; Cycloalkanes _ have one or more rings of carbon atoms
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Cycloalkanes _ have one or more rings of carbon atoms

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  • pg 1
									                    Cycloalkanes :
          have one or more rings of carbon atoms
•Cycloalkanes are alkanes that have carbon atoms that 
form a ring (called alicyclic compounds)
cycloalkanes 
• Nomenclature
               Naming Cycloalkane
Count the number of carbon atoms in the ring and the number in the 

largest substituent  chain. If the number of carbon atoms in the ring is 

equal to or greater than the number in the substituent, the compound 

is named as an alkyl-substituted cycloalkane 

For  an  alkyl-  or  halo-substituted  cycloalkane,  start  at  a  point  of 

attachment as C1 and number the substituents on the ring so that the 

second substituent has as low a number as possible.

Number the substituents and write the name
                                                         3
      ‫‪Conformation of Alkanes‬‬
 ‫• 1( ﺍﻟﺮﻭﺍﺑﻂ ﺍﻷﺤﺎﺩﻳﺔ ﻓﻲ ﺍﻟﻤﺮﻛﺒﺎﺕ ﺍﻟﻤﻔﺘﻮﺣﺔ  ﺗﻜﻮﻥ ﺣﺮﺓ ‬
                              ‫ﺍﻟﺪﻭﺭﺍﻥ ﺣﻮﻝ ﻣﺤﻮﺭﻫﺎ‬

‫• 2( ﺍﻟﺮﻭﺍﺑﻂ ﺍﻟﺜﻨﺎﺋﻴﺔ ﻭﺍﻟﺜﻼﺛﻴﺔ ﻭﻛﺬﻟﻚ ﺍﻟﺮﻭﺍﺑﻂ ﺍﻷﺤﺎﺩﻳﺔ ﻓﻲ ‬
  ‫ﺍﻟﻤﺮﻛﺒﺎﺕ ﺍﻟﺤﻠﻘﻴﺔ ﻻ ﺗﻜﻮﻥ ﺣﺮﺓ ﺍﻟﺪﻭﺭﺍﻥ ﺣﻮﻝ ﻣﺤﻮﺭﻫﺎ‬

‫• 3( ﻭﻟﺬﻟﻚ ﻓﻼ ﺗﻮﺟﺪ ﻣﺘﻤﺎﻛﺒﺎﺕ ﻫﻨﺪﺳﻴﺔ ﻟﻸﻠﻜﺎﻧﺎﺕ ﺍﻟﻤﻔﺘﻮﺣﺔ ‬
   ‫ﺍﻟﺴﻠﺴﻠﺔ ﺑﻴﻨﻤﺎ ﺗﻮﺟﺪ ﻣﺘﻤﺎﻛﺒﺎﺕ ﻫﻨﺪﺳﻴﺔ ﻟﻸﻠﻜﺎﻧﺎﺕ ﺍﻟﺤﻠﻘﻴﺔ‬
         Geometric Isomerism
 Cis-Trans Isomerism in Cycloalkanes
• Straight chain C-C (free rotation) -Cyclic (no 
  free rotation) 
• There       are      two      different       1,2-
  dimethylcyclopropane  isomers,  one  with  the 
  two methyls on the same side (cis) of the ring 
  and  one  with  the  methyls  on  opposite  side 
  (trans) 
               Reaction of cycloalkanes
• Ring less stable




• Ring more stable 5 and 6
    Conformations and
 conformational analysis of
         Alkanes
• Conformations: The temporary molecular 
  shapes that result from rotations of groups 
  about single bonds.
• Conformational analysis: the analysis of the 
  energy changes that a molecule undergoes as 
  groups rotate about single bonds
     ‫• ﺍﻟﻬﻴﺌﺔ ﺍﻟﻔﺮﺍﻏﻴﺔ ﻟﻸﻠﻜﺎﻧﺎﺕ ﺍﻟﻤﻔﺘﻮﺣﺔ ﺍﻟﺴﻠﺴﻠﺔ ﻫﻲ ﺍﻷﺸﻜﺎﻝ ‬
‫ﺍﻟﻤﺨﺘﻠﻔﺔ ﺍﻟﺘﻲ ﻳﻤﻜﻦ ﺍﻥ ﺗﺘﺨﺬﻫﺎ ﺫﺭﺍﺕ ﺍﻟﺠﺰﻳﺀ ﻓﻲ ﺍﻟﻔﺮﺍﻍ ﻧﺘﻴﺠﺔ ‬
                           ‫ﻟﻠﺪﻭﺭﺍﻥ ﺣﻮﻝ ﺍﻟﺮﺍﺑﻄﺔ ﺍﻷﺤﺎﺩﻳﺔ‬
              ‫• ﻭﺗﻤﺜﻞ ﺍﻟﺠﺰﻳﺌﺎﺕ ﻓﻲ ﺍﻟﻔﺮﺍﻍ ﺑﺎﺣﺪﻯ ﺗﻠﻚ ﺍﻟﻄﺮﻕ:‬
                                     ‫• 1( ﺍﺳﻘﺎﻁ ﻧﻴﻮﻣﺎﻥ:‬




               ‫ﺍﻟﺬﺭﺍﺕ ﺍﻷﻤﺎﻣﻴﺔ‬         ‫ﺍﻟﺬﺭﺍﺕ ﺍﻟﺨﻠﻔﻴﺔ‬
                             ‫• 2( ﺍﺳﻘﺎﻁ ﺳﺎﻭﻫﻮﺭﺱ‬




‫ﻫﻨﺎ ﻳﻨﻈﺮ ﺇﻟﻰ ﺍﻟﺠﺰﻳﺀ ﻣﻦ ﺍﺣﺪ ﺍﻷﺠﻨﺎﺏ، ﻭﺗﻤﺜﻞ ﺍﻟﺮﻭﺍﺑﻂ ﻣﻦ‬
  ‫ﺍﻟﺨﻠﻒ ﺑﺎﻟﺨﻄﻮﻁ ﺍﻟﻤﻘﻄﻌﺔ ﻭﺍﻟﺮﻭﺍﺑﻂ ﻣﻦ ﺍﻷﻤﺎﻡ ﺑﺎﻟﺨﻄﻮﻁ‬
   ‫ﺍﻟﺴﻤﻴﻜﺔ ﺃﻤﺎ ﺍﻟﺮﻭﺍﺑﻂ ﻓﻲ ﻣﺴﺘﻮﻯ ﺍﻟﻨﻈﺮ ﻓﺘﻤﺜﻞ ﺑﺎﻟﺨﻄﻮﻁ‬
                                           ‫ﺍﻟﻤﺴﺘﻤﺮﺓ‬
Conformation analysis in 
       Ethane
  Eclipsed conformation
                          0o
Staggered conformation for
         Ethane
                             60o
Conformation analysis in Propane
Conformation analysis in Butane
                  ‫‬ﺗﻤﺎﺭﻳﻦ‪‭‬‬
                ‫• ﺃﺮﺳﻤﻲ ﺇﺳﻘﺎﻁ  ﻧﻴﻮﻣﺎﻥ ﻟﻜﻞ ﻣﻦ :-‬
   ‫• ﺃ – ﺍﻟﺼﻮﺭﺓ ﺍﻷﻜﺜﺮ ﺛﺒﺎﺕ ﻟـ 1 – ﺑﺮﻭﻣﻮ ﺇﻳﺜﺎﻥ ‬
‫•  – ﺍﻟﺼﻮﺭﺓ ﺍﻷﻘﻞ ﺛﺒﺎﺗﺎ ﻭﺍﻷﻜﺜﺮ ﺛﺒﺎﺗﺎ ﻟﻠﺒﻴﻮﺗﺎﻥ ﻋﻨﺪ ‬
                      ‫ﺍﻟﻨﻈﺮ ﺇﻟﻰ ﺍﻟﻜﺮﺑﻮﻧﺔ ﺭﻗﻢ 2 .‬
• Cyclohexane Ring Stereochemistry


         Chair conformation              Boat conformation
The most stable conformation of the
cyclohexane ring is the “chair” conformation
1) The C—C bond angles are all 109.5°

‫ﻭﺿﻊ ﺍﻟﻜﺮﺳﻲ ﺃﻘﻞ ﻃﺎﻗﺔ ﻣﻦ ﻭﺿﻊ ﺍﻟﻘﺎﺭﺏ. ﻭﻟﺘﺤﻮﻝ ﻫﻴﺌﺔ ﺍﻟﻜﺮﺳﻲ ﺍﻟﻰ ﻫﻴﺌﺔ‬
                      6 Kcal/mol ‫ﺍﻟﻘﺎﺭﺏ ﻻﺑﺪ ﻣﻦ ﻭﺿﻊ ﻃﺎﻗﺔ ﺣﻮﺍﻟﻲ‬
 Chair conformation of cyclohexane
• Part I.
How do you draw the cyclohexane ring and position the
  substituents?
• Start by drawing the ring as one of the following:



  ‫( ﻋﻤﻮﺩﻳﺔ ﻋﻠﻰ ﺍﻟﻤﺴﺘﻮﻯ ﻭﺃﺨﺮﻯ‬a) ‫( ﻭ ﻳﺮﻣﺰ ﻟﻬﺎ ﺑﺎﻟﺮﻣﺰ‬axial) ‫ﻛﻞ ﺫﺭﺓ ﻛﺮﺑﻮﻥ ﻟﻬﺎ ﺭﺍﺑﻄﺔ ﻣﺤﻮﺭﻳﺔ‬
                             ‫( ﻣﻮﺍﺯﻳﺔ ﻟﻠﻤﺴﺘﻮﻯ‬e) ‫(ﻭ ﻳﺮﻣﺰ ﻟﻬﺎ ﺑﺎﻟﺮﻣﺰ‬equatorial) ‫ﻣﺤﻴﻄﻴﺔ‬




     (e)(equatorial) ‫ﺭﺍﺑﻄﺔ ﻣﺤﻴﻄﻴﺔ‬
                                                          (a) (axial) ‫ﺭﺍﺑﻄﺔ ﻣﺤﻮﺭﻳﺔ‬
• Now you need to place the axial substituent bonds. These bonds
  will point upward towards the top of the page or downwards
  towards the bottom of the page (3 in each direction). The
  direction of the bonds alternate up-down-updown-up-down as
  you go from one carbon to the next:
      • Now that the axial bonds are in place, the equatorial
        become much easier if you keep one thought in mind -
        “bondangles around C with 4 bonds are optimally
        ~109.5 degrees”. Draw the equatorial bonds so that they
        form a 109.5 deg angle (i.e. >90 deg) with the axial bond
        drawn above. Make sure they point a little up or a little
        down rather than pointing directly towards the left or
        right margin. This will be extremely helpful latter when
        we determine the cis-trans relationship between
        substituents.




When the ring flips, all of the bonds that were axial become equatorial
Part II. Determining the position of a substituent in the most stable
  conformer.
• The axial positions above the ring point into the same space as is
  true for the axial positions below the ring (see figure) thereby
  putting the substituents very close together. However, the equatorial
  bonds point out away from the ring providing much more room for
  the substituents (compare below). 




   Therefore, if possible all substituents would prefer to be in
   equatorial positions. However, if one is in the equatorial and one is
   axial, preference would be given to the larger group being
   equatorial.
                Part III. Cis-trans relationship between cyclohexane
                                     substituents

• cis - refers to two substituents being on the same side of the ring
  (or double bond)
• trans - refers to two substituents being on the opposite side of the
  ring (or double bond)
            Relationship between Substituents Carbons

                 Axial - Axial   Axial - Equatorial   Equatorial - Equatorial
1 and 2                Trans           Cis                  Trans
1 and 3                  Cis          Trans                 Cis
1 and 4                 Trans         Cis                   Trans
1 and 5                 Cis         Trans                   Cis
1 and 6                 Trans        Cis                    Trans

								
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