Spring 08 Exam 2 Key - CHEMISTRY 225 TEST#2 1_1(10 2(10...

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Unformatted text preview: CHEMISTRY 225 TEST #2 MAY 23, 2008 1. _____ _1_ (10) 2. (10) NAME ‘ m but 4 v 7 3. (29) G O 0 D L U C K I 4. _____F___ (14) Useful atomic numbers: H l. C 6. N 3". O 8, Cl 1?, Br = 35 5. (12) TOTAL (75) . (10 Points) ACIDS AND BASES IN THE CURRENT Cl-lEMICAL 1.,1'1‘ERATURE a. ( ___MMM f 7) Pmpargyl alcohol (structure below) was utilized recently as the starting material in a multistep synthesis of (+)-mueggelone, a novel inhibitor of fish development [Tetrahedron Lea. 2008, 49, 2848]. o (4) For the following reaction involving propargy] alcohol, in the left to right direction, identify the acid (A), the base (B), the conjugate acid (CA), and the conjugate base (CB). 0 O HCECCHg—O + CH3CH HCECCHg—OH + CHgCH propargyi alcohol g; a Cfa c;g I (3) The equilibrium favors the species on the left-hand side of the arrow. Identify the strongest acid in the reaction. Briefly justify your choice. \a- '5’ (It i If 4 £1 “-’ C L C“. II (l. " Lou—tf tin ifs.tt.ahh 3k 0% TL \.L.--eq.,<v omit-l /L~c=.-.-€ Fade. (‘l’TWé «n7ullul’v‘i‘u‘w w a. twirl «Pt-argujyl dijL-G-L-Cl L—Khdxéq‘i Th4, film 113‘, (haul - (3) BONUS QUESTION! Complete the equation below with the structure of the products formed when propargyi alcohol is treated with two equivalents of NaNHz. HCECCHQOH + 2&42 —» l :(E (:CHEO + 5. NH} b. ( ______ I 3) As noted in the April 21 issue of Chemical & Engineering News (C&EN), Linalool, a pleasant-smelling natural product, is emitted by plants to lure pollinators. Using the reactivity ol‘propargyl alcohol as a model, complete the equation below with structure for the product formed when Iinalool is treated with hydride ion (H-, a strong base). \ OH I \ /' + H ___._._.),_ ! 2. (10 Points) ROTATIONAL ANALYSIS. Consider the structure of 2,3-diinethylpcntane written to the right as a wedge and dot structure. l H30 H i =\ [cm a.( :3) . i .-C“"CI — HI \ —um-=—. a (2) Directly on the structure: —underline two alkyl groups that are anti to each other. MM" F” __ ___"“"‘:' J1 —circle two alkyl groups that are separated by a 60° dihedral angle. - (1) How many signals would be observed in the 13C NMR spectrum of this compound? b. ( {7) o (4) Convert the molecule above to a Newman projection looking down the C(2)—C(3) covalent bond and provide Newman projections for two additional staggered conformations. ,/ - (3) Circle the most stable rotational isomer and identify any sources of strain in this conformation. Be specific. _. ' ' l . 7 La » 5A 3 M "t In tr..- to M 1L3: w m '1 “'3- m ("l—W " w" ‘- + "1'? v— t. - * it t L J ~ - 11'.“ ' ., ' r. T1“! Lug.) .0 '3." e " cl 1 a: U r ‘5 l “"- ' " we" 1 L W4.x 16' J k \j‘rtw-II'JQ ‘7‘?”[76v6‘ soju ; L7 (‘5': {la lurch-4f 3 3. (29 Points) STRUCTURE AND NOMENCLATURE OF UNSATURATED COMPOUNDS a. ( r‘ 7’) Ocimene is another unsaturated hydrocarbon identified in C&EN as an odor component of snapdragon. The structure of ocimene is shown below. ocimene geometric isomer o (2) Directly on the structure of ocimene locate all bonds about which there is free rotation. One such bond has been identified for you. 0 (2) Write the structure of a geometric isomer of ocimene. - (3) Provide the IUPAC name for ocimene. HINT: ocimene is a triene. QED" 5, 7* ("Ilw-Mt‘l’ly-‘v? i. Z", if - Cfl‘ri't lulw‘mc’; b. ( _m_‘___w f 7) Myrcene is yet another of the unsaturated natural products featured in the C&EN article. Its structure is reproduced below. H .v “2 (excess) _____,_ a tr my rcene c (2) Directly on the structure of myrcene write in all vinylz'c hydrogens and label them as H». o (3) Complete the catalytic hydrogenation reaction of myrcene with a structure for the product. 0 (2) Which term best describes thestwructural relationship between myrcene and ocimene? Circle one. not isomeric (""I'structuralisomers stereoisomers '~».. ,1 geometric isomers (L L. OH b “X/ a/ linalool c. (' r’ 7) Linalool (problem 1b) is the final unsaturated compound mentioned in C&EN. Its structure is shown to the right. 0 (4) Which of the following terms describe linalool? Circle all that apply. one of two geometric isomers __'__._.——._—._______‘_ Clol-I140 " allylic alcohbh conjugated diene ./ ______ o (3) Are the two indicated (arrows) methyl groups of linalool equivalent oflyalent ? . (Circle one). Briefly defend your answer. “re-hm" .T-Lui L. cunt {.3 m; u [a .9. a ., g ‘l m {l Cal-LL L”? *4 fi v v a L‘NQ 5 V‘ “I! "'5 ‘" V“*‘~"~l17 - K- (LA-n {3 if: Tim: w «’- “1“; v Y 94 a?” fi£ c" Q v Li.) M r‘ L. {It-i u ._ __ ? met/9 n la" hi6» ‘lhct v1.9 \TL4 ('9 a I ('I :1 TL; (“as 3‘7 (it.- 4 d. ( / 8) More unsaturated compounds. 0 (2) Provide a condensed structural formula for l-bromo-2-pentyne, a compound formed from propargyl alcohol (see problem la) in the course of the synthesis of (+)-mueggelone [Tetrahedron Lett. 2008, 49, 2848]. c (2, BONUS QUESTION) A key intermediate in the (+)- mueggelone synthesis is (b)-2—octene-5-yne~1—ol (a primary ; / A alcohol). Write ajagged line formula for this compound. / o (3) The commercially available alkyne to the right was used as the starting material for a synthesis of louisianin alkaloids [Jerrahedron Lett. 2008, 49, 2865]. Provide its IUPAC name and directly on the structure write in - the most acidic hydrogen and label as Ha - all propargyl hydrogens and label as Hf, 5*6ixlcvweh— thi7ne. o (3) A 50:50 mixture of the (FD- and (Z)— isomers of 2-bromo-2-butene was used as a reactant by French chemists in the course of a study of palladium-catalyzed reactions [Tetrahedron Lett. 2008, 4‘9, 2928}. Using any appropriate formula write structures for these two compounds. \7;\ i ! L1 6V (Z)-2-bromo—2-butene (E)-2—bromo-2—butene _ (14 Points) CYCLIC COMPOUNDS AND ISOMERISM. a. (_ i’ 6) Cyclohexanone, structure below. is a cyclic ketone. Write structures for o (2) 4-terl-hutylcyciohexanone. ' o (2) A cyclic structural isomer of cyciohexanone with a diflerenrftmcrionai group. a (2) An acyclic structural isomer of cyclohexanonc without a carbonyl group. lcwga- 4—tert—butylcyelohexanone cyclohexanone f I 5 b. t f 5) Write structures for all monobromo» derivatives of 4—mcthylcyclopentene. Select ELIE and provide its IUPAC name. v _ [Guam ’” '-' 4* M1-bflg7’cficlcfcpume 4-methylcy lopentene derivatives 0- ( _ .._,_._.___F._ r’ 3) I Menthone, structure to the right, is a substituted derivative of cyciohexanone. A team of Canadian chemists recently developed an improved method of synthesizing menthone by oxidation of menthol, an alcohol [Tetrahedron Left. 2008, 49, 3199]. Identify the circled group of menthone with its IUPACname ("Niki/LAQ‘HJVI d and common name iérD v43 l 5. ( 12 Points) MULTIPLE CHOICE. Write the letter of the correct response in the space to the left of the question. A Estimate the potential energy difference between the gauche and the anti conformations of n—butane. A. '1 kcali’mole B. 3 kcallmole C. S kcalfmole D. 0 koalz’mole= the eclipsed and anti conformations have the same energy. FD Why would the compound to the right be identified as an unstable alkene? A. 'Ihere are two electrons in the pi antibonding molecular orbital. [ B. Catalytic hydrogenation of this compound is highly endothermic. ' \ C. The four atoms surrounding the double bond are forced to be c0planar. ---——--—--- ---—-—— D. There is virtually no overlap between the two C2,:I atomic orbitals forming the pi bond. A For which of the following isomeric alkenes would it be correct to describe the geometry at the double bond as trans? I /i\/\/ 23 Consider the acid-base reaction below: 9 6 (C H3)3COH + OH : (C H3)3CO + H20 pKa = 17 pKa = 15.7 Which two species would be favored at equilibrium? A. (CH3)3COH and OH" B. (CH3)3COH and H20 C. (CH3)3CO' and H20 D. (CH3)3CO' and OH" _ [*3 Determine the total number of monochloro- derivatives of the I ' compound to the right. I l E l CHgCHCHgCHgCHCHg, I A. Three B. Four C. Five D- Eight ___ i C- As unsaturated hydrocarbons, what _pmperty do alkenes and alkynes have in common? A. They have the same general molecular formula: ‘ B. The carbons of each multiple bond are hybridized sp2. C. They are both converted to alkanes upon treatment with hydrogen in the presence of a catalyst. D. They are both capable of geometric isomerism, ...
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This note was uploaded on 06/18/2010 for the course CHEM 225 taught by Professor Markdec during the Spring '10 term at University of Michigan-Dearborn.

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Spring 08 Exam 2 Key - CHEMISTRY 225 TEST#2 1_1(10 2(10...

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