Unformatted text preview: Name Spring 2005 Final Cumulative Examination – CHEM 235 Dr. James Poole Examination Instructions • This examination is worth 200 points in your final grade of 800 points. • This examination will take up to 120 minutes, and consists of 13 questions (including a brief multiple choice section on Lab learning outcomes), plus a bonus question. • You may not be required to answer all components of a question, so read each question carefully. Note also that some questions are worth more than others: if a section of a question can be expected to be worth, say, 4 or more points; it should be obvious that a one word answer will not suffice • • • For questions where you have made a choice of which section to answer, clearly indicate which sections you wish to have graded. After the examination, your graded laboratory reports and assignments will be available for collection. Note that any reports not collected after June 1 will be shredded. Note that the following may not be used in the examination: o o Molecular modeling kits Computers, Mobile phones, personal organizers, or any other device capable of electronic storage of significant amounts of information, or remote access to the internet. o Textbooks, reference books, lecture notes or any other written material. • • Please ensure that mobile phones, pagers, blackberries etc. are turned off, and placed in a bag or pack prior to the start of the examination. Please do not turn this page over until instructed to do so by the examination proctor. Common Abbreviations: NBS N‐bromosuccinimide BuLi n‐butyllithium PCC Pyridinium chlorochromate DMSO Dimethyl sulfoxide ‐OTs p‐toluenesulfonate (tosylate) ‐TMS trimethylsilyl group DMF mCPBA THF N,N‐Dimethyl formamide m‐chloroperbenzoic acid tetrahydrofuran ‐TBDMS tert‐butyldimethylsilyl group 1 Question 1 O OH Name (24 points) Provide systematic names for four of the following seven structures. F O O N O Cl O O2 N OCH3 N H OCH3 COCl H3C O H SH COOH 2 Question 2 m‐tert‐butylphenol (S)‐2‐fluoroethyl 2,4‐dinitrobenzoate (1S,5R)‐5‐fluorocyclohex‐3‐ene carbaldehyde 15‐crown‐5 Name (18 points) Draw the structures corresponding to three of the following five names. (R)‐N,N‐diethyl‐3‐methyl‐5‐aminopentanoic acid 3 Question 3 Name (30 points) Predict the outcomes (including any stereo‐ or regiochemical outcomes) for ten of the following fifteen reactions. N(CH3)3 I Ag2O H2O, ∆ 1) NaNO2/HCl/H2O O NH2 2) CuBr/HBr 1) NaBH4/EtOH 2) H+/H2O OCH3 NO2 O O O + Br2 FeBr3 N H SO3/H2SO4 Br 1) NaH/ether OH 2) conc. HBr O ∆ 1) NaH/ether P C6H5 Br 2) O C6H5 C6H5 O O H+/H2O CrO3 OH H+/H2O mCPBA CH2Cl2, 0oC NH2OH O OH H2SO4 ∆ EtOH/H2O pH 5 CH3I SH NaHCO3 4 Question 4 Name (10 points) Explain what is meant by the term “aromatic”, and provide examples of two features of the structure and reactivity of benzene that arises from the aromaticity of this compound. Question 5 (15 points) Choose three of the following four sets of compounds and rank them according to the criteria shown: (a) In order of increasing acidity (1 = most acidic, 4 = least acidic) O2N COOH OH COOH F COOH (b) In order of increasing acidity (1 = most acidic, 4 = least acidic) F OH OH OH F OH (c) In order of increasing basicity (1 = most basic, 4 = least basic) NC NH2 NH2 NH2 NH2 (d) In order of increasing reactivity toward electrophiles (1 = most reactive, 4 =least reactive) Cl NO2 OCH3 5 Question 6 Name (12 points) Describe and explain the differences between the two mechanisms for nucleophilic substitution, SN1 and SN2. Question 7 (12 points) Describe the three phases of a free radical chain reaction, using the free radical halogenations of alkanes as an example. You should include the mechanism of this reaction as part of your answer. 6 Question 8 Name (17 points) Predict the outcome of the following reaction, including any stereo‐ or regiochemical outcomes, with reference to the relevant reaction mechanism. You must include the reaction mechanism as part of your answer. You may include any additional structures or diagrams to illustrate your answer. Cl HNO3/H2SO4 ∆ 7 Question 9 Name (15 points) Predict the outcome of the following reaction, including any stereo‐ or regiochemical outcomes, with reference to the relevant reaction mechanism. You must include the reaction mechanism as part of your answer. You may include any additional structures or diagrams to illustrate your answer. OH O Cl 8 Question 10 Name (19 points) Predict the outcome of the following reaction, including any stereo‐ or regiochemical outcomes, with reference to the relevant reaction mechanism. You must include the reaction mechanism as part of your answer. You may include any additional structures or diagrams to illustrate your answer. O + OH H2SO4/H2O 9 Question 11 Name (10 points) Provide an explanation for the following: cyclopentadiene is a much stronger acid than 1,4‐pentadiene. +H pKa = 18 +H pKa = 35 Question 12 CO2CH3 + CO2CH3 CO2CH3 + CO2CH3 NO REACTION CO2CH3 CO2CH3 (8 points) Provide an explanation for the following: 10 Learning Outcomes Assessment Sophomore Organic Chemistry Name Spring 2008 This assessment exercise is worth 10 points of your final examination score, and consists of 10 multiple choice questions, dealing with the laboratory skills you have learned over the year. You are required to answer all ten questions. Question 1 For a vacuum filtration, you would most likely use funnel… (a) (b) (c) (d) Question 2 You are required to isolate a crystalline carboxylic acid from a mixture of compounds in ether solution. To achieve this you would… (a) Extract with dilute acid, and treat the aqueous layer with concentrated acid (b) Extract with dilute acid, and treat the aqueous layer with concentrated base (c) Extract with dilute base, and treat the aqueous layer with concentrated acid (d) Extract with dilute base, and treat the aqueous layer with concentrated base Question 3 The melting range of compound X is 132‐134°C. If X is contaminated with a small (<10%) amount of compound Y (165‐166°C), which melting range are you likely to observe? (a) 165‐166°C (b) 117‐128°C (c) 132‐134°C (d) 140‐155°C 11 Question 4 For the reaction + Name
Cl2 + FeCl3 4.50 112.56 Cl HCl Mass (g) MW (g/mol) 7.81 78.11 7.99 70.91 What is the % yield of the product? (a) 58% (b) 56% (c) 144% (d) 40% Question 5 During a recrystallization, it is important that the hot solution be (a) Rapidly cooled (b) Agitated or stirred constantly (c) Allowed to slowly cool down (d) Be filtered to collect product whilst still hot. Question 6 Which apparatus would you utilize to heat a reaction under reflux? (a) (b) (c) (d) 12 Question 7 Name Which apparatus would you use to perform a fractional distillation? (a) (b) (c) (d) Question 8 In order to successfully prepare a Grignard reagent, which of the following is essential? (a) The reaction mixture must be kept cold (b) The reaction mixture must be kept free of water (c) The ether solvent must be allowed to boil off during reaction (d) The reactants should not be overly agitated or stirred Question 9 Compound X forms an orange precipitate on reaction with 2,4‐dinitrophenylhydrazine (2,4‐DNP) reagent, but does not react with chromic acid solution. It has an infra‐red absorbance at 1715 cm‐1. Compound X is (a) An alcohol (b) A ketone (c) An aldehyde (d) An aromatic hydrocarbon 13 Question 10 Name The 1H NMR spectrum for compound Y is shown below. A reasonable structure for compound Y would be: Integrals: (a) Butanone (methyl ethyl ketone), CH3COCH2CH3 (b) Toluene, C6H5‐CH3 (c) Propanol, CH3CH2CH2OH (d) Isopropanol, (CH3)2CHOH 14 2H 3H 3H BONUS Name (15 points) Provide a rational mechanism for the following reaction O O + H2N NH H2O/EtOH pH 5 N N + 2H2O 15 ...
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