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Alcohols, Phenols, Thiols, and Ethers Chapter 13 Introduction • Alcohol – organic compound that contains a hydroxyl (-OH) group attached to an alkyl group • Phenol – organic compound that contains a hydroxyl (-OH) group attached to an aryl group • Ether – organic compound that has two alkyl or aryl groups attached to the oxygen atom; can be thought of as a substituted alcohol. Examples Alcohols -OH hydroxyl CH3-OH CH3CH2-OH OH OH Phenols Ethers -O- CH3-O-CH3 Practice Problem 1 Classify each as an alcohol (1), phenol (2), or an ether (3): A. _____ CH3CH2-O-CH3 OH B. _____ CH3 C. _____ CH3CH2OH Solution 1 Classify each as an alcohol (1), phenol (2), or an ether (3): A. ____ CH3CH2-O-CH3 OH B. _ __ CH3 C. ____ CH3CH2OH Structure and Properties • R-O-H portion of alcohol is similar to the structure of water. – The oxygen and two atoms bonded to it lie in the same plane. – The bond angle is 104° • Hydroxyl groups are very polar because of significantly different electronegativities. – Hydrogen bonding can form between alcohol molecules. Hydrogen Bonding O R H H O O R H H O H H Results of Hydrogen Bonding • Alcohols boil at much higher temperatures than hydrocarbons of similar molecular weight. • Alcohols with fewer than five carbons are very soluble in water. • Alcohols with five to eight carbons are moderately soluble in water. • As the nonpolar (R) portion of the alcohol gets larger, the water solubility decreases. Solubility of Alcohols • Very large alcohols are not soluble in water. • Hydrophobic – “water fearing”; used to describe nonpolar region of molecule • Hydrophilic – “water loving”; used to describe polar region of molecule CH3CH2CH2CH2CH2CH2CH2CH2CH2OH Hydrophobic Hydrophilic Solubility of Alcohols • An increase in the number of hydroxyl groups will increase the influence of the polar hydroxyl group. – Diols and triols are more water soluble than alcohols with only a single hydroxyl group. Practice Problem 2 • Circle the more soluble alcohol in each pair. H2 C OH A. H3C H2 C OR C H2 H3C C H2 OH OH B. C. OH OR OR OH OH Solution 2 • Circle the more soluble alcohol in each pair. H2 C OH A. H3C H2 C OR C H2 H3C C H2 OH OH B. C. OH OR OR OH OH Nomenclature of Alcohols • A carbon compound that contain -OH (hydroxyl) group • In IUPAC name, the -e in alkane name is replaced with -ol. CH4 methane CH3OH methanol CH3CH3 ethane CH3CH2OH ethanol (methyl alcohol) (ethyl alcohol) More Names of Alcohols • IUPAC names for longer chains number the chain from the end nearest the -OH group. CH3CH2CH2OH OH CH3CHCH3 CH3 OH CH3CHCH2CH2CHCH3 Alcohols that contain more than one hydroxyl group • Alcohols containing two hydroxyl groups are named –diols. • Alcohols containing three hydroxyl groups are named –triols. • A number giving the position of each of the hydroxyl groups is needed in these cases. Practice Problem 3 Name the following alcohols: A. OH CH3CHCHCH2CH3 CH3 OH B. Solution 3 Name the following alcohols: A. OH CH3CHCHCH2CH3 CH3 OH B. Homework Pages 379-380 13.1113.14 Page 360 13.1 – 13.2 Due Tomorrow!!!! Section 13.3 • It is your responsibility to read over section 13.3 – Medically Important Alcohols (pgs. 360361) and take notes on the material covered! • It will be on the weekly quiz and the test! Classification of Alcohols • Alcohols can be classified as primary (1°), secondary (2°), or tertiary (3°) depending on the number of alkyl groups attached to the carbon bearing the –OH group. H H CH3 H C H OH Methanol H3 C C H 1° alcohol ethanol OH H3 C C OH 2° alcohol 2-propanol CH3 H H3 C C CH3 OH 3° alcohol 2-methyl-2-propanol Practice Problem 4 Classify each of the following alcohols as primary, secondary, tertiary, or aromatic. 1. 2. 3. 4. 1-butanol 3-pentanol 1-methylcyclopentanol 2-methyl-2-pentanol Solution 4 1. 1-butanol 2. 3-pentanol 3. 1-methylcyclopentanol 4. 2-methyl-2-pentanol Homework • Pages 380-381: 13.15, 13.16, 13.18, 13.19, 13.20, 13.21, 13.22, 13.27, and 13.28 Due Tomorrow! Preparation of Alcohols • REVIEW: Hydration – an addition reaction in which a water molecule is added to an alkene; requires acid as catalyst R R R H + R R H R OH H R Alkene O H+ R Water Markovnikov’s rule applies!! Alcohol Hydration Examples • Ethene • 1-butene Preparation of Alcohols • Hydrogenation of aldehydes and ketones OH O H + R1 R2 Catalyst R1 R2 H H In an aldehyde, R1 and R2 may be either alkyl groups or H. In a ketone, R1 and R2 are both alkyl groups. We will discuss this in more detail in section 14.4. Hydrogenation Examples • Ethanal • 2-propanone Preparation of Alcohols YOU TRY THESE! + Dehydration of Alcohols • Alcohols undergo dehydration (lose water) when heating with concentrated sulfuric or phosphoric acid. • Dehydration is an example of an elimination reaction. • Elimination reaction – a reaction in which a molecule loses atoms or ions from its structure. • Dehydration is opposite of hydration! Dehydration of Alcohols • General Reaction H+ RCH2CH2OH RCH=CH2 + H2O Heat • Ethanol H+ CH3CH2OH Heat • 2-butanol H H H OH H C C C C H H H H H+ H Heat Dehydration of Alcohols • Zaitsev’s rule – in an elimination reaction, the alkene with the greatest number of alkyl groups on the double bonded carbon (more highly substituted alkene) is the major product of the reaction • Another example: Oxidation Reactions • Oxidation – loss of electrons; add O and/or lose H • Reduction – gain of electrons; add H and/or lose O • Common oxidizing agents: – Basic potassium permanganate (KMnO4/OH-) – Chromic Acid (H2CrO4) • [O] Any general oxidizing agent Oxidation of Primary Alcohols • General equation: – Primary alcohol aldehyde RCH2CH=O EXAMPLE: 1-propanol Oxidation of Secondary Alcohols • General equation: – Secondary alcohol EXAMPLE: 2-propanol ketone O R-C-R Oxidation of Tertiary Alcohols • General equation: – Tertiary alcohol NO REACTION!!! YOU TRY THESE! H H H OH H C C C C H H H H [O] H [O] OH [O] HO CH 3CH 2OH [O] Phenols • Phenols – compounds in which the hydroxyl group is attached to a benzene ring • They are polar compounds because of the polar hydroxyl group. • Smaller phenols are somewhat soluble in water. • They are found in fragrances and flavorings and are also used as preservatives and germicides. Common Phenols and their Uses (CH3)2HC CH3 Thymol (mint) OH (CH3)2HC CH3 OH Carvacrol (savory) Common Phenols and their Uses C(CH3)3 CH3 OH (CH3)3C OH Butylated hydroxytoluene, BHT(Food preservative) Phenol (Carbolic acid when dissolved in water) Antiseptic and disinfectant used by Joseph Lister to bathe wounds and sterlize instruments Ethers Ethers • What are they? • How are they used? • What do you know about them? Structure of Ethers • Similar structure to alcohols Alcohols: R-OH –OH is “hydroxy” group Ethers: R-OR –OR is “alkoxy” group Alkoxy group • “R” groups can be the same: • “R” groups can be different: CH3-O-CH3 CH3CH2CH2-O-CH3 • Both “R” groups have one carbon • One “R” group has three carbons while the other has one Alkoxy group • The root names are used with –oxy to name that portion of the ether: – meth- + -oxy – eth- + -oxy = methoxy = ethoxy – prop- + -oxy = propoxy Naming ethers – IUPAC Way 1. Find the root name of the smaller “R” group Ex: meth-, eth-, prop2. Add –oxy Ex: methoxy, ethoxy, propoxy 3. Add the full name of the larger “R” group EXAMPLE: O methoxypropane Name that ether O O O Draw the structure of: 1. methoxypropane 2. methoxyoctane 3. propoxypropane 4. ethoxypentane Naming Ethers – Common Name • Name by placing the names of the two alkyl groups attached to the ether oxygen as words in front of the word “ether.” Typically this is done in alphabetical order. O Diethyl Ether O Ethyl methyl ether O Butyl propyl ether Properties of ethers • The C-O bond in ethers is polar, making the molecule polar • Ethers have very low boiling points • Ethers are relatively inert, but flammable in air Let’s compare… Ether CH3 –O-CH2CH3 Alcohol CH3CH2CH2-OH Molecular Formula: C3H8O Molecular Weight: 60.09g/mol Boiling Point: 7.9°C Molecular Formula: C3H8O Molecular Weight: 60.09g/mol Boiling Point: 97.2°C Preparing ethers • Ethers are formed from alcohols R-OH + R’-OH R-O-R’ +H2O H+ – R and R’ can be the same or different – Called a dehydration reaction Predict the products CH3OH + CH3CH2OH H+ CH3CH2CH2OH + CH3CHCH3 OH H+ Common uses • Ethers as anesthetics: – Penthrane – Enthrane • Ethers as additives in gasoline – MTBE – methyl tert-butyl ether Thiols • Compounds that contain the sulfhydryl group (-SH) • Similar to alcohols in structure, but the sulfur atom replaces the oxygen atom • Have nauseating aromas – defense spray of North American striped skunk H Trans-2-butene-1-thiol H2C SH CH3 H Naming Thiols • Use the same rules as for alcohols except that the full name of the alkane is retained. • Add the suffix –thiol. CH3CH2SH ethanethiol CH3 CH3CHCH2CH2 3-methyl-1-butanethiol SH HSCH2CH2SH 1,2-ethanedithiol Uses of Thiols • Thiols are involved in protein structure and conformation. • Cysteine is an amino acid that contains a sulfhydryl group. • BAL (British Anti-Lewisite) is used as an antidote for mercury poisoning. • Coenzyme A serves as a carrier of acetyl groups in biochemical reactions. Homework •Pg. 381-382: 13.43, 13.44, 13.45, 13.48, 13.49, 13.51, 13.52, 13.53, 13.59, 13.60