Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Chapter4环烷烃

425 views

Published on

Published in: Technology, Education
  • Be the first to comment

  • Be the first to like this

Chapter4环烷烃

  1. 1. The Steroid SexThe Steroid Sex HormonesHormones TestosteroneTestosterone EstroneEstrone Regulate growth and function of reproductive organs;Regulate growth and function of reproductive organs; stimulate development of secondary sexual characteristicsstimulate development of secondary sexual characteristics OOHHCHH33 HH OO HH HH OO HH HH HH CHH33 CHH33 OOHH
  2. 2. CycloalkanesCycloalkanes Abundant in nature: “rigid scaffolding”.Abundant in nature: “rigid scaffolding”. Names:Names: CycloCycloalkanesalkanes Cyclopropane, , , etc.Cyclopropane, , , etc. Substituents:Substituents: CycloalkylCycloalkyl. Substituted cycloalkanes:. Substituted cycloalkanes: single substituent is automatically at “single substituent is automatically at “C1C1”.”. Ethylcyclobutane (no # needed)Ethylcyclobutane (no # needed) Alkylcycloalkane or cycloalkylalkane?Alkylcycloalkane or cycloalkylalkane? Larger stem controls:Larger stem controls: 11 22 33 44 55 11--CyclopropylCyclopropyl-- pentanepentane (CH(CH22))nn notnot CCnnHH22nn+2+2
  3. 3. DisubstitutedDisubstituted:: a.a. Lowest numberingLowest numbering b.b. Alphabetical orderAlphabetical order CCHH33 CCHH22CHCH33 11 22 1-Ethyl-2-methyl-1-Ethyl-2-methyl- cyclohexanecyclohexane 11 22 44 CCHH33 11 33 44 ClCl BrBr 1,2,41,2,4 notnot 1,3,41,3,4 1-Bromo-2-chloro-4-methyl-1-Bromo-2-chloro-4-methyl- cyclohexanecyclohexane
  4. 4. Cycloalkanes have two sides: “up”, “down”.Cycloalkanes have two sides: “up”, “down”. With two or more substituents, new type of isomerism:With two or more substituents, new type of isomerism: Same side: cisSame side: cis Opposite sides: transOpposite sides: trans StereoisomersStereoisomers CHCH33 CHCH33 CisCis-1,2-dimethyl--1,2-dimethyl- cyclopropanecyclopropane BrBr FF TransTrans-1-bromo-3--1-bromo-3- fluorocyclohexanefluorocyclohexane StereoisomersStereoisomers
  5. 5. Stereoisomers should be stable at roomStereoisomers should be stable at room temperature. Rotamers interconvert rapidly bytemperature. Rotamers interconvert rapidly by rotation, whereasrotation, whereas cis,transcis,trans isomerizationisomerization requires bond breaking.requires bond breaking. Same connectivitySame connectivity (not constitutional isomers), but(not constitutional isomers), but differing arrangement in space.differing arrangement in space. Note: This definition includes all rotamers (anti, gauche, etc.).Note: This definition includes all rotamers (anti, gauche, etc.). Definition of stereoisomers:Definition of stereoisomers: OperationalOperational (practical) definition:(practical) definition:
  6. 6. The Cal Katrina Relief Big Lecture Drive What: Why: How: When: Who: Big Lecture Drive Rather than going out to lunch or buying coffee later this week, make a contribution. Because funding is urgently needed for the disaster relief. Also, to foster school spirit, to win the competition and (maybe, we are still working on this!) get free ice cream or a mention in the Daily Cal! A fundraising competition for the American Red Cross’ hurricane Katrina relief efforts between the largest classes at UC Berkeley, organized in affiliation with Cal Katrina, the ASUC, and the Berkeley chapter of the American Red Cross. The 1st, 2nd, 3rd, 4th, 6th, and 7th largest lectures at UC Berkeley. We are still waiting to hear about the 5th largest lecture and others! After lecture, on your way out.
  7. 7. How do we quantify “ring strain”? Need anHow do we quantify “ring strain”? Need an ““unstrained” reference and a measure ofunstrained” reference and a measure of energetic content. We get numbers byenergetic content. We get numbers by measuringmeasuring heats of combustion.heats of combustion. spsp33 -Carbon wants-Carbon wants 109.5°109.5° 60°60° 90°90° 120°120° 108°108° RingRing StrainStrain
  8. 8. ~160 ~160 ~160 IsomersIsomers
  9. 9. An Application: The Relative HeatAn Application: The Relative Heat Content of the Two Isomeric ButanesContent of the Two Isomeric Butanes Most branched alkanes are slightly more stable than their linear isomersMost branched alkanes are slightly more stable than their linear isomers
  10. 10. Are cycloalkanes “normal”? DefineAre cycloalkanes “normal”? Define normal from heat of combustionnormal from heat of combustion ΔΔH°H°combcomb of CHof CH33(CH(CH22))nnCHCH33 AnyAny discrepancydiscrepancy withwith ΔΔH°H°expexp equalsequals ring strain.ring strain. Every additional (CHEvery additional (CH22) increment) increment gives an extragives an extra δΔδΔH°H°combcomb ~ -157.4.~ -157.4. We can therefore calculateWe can therefore calculate ΔΔH°H°combcomb (expected) (CH(expected) (CH22))nn:: nn x 157.4.x 157.4.
  11. 11. 60°60° 90°90° 120°120° 108°108°
  12. 12. 1.1. Bond angle,Bond angle, especially inespecially in small ringssmall rings 2.2. EclipsingEclipsing 3.3. Transannular,Transannular, especially inespecially in medium sizedmedium sized ringsrings RingRing StrainStrain ::
  13. 13. EclipsedEclipsed CyclopropaneCyclopropane
  14. 14. Strain Relief Through “Banana”Strain Relief Through “Banana” BondsBonds Trimethylene diradicalTrimethylene diradical Weakened:Weakened: 65 kcal/mol65 kcal/mol
  15. 15. Hot Recent Research!Hot Recent Research! J. Am. Chem. Soc.J. Am. Chem. Soc. 20052005,, 127127, 9370-9371, 9370-9371
  16. 16. Cyclobutane: “Puckering”Cyclobutane: “Puckering” Reduces EclipsingReduces Eclipsing
  17. 17. Cyclopentane:Cyclopentane: Envelope ConformationEnvelope Conformation Almost staggered
  18. 18. The UnstrainedThe Unstrained Cyclohexane:Cyclohexane: A “Chair” ConformationA “Chair” Conformation Move C1,4
  19. 19. A Newman View of aA Newman View of a Cyclohexane C-C Bond:Cyclohexane C-C Bond: Staggered!Staggered!
  20. 20. The Cyclohexane Boat isThe Cyclohexane Boat is StrainedStrained + 6.9 kcal/mol Move C1,4
  21. 21. ……So it Twists.So it Twists. But this is only part of its mobility.But this is only part of its mobility. The moleculeThe molecule “flips”“flips” from onefrom one chairchair to another chair form.to another chair form. -1.4 kcal mol-1 -1.4 kcal mol-1
  22. 22. Cyclohexane Ring FlipCyclohexane Ring Flip HH HH EEaa = 10.8= 10.8 ΔΔG°G° = O= O eqeq eqeq axax axaxHH HH HH HH HH HH HH HH HH HH () () TransannularTransannular strainstrain Eclipsing strainEclipsing strain ChairChair  Boat + 6.9 kcal molBoat + 6.9 kcal mol-1-1 . Boat is a TS.. Boat is a TS. Complex Movement:Complex Movement: Goes throughGoes through boatboat RingflipRingflip WalbaWalba MonkMonk
  23. 23. The Chair-Chair FlipThe Chair-Chair Flip ManifoldManifold RingflipRingflip 100,000 times/sec100,000 times/sec
  24. 24. How to Draw the ChairHow to Draw the Chair CyclohexaneCyclohexane ““down”down” ““up”up” This endThis end Equatorial bonds must beEquatorial bonds must be parallelparallel to the C–C bond(s)to the C–C bond(s) “one over”“one over” [not[not the attached one(s), but the nextthe attached one(s), but the next one(s)]one(s)]
  25. 25. The Chair-Chair FlipThe Chair-Chair Flip CausesCauses Equatorial-AxialEquatorial-Axial ExchangeExchange The two structures are the same. However, whatThe two structures are the same. However, what happens in substituted cyclohexanes?happens in substituted cyclohexanes? ∆Gº = 0
  26. 26. SubstitutedSubstituted cyclohexanes:cyclohexanes: ΔΔG°≠G°≠ 00 ΔΔG°G° = +1.7= +1.7 gauchegauche HH HH CCHH33() transannulartransannular HH CCHH33 axax eqeq Conformational Analysis:Conformational Analysis: Interplay ofInterplay of energetics of ax-eq substituents.energetics of ax-eq substituents. Example: MethylcyclohexaneExample: Methylcyclohexane
  27. 27. Axial-EquatorialAxial-Equatorial ConformersConformers AntiAnti toto ringring GaucheGauche to ringto ring
  28. 28. SizeSize vsvs bondbond lengthlength Note: These numbers doNote: These numbers do notnot reflectreflect absolute sizeabsolute size, but, but size with respect tosize with respect to transannular and gauchetransannular and gauche interactions ininteractions in cyclohexanecyclohexane..
  29. 29. The power of conformational analysis:The power of conformational analysis: ΔΔG°G° maymay bebe additiveadditive. Consider the. Consider the dimethylcyclohexanes:dimethylcyclohexanes: ΔΔG°G° = 0= 0 ΔΔG°G° == +3.4!+3.4! ΔΔG°G° = 0= 0 1,1-Dimethylcyclohexane1,1-Dimethylcyclohexane CisCis-1,4-dimethylcyclohexane-1,4-dimethylcyclohexane CCHH33 CCHH33 CCHH33 CCHH33 CCHH33 CCHH33 HH33CC CCHH33 CCHH33 HH33CC diaxialdiaxial diequatorialdiequatorialTransTrans-1,4-dimethylcyclohexane-1,4-dimethylcyclohexane CCHH33 CCHH33 But:But:
  30. 30. The largest group often enforcesThe largest group often enforces one conformation:one conformation: ΔΔG°G° = 3.4-5 = -1.6= 3.4-5 = -1.6axax eqeq eqeq axax axaxeqeq +1.7+1.7 +1.7+1.7-5-5 Large substituents, such asLarge substituents, such as tert-tert-Bu,Bu, are said to “lock” a conformation.are said to “lock” a conformation.
  31. 31. Br COOH H3C H3C Br COOH ΔΔG°G° = ?= ? Problem:Problem:
  32. 32. Br COOH H3C H3C Br COOH ΔΔG°G° = +2.56= +2.56 +1.70+1.70 +1.41+1.41 -0.55-0.55
  33. 33. All-All-cis-cis-hexamethyl-hexamethyl- cyclohexane:cyclohexane: All-All-trans-trans-hexamethyl-hexamethyl- cyclohexane:cyclohexane:
  34. 34. Medium Rings SufferMedium Rings Suffer Transannular StrainTransannular Strain
  35. 35. Bicyclo[2.2.1]heptaneBicyclo[2.2.1]heptane (norbornane)(norbornane) Bicyclo[4.4.0]decaneBicyclo[4.4.0]decane (decalin), trans and cis(decalin), trans and cis Bicyclic, Fused, Polycyclic, Polyhedral AlkanesBicyclic, Fused, Polycyclic, Polyhedral Alkanes FusionFusion transtrans ciscis BridgeBridge Locked boatLocked boat HH HH HH HH Home exercise: Make models and try the ring flip!Home exercise: Make models and try the ring flip!
  36. 36. Strained Hydrocarbons: What is theStrained Hydrocarbons: What is the limit? Exotic polyhedra: The Fivelimit? Exotic polyhedra: The Five PlatonicPlatonic oror Cosmic SolidsCosmic Solids (Plato 350(Plato 350 BC)BC) TetrahedronTetrahedron (fire)(fire) CubeCube (earth)(earth) DodecahedronDodecahedron (“ether”)(“ether”) Can we make the corresponding hydrocarbon frames (CH)Can we make the corresponding hydrocarbon frames (CH)nn ?? There are two more: icosahedron (water) and octahedron (air)There are two more: icosahedron (water) and octahedron (air)
  37. 37. Maier, Sekiguchi, 2002,Maier, Sekiguchi, 2002, tetrakis(trimethylsilyl)-tetrakis(trimethylsilyl)- tetrahedranetetrahedrane.. m.p. 135°C !m.p. 135°C ! Strain:Strain: 130 kcal130 kcal molmol-1-1 Strain:Strain: 166 kcal166 kcal molmol-1-1 Strain:Strain: 60 kcal60 kcal molmol-1-1 Eaton, 1964,Eaton, 1964, cubanecubane,, CC88HH88 Maier, 1978,Maier, 1978, tetra-tetra-tt-Bu--Bu- tetrahedranetetrahedrane.. SubstitutedSubstituted CC44HH44 Paquette, 1982,Paquette, 1982, dodecahedranedodecahedrane,, CC2020HH2020,, 12 faces12 faces m.p. 202°Cm.p. 202°C m.p. 126°Cm.p. 126°C m.p.m.p. 430°C !430°C !
  38. 38. Sekiguchi, Angew. 2005, 5821Sekiguchi, Angew. 2005, 5821
  39. 39. Octanitrocubane: aOctanitrocubane: a New Explosive andNew Explosive and Rocket FuelRocket Fuel Eaton,Eaton, Adv. MatAdv. Mat., 2000.., 2000.
  40. 40. The Allotropes ofThe Allotropes of Carbon: CCarbon: Cnn a truncated icosahedrona truncated icosahedron BenzeneBenzene
  41. 41.    Zuo, J. M. et al.Zuo, J. M. et al. ScienceScience 2003,2003, 300300, 1419, 1419 Atomic Resolution Imaging of a Carbon Nanotube
  42. 42. Carbon Nanotubes:Carbon Nanotubes: Novel Materials for theNovel Materials for the FutureFuture

×