September 19-26

September 19-26 - {Cim‘tfi #5 [3" i4 2...

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Unformatted text preview: {Cim‘tfi #5 [3" i4 2 igegfiabiéfaM/EJUL {szé’ "72:6 Stereochemistry C/gmfo-téz-L 7 (vomit? 6% 03% 73 9 8< 7. ISZ-uwiivfégx‘e. (Li/Lfifib wgé a ma. x1e cmth :4 s isomers (slams magamuem %’L’vmmv€a.) 0&6) / Constitutionai (structural) Stereoisomers isomers a ohfifexnbmxcwmnaecilfiéfi%fl “CMkMA£4&9MA4£Qt&O€Ei;; 49% Sui/Lch xisz was“; a W‘fi' 6/342; aiwmwsax&eéfimmd£d, Chiraiity: handedness; what is a chiral object? 4 n (ngf% «own/0L mjfii‘ lama, .- meuef—cdwué ,e'mofi, as? M. & dwagime, o. WWf/game, Ogile Xe We, AAA/LA. a— ma... “(MWSW' it’M/LybOtSGXLEJ’FQ. . O O O 0 ! NH N O i H A O (Spearmint) (caraway) i L - ammo’asod M 0 E 0 £3 . j E H i i ' C i / “7’” Ci H3 : N R : H?» (24:3;2 H R—carvone is an example of a molecuie that is not superimposabie :D __ S1 1 W on its mirror image. Thus, it is j chiral. JD __ 3 we "£3 ‘ " gig-i o H '5'] "OH H 0 3i, HquH Chirality and enan‘iiomers If an object is chiral, its mirror image cannot be superimposed upon it. This nonsuperimposabie mirror image is calied an enantiomer. Every chiral molecule has one enantiomer. If an object is achirai (meaning not chiral), it will not have an enantiomer, and its mirror image can be superimposed upon it. For example: ' l l i can 2 35a, 06 I 08 : ' : E W“ a i 542 m H‘“ : "9’s: 1 f 5 : bromochlorofiuoromethane vs. dichloromethane chiral (methylene chloride) achr'ral What structural features make a chiral molecule chiral? Asymmetry e 4— d":- MfiW—t W W Jfi’gL/jfLO-‘szDS wtCOLc/i/LecL 4x»— C/QA'fi/cve Gen/7.1.21, Stereocenter/Stereogenic atom a am mmmeEtQGL “[30 4— WW ficjfi—W‘jbfi Chiraiity center Clem/gem (Steam, ,ofi, amefiemc (LE/Wm Awfom£g€a asgmmfi ( Asymmetric carbon (chiral carbon atom) 12?: ) CW max/W [@WC’K/gfic- memme Two ways to draw an enantiomer. given a chiral molecule: 1) Draw the mirror image. 0R 2) Switch any two iigands. (Switch any two again, and you have the originai enantiomer back. Try this with models!) (A ligand is an atom or group of atoms attached to a central atom in a compound.) 3 I l l l I l l E i I l I ewatcfi, CB gee m I (game, as Ml;— /w’t‘o§t€ do neat/Wwa $501201: "575,6 a,st cmmeo'fi/‘wj A '60 cave'l‘fioa/E atom [8’06 Sofimj: :D 3M: wFosthELoo/L/ ,fLe, hatwwjict, . B {.VLAEE/j Poof-221% wfjow) wow: Wt; @ Physical properties of enantiomers A pair of enantiomers has identical phxsicai properties — with one exception: how they interact with plane-polarized tight. One enantiomer will rotate piane polarized light in one direction; the other enantiomer will rotate ptane polarized tight in an equal and opposite direction. fl flax—t Wcafiae ALA/b «AA/wng, Wcm’tffmm. @fifiQ/é Fges‘ld “Vi/g %;”m’%, Wank/{s Vc’/&Lcw wef.fame cam [OM/b fifflmQ—fgefmquL/ak W/eiseb)’ 4404163 0L9, camera/bat d, J14, [bo«€cwsec»{, b‘fiw ) CU'LéL meager/Levi, "£5. a, fd‘ck'e’t rfiémcet This rotation # optical activity Samples of molecules that demonstrate this rotation are said to be optically active We measure the optical rotation of a sample using poiarimetry to find the Specific rotation of the sample. Specific rotation, [0:3, is defined as 25 _ a (observed) .. . {c110 - maxim/w [sniffing-ma]: ‘\ ‘i amewuwmm .33 ~/&me 4:15: Nat, Racemic mixtures A racemic mixture is an equimolar mixture of enantiomers. Recemic mixtures are optically inactive. Me Me Et/kig; H‘" Et fbc’fm "7R'(-)-3-butanol .3» S~(+)—§—butanol fiffix/M _ ¢£W5,CCL 43.5 rotation +135 rotation a W/gma / MM, How would a racemic mixture form? Let's consider as an example a reaction we will see a little later: WI.ng ’ C 51 fflonwaP 3450'; c- 6?th CH3 MCPBA/Ii CH3 CH3 H \ H _ H + “‘5’ H3C)\l/ (an achiral reagent H3Cé>r H30 0 6H CH3 that converts an CH3 3 alkene into an epoxide) achiral - the molecule The two products of the reaction is flat, and there is a are enantiomers s mmet lane ‘ . m 1 y {yp a ~mx’tww. AAS ILCLce/vmc.) flew“) fifteen/2%, Determining chiraiity: some examples Things to look for: - are there any asymmetric carbons? — is the moiecuie superimposable on its mirror image? — is there a symmetry plane in the molecule? OH OH M came OH aofiooaxfi H . OH HO .5; .5 OH A/ l E l 0H ' What if a molecule is conformationaiiy mobile? @ BL C CW We. out/6L H H c: o“ .3 \{E—«Cm. (33‘ H/ CH3 “ .1 g 2*— C’us Lebé'fiC’EtA/TECL C [views :Ve, We Br arm Br Rapid interconversion at room temperature H (FEW crow-W3) Tim/pr: (it/Ma, m at Fer-j evaJL—é me. {514% Each conformation is chiral... but since the two chiral conformations are in equilibrium at room T, we consider this molecule to be . We could airs predicted this by drawing the flat, bond-line structure of the molecuie. This will old true for su stituted cyclohexane compounds. Br I, 1 'Br "cw ecs,1,2-* M‘ {7 ' Wat/we yam/gefégm ramc Cram {bx 0t, W50 WIDOLLmd‘L/gu/ Similarly, we shouid consider strai ht—chain molecules in their most 5 mmetric conformation which (—0“ “NM/CEM— often is eclipsed. Consider as an exampie the two chirai gauche conformations of butane 1:6,) C ' ML _ I CH3 if CH3 W ‘ l H i—z ' H I H l I ' H H i f ‘GL' Wmcmumm oil]? W i Cahn-lngold~Prelog priority rules Meow/cut AM Cufixmfn'iab 5) (+) and (—) refer to the direction in which the chiral molecule rotates pEane polarized light. d and I also refer to this direction. These must be determined by experiment. Nomenclature: We use designations of R and S to distinguish enantiomers from each other. Rules: Locate the asymmetric carbon and assign priorities to each group attached to it. Priority is based on atomic number. Higher atomic number means higher priority. H3 g<;/W%’t refit: weft , taro-mil: a. W «gvvxfe/sf {Mi-WW" m f 03 ‘5) W ~ 3 CGL‘L WGCEW :SL jy‘wofitig/ gob F@ @ “t” @ 4C9 "i ‘ $553523: Cfi'MfflM/Lm @ Q Q@ mm: 40eva All it takes is one higher priority atom c to break the tie. @ f] C ; C; H c H“ .- . H ' H3 @ C\c 2% a f’ ' \ For double and triple bonds, treat each bond separately. G5 «4236131921708 ©‘@ Orient the molecule so that the lowest priority group faces away from you. CH3 becomes becomes becomes K Hum‘" HZN CH3 Cahn~lngoid~Prelog priority rutes, continued The enantiomer would have the opposite designation. More exampEes: CH 3 “30 "Aw—ta]: myaewee, aofimé H afoaawtcwgmw? fifiafim tew 1L6 fir film? A . , ‘ ‘ 9 6 {fill/la 6’04 2 W53 WWW H {/bFO’imt/vg, awry @W‘t’éfl”€bvv\ap 4/ J $ 6% ' A jamfo‘s gt veg/7E2: :E/M’ 6W£7£Chfic4a : . @ gaH ' (3) gefifie fi/fji‘l/Lave Mfg},th WWW'D/W } R "E H G) Fischer projections Yet another way to draw organic compounds? The Fischer projection is composed of all vertical and horizontal lines. The vertical line regresents the longest carbon-carbon chain. All the vertical lines Qoint backwards. awa mm the Viewer. The horizontal lines are atoms or branches off that chain. They Eoint forward, towards the viewer. A Fischer Eroiection thus shOWS a motecule in a comgletelx ecligsed conformation (for chains having more than three carbons). A A A A 8+0 means Bpéqc based on B/klp or BVL o D '4 c y, C D I looking} from below The chain from A to D is the Ion est carbon-carbon chain. B and C are substituents on that chain (they can So groups, or single atoms IIEe Fli. A goes at the to if it is the end of the chain havin the lowest number accordin to IUPAC nomenc ature ru es (in ct er words, the chain extendin from A to D would be numbered from to _to bottom). Fischer projection No quarter turns: A ~ iionaJRCHOi-t} CHO 3- c: H O ‘t “ 4” 7‘? 3’ CM80’ CHDH . I I if: 1 L CHGH @ LU PA? {CH0 H No flilps: \ forgave ‘L Imp/ic- A A 3 C £-——}Q—>— 33166-441056. Ajeci—Lém/ 3W . CD/Fowesf IUPAC *5 JD 2~0Liwwstm A 2K oHo femaai @ cw We») as am ; as. 190;, fime Assigning R and 8 using Fischer projections Qutll'y‘t/"J'Wfi‘i’ 561» WVe/mi‘w If the lowest Eriorithg group is on a vertical, you can assign R or S to the stereocenter with ‘ th I ' ' ‘ . confidence because e owest group I5 painting back 4/ R 65L 3 gauge/a If the lowest priority group is NOT on a vertical, assign R or S, then switch®to reflect the fact that the lowest priority group was coming out of the plane, not going back. To draw an enantiomer of a Fischer projection, exchange 2 groups on the horizontal axis. IUPAC: J :2. 3 4. 6 E i : -' xamp as 73106 "VVLO’EQCAA/Eé’. Les @E—é CHZc H2043 3~Chgtwfiexeme fit/"R i . 5+ . . “a Et'“ H Wait {sake/=1, Aefsnefiew‘fww Wot/Eat, /6Q. Pr (a Et- Et‘: C55 '_ H 4% Cf .xfi? me1i a, ram/2 wt Cafiw~ jmjvgvb 1 ’3‘ R fiw’fl cat/e, ’9 .L W ' CH3 CH3 “’31 H 10H Same ab 6 e abs 5 C) an»: ,CH20H3 H n" “W . .t jib @ Et- 6 5 OH CHZCHB xféwi: W 14 (3) ME. “mo—f [3/33. CALI/3c H cameo-t Ci ad: 15:0}: 69 H IUPAC 14mm berm/1c; +5136 clam [9/9043 ewe cooH I M, PA C H q CH3 . 1 3 iUF’AC 14mm loam/C? i on Hooc man—CH ,/ ' 3 Coot—i 6 OH (SW-tr]? 6% H 2 L H 5W3 0V5 Stereoisomers with more than one asymmetric carbon Diastereomers: Wieso compounds: Stereoisomers that are Achiral molecules that belong not mirror images of to a Set of stereoisomers that 5 one another has chiral members. i (i.e., not enantiorners) or.... Achiral molecules that possess asymmetric carbons and have an internal plane of symmetry relating the asymmetric carbons to each other Examples of diastereomers: I grit—f , 1 $1317 I :11“ 513T ’ 2,: &fi ' r . 753ch CH9 i CHO CH0 i gal—lo 3.21.0 (Le, cams 0H E - 5...; I H OH . j H R ; HO HO : H ‘ chum-ave cme H OH 5 Ho ‘5 H H R 0“ ; H0 5 H (LE 66:61: 52.04: g I ) C Lma/tim 3 I 3 , 3 z 2, :54 ? CH3 ®mem Wham? R ' I fl 5:; 61wwe$mwems .em own/s Consider these three stereoisomers. What are the stereochemical relationships between each pair? R 0 Us“ ow : 'Br 2 Br ’Br ’7 Br jér éjBr K A B C “MW sifwwm £mew—E/W cos ~1, 2* ertij cgvfleycam £01,031, <1 ‘ f‘mm, «Ls own/C (gui— Mummflmw «of £WWWW¢LC ow/ffcfimcfitcm Kismet/e "bo- AAA/fiLc'tuUH ’ COMO/(.921. a, WLO’EecM/Ce, 2 {shawl/1mg comm , Our?ng Sfmaoi/sm W fossiga. H OH Ho H H Hos H H. 0H —; C, £Mcuwtmm 144.250 4%]:144, ,‘ofrtv'mflé’j WLQRQL éw‘g.’ Ls gotta/(53% mC/ffib’flfl i: (—3 a .. 'é'VL—tQJL’l/LCME [afoul/U?— flf OH mama m a m min w 6 Esfigoaofiaa “fig” and S @ mg m E Emaaosmsmz aim», is 6 msmumwmofiohfiwé “NAM?” £3 a Q mung 3 Essagfifiac‘m “3mm .8 2 Mm E 5 .2533; £23 . §5OQEOU m: 0 GEN: UQLMOU m um w a .3 9:5: :2 _ m we fimfifiuommg “mmowfimwflmoo 328% 2: 9:6 ___ Ea = h. a A 533:0 :ngm m cm is: a :2“. :m 5:5 a $233 :35 a E : 1:6 2 £0 c3063. 4 . IOOO-ZO.A 58 25m; Iooogfofofo 2 A3523108-9852“: a mfifia mom—.23 “$39 a 53:3 $3335 fiEg 3.2:? 6.5? $3039: emu”: mo ".255 ®®®N mam .WQQEQmew szozofizov a" .Imfioflofifim some 5 $52.50 HIE“: $3qu ufiemomhflm "83:3: 95 9% 33% 5 .EeEooImummmw Em IE III N 6 .Euficwgmam 93 @m MEN M 3m .mgmicfiflmflw 95 mm 35 m Q fig..me E Emfifimum £2599 9— in E m M.Iu mi. me qu I _ GI .10 _ I I0 I I “ CI 131%: :0 _ I glow." 201.141.4— OIU OIU OIU OIU "mammfihfi Iouommfia panama omen“ IoEmmeU mm “mm 5 In «mm 6 #5 mm .IN 5 mm .mm 2 Eli I: 5 molt II E qu .mcfluuwoum .azumE mi: E m III N mzcnhmu me mmowfimwwgu 2% bag—mm: >m Rm Em AU 3 § m Q.” >m E E H «Io me #4 Eu I W OI Io _ I IoEs_EEI I “ OI I|o_ I I0 _ I I|_ OI Iolll_ I omu OI“. 0:0 0:0 or 0:0 tomb—emmcafim $5 $53.58 «mun $3333 heaomwm €33, @533 a EIEEEII@ Q Eefiogfimma Am mEEOmM 3:933“?ch Q / umI mIo \ of as mom Wfiwwfigh mammyQQmQfim @mQSw @afi 36$ ...
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September 19-26 - {Cim‘tfi #5 [3&amp;quot; i4 2...

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