Organic Chemistry

CHM1240: PROBLEM SET # 6 1. Show the major products in the following reactions. Pay attention to stereochemistry and regiochemistry when appropriate. 2. Show the major products in the following reactions. Pay attention to stereochemistry and regiochemistry when appropriate. 3. Many additions of bromine to alkynes give only trans dibromide products. However, there are exceptions. Here is one. Explain why phenylacetylene 1 give both cis- and trans-dibromomide products 2 and 3 on reaction with 1 equivalent of bromine. 4. Please propose an efficient synthesis of the following compounds 3 and 4 from starting materials 1 and 2 , respectively. You may use inorganic and organic reagents of your choice. Mechanism are not required

CHM | 1240 | Organic Chemistry | homework | CHM1240: PROBLEM SET # 6 1. Sh

CHM1240: PROBLEM SET # 10 1. Predict the product(s) in the following reaction. If more than one products are formed, predict which one will be the major product. 2. Propose a detailed mechanism for the following reaction 3. Explain the difference in reactivity between cis -2-bromocyclohexanol 1 and trans -2-bromocyclohexanol 2 in the following reaction. 4. Suggest reagents for the preparation of the following isomeric epoxides 2 and 3 from starting material 1 : 5. Please propose an efficient synthesis of the following compound 2 from starting material 1 . You may use inorganic reagents, organic reagents, and alkyl halide of your choice. Mechanism are not required. 6. MCAT question : The following carcinogenic diol epoxide 2 is formed when the liver enzymes metabolize benzo[a]pyrene 1 that is found in cigarette smoke and auto exhaust. This epoxide 2 survives long enough to react with some of the nucleophilic sites of the cell’s DNA, causing mutations. Among these reactions, is the one that occurs between the C(2)-nitrogen (boxed) of a guanosine residue 3 (one of the DNA bases) and the epoxide 2 . Draw two possible products 4 and 5 of this reaction and indicate the relevant stereochemistry in each case (Hint: these reactions are analogous to those involving epoxides and hydroxide anions).

CHM | 1240 | Organic Chemistry | homework | CHM1240: PROBLEM SET # 10 1. P

CHM1240: PROBLEM SET # 4 - ANSWER KEY 1. Explain why the O-H hydrogen in acetic acid is much more acidic than any of the C-H hydrogens. The oxygen of the O-H is more electronegative than the carbon of the C-H, and consequently, the O-H bond is more strongly polarized than the C-H bonds. In addition, the acetate anion is stabilized by resonance. 2. Explain which of the following are likely to act as Lewis acids and which as Lewis bases. The Lewis acids shown below can accept an electron pair because they have a vacant p orbital. The Lewis bases have nonbonding electron pairs Lewis acids: AlBr 3 and BH 3 Lewis bases: 3. Predict the structure of the product formed in the reaction of the organic base pyridine with the organic acid benzoic acid, and use curved arrows to indicate the direction of electron flow. 4. Which one is a strong acid (phenol or methanol)? Explain your reasoning. Phenol (pKa = 9.9) is stronger acid than methanol (pKa = 15.5). When phenol loses its hydrogen the resulting anion is stabilized by resonance. 5. Arrange the following carboxylic acids in order of increasing acidity (least acidic →most acidic). Briefly explain your reasoning. The order of acidity is as follows: A < C < B < D, with D being the most acidic in the series. The acidity of the carboxylic acids enhanced by the electronegativity of the substituents at the  -position. However, this effect levels off as the distance from the carbonyl group increases. Thus, C is less acidic than B . Fluorine is more electronegative than chlorine, and so D is more acidic than B 6. Carbocation reacts with water to give an alcohol How can you account for the fact that the following carbocation A gives a mixture of two alcohols B and C on reaction with water? The carbocation A can be represented by two resonance forms. Reaction with water can occur at either positively charged carbon, resulting in two products B and C .

CHM | 1240 | Organic Chemistry | question bank | CHM1240: PROBLEM SET # 4 - ANS

NAME: _____ key __________________ CHEMISTRY 2220 Fall 2017 Hour Exam #4 Monday, December 8, 2017 I. (25 Pts) A. (4 pts) Which of the following structures can undergo retro (reverse) aldol reactions? Circle your answers. B. (12 pts) Give the structure of the products that would be formed if a retro-aldol reaction can occur. OH CH 3 O a. b. c. HO O CH 3 d. O OH Prob 1

EXAM4.pdf.pdf-NAME: _____ key __________________ CHEMISTRY 2220

CHM1240: PROBLEM SET # 4 1. Explain why the O-H hydrogen in acetic acid is much more acidic than any of the C-H hydrogens. 2. Explain which of the following are likely to act as Lewis acids and which as Lewis bases. 3. Predict the structure of the product formed in the reaction of the organic base pyridine with the organic acid benzoic acid, and use curved arrows to indicate the direction of electron flow. 4. Which one is a stronger acid (phenol or methanol)? Explain your reasoning. 5. Arrange the following carboxylic acids in order of increasing acidity (least acidic →most acidic). Briefly explain your reasoning. 6. Carbocation reacts with water to give an alcohol How can you account for the fact that the following carbocation gives a mixture of two alcohols on reaction with water?

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