Organic chemistry university of california riverside. What is the mechanism by which nabh4 attacks in demercuration. The organic radical abstracts the hydrogen atom and the product is formed. Now that were familiar with the reaction itself, lets take a look at a specific example to get a better visual aid of what it. The addition of water by oxymercuration reduction has two advantages over acidcatalyzed addition. Oxymercurationdemercuration alkene reaction mechanism. Oxymercurationdemercuration is an alternative reaction to acidcatalyzed hydration with the advantage of preventing possible rearrangements. Actually, the oxymercuration involves the formation of a cyclic carbocation. However, under normal laboratory conditions, water is added to an alkene by a procedure known as oxymercuration reduction. Chapter 8 reaction examples based on the 6th edition of the textbook solved problem 81, p. Oxymercuration is a process by which water is added to an alkene through treatment of the alkene with mercury ii acetate hg o 2 cch 3 2, usually abbreviated hg oac 2 in an aqueous tetrahydrofuran solvent.
Oxymercuration organic chemistry video clutch prep. View notes mechanism of oxymercuration demercuration from econ 2a at cornell college. Oxymercuration and demercuration reduction of alkene, diene, conjugated diene and conjugated carbonyl compounds. Oxymercuration is very regioselective and is a textbook example of reaction obeying markovnikovs reaction. Merge pdf files combine pdfs in the order you want with the easiest pdf merger available. Oxymercuration demercuration rn omdm rn mechanism preperation of alcohol file d1ew8zl3xt6ffu37zg5krflkcexh3a1rxmview. Oxymercuration demercuration, also referred to as oxymercuration reduction is slightly more confusing than that average alkene reaction.
How to merge pdfs and combine pdf files adobe acrobat dc. The reaction proceeds in a markovnikov manner and is stereospecific anti addition. Markovnikov hydration of vinylcyclopropanes by oxymercuration demercuration. In oxymercuration, the alkene reacts with mercuric acetate acohgoac in aqueous solution to yield the addition of an acetoxymercuri hgoac group and a hydroxy oh group across the double bond.
What is the mechanism of oxymercurationdemercuration of. Provide the alkene needed to synthesize each of the following by oxymercuration demercuration provide the alkene needed to synthesize each of the following by hydroborationoxidation. In oxymercuration, the alkene reacts with mercuric acetate in aqueous solution to yield the addition of an acetoxymercury group and a. Chapter 85 hydration by oxymercurationdemercuration. This mechanism is similar to the previous electrophilic addition reactions. The mechanisms of oxymercuration canadian journal of. Carbocation rearrangement is a process in which the carbocation intermediate can form a more stable ion.
Why does water attack the more substituted carbon in oxymercuration. A specific example of an alkoxymercuration demercuration reaction. Oxymercuration followed by reductive demercuration is called an oxymercurationreduction reaction or oxymercurationdemercuration reaction. To change the order of your pdfs, drag and drop the files as you want.
Noncatalytic, direct hydration of alkenes requires very drastic conditions, lacks regioselectivity and can give rise to side reactions. With this quizworksheet, youll be answering multiplechoice questions on the alkoxymercuration demercuration of ethers. This with oxymercuration demercuration synthesis by oxy mercuration demercuration procedure. Oxymercuration demercuration omdm alcohol preparation. Not because its any more difficult than oxymercuration, but simply because students tend to overlook the alcohol reagent and miss the alkyl group in the product. Media in category oxymercuration reactions the following 19 files are in this category, out of 19 total. In order to achieve markovnikov addition on a laboratory scale, an organometallic reaction, oxymercuration, is used.
Oxymercuration demercuration of alkenes overall reaction overall reaction. Synthesis of a sialic acid ketoside by an intramolecular oxymercurationdemercuration reaction. Mechanism of oxymercurationdemercuration mechanism of. Demercuration is the removal of the mercury containing species, which is achieved by reaction with sodium borohydride, a powerful reducing agent, which replaces the mercury species with a hydrogen atom giving the desired alcohol. This is a non traditional carbocation, but the final reaction becomes nonstereospecific, as you will later find out. In oxymercuration, the alkene reacts with mercuric acetate acohgoac in aqueous solution to yield the addition of an acetoxymercury hgoac group and a hydroxy oh group across the double bond. Characteristics of oxymercuration demercuration are. The oxymercuration reaction is an electrophilic addition organic reaction that transforms an alkene into a neutral alcohol. Mechanism of alkenes oxymercuration demercuration rch oh 1 ch3co2hg, h2o ch2 r 2 nabh4, naoh, h2o ch3 r. The major difference is that a mercurium ion bridge stabilizes the carbocation intermediate so that it cannot rearrange. Illustrated glossary of organic chemistry oxymercuration. Click, drag, and drop to reorder files or press delete to remove any content you dont want.
No rearrangements no carbocation intermediate, cyclic mercurinium ion is the intermediate 2. The stereochemistry of oxymercurationdemercuration there is no stereochemical control in this reaction because the addition of the mercuric ion and the hydrogen in the demercuration step occurs both as syn and anti orientation. Ppt on oxymercuration and demercuration free download as powerpoint presentation. As a result, the new stereogenic center forms in r and s configuration leading to a racemic mixture. The two steps of oxymerecurationdemercuraton takes place on opposite faces of the double bond creating trans stereochemistry. Typical reagents are mercury acetate, hgoac 2 in roh thf unfortunatley, mercury compounds are generally quite toxic. But it turns out that theres actually more than one way to add alcohols to double bonds and thats actually a huge focus of this section. The reaction is useful, however, because strong acids are not required, and carbocation rearrangements are avoided because no. Markovnikov addition the rst step, known as oxymercuration, has the water and mercuric acetate adding to the double bond the second step, known as demercuration, has sodium borohydride. I put up chapter 11 from basic chemistry concepts see above under useful links. Journal of organometallic chemistry 1978, 159 3, 237249.
Oxymercurationdemercuration of alkenes mechanism for reaction of alkenes with hgoac 2 h 2 o step 1. Notice that overall, the oxymercuration demercuration mechanism follows markovnikovs regioselectivity with the oh group is attached to the most substituted carbon and the h is attach to the least substituted carbon. This reaction is very fast and proceeds with 90% yield. Click add files and select the files you want to include in your pdf. I think its a combination of the extra steps, involvement of mercury, and the mysterious reduction by sodium borohydride. The latest example is the best to explain aminomercuration idea. Mercury carries a partial positive charge in the acetate complex and is the electrophile. The oxymercuration demercuration of alkenylsilanes in aqueous tetrahydrofuran. Chapter 8 reaction examples based on the 6th edition. This reaction is regioselective markovnikov and stereoespecific anti. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Alkoxymercuration demercuration reduction is a tricky mechanism for organic chemistry students. Please, select more pdf files by clicking again on select pdf files. Oxymercuration demercuration, also called oxymercuration reduction hgaco2 h2o nabh4 ho a markovnikov alcohol hgaco2 h2o nabh4 oh markovnikov.
Mar 27, 2015 ericminikel cambridge, ma chem20 these are my notes from lecture 20 of harvards chemistry 20. Alkoxymercuration demercuration of 2methyl2butene draw the structure of the product that is formed when the compound shown below is treated with the following reagents. Information from its description page there is shown below. The electrons act as the nucleophile with the electrophilic hg and loss of an acetate ion as a leaving group, forming the mercurinium ion. Ppt on oxymercuration and demercuration alkene chemical. Oxymercuration demercuration also gives markovnikov orientation of the alcohol. First, the mercuric acetate breaks apart into ions, the acetate anion, and the mercuroacetic cation, which you have correctly depicted. Organic chemistryintroduction to reactionsoxymercuration. Oxymercuration demercuration is a two step pathway used to produce alcohols. Oxymercuration and demercuration reduction of alkene, diene, conjugated. You can merge pdfs or a mix of pdf documents and other files. Rearrange individual pages or entire files in the desired order. This is the way alkenes are converted into alcohols industrially.
So what im going to do now is im going to show you guys an alternate reaction that we could use that also adds alcohols to double bonds and its called oxymercuration demercuration. Additionally, there may be errors in any or all of the information fields. With carbocation rearrangement, the reaction would not be able to hydrate quickly under mild conditions and be produced in high yields. The oxymercuration of norbornenes has been found to be acidcatalyzed, and to give oxymercurials which have a higher dipole moment and greater stability toward deoxymercuration than do their diastereomers in which the configuration of the mercuri linkage has been inverted. If the oxymercuration is carried out in a presence of a hydroperoxide instead of water or alcohol, the product after demercuration with nabh 4 is an alkyl peroxide peroxymercuration. However, oxymercuration demercuration is not susceptible to the rearrangements. The pdf file was rather large so i tried to break it down. Product is analogous to almost exclusive markovnikov addition of water regioselectivity pred. Alkoxymercuration demercuration reduction alkene reaction. Oxymercuration oxymercurationdemercuration of alkenes. Treatment of an alkene with mercury acetate in presence of water produce the corresponding alcohol.
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