Organic Chemistry Theme 2 SaturatedHydrocarbonstConformationmm Sat hydrocarbon alkanes and cyclo alkane single bonds of hydrogen Conformation single o bonds can rotate allowing them to fold into specific shapes and affecting chemical properties Structualisomerisminalkanesmmm Alkanes Cn Hantz Cyclic alkanes have 2 H's fewer than max for each Conformers remain W molecules can ring fold into different 3D shapes but same molecule M pentane These compounds with same molecular formula Cst iz different structural formulas but Structural constitutional iso No Of structural iso Nas size of alkane A Saturated carbons secondary 20 can 30 tertiary depends on in be classified into primary 10 no quarternary 40 of attached it carbos m 8 i gag to oi p re o Alkylgroup removing one hydrogen from the alkane chain e g n propyl Common substituents alkylgroups chain Mfjymain If TX Propylgroup isopropyl group pr secbutyl group isobutylgroup Bu un.my guy Bu was IpacNamingm prefix part s C atoms a most important tix functional group where twhat ents Substituents atom group of atoms attachedto main chain eg alkyl group R implies random alkylgroup D isobutyl i e A methyl H gee buoy nospaceinnameoramane Cycloalkants Saturated hydrocarbon with C atoms bonded in a ring not parent chain it becomes a substituent If C's in a ring are name just as alkane Parent 7 carbons heptane I 2 methyl isopropyl Substituents Name i start numberingwhere subs is closest before m 4 isopropyl z methylheptane Parent Subst gfk nonane 2 methyl z ethyl 6 tert butyl methyl Name f 6 tert butyl 3 ethyl 2,7 dimethylnon ane any burn s amethyl Ijispror cyclopentane both are 1,3 combos lookat alphabetical order Name l isopropyl 3 methylcyclopentane bring isobuty cyclohexane eighty imethyl cethyl cyclohexane ut gigIng Parent butane Subst 2 cyclopropy Name 2 cyclopropybutane Propertiesotalkanese Bp Mp M with Soluble in organic a size solvents not water Efftnffmfff.fmfta molecule by therotation of a single bond in that differs from another isomer the molecule Conformation 3D shape of atoms in molecule from rotationaround sin le bar Newman projections show conformation Electrons in O bonds repel so e Dihedral angle angle between can be further apart two planes g g Video explanation staggeredcontormatia e.g ethane H É H É H Newman H y atethane It y if Which is more stable Staggered because in eclipsed conformation there is torsional strain e g f f fd cH3CHzCHzCH3 7 I 180 CH3 staggered fyh but specifically anticonformatia moststable bee methylgroups are far apart me anew ang between men group go Moststable other conformations Dihedral c between dimethyl groups 600 H Is some steric strain betweenmethylgroups H H iii Methylgroups 1200 apart third most stable secondmost stable H 36 00 apart methyl groups eclipsed totally H CH least stable H Potentialenergydiagraminnn Ep win 00 totaleclipse we see as F 600 1200 Gauche Eclipsed pl mfabietergy 1 2400 3000 3600 Anti eclipsed Gauche totaleclipse 1800 PEM stability 1 Dihedral angle e g 2,3 dimethylpentane Which conf is most stable 9109 and Cz 1 Staggered conformations carbon 2 2methylgroups I hydrogen carbon 3 methylethylhydrogen CH These two are identical H I CH CHZCH one H CH3 i Hz 3 H ethylmethyl gauge interaction i Least stable one methyl only methyl interactions ed mat gauge only one ethyl methyl interaction 2nd most stable has two methylmethyl interactions staggered most stable two stored ethyl methyl gauge interactions Ct H H ethylmethyl more energy than methyl methyl interaction y 2 hydrogen atoms eclipsed Ctb ÉI iii interaction 15kgmol lessstable e g enginery strai torsional L 4kgmoi ti eliciped CH3 g H calculate ethylonnyaro amethyl methyl guy ima Zkjimo i morestable 02 03 bond Drawthe moststable conformation of 2 methylbutane along ay H H Cats H H Hi 413 fall possible staggered n onegaugeinterac twogauge interact tion ions 3,8Kjmot skjima we knoweclipse is one gauge Same as less stable wontdraw 1st conformation lowestenergy i moststable e g I Anticonformation Totally eclipsed almostno energy KJ 4 2 guy no gauge eclipse interacting i Energy barrier to rotation In order to rotate butane from its anti conformations totally eclipsed conformation lakJ of energy per mole t 5hhsm fgntmamnatij.sn Alkanes O bonds distance between e grey conformation around c c can rotate is closer when eclipsed Shows Sta ere d diff conformations are distance is further when they staggered conformation more stable DrawingNewmannProjectionmmmm tag F H Draw 3 bonds toothergroup outwards from frontC F egg Draw a circle to represent the back C CI F he Fromtheedgeof thecircledrawthe 3 bonds fromthebackC to other groupsexactly as bonded Ce H F he ReadingNewmanProjectionsumm carbon backbone in the plane of paper to will11 bonds projecting forward bonds behind the plane F OH stable form If sings Hoh H O carbon front hydrogen Jon gap carbon back IoT yetifoup misoprop group look at front carbon OH biggest group back carbon isopropyl biggest i twist so that they Take model turn sideways Turn t are group opposite to see isopropyl group donthave to yH How ÉÉNce hydrogen Draw following YI OH Back carbon Front carbon et Ce H et p OH Cthy's biggest groups rotate them so that they are at opp ends TY a Et y two biggest groups further apart Totten fly Ma Br ice other ways too 4 other ways of drawing e g Backcarbor Frontcarbon He Bu E't me H Final OH i At but Rotate so t butyl and Top ethyl to be further away Views Within É É I l I cmgndngoigt im view front I H p 2 methyl butane C B A back carbon is stil a staggiediatormations To change conformation rotate the front or back carbon D E F eclipsed conformers J which is stable Staggered more stable stable A B C has 2 cuz'sclose to each other i A B min energy 9h3 413 iifa y CH which are most H Which z are least stable H ay I 2 most stable Eclipsed less stable D F III it CH t Max teststable energy eclipse Minima staggered É maxima eclipsed most stable cyclamens D 3 C's f cyclopropane cyclobutane cyclopentane cyclohexane É Naming of ethyl cyclohexane t ethyl 2 methylcyclopentane men heptane phlonger 3 cyclohexylheptane trans 112 dichlorocyclohexane Jace Ot y 015112 dibromocyclopentane Stateggtyotcycloalkanesmmm C D 108 C aogo 2 silane q Ideal most stable gregimestantot ringstrain reactive very weakbonds For sp carbon e CH g and 108 from cyclopentane But cyclohexane tetrahedral geometryIdeal angle is 109,50 very close flat It can moveits 1200 angle to switch It forms chair conformation Chair Conformations axygha stgightyp agialup É I axitfth laxdownsantiann he equitorialstandoln side I slanted up a P agg e g Draw the most stable chair conformation of methylcyclohexane equitorial bothmethylcyclohexane Chs less e g sttie stable more methylgroup will avoid 1,3 diaxial interaction Draw most stable chair conformation of 1 tert butyl 4 methylcyclohexane i Y axial ia g 4 types of stabilities axial axial eq eq eq ax ax eq more stable if bigger molecule is off to the side MET it leaststable bothgroups in axial 3rd most stable 2ndmost stable most Stable both groups in equitorialposition axidup i trans earn egg i cis axialdown gown trans cis Whether its eq i cis axial up ax doesnt matter opposite directions up down stereoisomers transf same direction cis e g constitutional O 61412 Cyclohexane isomer same MF different connectivity 9420143 CH 61412 l ethyl zmethylcyclopropane y e.g stereoisomers same connectivity diff arrangment CH3 WAH H WH H CH3 61712 61412 Ringfips cyclohexane s y 2 143 I s ringflip 11 Slant 3 towards Igt ax p p y y y timbering left 2 1 CH3 ÉÉstabe move no in www se less 113 diaxial interactions eq up up o down down e g Perform I a ring flip 6 2 stability are same T Br oneaxial one eq 4 b g N Br ry Remain up BT m y T down e ring 4 p HSC e g more stable bigger tertbutyl gro is to theside Convert following into their corresponding chair conformations MEI.gegpipggfgIoraxid 3 y Bp going canbegin trans OH e pi g Cis 9 oi p s ce up both up I My OH down B Ag p Br Cyclohexane Fold one up t a corner down and one i Forms a chair conformation Chair conformation has two positions for its substituents axial and equatorialposition Chair cyclohexane equatorial H's 6 axial H's perpendicular to the near plane of the ring and ring Red ring axis White ring equator Conformationalmobilityotcyclohexanmmmmm Relative St d 6 I F r Both fluorines equitorial position Dont turn molecule as This is a ring flip be ringflip theywillstill eq grotgunupcorne A rotatedown Now 2 09 groups are a axialgroups corner up Ringflip only rotates bonds cis bonds remain cis axial up aup up down yequitorial Lock fingers e g 4 push a up push Cy down 60 OH axial position bring flip Ya fed ax gaxial cis MEH pushc e.g up push Cs John Tons axial OH axial Ring flip Cy 3 a e g ft 0 Trans push CI up pushCydown bothsubst are axial Hz Ring flip Ho stays facing up but changes position m
