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Cycloalkanes : * are hydrocarbons with the carbons joined in a loop or ring; *have all C in ring connected by single

Cycloalkanes : * are hydrocarbons with the carbons joined in a loop or ring; *have all C in ring connected by single bonds; and * have general formula C n H 2n . Names for cycloalkanes are like those for linear alkanes: prefix the name with the term “cyclo”:

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Cycloalkanes : * are hydrocarbons with the carbons joined in a loop or ring; *have all C in ring connected by single

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  1. Cycloalkanes: * are hydrocarbons with the carbons joined in a loop or ring; *have all C in ring connected by single bonds; and * have general formula CnH2n.

  2. Names for cycloalkanes are like those for linear alkanes: prefix the name with the term “cyclo”: CH2 is cyclopropane CH2 CH2 or each vertex = C

  3. H H H C H H C C H H C C H H H cyclopentane each vertex = C

  4. CH3 H methylcyclohexane any vertex without extra attachments shown is a CH2.

  5. Naming rings with more than one substituent 1. number around ring to give lowest set of locant numbers to substituents. 2. ring C #1is connected to the most important functional group (if there is one), else to the alphabetically first group.

  6. 1 Br 2 3 CH3-CH-CH3 1-bromo-3-isopropylcyclohexane

  7. Review from earlier lectures: • Isomers are different compounds with same molecular formula. • * Constitutional Isomers are those which have a different structure or connectivity among the atoms. Examples...

  8. C3H8O could be CH3-CH2-CH2-OH OR CH3-CH-CH3 OH OR CH3-O-CH2-CH3 These are all constitutional isomers.

  9. Stereoisomers are: • * isomers (= same formula), • having same constitution (= same kinds & sequence of bonds), • * but permanently different arrangements of groups in space.

  10. Stereoisomers are of several types, depending on what phenomenon causes them to exist. Geometric isomers also result from restricted rotation around C-C single bonds in ring compounds: it is impossible for a C-C bond to rotate 360° in a ring.

  11. A cyclopentane ring viewed on edge: bond pointing up bond pointing down this heavy bond points out towards you

  12. H Cl Br H 1-bromo-2-chlorocyclopentane there are two geometric isomers, each a very different compound...

  13. cis H Cl H Cl H H Br Br trans

  14. The proper names are: cis-1-bromo-2-chlorocyclopentane cis => on the same side of ring and trans-1-bromo-2-chlorocyclopentane trans => on opposite sides of ring

  15. Cyclohexane rings also may have cis & trans geometric isomers. true shape, “chair” Haworth, “flat”

  16. The flat hexagons are commonly used in biochemistry and biology because they are easier to draw. In CHM 1020 we will show cyclohexane compounds this way most of the time.

  17. H Br Cl H has two geometric isomers:

  18. Cl Br cis Br H H H Cl H

  19. H Br trans Br H Cl H H Cl

  20. What would be the proper names for these geometric isomers? Give it a try!

  21. Cl Br H H cis–1-bromo-4-chlorocyclohexane

  22. Cl H Br H trans-1-bromo-4-chlorocyclohexane

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