Ethers, Epoxides, Sulfides - Fundamentals of Organic Chemistry II | CHEM 3332, Study notes of Organic Chemistry

Download Ethers, Epoxides, Sulfides - Fundamentals of Organic Chemistry II | CHEM 3332 and more Study notes Organic Chemistry in PDF only on Docsity! bea n-2 CHAPTER 14: Ethers, Epoxides, Sulfides Chem 3337 Importance: Structure / Polarity / Physical Properties @) & CH3-0-CH3 CH3CHoCH3 CH3CH2-O-H dipole moment ZN boiling point Ethers as Solvents: - limited reactivity - Not as toxic as chlorinated solvents such as CCl4 / CHClg / CHaClo - low boiling, so easily removed - large dipole 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 conditions 0. o 18-crown-6 GHgCH3 —O—CH2CH3 ( } oO CHg—O—CH,CH,—O—CH, Ether Complexes: a. Grignard reagent - b. Boron reagents - c. Crown ether / cations - Nomenclature of Ethers |. Acyclic Ethers - 2 accepted systems A. As alkyl alkyl ether: Name each alkyl group attached to oxygen in alphabetical order and add “ether.” (common name) Gt oh CHyCHsCHy—O —CH,CH, CHa — O—CH.CH, CHsCH,CH,~O —CHCHy-OH CHg B. As alkoxy alkane: Name the RO- group as an alkoxy group. The larger or more complex group is chosen as the parent name. Clg CHa CHgCH2CH»~O —CHCH, CHe-C— O—CH-CH, CHaCHaCHp ~O — CH GHy-OH CH, Il. Cyclic ethers (Epoxides) - 3 accepted systems A. Common name: Name of alkene used to form the epoxide plus "oxide." (industry uses) 0 0 RCO3H RCO3H CHp=CH, ——S0 4 CH)=CHCH, —~3" 4 eee HC oN on, 2 3 HoC————CH-CHy B. Name the oxygen of the epoxide ring as an epoxy substituent. Use both numbers of the carbons bonded to oxygen to designate position. Oo ° oN *, ot oy HeC——-—CH.CH, \ 1 CH CH>-CH-CHy 3 C. Name as derivative of oxirane. 0. 0. 0. 4 \ My, awl Cs CHg HyC————cH, ¢ CH-CH-CH CH3GHCH," ‘OH ! CHg CHg Synthesis of Epoxides: |. Epoxidation of alkenes with peroxyacids: 0 \ YL I C=C” + R-0-0-0H —» ZN + a \ Mech: a concerted process \7 ¢ an A NoX OQ va an bm ¢ S™ 0 4N\ H-.g Electron rich x bonds react fastest: Cl MCPBA —uo 1 eq. Stereochemistry of the alkene is maintained: MCPBA ——o— | x —_— —CcC— — I | ” x NaOH Geo As 1. BrofH20 LoS OP H3C H 2. NaOH Larger cyclic ethers can also be formed: O-H NaOH ay — ci oO REACTIONS OF EPOXIDES |. Acid - catalyzed cleavage H Ht +0 Nu — ZN Hl. Base - catalyzed cleavage If the epoxide is symmetrical, the results of acid cat. and base cat. are the same. Consider each process with asymmetrical epoxides: |. Acid - catalyzed cleavage ae oH H,C—G——CH, — (cat) _c— eN 2 CHROH Ago CH oO ° +. H ll. Base - catalyzed cleavage CHg ! “Nat HaC—G—CH, —CHgO"Na* : \ ? “CH3OH Summary: 1. Weak nucleophiles (H20, ROH, Cl’) only react with protonated epoxide. 2. Strong nucleophiles (OH ~, RO, NHa ~, CN °, carbanions) react with unprotonated epoxide. 3. Acid - cat. process: Nu attacks the more substituted carbon. 4. Base cat. process: Nu attacks the less substituted carbon. Ill. Reaction of Epoxide with Grignard/Organolithium Reagents Oo HgC CH,CH MOT NAPS CHgCHo-MgBr < “4 | nin ol H “CH IV. Reaction of Epoxide with Acetylide lon O ax “ CHs-C=C- Nat -_—_—— CH3 Compare to: oO ul CH3-C=C~ Nat CHs—C —CHz, =£=———_»