Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
OBJECTIVES:

Use e- dot structures and model kits to build organic molecules

Use VSEPR Theory to determine geometry, bond angles, and symmetry of a molecule

Recognize basic nomenclature and functional groups of organic molecules

Understand the connection between molecular geometry and the properties of molecules
PROCEDURE: On separate paper…
1. Write the problem number, chemical formula, and name of the molecule.
2. Draw the e- dot structures and circle shared pairs of e3. Build the molecule using models.
4. Re-draw the molecule in 3D (using the model). Use lines, dashes, or wedges. Use subscripts for multiple central atoms.
5. For each central atom, write the molecular geometry (name of the shapes).
6. For each central atom, write the bond angle(s)
7. Write whether the molecule is Symmetrical OR Unsymmetrical
PRE-LAB SIMPLE MOLECULES #1-15: JOE WILL PROVIDE HELP IF ASKED
 1. Cl2
Chlorine Gas is a yellow-green toxic gas that has been used as a weapon in war.
 2. O2
Oxygen gas is a product of photosynthesis and consumed by humans during respiration.
 3. H2S
Hydrogen Sulfide is a colorless, very poisonous, flammable gas with the foul odor of rotten eggs.
 4. HCl
Hydrogen Chloride is a colorless gas that forms an acid when dissolved in water.
 5. BCl3
Boron Trichloride. Boron bonds covalently to become stable without an octet, stable with just 6 v e-
 6. NH3
Ammonia is used as cleaning product and is recognized by its strong odor.
 7. H2O
Water is essential to life on earth and has many unique chemical and physical properties.
 8. H2O2
Hydrogen Peroxide has a wide of range of uses including: rocketry, disinfection and bleaching.
 9. CH4
Methane is the simplest “hydrocarbon” meaning made of C and H atoms.
 10. CH3Cl
Chloromethane is a colorless, extremely flammable, slightly sweet smelling gas.
Common Prefixes: meth = 1, eth = 2, prop = 3, but = 4, and pent hex hept oct non dec = 5 6 7 8 9 10, respectively.
MOLECULES #11-15: JOE WILL PROVIDE LIMITED HELP IF ASKED
 11. CH3OH
Methanol is colorless, flammable, and has a sweet smell.
 12. C2H6
Ethane is a hydrocarbon and is an odorless, colorless, and flammable gas.
 13. C2H4
Ethene is one of the chemicals that triggers fruits to ripen.
 14. C2H2
Ethyne can be used for the welding of metals.
 15. C6H14
Hexane, like other hydrocarbon fuels it can undergo combustion reactions to produce CO 2 + H2O
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
MOLECULES #16-24: JOE WILL PROVIDE VERY LIMITED HELP
#16 on may have multiple geometries around different Carbons. Use C1, C2, etc. to differentiate.
16. C6H12
Cyclohexane is a simple 6 Carbon ring that is colorless and flammable liquid.
17. C6H6
Benzene is a colorless, highly flammable liquid with a sweet smell.
18. CH3CN
Acetonitrile is a colorless liquid solvent used in battery application and pharmacueticals.
19. CH3CH2NH2
Aminopropane is colorless gas that has a strong fishy and ammonia-like odor.
20. CH3CHO
Ethanal occurs naturally in coffee, bread, and ripe fruit.
21. CH3OCH3
Dimethyl ether is a colorless gas used as a precursor (use to make other chemicals).
22. (CH3)2CO
Acetone is the common ingredient in nail polish remover. ( C=O in the middle )
23. CH3COOH
Ethanoic Acid, commonly known as Acetic acid or Vinegar. ( Both O’s bonded to C2)
24. CH3COOCH3
Methyl acetate is used as a solvent in paints, glues, and nail polish removers. (O’s bonded like #23)
CHALLENGE MOLECULES
Choose ___ FLAVOR, SCENT, or PHARMACUETICAL
C9H8O
Cinnamon
C8H8O3
Vanilla
C6H12O2
Apple flavor
C9H8O4
Aspirin
Cinnamaldehyde is the primary flavor molecule in cinnamon. It has a benzene ring base.
Off a single carbon on the ring there is a C=C followed by an aldehyde –CHO group.
Vanillin is the primary component of the extract of the vanilla bean.
It has a benzene ring base, with a –COH on C1, -OCH3 on C3, and a -OH on C4.
Butyl Acetate is the main components of apple flavor.
As an ester (RCOOR’), after it’s “butyl” chain (meaning 4 C) the R’ is a simple methyl group –CH3
Acetylsalicylic acid or asprin is used as an analgesic to relieve minor aches and pains
It has benzene ring, -COOH on C1 and on C2 an –O –CO –CH3.
Choose ___ ENDOCRINE DISRUPTORS – Ideally, choose the one you studied in 9th Grade Science!
For these molecules no e- dot structure is required. Re-draw the structure  then label all of the geometries.
Butyl Benzyl
Phthalates - C10H10O4
Aldrin - C12H8Cl6
Atrazine - C8H14 N5Cl
Phthalate (BBP)
C19H20O4
Glycol Ethers - C3H8O2
Perfluorooctanoic acid
C8HF15O2
Polybrominated Diphenyl
Ethers (PBDE's)
C12H(8)Br2O
Bisphenol A - C15H16O2
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
DISCUSSION QUESTIONS:
1. The dot structure of water (H20 - ex. #7 from the lab) shows that the central Oxygen atom is surrounded by four pairs of
electrons, but measurements show that the bond angles in water are not 109.5° as expected for tetrahedral geometry.
Describe what VSEPR theory is and then use it to explain why the bond angles in water are less than the 109.5º
predicted for tetrahedral geometry.
2. Bond dissociation energy is one way to measure bond strength
because it is the energy required to break that bond. Make a
claim about the relationship between the number of bonds and
bond length vs. bond strength. [use “As the… inc or dec … the
inc or dec…] style claims defended by evidence from the data table.
Bond
C–C
C=C
C≡C
alkane
alkene
alkyne
Dissociation
Energy (in kJ)
C-to-C Distance
(in picometers)
346 kJ
600 kJ
835 kJ
154
134
120
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
3. Ethane is a molecule that can rotate around the single bond
between the two Carbon atoms to make either the staggered
and eclipsed arrangements of Ethane.
Make a claim about which arrangement of ethane is more
stable. Defend your claim using VSEPR theory.
Staggered
Rotate 180º
Eclipsed
4. Organic chemistry is the study of molecules containing carbon. Almost every biological molecule in your body, the food
you eat, and the medicines you take are made of mainly just six elements (H, O, S, P, N, Cl, C)!!
Using what you have learned of covalent bonding and molecular geometry, explain what is responsible for the nearly
infinite diversity of organic molecules important to life on Earth. Refer to specific examples from your lab as evidence to
support your answer.
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
Cyclohexane, C6H12, has different conformations (arrangements).
Which is more stable, the boat or chair conformation of cyclohexane?
Make a claim about which conformation of cyclohexane is more stable
and defend it using what you know about VSEPR Theory.
Chair
Boat
Cyclohexane, C6H12, has different conformations (arrangements).
Which is more stable, the boat or chair conformation of cyclohexane?
Make a claim about which conformation of cyclohexane is more stable
and defend it using what you know about VSEPR Theory.
Chair
Boat
Cyclohexane, C6H12, has different conformations (arrangements).
Which is more stable, the boat or chair conformation of cyclohexane?
Make a claim about which conformation of cyclohexane is more stable
and defend it using what you know about VSEPR Theory.
Chair
Boat
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
For molecules #11 and on, write “This molecule is a(n) [ see Functional Group Chart ] because there is a _____ group”
Functional Group Reference Chart:
CYCLIC
Naming: cycloe.g. cyclopentane
For molecules #11 and on, write “This molecule is a(n) [ see Functional Group Chart ] because there is a _____ group”
Functional Group Reference Chart:
CYCLIC
Naming: cycloe.g. cyclopentane
For molecules #11 and on, write “This molecule is a(n) [ see Functional Group Chart ] because there is a _____ group”
Functional Group Reference Chart:
CYCLIC
Naming: cycloe.g. cyclopentane
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
CYCLIC
Naming: cycloe.g. cyclopentane
CYCLIC
Naming: cycloe.g. cyclopentane
CYCLIC
Naming: cycloe.g. cyclopentane
Organic Chemistry Lab – Molecular Geometry & VSEPR Theory
Name_______________
Date___________B____
CHALLENGE MOLECULES to BUILD - Molecules of Life
For these molecules no e- dot structure is required.
Simply build it  Show Joe  Re-draw the structure  then label all of the geometries.
C6H12O6 Glucose
C4H5N3O Cytosine
C9H13NO3 Adrenaline
Glucose is one of the simplest sugars. Cells use
it as the primary source of energy and it is one
of the main products of photosynthesis.
Cytosine (C) is one of the four main
bases found in DNA and RNA, along
with adenine, guanine, and thymine.
It increases heart rate, constricts blood
vessels, dilates air passages and
participates in the fight-or-flight response.
CHALLENGE MOLECULES to BUILD - Molecules of Life
For these molecules no e- dot structure is required.
Simply build it  Show Joe  Re-draw the structure  then label all of the geometries.
C6H12O6 Glucose
C4H5N3O Cytosine
C9H13NO3 Adrenaline
Glucose is one of the simplest sugars. Cells use
it as the primary source of energy and it is one
of the main products of photosynthesis.
Cytosine (C) is one of the four main
bases found in DNA and RNA, along
with adenine, guanine, and thymine.
It increases heart rate, constricts blood
vessels, dilates air passages and
participates in the fight-or-flight response.
CHALLENGE MOLECULES to BUILD - Molecules of Life
For these molecules no e- dot structure is required.
Simply build it  Show Joe  Re-draw the structure  then label all of the geometries.
C6H12O6 Glucose
C4H5N3O Cytosine
C9H13NO3 Adrenaline
Glucose is one of the simplest sugars. Cells use
it as the primary source of energy and it is one
of the main products of photosynthesis.
Cytosine (C) is one of the four main
bases found in DNA and RNA, along
with adenine, guanine, and thymine.
It increases heart rate, constricts blood
vessels, dilates air passages and
participates in the fight-or-flight response.