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Carey Chapter 3 – Conformations of Alkanes and Cycloalkanes

Carey Chapter 3 – Conformations of Alkanes and Cycloalkanes. Figure 3.5. Conformational Analysis. Cytosine (C) (from TGCA alphabet in DNA. Hemoglobin. Thymidine – incorporated into DNA as “T”. Zidovudine (AZT) – incorporated into DNA instead of T – stops chain growth.

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Carey Chapter 3 – Conformations of Alkanes and Cycloalkanes

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  1. Carey Chapter 3 – Conformations of Alkanes and Cycloalkanes Figure 3.5

  2. Conformational Analysis Cytosine (C) (from TGCA alphabet in DNA

  3. Hemoglobin

  4. Thymidine – incorporated into DNA as “T” Zidovudine (AZT) – incorporated into DNA instead of T – stops chain growth

  5. 3.1 Conformational analysis of Ethane Single bonds can rotate around the bond axis, different conformations are possible -conformational analysis Figure 3.1 (use SpartanModel)

  6. 3.1 Conformational analysis Different 3-D depictions of Ethane Wedge/dash Newman Projection Sawhorse Rotation aroundthe central C-C bond will cause the hydrogens to interact -rotamers or conformers

  7. Definitions Gauche torsion angle 60o Anti torsion angle 180o Eclipsed torsion angle 0o Both gauche and anti conformers arestaggered Eclipsed conformers are destabilized bytorsional strain

  8. 3.1 Conformational analysis of Ethane Figure 3.4

  9. 3.2 Conformational analysis of Butane Figure 3.7

  10. 3.3 Conformations of higher alkanes eclipsed eclipsed Anti (staggered) Gauche (staggered) Applicable for any acyclic molecule

  11. 3.4 Cycloalkanes – not planar Cyclohexane

  12. 3.5 Cyclopropane and Cyclobutane Figure 3.10

  13. 3.6 Cyclopentane Figure 3.12

  14. 3.7 Conformations of Cyclohexane Conformationally flexible (without breaking bonds) Chair Boat Chair

  15. 3.7-3.8 Cyclohexane – axial and equatorial positions Figure 3.13-3.14

  16. 3.9 Conformational inversion – ring flipping Figure 3.18

  17. 3.10 Analysis of monosubstituted cyclohexanes Based on unfavourable1,3-diaxialinteractions

  18. 3.11 Disubstituted cycloalkanes - Stereoisomers Cis-1,2-dimethylcyclopropane is less stable than the trans isomer Cis-1,2-dimethylcyclohexane is less stable than the trans isomer Cis-1,3-dimethylcyclohexane is more stable than the trans isomer Cis-1,4-dimethylcyclohexane is less stable than the trans isomer All based on interactions between substituents and other groups on the ring

  19. 3.11 Disubstituted Cyclopropanes Figure 3.20

  20. 3.12 Disubstituted Cyclohexanes

  21. 3.13 Medium and large rings – not covered 3.14 – Polycyclic compounds – covering bicyclics Bicyclobutane Bicyclo[3.2.0]heptane Bicyclo[2.2.2]octane

  22. 3.15 Heterocyclic compounds tetrahydrofuran pyrrolidine piperidine morphine ritilin librium

  23. 3.15 Heterocyclic compounds D-Glucose (dextrose, blood sugar)

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