Properties of Ethers, Sulfides and the Epoxides | CHEM 333, Study notes of Chemistry

Download Properties of Ethers, Sulfides and the Epoxides | CHEM 333 and more Study notes Chemistry in PDF only on Docsity! 11. Ethers, Sulfides and Epoxides Structure, nomenclature, properties Ether synthesis - Williamson synthesis (SN2) H+/ROH addition to olefins (chapt 6) Reactions - acid catalyzed cleavage of ethers (SN2/SN1/E1) [oxidation out] Ethers as Protecting Groups (Gps). Epoxides - oxirane nomenclature Preparation: epoxidation, halohydrin Reactions - nucleophilic cleavage (SN2/SN1/E1) [sulfides out] Synthesis (continued) [blue - repeat of earlier chemistry]ss12 19 O H CH3 CH3 H chapter 11 11. Structure - tetrahedral (sp3) oxygen & carbon Ethers, Sulfides and Epoxides - 11 diethyl ether O ~109 tetrahydrofuran or THF O dihydropyran O 11. X HO ? OH X ? O Two ways to prep benzyl ethyl ether Ethers, Sulfides and Epoxides - 11 Williamson ether synthesis SN2 substitution recall similar problems in chapter 9 (9.46, 9.48 and 9.49) 11. O OH X X HO ?? Two ways benzyl ethyl ether can be prepared Specifically how would each be done? Nucleophic form of the alcohol? Solvent? - alkoxide - polar - aprotic - benzylic substrate Which way should be best? Others? SN1, some cases Ethers, Sulfides and Epoxides - 11 11. H+/ROH addition to olefins, “hydration-like” Ethers, Sulfides and Epoxides - 11 OO H H++ Recall/review addition problems 6.29, 6.34a Familiar? OO H H+ O H H+ 11. Ether Protecting Groups (ref. problems 6.33) Ethers, Sulfides and Epoxides - 11 Problem 6.33: alcohol “interferes” with Br2 addition protecting group (Pg) = blocking group O Pg +Pg Br2 O Pg Br Br -Pg1 2 3 O H want O H Br Br O H H2N- (xs) 11. Ethers, Sulfides and Epoxides - 11 TMS ethers O Si pyridine Si Cl CH3 H3C CH3 O Si Br BrBr2 O H O H Br Br O H H2N- (xs) O TMS H2N- (xs) H+/H2O F-or 11. Crown Ethers - not covered Cyclic polyethers The parent name is crown, preceded by a number describing the size of the ring followed by the number of oxygen atoms in the ring, e.g 18-crown-6 O O O O O O 11. Ethers, Sulfides and Epoxides - 11 Prep of epoxides - better mechanistic view O O R OH + O O R O H + O H O R O + O O R OH stereospecific like bromine addition 11. other epoxide sources - halohydrins/base mechanism intramolecular “SN2” See problem 9.50, same reaction R C C H H H Br2 H2O (xs) R C C H H H O Br R C C H H H O:BH 11. chapter 6 Other sources of epoxides - halohydrins/base Et C C H H H OH Br Et C C H H H O:B Et C C H H H O H :B Et C C H H H Br2 H2O Et C C H H HBr H O H 11. Regioselectivity O 1o-less hindered3 o more hindered SN2 like O O OCH3:NuOCH3 O OCH3 H proton source 11. O H+ O O-H CH3HO-CH3 O H Regioselectivity SN1 like H O CH3 O H O CH3 H 11. Regioselectivity O H+ O O-H CH3HO-CH3 O O O-CH3 DMF O CH3 H2O O O CH3 H OH+ 11. O O + H2N NH22 1 R R' N H H N H HO O _ R R' N H N H HO OH R R' Reaction Continues ami ne epox ide Application of Epoxy Chemistry 11. N R' N H2 C C H OH R C H2 H C OH CH2C H OR H H N R' N H2 C C H OH R H2 CC H OH R C H2 H CC H2 H C OH OH N H2 C C H OHH2 CC H OH R N H2 C C H OH R H2 CC H OH N C H2 H CC H2 CHR OH OH R' N C H2 H C RC H2 H C OH OH R' N R' N H2 C C H OHH2 CC H OH C H2 H CC H2 H C OH OH R R R R N H2 C C H OHH2 CC H OH R N C H2 H CC H2 CHR OH OH R' R R N H2 C C H OH R H2 CC H OH N C H2 H C RC H2 H C OH OH R' R R Application of Epoxy Chemistry 11. O C N: HOR O C N: H O C C R1. O C C R O C C H R 2. H O R C H H C CH3 H H O 1. O C H H C CH3 H H H2. H2O