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Stereochemistry M H MPOC Ch 6 Stereochemistry Isomers Different compounds with the same molecularformula Constitutional Isomers different connectivity B Br CeeHnBr Br xx Stereoisomers identical connectivity butdifferent spatial arrangements Br Br µ and I Enantiomers Chirastereoisomers that are non superimposable mirror images a moleculethat is not superimposable on its mirror image recognized by a lack of an internalplane ofsymmetry Br Br M and I Diastereomers stereoisomers that are not enantiomers Br Br R and H I and I H d Br Br ChiralCenter atom with fourdifferent attached Colderterm groups Ein Stereosenic Center an atom at which the interchange of two produces a groups stereoisomer Br Br G 4 Tn in 1LHE L enantiomers diastocomers H H Stereocenter as most P Stereogenic unit an atom or grouping of atoms at which interchangeof twogroups produces a stereoisomer any nd Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry Non carbonstecocerthfill t neitherenantiomer Low inversion and is isolable barrier Stable e Chiral phosphineligands cBum fifths Phd isolable Canbeused for asymmetric synthesis ChiralmoleculeswithoutchiralcertosI Chiral if R Rz Rie Ry C c c and R R Rs t Ry i H Hi KC c dk 1kC c O Hy c jH ketene ACO f f me Me J ope sp enantiomers I allere Atropisomers stereoisomers resultingfromrestricted bondrotation BINAP pph can'toccupythesame pith Plane as thetwoH's would bump Hinderedrotation AchiralMolecules Possess a plane of symmetry mesocompound compound Hsc with one or morechiral is centersthatis achiral ITIII achiral dueto a planofsymmetry 01T OH CHS 1 Ht 3stococentos It tf III CB Draw allstereoisomers e identifyrelationships Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry SkrochemicalDescriptorst Re S for chiral centers Lone Prioritize the four around the Chiral Center Pair H C DST groups Highest AN 1 Lowest AN 4 usuallyH Tie examine connected tie move out one atom I compare groups Point 4 to back 1oz 3 Canalso use for Elz cc H y E config ooo CHH B g 2 Axial Chirality H H Sight down the axis Ttm PrioritizeGroups G H bI g CI LP f f Be p Highest priority her group tohighest priorityforgroup P to I fIipm P q 3 De L Used in Fisher Projections carbohydrates e amino acids Typically H It 50 Naturally 50 Convention H OH H occurring HO COOH COOH HO H H OH OH H Ho H 12N H NINH NINH Hl OH on H Hotl H Right D i CHEH CHOH CILOH L serine D Glucose L Glucose naturallyoccurring Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry Opticalactivityandchirality PlanePolarized Light Chiral one enantiomer of light is I slowed morethantheother chiral enantiomers to different indices ofrefraction all electricfieldsoscillating 6 in the same detected togiveopticalrotation plane OH OH pot pot B pBr Mr Es rien achiral achiral 50 150 50 1 150 opticallyinactive opticallyinactive active active optically optically OH so so e racemic mixture t inactive optically rotation Observedrotation specific GTF pathlength dm Concentration gloms Ex A of cocaine dissolved in 7 S ML of in a 1.20gsample Chaz 5.0cm tube had an X 1.30 What is CDD sample G D 16 1,306.50dmt.zogf.cm Chiral non racemic mixture of enantiomers that is not I When a rxn produces a non 50 so mixture of enantiomers have an excess you of one enantiomer enantiomeric excess ee x too EiEz_x 100 Infix t Et Ez Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry ee 20 60 80 R 2 80 100 123 1 12,0 801 20 160 er 80.20 4 1 71 1 Racemic excess of R denatiomericratio OH Ex CDF the7 You prepare the molecule t record Et CiHas pure en CABO t5.10 What is ee t ee too 76 t ee 6.7 Enantiomers most interaction strong Interact with achiralentities in an identical manner Common racemiccompound i heat same Same Mp bp 0 Same refractiveindex light Mp silica gel can't be separated conglomerate i Enantiomerssmell differently our body is chiral R S separation 1 Direct resolution Ph Ph ph Gt Ph Ph B 1tgN E I Nb ip TOO f B t T B ipr OH iPrXO t O n h Arechiral 0 o.o of base p 2 Kinetic Resolution Takingadvantage of the fact that enantiomers will react w chiral reagents through diaster transitionstates unequal ratedifference energy BuOH O O t flow1 yeast IOB Lh OI Br lipase Br 96 ee easilyseparate 454Conversion Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry Jacobsen HydrolyticKinetic Resolution JACS 2002,124 1307 PostDoc w Sharpless Yz of 2001 Nobel Prize for asymmeticepoxidation Nu epoxide opering OH OH t OH r r r I L Jacobsen destroy OH R o M sales E OH t f 1 t tho p r 7991 ee T r keep M sales M for sis will the in give f Ny other epoxide enantiomer OF Her r X OAC F F I F CES 3 Chiral Shift Reagent Ao Lanthanide metal w chiral ligand EuChfd3 Xx O Ev y Amein Enid T Agim 4 Chromatography HPLC GC TLC etc ominimally destructive Highselectivity ChiralstPhag R t S Low detection limit puts mix different Limit no universal chiralstationery retention plase times Limit Chiralcolumn 51 Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry TopicityRelationships Br Br Br Br and Br Br w homotopicprotons Identical have same NMR signal and B B Br B B entatiotopicprotons enantiomers have same NMRsignal unless a shift reagent is used OH OH OH AH M D M t and l T l 779 l 779S diasterotopic protons diastocomers havedistinct 1H Nmr signals I OH S µ pro D or Br Bite diaslerotopic Gtsgroups Prochiralface the 3 like Rts Assign groups O si face y µ Brmsop MSBr H j IBC 010 Si 11 Re attack attack H Re face lit Enantiomers Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry Rxn of an achiral molecule w a chiral reagent CIMB Blank t BC p off t Kg H g H H Hsc di isopinocampheylborane Diastercomers formed in different Ipc amounts H Bm he StereospecificandstocoselectiveRXI Stereospecific rxn Sterochem of the material dictates the starting stereochemof the product Stereoselective an rtn that produces an excess of one stereoisomer SNZ Rin stereospecific AnyStereospecific I A e rxn is CN OTS stereoselective stereoselective me Stereospecific t e Ph Ph mI Ph µ 15 stereoselective 67 33 M to sole OAC Bison product Sakurai Rin 11 Stereoselective rn OAC not stereospecific Chemistry 531 – Physical Organic Chemistry Josh Osbourn Stereochemistry Diels Alder Regioselective e stereoselective 09 1 NotFormed one Home if one Iem Timpone of regioisomers Correct alignment regioselective part Use endo rule to predict stereoisomers t it i'ten Rome skpggsekd.ve en 11 phone K TimescaleImplicationI Time scale is important for all stereochemical concepts But is achiral because the ii as i i is enantiomers achiral because a fast ringflip interconverts the enantiomericforms enantiomers Chemistry 531 – Physical Organic Chemistry Josh Osbourn .
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