the simplest glycol; propylene glycol is often used as a solvent for medicines that need to be inhaled or rubbed onto the skin. Numbering starts from the end closer to an OH group, and the -diol name ending is used. Chapter Fourteen 9

10 Alcohols are classified as primary, secondary, or tertiary according to the number of carbon substituents bonded to the hydroxyl-bearing carbon. Alcohols with one substituent are said to be primary, those with two substituents are secondary, and those with three substituents are tertiary. Chapter Fourteen 10

11 14.4 Properties of Alcohols Alcohols are much more polar than hydrocarbons. Hydrogen bonding also occurs and has a strong influence on alcohol properties. Straight-chain alcohols with up to 12 C s are liquids, and each boils at a considerably higher temperature than the related alkane. Alcohols with a small organic part resemble water. Methanol and ethanol are miscible with water and they can dissolve small amounts of many salts. Alcohols with a large organic part are more like alkanes. 1-Heptanol is nearly insoluble in water and can t dissolve salts but does dissolve alkanes. Chapter Fourteen 11

12 Primary and secondary alcohols are converted into carbonylcontaining compounds on treatment with an oxidizing agent. A carbonyl group is a functional group that has a C=O. The symbol [O] will indicate a generalized oxidizing agent. An organic oxidation is one that increases the number of C-O bonds and/or decreases the number of C-H bonds. Chapter Fourteen 12

13 Primary alcohols are converted either into aldehydes if carefully controlled conditions are used, or into carboxylic acids if an excess of oxidant is used. Chapter Fourteen 13

14 Secondary alcohols are converted into ketones on treatment with oxidizing agents. Chapter Fourteen 14

15 Tertiary alcohols do not normally react with oxidizing agents because they do not have a hydrogen on the carbon atom to which the OH group is bonded. Chapter Fourteen 15