F06 final key

F06 final key - Afléwa” Key Manashi Chatterjee Ph.D....

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Unformatted text preview: Afléwa” Key Manashi Chatterjee Ph.D. Fall 2006-Chem 30 A-Final page -1 Discussion Section - Day : Time: Chem 30 A Fall 2006 Final - f f , (180711,!1171'5) 1 f ' r ’ Thursday ‘ December ,14, 2006 Electronegafivity values for some atoms (Pauling scale) DO NOT OPEN THIS EXAM UNTIL INSTRUCTED TO DO SO page -2 5 m g 12 200 Manasht Chatterjee Ph.D. Fall 2006-Chem 30 A-Final Manashi Chatterjee Ph.D. ‘ . page —3 Fall 2006-Chem 30 A—Final ' 1. [10 marks] Circle the alkyl halide among each of the given pairs, that you expect to react more rapidly by an SNZ mechanism? Give a concise explanation of your selection in less than 10 words. _ ~ Br 9*??? 1. (A) (B) \Oolqunolide \6 3003613; Cg? /\/\/cI 2. (A) (B) j. is belkler \eovfig W "Q hind/PQDC a " back side attack 5N1 €306,504 Os} 6? (1‘5 plnehyl bromide (A) doesnol- reach 5. fi— Br 6N2; doesnxl Wm ca Sp C‘s vinyl bromide (I3) does nol: read: Manashi Chattérjee Ph.D. \ page -4 Fall 2006-Chem 3O AeFinal ' 2. [8 marks] Draw at least $15 other significant resonance contributing structure :for each of the following ions. . ' I \ _ /\\ ~\— Cd) 35" ' An one ' u .\ 5 strut:an 06‘ 3 / .02 Was required ~, ~ v m (as) H 1 69.0 3’“ (a) (4) 2. .___. 3. ‘1?! (a) Manashi Chatterjee Ph.D. page —5 ‘Fall 2006-Chem 3O A-Final ‘ 3. [14 marks] Consider five different cycloalkenes (A-E) of the composition C6H10 that will each provide methylcyclopentane upon catalytic hydrogenation according to the scheme below. ’ H 9336 A, B, c, D and E __3——» w + Pd (catalyst) O ‘0 (a) Draw the structures of 2 of the above cycloalkenes which will be chiral and constitute a pair of enantiomers. Draw the (R)-isomer as A and the (S)—isomer as B. (R) -isomer ‘ (S) -isomcr (c) Draw the structure of isomer D (an achiral isomer) which be such that it will produce a pair of enantiomers upon dihydroxylation reaction with OsO4. Fill in the structures below. |Note:' D must be achiral, and G and H must be chiral] ‘5? 3‘ \5 Manashi Chatterjee Ph.D. page —6 Fall 2006-Chem 30 A-Final _ (d) [3 marks] Draw the structure of isomer E (also an achiral isomer) which be such that it will produce a pair of diastereomers upon dihydroxylation reaction with OsO4. Fill in the requisite structures below. [Note: E is achiral, and I and J be a pair of cis/trans diastereomers]. ' 4. [5 + 5 marks] (a) Classify the following solvents as being protic or aprotic. Formic acid (Héoz'H)? i Acetone: ,(cchoCHax pm! he Acetonitrile: (CH3CN): Chg g JESC Formamide: (HCONHz): Q C Dimethylsulfoxide: (CHgSOCHs): Clggig‘c (b) Explain why dimethylsulfoxide (DMSO) is a better solvent for 8N2 reactions compared to methanol (MeOI-I). (No more than 15 words; use a cartoon diagram to explain your answer.) . DMSO saw/0&6: use“ \bufir ndt Onims a meOH sowozlres bcrpn wali, Dmeo CLMCUUS Ame, Lnudaopwms) +0 rendt befiAefW meOH, 5 \ __ _,/ ,5; \\ 50v .%0 N05, 03’ 060/ // \\ Manashi Chatterjee Ph.D. ' page -7 Fall 2006-Chem 30 A-Final ‘ ' 5.(a) [5 + 1 marks] Note the formation of compounds B and C from heating of the tosylate derivative A in methanol, as shown below. Provide a reasonable mechanism to account for the transformation of A into B - show all steps including the properly drawn curved arrows and all intermediates. Make sure each individual step is mass- and charge-balanced. OTs . * OCHS MeOH ¥ ——.—> Heat + A B C , 9if¢“’b°¢f‘f"§i ELM Compound B is formed by l: l mechanism. Compound C is formed by 3|)! mechanism. stereoisomers Compound C will have page -8 Manashi Chatterjee Ph.D. - Fall 2006-Chem 30 A-Final 5.(b) [5 + 1 marks] Note that compounds D and E can also be formed from heating of the tosylate derivative A in methanol, as shown below. Provide a reasonable mecfl' m to account for the transformation of A into D — show all steps including the properly drawn curved arrows and all intermediates. Make sure each individual step is mass- and charge-balanced. OTs I ‘ 0M6 MeOH . a . + Heat A, _ D Compound D is formed by \ mechanism El Compound E is formed by mechanism. Manashi Chatteflee Ph.D. page —9 Fall 2006-Chem 3‘0 A-Final , 5.(c) [3 marks] Write the product of the reaction of tosylate A with sodium cyanide in DMSO. Provide stereochemistry if applicable. OTs Mechanism : Circle one 5.(d) [3 marks] Write the product for the reaction of tosylate A With sodium methoxide in V 7 MeOH. Provide stereoehemistry if applicable, 7 t 7, OTs Circle one 5N1 E1 SN2@ Manashi Chatterjee Ph.D. page '-10 Fall 2006—Chem 3O A-Final v 6. [10 marks] Consider the conversion of enantiomerically pure (R)—(-)-2-bromooctane with [specific optical rotation {a}: = ' 3‘25 °] to enantiomerically pure (S)-(+)-2-octanol with its [specific . _ [GP = 0 optical rotation of D + 9'90 ]. . Using the above information - provide accurate stereochemical designations (R/S) for the four structures given below and give their matching optical rotation values with correct signs and values. Complete the following statement: The above reaction confirms that A (give structure number) was converted to X5 compound 5 2 (give structure number) by ;2 (which?) (952 mechanism. Manashi Chatterjee Ph.D. I V page —11 Fall 2006-Chem 30 A—Final 7. [4 marks] Even though they are primary halides, the neopentyl halides are very unreactive towards SNZ substitution. Explain in less than 15 words. s. _ [4 marks] Draw all possible monoszgminaxgdproducts.5in the,__f0119_wingL§@9,ti9n- Cfislg. -7 V the one that is fermedfsthfmajo‘r’ product * A C sbcrcod‘xcm > Circle the major product not: included. Manashi Chatteljee Ph.D. V page ~12 Fa112006-Chem 3O A—Final ' ' 9. [10 marks] Draw any one correct alkyne that you would start with to prepare each of the following compounds? Give the necessary reagents for your conversion. Compound A Manashi Chatteljee Ph.D. Fall 2006-Chem 30 A-Final ' page -13 10. [10 marks] Synthesize 1-hexanol and 2-hexanol from acetylene and appropriate alkyl halide (will require more than 1 step). Give all the reagents that you will use for the transformation 8) \/WQH CompoundA v _ a /‘A H ,:_.\—\ W 7 \-\”“e a _ ‘ L ( 7 gfifigeJ/Wmcg a/ b/ C > “"3 W51“? ‘ ‘37:? or V L 7' NO)“ “3 , ,C’FV i CompoundB smearing: as _ » a a, ‘ both reagents WO" same I \63r 3 ObOVe khan ' W?“ “73504 \—\ “to Cl Waz Manashi Chatterjee Ph.D. page —14 Fall 2006-Chem 3'0 A-Final ' 11. [10 marks] Which isomer would You expect to undergo E2 elimination faster, trans-1- bromo-4-tert-butylcyclohexane or cis-l-bromo-4-tert-butylcyclohexane? Complete the chair and planer hexagon representation of both the compounds to explain E2 elimination. ,,________.. a) trans-l-bromo-4-tert-butylcyclohexane 6’ e \“r Q Br *5 i stable but no anti 'H' 4:0 Bit 1 ‘ anH‘H. Elimination '5 s 093 less stable complete the tgiplate to make 7 WW ¥ i -b)r Cis-1-bromo-44te|‘t-bntylcyclohexane> Manashi Chatterjee PhD. page -15 ' Fall 2006-Chem 30 A—Final 12. [10 marks] Give the major product of the following reactions. Show stereochemistry where appropriate. - a) 0) ‘1,Hg(OAc)2, H20 ' , , , _ N 7 . ' 2. NaBH4 d) \.\« ¢ \ Na/NH3 H 6) Br2/ H20 Manashi Chatterjee Ph.D. I page -16 Fall 2006-Chem 30 A-Final l3. [6 marks] Compound A is subjected to ozonolysis and produces two equivalents of the aldehyde shown below. When compound A is subjected to Os04 and then to sodium bisulfite a pair of enantiomers (racemic mixture) is produced. What is the structure of compounds A and B? Draw the structures in the boxes provided. Manashi Chatterjee Ph.D. page -17 Fall 2006-Chem 30 A-Final ‘ 14. [10 marks] What stereochemistry do you expect for the alkene obtained by E2 elimination of (IS, ZS)-1,2-dibromo-l,2-diphenylethane ? Use the sawhorse perspective formulas of the compound to demonstrate E2 elimination and the structure of the alkene obtained. Is (IS, ZS)-l,2-dibmmo-l,2-diphenylcthane optical] inactive ? If inactive give a reason: What stereochemistry do you expect for the alkene obtained by E2 elimination of (IR, 2R)-1,2- dibmmo-1,2-diphenylethane? Z Manashi Chatterjee Ph.D. _ ' page - l 8 Fall 2006-Chem 30 A-Final / 15. [12 + 2 marks] Give the major product of the following reactions. Please indicate stereochemistry where ever possible. tert-BuO'K+ _ tert-BuO'K+ e tert-BuO’K+ . ———> / W ‘ ten-BuOH \/\/ Br r f. Ak CZHSO-Nf M . ________> ethanol ' Manashi Chatterjee Ph.D. page -19 Fall 2006-Chem 3'0 A-Final ' g. H3C NaCN H\\\\\\I BI' -————-—-> DMF . CH C - 2p01nts H3 2 f— 16 a. [3 marks] Draw the Transition State for the SN2 reaction of the anion of phenyl acetylene and ethyl bromide. Be sure to indicate which atoms have a partial charge. e 69 03c Na + CH3CH2Br ——> Ph-‘CECCHZCHa 16 b. [5 marks] Draw the energy diagram for the above reaction with all the necessary information? Manashi Chatterjee Ph.D. Fall 2006-Chem 30 A-Final page —20 17. [8 points] Using the table of oK. values given below, examine the acidzbase equilibria presented in (i) through (iv). Circle the acid and the conjugate acid and darken one of the dotted arrow which points in the direction taken by the equilibrium in each set of reaction below. m Manashi Chatterjee Ph.D. page -21 Fall 2006-Chem30 A—Final 18. [10 marks] The following Lewis structures A through L are isomeric (molecular formula CNsz). The question requires you to locate formal charges and electron deficient atoms (atoms that have not achieved a valence shell electron octet through covalent sharing). H H—CEN—H—H :C=N—NHZ HzN—CEN: :cznzjg A B c H D 53:3 =NH2 He'd—Nam: H—N=C =N—H :CEN—NHZ E r a H :N=i~J—6H2 H—6=N=i~i—H fizN—cuz H-514] =C_H I .1 K L m Enter appropriate letters (from A to L) in each answer box. If no structure fits the property enter the letter X. ‘ Do not enter superfluous characters, since they will be counted as incorrect answers. 1. Which structures have no formally charged atoms? 2. Which have at least one nitrogen atom with a (+) formal r V . .; 3. Which have at least one nitrogen atom with a f-) formal charge?i 4. Which have at least one carbon atom with a (+) formal charge? 5. Which have at least one carbon atom with a (-—)l formal charge? . 6. Which have electron deficient heaVy atoms (N or C)? ' K)l’ Manashi Chatterjee Ph.D. page -22 Fall 2006-Chem 30 A-Final 19 [10 marks] How can you separate a mixture of the following compounds (AgB & C)?7The reagents available to you are water, dichloromethane, 1.0 M HCl, and 1.0 M NaOH and saturated NaHCOs. Explain your method of separation describing the reactions that are taking place. (Use additional pK.values from the table on page 20.) CO OH ‘ a A C ' Emmeme I, “5335 L , R009 V CHILE—’17 Mafia B (amine Aim) C A“ Ladifogodd} l extract back I“ CHzClz Manashi Chatteijee Ph.D. Fall 2006-Chem 30 A-Final 20. [5 marks] Identify all the functional groups in the following molecule called “Taxol”. Circle them and write the functional group beside the circle. Identify the alcohols and classify as primary, sec or tert. page —23 Manashi Chatterjee Ph.D. ‘ page -24 Fall 2006-Chem 3’0 A-Final ‘ 21. [8 marks] Describe using Valence Bond Theory the orbitals used in bonding for CH3CN. ' Show ground state C and N, excited electronic configuration state for C and hybridization of atomic orbitals for C and N and their overlap using proper orbital diagram. Using VSEPR predict the bond angles and geometry around the CCN bond. ' k . w» m —-—-7c; in I‘i‘im WC L33 1? weevil? N E ‘.:4 i ' 0'1 X5 25 \21» ~ ‘ Orbi’mls ‘ 25F hybrid. I ~ has [one a pair. ...
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F06 final key - Afléwa” Key Manashi Chatterjee Ph.D....

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