Here, we start with a cis alkene and if you draw the OH groups as trans you should also keep the “bent” geometry of the carbon chain. if the alkene was originally trans not cis, then the backside attack of H2O after the epoxide forms would create a molecule where if u rotate it, it would look like B. but since the alkene was cis to start with, i think the backside attack of H2O after the epoxide forms would yield C. For question 34, I thought bromination is an anti-addition, so on the Fischer projection the Br atoms should point away from each other…? Predict the products if the following alkenes were reacted with catalytic hydrogen. They should be there by the end of the week. Click for the reaction video. Your videos are sooo awesome! Vincent: There’s a link at the bottom for the solution set. or were they just rotated to make both OH bonds look the same since it’s a meso compound? , Oh wow you are absolutely correct Feldan. Hi Leah, 1) Q12: Would we end up with a racemic product? Stuck? Identify the product when the alkene below is reacted with sulfuric acid. In Question 10 as six membered ring are more stable than seven membered ring (due to more angle strain in seven membered)the carbocation rearrangement results into hydrogen shift instead of ring expansion.Am I right? Stuck? Yes, that is correct. Glad to help. HOlly: Should have been instant. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. 1) o hcl ch3oh 2) hcl ch3 3) hcl 4) hcl 5) hbr 6) hcl 7) ch3 h3o + 8) h3o + 9) h3o + 10) hg(oac)2, h2o nabh4 ch3 11) hg(oac)2, h2o nabh4 Hint: Stuck on the stereochemistry of this question? Identify the structure of the unknown based on the two reactions provided below: Determine the major product(s) of the following reaction: Where are the hints or direct link to get help for these questions. Great practice, thank you Leah! All the topics in the quiz are covered in the Alkenes chapter which you can find on the index page: Is there a particular one you had a question about? Need help? The products (Markovnikov) are diastereomers of one another. Your considerations about the stereochemistry of the anti-hydroxylation are absolutely correct. watch this video. Specifically, go to the “Wedge and dash in Meso compounds” paragraph. Identify the reagents required to bring about this alkene to alcohol transformation. Maybe it is only a typo error but it is better to correct it in order to avoid confusion. This is, essentially, the same thing. 8.E: Alkenes: Reactions and Synthesis (Exercises), [ "article:topic", "Exercises", "showtoc:no" ], 8.1 Preparation of Alkenes: A Preview of Elimination Reactions, 8.2 Halogenation of Alkenes: Addition of X2X2, Predict the products for 1,2-dimethylcyclopentene reacting with Br. Stuck on this reaction? No they will not be the same product, they will be isomers of each other. S8.1.1. Show the stereochemistry of the final product. Alkene reactions are the foundation for all future organic chemistry reactions and mechanisms. Once finished scroll down and grab a free copy of the solutions. For help with this reaction click to watch the mechanism video, Identify the product formed when the following alkene is reacted with BH3 and THF, then followed up with H2O2 and NaOH. Take your time and think through each question. Have questions or comments? If you convert this into the more traditional zig-zag conformation, the OH groups now end up on the same side and it looks like it is a product of a sun-dihydroxylation, but it is not. Watch the recordings here on Youtube! Alkene reactions are the foundation for all future organic chemistry reactions and mechanisms. the answer for #18 is wrong, it should be D not C. It is C. Draw the alkene and cross each double bond replacing it with a carbonyl. The typical catalysts for the alkene hydrogenation are the platinum (Pt), palladium (Pd), and nickel (Ni). Hint: This is an anti-markovnikov reaction. For more information contact us at or check out our status page at Watch the reaction video here to review this reaction. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Give a reaction scheme with starting alkenes and required reagents to produce the following compounds. Hint: Consider how the intermediate impacts the regioselectivity of this reaction. Hint: Water and alcohol undergo similar reactions. They were indeed rotated, but this is not a meso compound since there is no plane of symmetry. Predict the E/Z isomers for the following molecule when reacted with H 2 SO 4. Watch this video. Hint: Don’t overthink it. Click the button below for details Yes. Since the bromine is the first addition to the alkene, this addition would be an anti-Markovnikov addition. By the way i’m from Papua New Guinea. What is the relationship between the two products? Predict the following products. I wish I’d seen this earlier! If you’re not sure how to proceed click the ‘hint’ link for the related mechanism tutorial video. The meso compound would have been produced if a syn dihydroxylation was performed. You should get three products – A, B, and D. I will try to find a better way of showing this but for now, consider the left carbonyl in product C – it cannot be formed. Notify me of followup comments via e-mail. If so, where? However, you should also pay attention to the stereochemistry of the alkene. Find this article on the index page which explains this in more detail: “Cis product in an anti Addition Reaction of Alkenes“. Hint: There is no given solvent, don’t make any assumptions , Compare your solutions to the answer key. Anyways, thank you for all the hard work. 8.3: Halohydrins from Alkenes: Addition of HOX, 8.4 Hydration of Alkenes: Addition of H2OH2O by Oxymercuration, 8.5 Hydration of Alkenes: Addition of H2OH2O by Hydroboration, 8.7 Oxidation of Alkenes: Epoxidation and Hydroxylation, 8.8 Oxidation of Alkenes: Cleavage to Carbonyl Compounds, 8.9 Addition of Carbenes to Alkenes: Cyclopropane Synthesis, 8.10 Radical Additions to Alkenes: Chain-Growth Polymers, 8.11 Biological Additions of Radicals to Alkenes, 8.12 Stereochemistry of Reactions: Addition of H2OH2O to an Achiral Alkene, 8.13 Stereochemistry of Reactions: Addition of H2OH2O to a Chiral Alkene, 7.E: Alkenes: Structure and Reactivity (Exercises), 9.E: Alkynes: An Introduction to Organic Synthesis (Exercises). I`m just wondering for Q12 and Q8, if it is possible to get some additional products. The videos i saw from you are the best, more then what my tutors gave and i really love it. Hint: Other than degree of substitution, what ELSE can cause a carbocation rearrangement? Pay particular attention to the stereochemistry of product. When you convert the product of anti addition to a Fischer projection, the Br atoms then appear to be on the same side. You can also check this by the R and S configuration; in a meso compound every S is converted to an R and vise versa. In elimination reactions there tends to have a mixture of products. Meso Compounds” on the index. The quiz covers all the main reaction of alkenes covered in a typical undergraduate organic chemistry course,, Predict the products for 1,2-dimethylcyclpentene reacting with HCl, give the proper stereochemistry. Changing the Position of a Leaving Group. Organic Chemistry 1 and 2 Summary Sheets – Ace your Exam. thanks for pointing it out, The true key to successful mastery of alkene reactions lies in practice practice practice. I fell for my own trick!!!!! Be sure to include all possible products. Predict the E/Z isomers for the following molecule when reacted with H2SO4. Alkene Reactions Practice Problems. Solutions. The Stereochemistry of Alkene Addition Reactions, Free-Radical Addition of HBr: Anti-Markovnikov Addition, Hydroboration-Oxidation of Alkenes: Regiochemistry and Stereochemistry with Practice Problems, Halogenation of Alkenes and Halohydrin Formation, Ozonolysis of Alkenes with Practice Problems, Syn Dihydroxylation of Alkenes with KMnO4 and OsO4, Anti Dihydroxylation of Alkenes with MCPBA and Other Peroxides with Practice Problems, Oxidative Cleavage of Alkenes with KMno4 and O3, Cis product in an anti Addition Reaction of Alkenes. Sometimes tricky looking reactants yield simple products. Click for the mechanism video, Identify the product when the following alkene reacts with Hg(oAc)2 in alcohol followed by NaBH4, Hint: Pay close attention to each of the given reagents. Sometimes you’ll see the Pd/C instead of just the pure metal. In elimination reactions there tends to have a mixture of products. review this video, Identify the product formed when the given alkene reacts with hydronium, Hint: Pay special attention to the stability of the reaction intermediate. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. For question 6, I think OEt should have added since ethanol is used as nucleophile not water. organic chemistry i – practice exercise alkene reactions and mechanisms for questions 1-24, give the major organic product of the reaction, paying particular attention to regio- and stereochemical outcomes. You’re correct Wanda, it’s a mistake on the key, can you please send the solutions to my email?