22'3 Isomers Chapter 22 Hydrocarbon Compounds

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22.3 Isomers Chapter 22Hydrocarbon Compounds
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Vocabulary to Know

• Isomers
• Structural Isomers
• Stereoisomers
• Geometric Isomers
• Trans configuration
• Cis configuration
• Optical Isomers
• Asymmetric carbon

Take out your notes and keep track of ALL
definitions!
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Before we begin

• Remember that all molecules are in reality 3-D!

Video showing 3-D molecules-remember molecules
are 3-D structures!
Photo source www.wikimedia.og
Video source Rasmol
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Isomers
Isomers Compounds that have the same molecular
formula but different molecular
structures Different structure different
substance
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2
1
1
2
1
2
2
2
1
1
Photo source chemguide.co.us
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Still confused?
Lets look further into the definition of an
isomer (240-332)
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StructuralIsomers

• Are these molecules isomers or are they the same?

• Structural Isomers compounds that have the same
  molecular formula, but the atoms are joined
  together in a different order.

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2
3
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5
1
2
3
4
1
2
3
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Photo source http//www.slc.ac.nz/WorkshopClub/Wo
rkshop/problemsonstructuralisomers.htm
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Structural Isomers

• Which has lower boiling point?

• Different physical properties
• (mp bp)
• High number of
• branches
• low boiling point

Photo sources www.lsbu.ac.uk, wikipedia.org
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STOP AND CREATE!

• Use your model kits to create 2 structural
  isomers for C6H4
• (there may be more than two options)

Photo source www.kaboodle.com
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Stereoisomers
Stereoisomers Molecules in which the atoms are
joined in the same order, but the positions of
the atoms in space are different.
Two Types 1. Geometric 2. Optical
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Geometric Isomers

• Two Types
• 1. Cis-configuration
• Cis same side
• 2. Trans-configuration
• Trans opposite side

• Geometric Isomers
• When atoms are joined in the same order, but
  differ in their orientation of groups around a
  double bond.

Photo source chemguide.co.us
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Lets look into this a little deeper

• Still wondering about stererisomers? And what
  does Cis and Trans mean?
• (130-341)

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Which is these is Cis and which is Trans?
Same Side
H CH2CH3 C C H3CCH2 H
Opposite Sides (across)
Photo source www.uwplatt.edu
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STOP AND CREATE!

• Use your model kits to create the
• Trans-configuration for this molecule

Photo source www.tennoji-h.oku.ed.jp,
www.kaboodle.com
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Optical Isomers

• Which is Asymmetric?

Asymmetric carbon A carbon with four
different atoms or groups attached
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Optical Isomers

• Optical Isomers
• Pairs of molecules that differ only in the way
  that four different groups are arranged around a
  central atom. Mirror images!

• Are these molecules Optical Isomers? Why?

CH3CH2CH2 CH3 C
CH3CH2 Cl
CH3CH2CH2
CH3 C CH3CH2 Cl
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Optical Isomers
They are mirror images of each other Take out
your mirrors and lets play!
Photo source astrobiology.berkeley.edutures
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Optical Isomers
Mirror Images
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Optical Isomers
Can not be Superimposed! (no matter how you move
them, you can not make them look alike)
Try it with your own hands
Photo source www.flicker.com
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STOP AND CREATE

• Use your model kits to create an example of an
  optical isomer try to superimpose them. Can
  you?
• (Remember you must have four different
  substituents around the carbon atom!)

Photo source www.kaboodle.com
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Review

• 1. How can you tell if two compounds are isomers?
• 2. What different types of Isomers did we learn
  about?

They have the same molecular formula but
different structure
Structural, Stereoisomers including both
Geometric and Optical isomers
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Review

• What type of Isomer is this?

Geometric Cis and Trans configurations
Photo source www.chem.purdue.edu
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Review

• Draw the optical Isomer

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Review

• Is this a Cis or Trans configuration?

• Is this an asymmetric carbon?

Cis configuration
Yes, this is asymmetric
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Before we move on

• Before we start our lab for this lesson, lets
  review how to name molecules that have branches
  (substituent groups).
• (000-220)

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Quick Lab Time

• Structural Isomers of Heptane
• Purpose To build ball-and-stick models and name
  the eight structural isomers of Heptane (C7H16)
• Draw structures on paper to keep track of all
  eight isomers draw as condensed and line-angle
  with names

Photo source www.wikimedia.org
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In Class Group Project

• Working in small groups and using the materials
  provided
• Create a poster outlining the different types of
  hydrocarbon isomers
• Name and define each type and give examples!