This organic chemistry video tutorial focuses on alcohol reactions. Epoxides in complex molecule synthesis aziridines and. Providethemajorproduct of each of thefollowing reactions. Epoxides oxiranes are threemembered cyclic ethers that are easily prepared from alkenes by reaction with peracids.
This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. Mediated reactions of epoxides muzart 2011 european. If the epoxide reacts with a biological macromolecule, the result is potentially devastating. Organic reactions summary alkenes, alkynes and variations for. Compound contains oxygen, but oh and co stretches are absent. Organic reactions summary for use as a study guide beauchamp. Providethemajorproductofeachofthefollowingreactions. Ethers, sulfides omit, and epoxides chapter 11 2 structure the functional group of an ether is an oxygen atom bonded to two carbon atoms. Ethers have two alkyl groups bonded to an oxygen atom. We will also think about how those reactions are occurring on a molecular level with reaction mechanisms. Ethers ethers are organic compounds with two alkyl groups. A nickelcatalyzed cc bondforming reaction between alkynes and epoxides has been developed.
Typical first year organic reactions beauchamp 2 y. Structure ethers can be thought of as alkyl analogues of water. Alcohols, ethers, epoxides, sulfides organic chemistry. Thus, epoxides have angle strain, making them more reactive than other ethers. When ethers are exposed to air for a long time, they form peroxides and may result to explosives. Usually itll be either mcpba or mmpp, but peroxyacetic acid is an older reagent that also works. So in this video, well look at the ring opening reactions of epoxides using strong nucleophiles. Ochem cheat sheet alcohols and epoxides handout chem. The proposed mechanisms are described, with some personal observations in some cases.
Epoxides can be transformed into a variety of products. Pdf pdmediated reactions of epoxides jacques muzart. Epoxides are produced biologically as oxidation products of alkenes and aromatic compounds. Synthesis of complex molecules by rearrangement reactions of epoxides. You do not need to draw or indicate any inorganic ionic products. Simply put, organic chemistry is like building with molecular legos. Alcohol and thiol groups are important functional groups for applications ranging from enzyme reactions to making flexible contact lenses. Ochem cheat sheet alcohols and epoxides handout chem 2310.
Uses since ethers are relatively unreactive and are strongly polar due to the lone pairs on the oxygen, they are commonly used as solvents for organic reactions. An example is the reaction of ethylene oxide with a grignard reagent discussed in section 15. Epoxide opening reactions recent advances and synthetic. It contains plenty of examples and practice problems for you work on. Epoxides that are formed in the liver by cytochrome p450 undergo ringopening reactions. The oxygen of the epoxide comes from molecular oxygen. This low reactivity makes them useful as solvents, e. Epoxides can also be synthesized by the treatment of halohydrins sec. Reactions of epoxides ringopening chemistry libretexts. They are produced on a large scale for many applications. Reaction pathway overview for alkene and alkyne reactions including radicals, alcohols, carbonyls, epoxides and grignards. The first reaction, cleavage of ethers by hydrogen halides, is exemplified overall below for the case of ethoxypropane and hydrogen bromide. European journal of organic chemistry 2017, 2017 12, 16471656.
Janice gorzynski smith university of hawaii chapter 9. The base catalyzed opening of epoxides goes through a common s n 2 mechanism. This protonated oxygen can equilibrate to an open form that places more. If you find this helpful please click the share buttons above filed under. Nov 26, 20 reaction pathway overview for alkene and alkyne reactions including radicals, alcohols, carbonyls, epoxides and grignards. Coppercatalysed reactions of allylic grignard reagents with. In contrast to alcohols, ethers are fairly unreactive except to very strong acids such as hi or hbr. Epoxides are ethers having the oxygen atom in a threemembered ring. In dialkyl ethers, oxygen is sp3 hybridized with bond angles of approximately 109. Aug 03, 2016 this organic chemistry video tutorial focuses on alcohol reactions. An epoxide is a cyclic ether with a threeatom ring. Hence, milder conditions can be used for the ringopening reactions of epoxides than are required for the cleavage of ordinary ethers. Acidic cleavage of ethers alcohols, ethers, epoxides. Directing group heteroatom oxygen was essential for optimal reactivity sharpless, k.
Alcohols, ethers and epoxides complete the equations for the following reactions. If oxides have a lot of ring or angle strain, this makes them very reactive towards ring opening. Reactions of epoxides, contd the value of epoxides is the variety of nucleophiles that will open the ring and the combinations of functional groups that can be prepared from them. Ringopening reactions can proceed by either s n 2 or s n 1 mechanisms, depending on the nature of the epoxide and on the reaction conditions. Epoxides can be prepared from a variety of precursors. Introduction alcohols, ether, and epoxides are 3 functional groups that contain c. Organic reactions summary for use as a study guide. Alcohol reactions phenols, ethers, epoxides, preparation. Ethers and epoxides ethers are a class of compound of the general formula ror. So in the first step, we add a strong nucleophile to our. Organic reactions summary alkenes, alkynes and variations.
Epoxides can be used as nucleophiles in intramolecular nicholas reactions. The coc bond angle for an epoxide must be 60, a considerable deviation from the tetrahedral bond angle of 109. Reactions of alcohols, ethers, epoxides, amines, and sulfurcontaining compounds 10 chemists search the world for plants and berries and the ocean for flora and fauna that might be used as the source of a lead compound for the development of a new drug. Draw the major organic product from each of the reactions shown below. Reactions of epoxides with neighbouring nucleophiles. E1 practice exam 2 2016, questions and answers lab 5 base extraction of benzoic acid from acetanilide jan william simek l g wade solutions manual for organic chemistry, sixth edition by l. Acid catalysed reactions of epoxides i mechanism of acid catalysed reactions of epoxides with nucleophiles ii ring formation by acid catalysed intramolecular 1 1 4 nucleophilic attack of epoxides 10 iii mechanism of acid catalysed rearrangements of epoxides to give carbonyl compounds.
Lets consider a couple reactions that involve ethers and epoxides. Ochem cheat sheet addition to alkenes handout ochem cheat sheet oxidation and reduction handout ochem cheat sheet sn2 vs e2 vs. To draw a formula use the drawing window opened by the draw formulas button. This reaction is an intramolecular variation of the williamson ether synthesis sec. Because of the large angle strain in this small ring, epoxides undergo acid and basecatalyzed co bond cleavage more easily than do larger ring ethers.
The nonenzymatic ringopening reactions of epoxides provide a nice overview of many of the concepts we have seen already in this chapter. Ringopening reactions of epoxides acidcatalyzed epoxide opening. However, epoxides are much more reactive than ethers under acidic conditions because of their angle strain. Stereoselective ringopening reactions of epoxides in water. Then we will be ready to learn about some reactions that involve alcohols, ethers, epoxides, thiols, and sulfides as both reactants and products. Sep 22, 2012 we will also think about how those reactions are occurring on a molecular level with reaction mechanisms.
If the epoxide is asymmetric, the structure of the product will. All reactions involve nucleophilic attack at carbon and lead to opening of the ring. Although the most substituted epoxide is favored, the terminal epoxide is more reactive toward nu attack. For example, very low concentrations of acid catalysts are required in ringopening reactions of epoxides.
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