CHEM 3332 1st Edition Lecture 7Outline of Last Lecture Chapter 14: Ethers, EpoxidesImportance: ether, not a goof synthetic intermediate, it’s an important solvent. Epoxide is excellent synthetic intermediate Structure/ Polarity/ Physical PropertiesEthers as solvents:- Limited reactivity- Not as toxic as chlorinated solvents such as CCl4/ChCl3/CH2CL2- Low boiling, so easily removed- Large diploe moments and H – bond acceptors, so dissolve polar substances- No H- bonds between ether molecules, so dissolve nonpolar substances (no-H bonds to disrupt)- No acidic hydrogens, so can serve as solvents under strong basic conditionsEther Complexes:a. Grignard reagen-b. Boron reagents-c. Crown ether/ cations –Nomenclature of EthersI. Acyclic Ethers – 2 accepted systemsA. As alkyl alkyl ether: Name each alkyl group attached to oxygen in alphabetical order and add “ether” (common name)B. As alkoxy alkane: Name the RO- group as an alkoxy group. The larger or more complexgroup is chosen as the parent name.II. Cyclic ethers (Epoxides) – 3 accepted systemA. Common name: Name of alkene used to form the epoxide plus “oxide”. (industry uses)B. Name the oxygen of the epoxide ring as an epoxy substituent. Use both numbers of the carbons bonded to oxygen to designate position.C. Name as derivative of oxiraneSynthesis of EthersI. Williamson Ether SynthesisII. Alkoxymercuration/demercurationMechanismIII. Symmetrical ethers through intermolecular dehydration of 1 alcohols. – DO NOT USE THIS!!! LIMITED REACTION!Outline of Current Lecture Reactions of Ethers-ethers are unreactive to many organic reagents-ether bond (C-O) is stable to strong Nu/strong base oxidation reactionsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Cleavage by strong acids HI and HBR, not HCLMechanismII. Autoxidation (DANGER!!!): peroxidesSynthesis of EpoxidesI. Epoxidation of alkanes with peroxyacidsMechanism: a concerted processElectron rich pi bonds react fastesStereochemistry of alkene is maintainedII. Intramolecular WilliamsonLarger cyclic ethers can also be formed:Reaction o EpoxidesI. Acid – catalyzed cleavageII. Base – catalyzed cleavageIf the epoxide is symmetrical, the results of acid cat. and base cat.are the same. Consider each process with asymmetrical apoxides:I. Acid – catalyzed cleavageII. Base – catalyzed cleavageSummary1. Weak nucleophiles (H2O, ROH, Cl-) only react with protonated epoxides in acidic conditions2. Strong nucleophile (CH-, RO-, NH2-, CN-, carbanions) react with unprotinated epoxide3. Acid- cat. process Nu attacks the more substituted carbon4. Base cat. process Nu attacks the less substituted carbon.III. Reaction of Epoxide with Gringard/Organolithium ReagentsIV. Reaction of Epoxide with Acetylide IonCompare to: Current LectureReactions of Ethers-ethers are unreactive to many organic reagents-ether bond (C-O) is stable to strong Nu/strong base oxidation reactionsI. Cleavage by strong acids HI and HBR, not HCLMechanismII. Autoxidation (DANGER!!!): peroxidesSynthesis of EpoxidesI. Epoxidation of alkanes with peroxyacidsMechanism: a concerted processElectron rich pi bonds react fastesStereochemistry of alkene is maintainedII. Intramolecular WilliamsonLarger cyclic ethers can also be formed:Reaction of EpoxidesI. Acid – catalyzed cleavageII. Base – catalyzed cleavageIf the epoxide is symmetrical, the results of acid cat. and base cat.are the same. Consider each process with asymmetrical apoxides:I. Acid – catalyzed cleavageII. Base – catalyzed cleavageSummary1. Weak nucleophiles (H2O, ROH, Cl-) only react with protonated epoxides in acidic conditions2. Strong nucleophile (CH-, RO-, NH2-, CN-, carbanions) react with unprotinated epoxide3. Acid- cat. process Nu attacks the more substituted carbon4. Base cat. process Nu attacks the less substituted carbon.III. Reaction of Epoxide with Gringard/Organolithium ReagentsIV. Reaction of Epoxide with Acetylide IonCompare