Download Problem Set 9 for Chem 220a: Organic Chemistry Reactions and Grignard Reagents and more Assignments Organic Chemistry in PDF only on Docsity! PS9.html copy Page 1 Wed, Oct 31, 2001 2:34 PM Chem 220a Problem Set 9 Chapters 10 and 11 Due: Monday, December 3, 2001 1. The alcohol module in ORGO will give you a good review of some of the fundamental reactions discussed in class and in Chapters 10 and 11. The topic of oxidation levels of organic compounds is addressed in passing on pg. 458. We will consider the issue in more detail as described in Oxidation Levels. See also Web of Reactions-I. 2. The generic Grignard reagent, RMgX, is the conjugate base of a very weak acid, R-H (pKa ~45- 50). Accordingly, Grignard reagents can deprotonate stronger acids than R-H. When methyl magnesium bromide reacts with 1-propyne, methane and CH 3 CCMgBr (1) are formed. However, 3-bromo-1- propyne (2) forms a normal Grignard reagent (HCCCH 2 MgBr) 3 with magnesium in ether without undergoing conversion to 1. Explain. [Hint: Consider the resonance structures of 3.] 3. Chemist Courtney needs to prepare a large quantity of n-propyl magnesium bromide in ether. She finds two cans of ether in the lab. Can A contains 600 mL and can B contains 100 mL of ether. She notices that can A is contaminated with 5% of ethanol from manufacturing while can B is free of ethanol. She is fully aware of the downside of having alcohols in the presence of Grignard reagents but she needs 500 mL of pure ether for her experiment. She has access to magnesium and n-propyl bromide but no more ether. How did she cleverly resolve her dilemma? Victor Grignard (1871-1935) Co-Nobel Prize (1912) 4. You will remember that Alexander Williamson attempted to convert ethanol, via the agency of its sodium salt, into its higher homologue, n-butyl alcohol, by reaction with ethyl iodide. Instead, he formed diethyl ether. How would you, with the wisdom of 150 years and the aid of chapters 10, 11 and all that has prece them, accomplish Williamson's objective? PS9.html copy Page 2 Wed, Oct 31, 2001 2:34 PM 5. Compound A, C 8 H 16 , undergoes hydroboration and alkaline peroxide oxidation to provide B, C 8 H 18 Treatment of B with excess Jones' reagent gives C, C 8 H 16 O. Ozonolysis of A affords a single compoun D, C 4 H 8 O. D is converted into E, C 4 H 8 O 2 , upon treatment with Jones' reagent. Compound F, C 4 H 8 , yields two products, G and H (a ketone) upon ozonolysis. Hydroboration and alkaline peroxide oxidation F gives I, which, upon reaction with PCC, affords D. What are the structures of B-I? Explain and illustr What structures satisfy A? How can you distinguish between your options for A? 6. How many grams of CrO 3 are required to oxidize 1.5 moles of cyclohexanol? Show work. 7. Each of the following chemical transformations requires more than one step. Provide solutions.
