Ch 18 Free Essays

Part 18 Ethers Epoxides; Thiols and Sulfides Assigned Reading from McMurry: Read Sections 18. 1 through 18. 9; not answerable for â€Å"Focus on †¦ Epoxy Resins Adhesives, pp. We will compose a custom paper test on Ch 18 or on the other hand any comparable point just for you Request Now 697-698). Suggested Problems from McMurry: 18. 1a-e;18. 18. 2;18. 3a-d; 18. 4; 18. 5a-d; 18. 6a-b; 18. 7a-b; 18. 8; 18. 9; 18. 10; 18. 11; 18. 12a,b; 18. 13a,b; 18. 14a-c; 18. 16a-f; 18. 17; 18. 18; 18. 19a-c; 18. 20; 18. 21; 18. 22; 18. 23a-e; 18. 24a-I; 18. 25a-f; 18. 26a-d; 18. 27; 18. 28; 18. 29ad; 18. 30a-e; 18. 31; 18. 32; 18. 33; 18. 34; 18. 35a-d; 18. 36; 18. 37; 18. 38; 18. 39; 18. 40a,b; 18. 41a-d; 18. 2; 18. 43; 18. 44; 18. 45; 18. 45; 18. 46; 18. 47; 18. 48; 18. 49; 18. 51; 18. 52; 18. 53; 18. 54; 18. 551-e; 18. 56; 18. 57; 18. 58a-b; 18. 59a-b; 18. 60; 18. 61. 18. 1 Names and Properties of Ethers Method A: Simple ethers; order if two natural substituents. CH3â€CH2â€Oâ€CH2â€CH3 Diethyl ether Methyl propyl ether O CH3â€CH2â€CH2â€Oâ€CH3 CH3 Methyl phenyl ether SP 18. 01 Provide orderly names for the accompanying ethers. CH3â€CH2â€Oâ€CH2â€CH2â€CH2â€CH3 O SP 18. 02 Provide structures for the accompanying orderly names. Methodical name : Isopropyl phenyl ether Systematic name: Cyclohexyl ethyl ether Technique B: Other utilitarian gatherings present, ether segment is a â€Å"alkoxy† substituent. Alkoxy models: methoxy - OCH3, ethoxy - OCH2CH3, propoxy - OCH2CH2CH3, and so on. O C H3 O CH3 O C H3 para-Dimethoxybenzene 3-Methoxy-1-cyclopentene SP 18. 03 Provide orderly names for the accompanying complex ethers. OCH3 O CH2CH3 Cl SP 18. 04 Provide structures for the accompanying precise names. Methodical name: meta-Bromopropoxybenzene Systematic name: 1-Isopropoxycyclopentene 18. 2 Synthesis of Ethers The Williamson Ether Synthesis R + O an alkoxide C X R SN2 an alkyl halide methyl 1o best; X = Cl, Br, I, OTos O C ether item Model: O Na + Sodium phenoxide CH3 Br O CH3 Phenyl methyl ether (anisole) + Na Br + X SP 18. 05 Complete the accompanying responses. CH3 C O Na + CH3 I + Na I CH3 C CH3 I + Na O CH3 + Na I SP 18. 06 Provide the appropriate alkoxide and alkyl halide important to deliver 2-ethoxy-2-methyl butane in great yield. CH3 CH2 C O CH3 CH2 CH3 + Na Br 8. 4 Oxymercuration Intermediates †¢ For lab scale hydration of an alkene †¢ Use mercuric acetic acid derivation in THF followed by sodium borohydride Markovnikov direction †by means of mercurinium particle Alkoxymercuration of Alkenes General Reaction: R C 2) NaBH4 H C R Ether Alkene RO Step #1 RO C 1) Hg(OAc)2, ROH H g OA C Step #2 R + HOAc Markovnikov expansion SP 18. 07 Complete the accompanying responses by showing the last significant natural item. H C 1) Hg(OAc)2, CH3OH H C 2) NaBH4 H CH3 C H CH3 1) Hg(OAc)2, CH3OH 2) NaBH4 SP 18. 08 Specify the alkene and liquor expected to deliver the accompanying ether. Liquor OCH2CH3 1) Hg(OAc)2, CH3 2) NaBH4 Alkene 18. 3 Reactions of Ethers: Acidic Ether Cleavage General Reaction: HX C O C OH + X C (solid corrosive) Ether Alcohol Alkyl halide SP 18. 09 Predict the item for the accompanying ether-cleavage response. CH3 C O CH3 HBr CH2CH3 8. 4 Reactions of Ethers: Claisen Rearrangement O OH 1,3 O to C move Thermodynamically progressively stable o 250 Allyl phenyl ether C9H10O ortho-Allyl phenol C9H10O Mechanism (includes six-membered change state): 1 O TS 2 3 1 O 2 H keto-enol tautomerization 3 O H SP 18. 10 Predict the structure for the accompanying Claisen modification. O 250 2-Butenyl phenyl ether C10H12O 18. 5 Cyclic Ethers: Epoxides (2 strategies) General Reaction 1: O C + R Alkene C O C H A peracid C An epoxide R C O A carboxylic corrosive Specific Example 1: O Cl C O H m-CPBA o H O + CH2Cl2, 25 C H 1,2-Epoxycycloheptane Cl H C O H 18. Cyclic Ethers: Epoxides (2 techniques) General Reaction 2: C OH X2, H2O C X A halohydrin Alkene O NaOH H2O C + H2O + NaX C An epoxide Review Section 7. 3 Specific Example 2: H CH3 C H CH3 cis-2-Butene Br2 H2O H CH3 Br C OH C H CH3 NaOH H2O O HC CH3 C H + H2O + NaBr CH3 meso-2,3-Dimethyl-oxirane (or cis-2,3-epoxybutane) SP 18. 11 Fill in the fitting intermediates demonstrating the right stereochemistry. H CH3 C CH3 Br2 NaOH H H2O trans-2-Butene + H2O + NaBr 18. 6 Reactions of Epoxides: Ring-Opening General epoxide structure: O C Since every molecule is sp3 there is impressive point strain in the epoxide ring-framework. C Acidic Conditions: Epoxide opening under acidic conditions (fluid corrosive) yields 1,2-diols General Reaction: H O C H C HO C H2O An epoxide C OH A 1,2-diol (glycol) H O C H C + O H O C + C H O H O H Specific Example (utilizing balanced epoxide): H + H H3O OH H2O OH O H trans-1,2-Cyclohexanediol SP 18. 12 Predict the right structure of the item diol demonstrating the right stereochemistry. O H CH3 C CH3 H trans-2,3-epoxybutane H3O+ H2O Note: Epoxide opening under anhydrous acidic conditions yields halohydrins. Explicit Example (2â ° and 1â ° carbons): o 1 carbon o 2 carbon O CH3 H C H 1,2-Epoxypropane Gracious HCl Et2O CH3 C Cl CH2 Cl + CH3 H 1-Chloro-2-propanol (90%) C CH2 OH H 2-Chloro-1-propanol (10%) SP 18. 13 Using the above model anticipate the major halohydrin. O H C H C HCl H Et2O O H C H HCl OH C Et2O H Cl CH2 Cl + C CH2 OH H Explanation: In situations where a 2â ° carbon and a 1â ° carbon structure the epoxide ring, the major halohydrin item will be where the beginning liquor is 2â ° and the halide is 1â °. Endless supply of the epoxide oxygen the halide particle straightforward assaults the less-obstructed 1â ° carbon with a more prominent recurrence to give the major regioisomer. Explicit Example (3â ° and 1â ° carbons): SP 18. 4 Using the above model anticipate the major halohydrin. Circle one. O C H HCl OH C Et2O + C H Cl H C OH C H Explanation: In situations where a 3â ° carbon and a 1â ° carbon structure the epoxide ring, the major halohydrin item will be where the nascent liquor is 1â ° and the halide is 3â °. Endless supply of the epoxide oxygen the ha logen assaults the more-balanced out (same as moresubstituted) carbon particle to give the major regioisomer depicted. Fundamental Conditions: Note: Nucleophile will consistently assault least-thwarted position. Explicit Example: o 3 carbon 1o carbon O CH3 C H OH NaOH H2O, ? CH3 C CH2 OH CH3 - Methyl-1,2-propanediol SP 18. 15 Predict the structure of the 1,2-diol from the accompanying response. O C H NaOH H2O, ? Response with Grignard Reagents: O CH3 C H OH 1) CH3CH2MgBr, Et2O 2) (aq) NH4Cl CH3 C CH2 CH3 CH2 CH3 SP 18. 16 Predict the structure of the natural item from the accompanying Grignardepoxide response. O H C H 1) CH3MgBr, Et2O 2) (aq) NH4Cl Reaction with a 1â ° amine: O H C OH CH2 H H2NCH2CH2CH3 C CH2 N CH2 H Reaction with a 2â ° amine: O H C OH H H3C CH2 + N H3C H C CH2 N CH3 SP 18. 17 Predict the structure of the epoxide and amine expected to create the amino liquor appeared to one side. Goodness + CH3 C CH3 Epoxide Amine CH2 N H 18. 7 Crown Ethers †¢ Large rings comprising of rehashing (- OCH2CH2-) or comparable units †¢ Named as x-crown-y †x is the all out number of particles in the ring †y is the quantity of oxygen iotas †18-crown-6 ether: 18-membered ring containing 6 oxygen molecules †¢ Central pit is electronegative and draws in cations 18. 8 Thiols and Sulfides †¢ Thiols (RSH), are sulfur analogs of alcohols †Named with the addition - thiol †SH bunch is called â€Å"mercapto group† (â€Å"capturer of mercury†) Thiols: Formation and Reaction †¢ From alkyl halides by relocation with a sulfur nucleophile, for example, â€SH The alkylthiol item can experience further response with the alkyl halide to give a balanced sulfide, giving a less fortunate yield of the thiol Sulfides †¢ Sulfides (RSR? ), are sulfur analogs of ethers †Named by rules utilized for ethers, with sulfide instead of ethe r for straightforward mixes and alkylthio instead of alkoxy Using Thiourea to Form Alkylthiols †¢ Thiols can experience further response with the alkyl halide to give dialkyl sulfides †¢ For an unadulterated alkylthiol use thiourea (NH2(C=S)NH2) as the nucleophile †¢ This gives a moderate alkylisothiourea salt, which is hydrolyzed neatly to the alkyl thiourea Oxidation of Thiols to Disulfides Reaction of an alkyl thiol (RSH) with bromine or iodine gives a disulfide (RSSR) †¢ The thiol is oxidized all the while and the halogen is diminished Sulfides †¢ Thiolates (RS? ) are framed by the response of a thiol with a base †¢ Thiolates respond with essential or optional alkyl halide to give sulfides (RSR’) †¢ Thiolates are amazing nucleophiles and respond with numerous electrophiles Sulfides as Nucleophiles †¢ Sulfur mixes are more nucleophilic than their oxygen-compound analogs †3p valence electrons (on S) are less firmly held than 2p e lectrons (on O) †¢ Sulfides respond with essential alkyl halides (SN2) to give rialkylsulfonium salts (R3S+) Oxidation of Sulfides †¢ Sulfides are handily oxidized with H2O2 to the sulfoxide (R2SO) †¢ Oxidation of a sulfoxide with a peroxyacid yields a sulfone (R2SO2) †¢ Dimethyl sulfoxide (DMSO) is regularly utilized as a polar aprotic dissolvable 18. 9 Spectroscopy of Ethers †¢ Infrared: Câ€O single-bond extending 1050 to 1150 cm? 1 covers numerous different assimilations. †¢ Proton NMR: H on a C close to ether O is moved downfield to ? 3. 4 to ? 4. 5 †The 1H NMR range of dipropyl ether shows this sign at ? 3. 4 †In epoxides, these H’s ingest at ? 2. 5 to ? 3. 5 in their 1H NMR spectra Carbon NMR: C’s in ethers display a downfield move to ? 50 to ? 80 Let’s Work a Problem When 2-methyl-2,5-pentanediol is treated with sulfuric corrosive, drying out happens and 2,2dimethylte