Summ09Ex3

Summ09Ex3 - l . "Grade or Education" =1 CHEM...

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Unformatted text preview: l . "Grade or Education" =1 CHEM 2261/01 Summer 09 Exam 3 Chapters 7-9 Figure out which speciec in each of the pairs shown below is more stable. Pairs of structures share the same letter, like a1 and a2 . Pick the CORRECT statement from the multiple choices. — — + + CHSCHCHZCH3 CH3CH2CH2CH2 CH2CH2CH=CH2 CH3CHCH=CH2 a1 a2 c1 02 + + CHSCHCHZCHs CHSCHZCHZCHZ b1 b2 CH2CH2CH=CH2 CH36HCH=CH2 CHéCH-CHZCHZ CHéCH-2C=CH2 d1 d2 ('3H3 ('3H3 e1 92 A e1 is more stable than 62 . B d2 is more stable than d1 . —— C- c1 is more stable than 62 . D b2 is more stable than b1 . —— E- a1 is more stable than a2 . Rationale: Chapter 9 Problem 35(a,b,C,d,e) 2' Find the structures of the major 1,2 and 1,4 addition products resulting from the reaction of diene a (shown below) with HCI. Figure out which structure is the kinetic product of this reaction and which structure is the thermodynamic product. Choose the CORRECT statement from the multiple choices. CH 2 CH2 Cl CH3 CH2C| CH3 CH3 :ll CI :4 l i CI Cl 1 2 4 5 3 The kinetic product has structure 1 and the thermodynamic product has structure 3. The kinetic product has structure 2 and the thermodynamic product has structure 4. A B C. Both the kinetic and the thermodynamic products have structure 5. D The kinetic product has structure 4 and the thermodynamic product has structure 2. E The kinetic product has structure 3 and the thermodynamic product has structure 1. Rationale: Chapter 7 Problem 31a What diene and what dienophile could be used to carry out the reaction shown below? Find the answer corresponding to a CORRECT choice of diene and dienophile. A COOH ? + ? —> “COOH l? .9 CH2 HOOC\C,CH2 H\ /C-OH / Hooc\C;CH2 H\C/C.OH || ('3 ICE E | ICI3 CH2 HOOC/ \CH2 H/ \QOH \ H2C7C\COOH HO-C/ \H || || 1 2 3 o 4 5 O 6 Compound 4 is the diene and compound 3 is the dienophile. Compound 6 is the diene and compound 1 is the dienophile. A B C. Compound 5 is the diene and compound 1 is the dienophile. D Compound 2 is the diene and compound 1 is the dienophile. E Compound 4 is the diene and compound 6 is the dienophile. Rationale: Chapter 7 Problem 40f Find all of the resonance contributor(s) for the species whose structure is labelled 1 below. Choose the statement which is CORRECT about the relationship between the structure labelled 1 and its resonance contributor(s) _ +//O _+,O_ _ 00 _ 00 — +’O— CH-SCH—N\ CH§H_N\ CH'3CH_N\ CH§H— N\\ CHgH—NQ A. 1, 2, and 5 are the resonance contributors of this species; 1 and 5 are the major contributors and 2 is the minor contributor to the resonance hybrid. B. 1, 2, and 5 are the resonance contributors of this species; 2 is the major contributor and 1 and 5 are minor contributors to the resonance hybrid. C. 1 and 2 are the resonance contributors of this species; 1 is the major contributor and 2 is the minor contributor to the resonance hybrid. D. 1, 3, and 4 are the resonance contributors of this species; 3 is the major contributor and 1 and 4 are minor contributors to the resonance hybrid. E. 1, 3, and 4 are the resonance contributors of this species; 3 and 4 are the major contributors and 1 is the minor contributor to the resonance hybrid. Rationale: Chapter 7 Problem 48(a5) 5. Use the numbered structures shown below to choose the CORRECT statement from the multiple choices. /\/\C| fig “1 %—CI CI a /\ 0/\ CI c1 b2 c2 a will react faster with CH3S_ than it will with (CH3)2CHS_. b1 will react faster with HO_ than b2 will. A B —— C- c1 will react with H20 faster than 62 will. D (CH3)3CBr will react faster with CH3CHZOH than it will with H20. E —— - 62 will not react with H20. Rationale: Chapter 8 Problem 48 A student proposed the 5—step mechanism shown below to convert the substance with structure 9R into 9P. Which steps are WRONG in this proposed mechanism? I 3 step1 | 3 I step2 (EH3 ste W: CH3 —’ H —’ CH_CH2 —’ + (3' CI‘ H 9B H20\ CH3 H B CH3 H step 4 CH3 step 5 CH3 CH3 + 9P Steps 1, 2, and 3 are wrong. Steps 3, 4, and 5 are wrong. A B C. Steps 1 and 5 are wrong. D Steps 2, 3, and 4 are wrong. E Step 5 is wrong. Rationale: Chapter 9 Problem 9 7. Find the elimination product(s) of (2R,3R)—2—chloro—3—methylpentane + high concentration of CH30— among the numbered structures below. Choose the CORRECT product(s) of this reaction. H C H CH CH CH CH H C CH 3 : — , \\2 : 3 3 3 3 — 3 CHZCH3 CH3 H CH'2CH3 H CHZCH2 CH'2CH3 H 1 2 3 4 A. 1 is the product of this reaction. __ B. 3 is the product of this reaction. __ C. 2 is the product of this reaction. __ D. 4 is the product of this reaction. __ E. 1 and 3 are both products of this reaction. Rationale: Chapter 9 Problem 48d Pick the statement which CORRECTLY indicates which compound in a pair will give a higher substitution—product to elimination—product ratio when it reacts with isopropyl bromide. __ A. CH30— will give a higher substitution—to—elimination ratio than CH38—. __ B. —OCN will give a higher substitution—to—elimination ratio than ‘SCN. Ethoxide ion will give a higher substitution—to—elimination ratio than tert-butoxide Ion . __ D. None of the other choices is correct. __ E. Cl— will give a higher substitution—to—elimination ratio than Br‘. Rationale: Chapter 9 Problem 40 Rank the ions whose structures are shown below in order of DECREASING nucleophilicity in methanol (strongest nucleophile listed first). 0 || - CH'3C'O ' CH'SCHéS ' CHéCHEO 1 2 3 __ A 3 > 2 >1 __ B 1 > 2 > 3 __ C. 1 > 3 > 2 __ D 2 >1 > 3 __ E 2 > 3 >1 Rationale: Chapter 8 Problem 42a 10. Find the MAJOR product of the Diels—Alder reaction shown below among the numbered structures shown below the reaction. Make certain that you use the preferred alignment of the reactants to generate the major product. Pick the choice which gives the number found under the correct structure of this product. 0 || CH2:CH—C=CH2 + CHECH-C-CHS __ A. 4 __ B. 1 __ C. None of the numbered structures is the major product of this reaction. __ D. 2 __ E. 3 Rationale: Chapter 7 Problem 71 b ll. 12. Figure out which species is the more stable of each of the labelled pairs shown below. A pair of species share the same letter, like a1 and a2 . Choose the statement which is CORRECT about the relative stabilities of these pairs of species. ii“: + 9 9 CH-SCH-ZC-CHZ CH-SCH-ZCHICH-CHZ CH-3C-CHZCH2 CH-3C-CH:CH-CH3 a1 a2 b1 b2 9' 9' || CH-SCH-CHICHZ CH-SCZCH-CHS CH-3C-NH2 CH-3c-NH2 c1 c2 d1 d2 A b2 is more stable than b1. B a1 is more stable than a2. C. d2 is more stable than d1. D None of the other choices is correct. E c1 is more stable than c2. Rationale: Chapter 7 Problem 7 Work out the mechanism for the reaction shown below. The first step generates a carbocation and the second step involves the rearrangement of this carbocation to form a more stable carbocation. Choose the statement which is CORRECT about the PRODUCT of the SECOND step of this reaction (ie. the rearranged carbocation). H20 OH CH3 _. + H30 (IDHCH3 CH3 0” Br CH3 CH3 The carbocation is located on a tertiary carbon atom which is part of a 4—membered ring. B. The intermediate which is the product of the second step is a 4—membered ring with a secondary carbocation located on one of the ring carbons and an ethyl group attached to the ring carbon on the opposite side of the ring from the carbocation.. C. The intermediate which is the product of the second step is a 4—membered ring with an ethyl group attached to one of the ring carbons and a secondary carbocation on an adjacent carbon atom. D. The carbocation is located on a tertiary carbon atom which is part of a 3—membered ring. E. The carbocation is located on a secondary carbon atom which is part of a 4—membered ring. Rationale: Chapter 8 Problem 62 l 3- Examine the Fischer projections shown below. Choose the one which CORRECTLY shows the structure of the product of the reaction of (R)—2—bromopentane + high concentration of CH3O . OC H3 CH3 CH3 H H—’—CH3 CH30—~—H H—'—OCH3 H3C—‘VOCH3 CH-2CH-2CH3 CH'ZCH'ZCH3 CH'2CH'2CH3 CH'2C H'2CH3 a1 a2 a3 a4 Structure 82 is correct. Structure a4 is correct. A B C. None of these structures is correct. D Structure a1 is correct. E Structure a3 is correct. Rationale: Chapter 8 Problem 45a 14. Find ALL of the CORRECT structures of the products obtained from the solvolysis of the compound with structure b (shown below) in ethanol. Choose the answer which gives all of the correct product structures and no wrong structures. 9/0428" Q/CHZOH CH'3CH'20\ \/‘ —\/¢CH2 2 CH b Q/CH-ZO-CH-ZCHS / 2 4 1 3 OCH'ZCH3 The products have structures 1 and 3. The products have structures 1 and 4. A B C. The products have structures 2 and 4. D The products have structures 1 and 2. E The products have structures 2 and 3. Rationale: Chapter 8 Problem 46b 15. Indicate whether the alkyl halides listed in the table below will give primarily substitution products (S), only elimination products (E), both substitution and elimination products (S & E), or no products (X) when they are treated with the reagents under the reaction conditions shown in the table below. Put the correct abbreviations for substitution (S), Elimination (E) or no reaction (X) in the product column of the table for each reaction shown. These reactions are designated a1 through b4 in the multiple choices as presented in the table. Pick the CORRECT statement from the multiple choices. — — — m— — — — m— B/Y Br>< 2—bromobutane 1-bromo-2—methylpropane 2—bromo-2—methylpropane 2 4 Br/\/\ 1-bromobutane 1 Reaction b3 gives only elimination products. Reaction a4 gives no products. A B C. Reaction a2 gives both substitution and elimination products. D Reaction a1 gives no products. E Reaction b4 gives primarily substitution products. Rationale: Chapter 9 Problem 22 10. 11. 12. 13. 14. 15. Answer Key "Grade or Education" CHEM 2261/01 Summer 09 Exam 3 Chapters 7-9 1 10 ...
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This note was uploaded on 12/30/2011 for the course CHEM 2261 taught by Professor Crowe during the Fall '08 term at LSU.

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Summ09Ex3 - l . "Grade or Education" =1 CHEM...

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