Terrence P. Sherlock Burlington County College 2004

CHE 242Unit VStructure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR SpectroscopyCHAPTER TEN Terrence P. Sherlock Burlington County College 2004

=> Classify these: Chapter 10

Name these: 2-methyl-1-propanol 2-butanol 2-methyl-2-propanol 3-bromo-3-methylcyclohexanol => Chapter 10

Acids Esters Aldehydes Ketones Alcohols Amines Alkenes Alkynes Alkanes Ethers Halides => Naming Priority Chapter 10

Hydroxy Substituent • When -OH is part of a higher priority class of compound, it is named as hydroxy. • Example: also known as GHB => 4-hydroxybutanoic acid Chapter 10

Glycols • 1, 2 diols (vicinal diols) are called glycols. • Common names for glycols use the name of the alkene from which they were made. 1,2-ethanediol 1,2-propanediol propylene glycol => ethylene glycol Chapter 10

Naming Phenols • -OH group is assumed to be on carbon 1. • For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para- for 1,4. • Methyl phenols are cresols. 4-methylphenol para-cresol => 3-chlorophenol meta-chlorophenol Chapter 10

Physical Properties • Unusually high boiling points due to hydrogen bonding between molecules. • Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases. => Chapter 10

=> Boiling Points Chapter 10

Solubility decreases as the size of the alkyl group increases. => Solubility in Water Chapter 10

Acidity of Alcohols • pKa range: 15.5-18.0 (water: 15.7) • Acidity decreases as alkyl group increases. • Halogens increase the acidity. • Phenol is 100 million times more acidic than cyclohexanol! => Chapter 10

Table of Ka Values => Chapter 10

=> Formation of Alkoxide Ions React methanol and ethanol with sodium metal (redox reaction). React less acidic alcohols with more reactive potassium. Chapter 10

Formation of Phenoxide Ion Phenol reacts with hydroxide ions to form phenoxide ions - no redox is necessary. O O H O H + + H O H p K = 1 5 . 7 a p K = 1 0 a => Chapter 10

Synthesis (Review) • Nucleophilic substitution of OH- on alkyl halide • Hydration of alkenes • water in acid solution (not very effective) • oxymercuration - demercuration • hydroboration - oxidation => Chapter 10

Glycols (Review) • Syn hydroxylation of alkenes • osmium tetroxide, hydrogen peroxide • cold, dilute, basic potassium permanganate • Anti hydroxylation of alkenes • peroxyacids, hydrolysis => Chapter 10

Organometallic Reagents • Carbon is bonded to a metal (Mg or Li). • Carbon is nucleophilic (partially negative). • It will attack a partially positive carbon. • C - X • C = O • A new carbon-carbon bond forms. => Chapter 10

Grignard Reagents • Formula R-Mg-X (reacts like R:-+MgX) • Stabilized by anhydrous ether • Iodides most reactive • May be formed from any halide • primary • secondary • tertiary • vinyl • aryl => Chapter 10

=> Some Grignard Reagents Chapter 10

Organolithium Reagents • Formula R-Li (reacts like R:-+Li) • Can be produced from alkyl, vinyl, or aryl halides, just like Grignard reagents. • Ether not necessary, wide variety of solvents can be used. => Chapter 10

=> Reaction with Carbonyl • R:- attacks the partially positive carbon in the carbonyl. • The intermediate is an alkoxide ion. • Addition of water or dilute acid protonates the alkoxide to produce an alcohol. Chapter 10

=> Synthesis of 1° Alcohols Grignard + formaldehyde yields a primary alcohol with one additional carbon. Chapter 10

=> Synthesis of 2º Alcohols Grignard + aldehyde yields a secondary alcohol. Chapter 10

=> Synthesis of 3º Alcohols Grignard + ketone yields a tertiary alcohol. Chapter 10

=> How would you synthesize… Chapter 10

Grignard Reactions with Acid Chlorides and Esters • Use two moles of Grignard reagent. • The product is a tertiary alcohol with two identical alkyl groups. • Reaction with one mole of Grignard reagent produces a ketone intermediate, which reacts with the second mole of Grignard reagent. => Chapter 10

Grignard + Acid Chloride (1) • Grignard attacks the carbonyl. • Chloride ion leaves. Ketone intermediate => Chapter 10

Grignard and Ester (1) • Grignard attacks the carbonyl. • Alkoxide ion leaves! ? ! Ketone intermediate => Chapter 10

=> Second step of reaction • Second mole of Grignard reacts with the ketone intermediate to form an alkoxide ion. • Alkoxide ion is protonated with dilute acid. Chapter 10

=> How would you synthesize... Using an acid chloride or ester. Chapter 10

=> Grignard Reagent + Ethylene Oxide • Epoxides are unusually reactive ethers. • Product is a 1º alcohol with 2 additional carbons. Chapter 10

Limitations of Grignard • No water or other acidic protons like O-H, N-H, S-H, or -C—C-H. Grignard reagent is destroyed, becomes an alkane. • No other electrophilic multiple bonds, like C=N, C—N, S=O, or N=O. => Chapter 10

Reduction of Carbonyl • Reduction of aldehyde yields 1º alcohol. • Reduction of ketone yields 2º alcohol. • Reagents: • Sodium borohydride, NaBH4 • Lithium aluminum hydride, LiAlH4 • Raney nickel => Chapter 10

=> Sodium Borohydride • Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion. • Then the alkoxide ion is protonated by dilute acid. • Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids. Chapter 10

=> Lithium Aluminum Hydride • Stronger reducing agent than sodium borohydride, but dangerous to work with. • Converts esters and acids to 1º alcohols. Chapter 10

Comparison of Reducing Agents • LiAlH4 is stronger. • LiAlH4 reduces more stable compounds which are resistant to reduction. => Chapter 10

=> Catalytic Hydrogenation • Add H2 with Raney nickel catalyst. • Also reduces any C=C bonds. Chapter 10

POWER POINT IMAGES FROM “ORGANIC CHEMISTRY, 5TH EDITION”L.G. WADEALL MATERIALS USED WITH PERMISSION OF AUTHORPRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGEORGANIC CHEMISTRY COURSEBY:ANNALICIA POEHLER STEFANIE LAYMAN CALY MARTIN Chapter 10

Terrence P. Sherlock Burlington County College 2004