Spring 07 Exam 4 Key - CHEMISTRY 225 TEST#4 JUNE 8 2007...

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Unformatted text preview: CHEMISTRY 225 TEST #4 JUNE 8, 2007 1. (19) f l K 2. ____(20) NAME 1A 9w E 1/ l ,{_7_ 3. ____ (24) Useful atomic numbers: H==1, C = 6, N = 7, O = 8, Si = 14, C] = 1?, Br = 35 4. — (12) TOTAL (7’5) GOOD LUCK! 1 . (19 Points) CONFORMATIONAL ANALYSIS AND CYCLIC STEREOCHEMISTRY. a. ( f 10) Consider the trisubstituted cyclohexane (compound A) below: NH2 H N l Ho- Emmy, t l- .. j compound Ari x..___..F ('l' o (2) Directly on the structural formula of A, write in all axial hydro gens. o (2) Determine the absolute configuration at the indicated carbon atom (arrow). 2 a (3) Complete the conformational equilibrium with a structure for the other chair conformation. o (3) Assuming conformational equilibrium, which chair conformation will be present in higher concentration? Justify your choice. A K {t ...u L. W...) 7L. mt-...-i.... la a... t. \L; law“ mucem‘lvar Lau— €7ui tinker“. . “re- tutu manna L.......,._ OM17 M if? ale- flv‘fie 4WL9L.l.ufcc-l- jinn-«f;- “psv “Mitzi. build; an... tame when..- “jut L... C.L\(‘*..c:ll Mu 9 fiwfl nitrite? I U may 51 7 ‘7 tr 5 2 b. ( X 9) The bridged bicyclic hydrocarbon bicyclo[2.2.2}octane is shown below in two different perspectives. i r: i i a} ' '3 sis—fused isomer ' tw'stane (9 g (4. {a as (F 1 o {1) On one of the structures of bicyclo[2.2.2]octane write in all bridgehead hydrogens. 0 (2) Write a structure for a oils-fused isomer of bicyclo[2.2.2]octane. o (1) What nautical term describes the conformations of 19 l— I each ofthe three six-membered rings of bicyclo[2.2.2]octane? 0 CL - (2) Linking two carbons of bicyclo[2.2.2]octane with a two—carbon bridge produces the novel, tricyclic (and chiral!) hydrocarbon twistane (structure C ‘ above). Determine the molecular formula of twistane. u"; “(52— (five? L w} v3.4 0 (3) Identify the principal source(s) of strain in bicyclo[2.2.2]octane. Be specific. HINT: Inspect a molecular model. #14, vwa'o-v LC-U’Cf T1 Lima”.w ‘lh-n. Lie-73in fz-ZJJOe'i-nwe / T . . . _ r, “19 ‘i‘fi/é‘wmal Letia 4- ) G- -u- (in-«L ‘iO 1—! r L M0” CG‘L’CH @Cil éetl L7Av¢9 em;— aioh par \mwtgb- Ww... we; Le :3 Fug-a” awewu‘i ‘iv-aus- QmMLLClV 94vfii- 2. (20 Points) NOVEL CYCLIC COMPOUNDS IN THE NEWS. Each of the following questions is based on a compound in the current chemical literature. a. ( f 3) An Italian chemist has synthesized the highly strained 0\ compound B to the right from squaric acid [Tetrahedron Left. 2007, 48, 3595]. Account for the strain in compound B on the grounds of structure and bonding. Be 5 / specific. = O/ glvm‘cw I.» mm... o'uwA 12. (an. Lt compoundB an». Luivri 49 eeveveg (laxative-14} LDMJ eU-L4' TLL “Ami-Peptic. ire- Fiat haw “Iva flmar'L can-L \{LL ‘f.w|-?t—v~_a\ Ov-j 9- (r-w ac w“\~ c2»: Lee-v7 6,0441 it? 909. However/I at“ {our Ciav «5.49 7/! m (“th- aw L7L—arivuwi 67’2— «As-fl {va‘lih’éé’ Lowfll- athlS- 3 b. ( f2) Compound C to the right contains the same tricyclic skeleton as the marine natural product elisabethane. A research group in India has recently completed the synthesis of this 1 molecule from carvone [Tetrahedron Lett. 2007, 48, 4087]. Directly on the structural formula of compound C, highlight tho two rings that ‘ are linked by a Spirocyclic ringjunction. compound C c. ( _______ ‘__ f 7’) Chemists in Italy have synthesized the symmetrical diol D below from (Sis-1,4- dimethylcyclohexane [Tetrahedron Lea. 200?, 4'8, 3575]. 0H CA a f, - —: HOXE r/ /\CH3 ,;___.—---' r "--.r CH3 compound D Cris-1,4%methyicyclohexane HFO‘: a; l plana ejection stereoisomer o (2) Write a structure for cis-1,4—dimethylcyclohexane in its chair conformation - [3) Convert D to a planar projection formula and locate the plane of symmetry. 0 (2) Using any appropriate stereochemical formula, write a structure for a stereoisomer of D. d. (_ f 8) Polish chemists utilized (lR,2R)—l,2—diaminocyclohexane as the chiral reactant in the synthesis of certain chiral ligands [Tetrahedron Lett. 2007, 48, 3331]. o (4) Using any appropriate stereochemical notation write a structural formula for ( 1R,2R)—1,2— diaminocyclohexane. - [4) Write stereochemical formulas for ~the achr‘ra! stereor‘somer of (lR,2R)-l ,2-diaminocyclohexane. -a chiral structure? isomer of(1R,2R)—1,2—diaminocyclohexane. (1R.2R)—t,2-oiamtno- achira! stereoisomer chira: structural isomer cyclohexane 4 3. (24 Points) STERBOCHEMISTRY WITH TWO (OR MORE) STEREOGENIC CARBONS. a. ( _ t 3) The unsaturated carboxylic acid below (compound E) has been employed as a key intermediate in the synthesis of the complex antibiotic elaiolide. Japanese chemists have recently achieved a new synthesis of the acid [Tetrahedron Lett. 2007, 48, 3163]. To the right of compound E is a structure for one of its slereoisomers. How would the properties of these two molecules compare? (Select one option). Justify your choice briefly. 9H3 CH3 CH3 CH3 a : OH OH HOZC/ kw H020 \‘ \‘ x y. OH oH compound E All chemical and physical properties are identical. Chemical properties are identical, physical properties are different. All properties are identical except for equal and opposite specific rotations. Physical properties are identical, chemical properties are different. TLC iwt? comm cit-“(is ABM“ 1“" aim}; “wither 7L Mot.th I . get (liqaci-rvwwa‘ve, iii-9' ()C‘H'ovaa‘i szifi} (hank-«came; Lkflwé‘. Qch ieit i7 Aifiécew.’i’ 71¢Ievi-Cz; a b. (______;’ 6) The alkaloid (+)-muscarine, has playe prominent role in the development of modern pharmacology and drug design. Interest in muscarine has been stimulated by the discovery that the compound could alleviate the symptoms of short-term memory loss in Alzheimer’s patients. Chemists in Quebec have recently completed a short asymmetric synthesis of (+)—muscarine iodide (structure below) (Tetrahedron Lett. 2007, 48, 2921]. - HOG ‘ 7 ti 5 ® ‘9 s "l . ‘ Hie/\o crithCHm Rh". \9/ 'a-sw Q i (+)—muscarine iodide l {-)-musoarine iodide diastereomer - (2) Write a structure for (—)-muscarine iodide o (2) Write a structure for a diastereomer of (+)~muscarine iodide - (2) From the set of structures below, circle an alternate representation of (+)-muscarine iodide. OH OH OH I HO ‘/ \m e “i -/—\ a; e ."f \ (+3 (CHahNCHz/Ko "'CH3 ch/\o/\CH2N{CH3)3 ( H3)3NCH2=" H3C"'\o/\CH2N(CI-13)3 {3 u E} 5 c. ( I 15) As reported in the June 4, 2007 issue of Chemical & Engineering News, chemists at the University of Illinois have developed a method for the synthesis of 1 ,2-amino alcohols. The structure of one of the amino alcohol products (compound F) is shown below. . (LA . Cl Cl .61 CHQCHg : J2 g ' J! g HO NH -. ' ' - .c —c ,. I CHscHz/ \H 1 H?“ H H CHZCHE : compound F : compound F ' the enantiomer a diastereomer - (4) Determine the configurations at the two stereogenic carbons of compound F. ( 3 {Z , 4 [Z- ) o (3) Convert compound F to 21 Fischer projection with the longest carbon chain vertical. 0 (4) Write a Fischer projection for the enantiomer and a diastereomer of compound F. c (4) Hydrogen bromide adds to terminal double bonds HB ( ) " r g ; according to the following general reaction to the right. RCHZCH2 ___._,. RCHCH3 j Describe the stereochemicaf outcome of the reaction if Blr ' compound F were treated with hydrogen bromide. Explain your answer brie y. You may include structures to support your ans 'BI'. (1‘619l-fvww-(vé- woulfiJ 17" FFW’FL TLL Vffit'i‘fiu'l» A Fair \xotb lager; ELM-«44:9 is»): OAVLe-uc. avail W/LL («arisma FWAMC--*”7 0‘ fluan TL’C muifluvi‘lxmug MAUI-Vi Viv—ad.“ U‘w0\1-—fi-d.1(i TLL QWKfl‘H—cl QLVLDGEM‘A. Cfg/ er‘i"\ \H,{ mom “ask—~— ln-drvc; £4714“ by) mix :. uma'LaBMfi, mvl Ln; (L‘le-(vwwf-«Iag J . \ ' c. Pv‘or‘uflfir (l% J tut mania airs... Q d. ( f 3) BONUS QUESTION! The compound below was the immediate precursor to RCAI-Sé, a newly synthesized compound with potent biological activity [Tetrahedron Len“. 200?, 48, 3343]. Write a structural formula for the enantiomer of this compound. HO | OH HO& 9” I OH 7 OW(CH2)120H3 NH2 OH the enantiomer 6 4. (l 2 Points) MULTIPLE CHOICE. Write the letter of the most correct response in the space provided to the left ofthc question. _ The polycyclic molecule to the right was formed from (2E,4Z,6E,8E)— | CH3? 2,4,6,8—decatetraenc (Bonus question, Test #2) [Tetrahedron Lett. 2007, 48, ' 3281]. Which term best describes the structure of this compound? V \ If; Estimate the strain in the conformation of methylcyclohexane in which the methyl group is axial. A. 0.0 kcalfmole B. 1.? kcaL’mole C. 3kcah’molc C. ll kcalfmole H30 ' l A. Bicyclic B. Tricyclic C. Tetracyclic D. Spirocyclic L J D _ ]n which set are the cycloalkanes listed correctly in order of increasing strain? A. cyclopropane < cyclobutane 4 cyclopentane < cyclohexane B. cyclohexane é cyclopropane < cyclopentane < cyclo‘outane C. cyclopentane é cyclohexane 4 cyclobutane < cyclopropane D. cyclohexane é cyclopentane < cyclobutane : cyclopropane 0 The compound to the right was used as a reactant in the synthesis of an l_”' OH analogue of a potent anticancer drug [Tetrahedron Lett. 2007, 48, 3343]. SIOH Determine the structural or stereochemical relationship between the two 'H /O indicated (arrows) hydroxyl groups. HQX/W-A OH ' A. They are trans B. They are cis : / (50H3 C. They are anti D. They are eclipsed | | D Which conformation is not involved in the eyclohexane ring flip? A. Half-chair B. Boat C. Twist—boat D. EnveIOpe r; Which of the following molecules can exist in mesa form? OH I OH Br . l '—\ A A B_ CHscHgCHCHCHgCHs C. ,O\ D. K/ (Bl-f Br Cl Br ...
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Spring 07 Exam 4 Key - CHEMISTRY 225 TEST#4 JUNE 8 2007...

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