Epoxide acid-catalyzed ring opening

Predict which carbon undergoes nucleophilic attack on acid catalyzed ring opening of cis 3 3 3 tnfluoro 2 3 epoxybutane Examine the C—O bond distances of the protonated form of the epoxide on Learning By Modeling How do these bond distances compare with your prediction" ... 

Acid-catalyzed ring opening of epoxides is discussed in Section 16.13. 

Under some circumstances, acid-catalyzed ring opening of 2,2-disubstituted epoxides by sulfuric acid in dioxane goes with high inversion at the tertiary center.116... 

If the epoxide is unsymmetrical, the nucleophile attacks primarily at the more substituted carbon atom in acid-catalyzed ring opening. 

Nichols and co-workersstudied the formation of j8-hydroxy nitrate esters via the acid-catalyzed ring-opening of epoxides with nitrate anion. Reactions were conducted in aqueous media using solutions of ammonium nitrate is nitric acid and under nonaqueous conditions using solutions of pure nitric acid in chloroform. 2-Nitratoethanol (32) is formed in 58 % yield from ethylene oxide (30) using either of these methods. ... 

The ethylene glycol, bp 198°C, is readily vacuum distilled and separated from the DEG, bp 246°C, and TEG, bp 288°C. The mechanism of the reaction follows the general scheme for acid-catalyzed ring openings of epoxides. 

Summary Epoxide Syntheses 648 14-12 Acid-Catalyzed Ring Opening of Epoxides 649... 

The regiochemistry of acid-catalyzed ring opening depends on the epoxide s structure, and a mixture of products is usually formed. When both epoxide carbon atoms arc cither primary or secondary attack of the nucleophile occurs primarily at the less highly substituted site. When one of the epoxide carbon atoms is tertiary,however nucleophilic attack occurs primarily at the more highly substituted site. Thus, L,2-epoxypropane jeac t with HCl to give primarily l-chloro-2-propanol, but 2-methyl 1,2-cpoxypropane gives 2-chloro-2-methyl-l-propanol as the major product. 

Cadogan et al. have prepared epoxide 14 from bicyclic sulfone 13. Acid-catalyzed ring opening gives a mixture of exo,exo- and exo,endo-htov[io yAnns (Scheme 6) <1996J(P2)2309>. 

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