Chemistry 350 Organic Chemistry I

Study Guide :: Unit 1

Structure and Bonding

Unit Preview

This unit provides a review of material covered in a standard freshman general chemistry course (such as Athabasca University’s Chemistry 217/218) through a discussion of the following topics:

  • the differences between organic and inorganic chemistry.
  • the shapes and significance of atomic orbitals.
  • electron configurations.
  • ionic and covalent bonding.
  • molecular orbital theory.
  • hybridization.
  • the structure and geometry of the compounds methane, ethane, ethylene and acetylene.

We recognize that students who are thoroughly familiar with a topic need not review it; therefore, we include an Entry Level Test designed to allow you to assess your mastery of the material. If you answer all test questions correctly, begin Unit 2; if you correctly answer 25 or more questions, review the topics that posed problems and then go on to Unit 2; if you give correct answers to fewer than 25 of the 34 test questions, work through Unit 1.

Download Unit 1 Entry Level Test

Download Unit 1 Entry Level Test Answer Key

1.0  Introduction to Organic Chemistry

Objectives

After completing this section, you should be able to

  1. define organic chemistry as the study of carbon-containing compounds.
  2. explain why the results of the experiments carried out by Wöhler contributed to the demise of the “vital force” theory.

Learning Activities

  1. Read 1.0 Introduction to Organic Chemistry in the LibreText for a brief introduction to the discipline of organic chemistry.
  2. Identify and explore all components of this course in the online environment, paying careful attention to the Course Orientation.

1.1  Atomic Structure: The Nucleus

Objective

After completing this section, you should be able to describe the basic structure of the atom.

Learning Activities

Read 1.1 Atomic Structure: The Nucleus.

1.2  Atomic Structure: Orbitals

Objectives

After completing this section, you should be able to

  1. describe the physical significance of an orbital.
  2. list the atomic orbitals from 1s to 3d in order of increasing energy.
  3. sketch the shapes of s and p orbitals.

Learning Activities

Read 1.2 Atomic Structure: Orbitals and do any associated exercises.

1.3  Atomic Structure: Electron Configurations

Objective

After completing this section, you should be able to write the ground-state electron configuration for each of the elements up to and including atomic number 36.

Learning Activities

Read 1.3 Atomic Structure: Electron Configurations and do any associated exercises.

1.4  Development of Chemical Bonding Theory

Objectives

After completing this section, you should be able to

  1. describe the three-dimensional nature of molecules.
  2. sketch a tetrahedral molecule, CX4, using the “wedge-and-broken-line” method of representation.
  3. make a ball-and-stick model of a simple tetrahedral molecule, such as methane, CH4.

Learning Activities

  1. Read 1.4 Development of Chemical Bonding Theory and do any associated exercises.

  2. Construct a methane molecule using a molecular model set.

    Note: If you do not have access to a molecular model set, you can order one from the Athabasca University Library (email: library@athabascau.ca).

    Molecular models help us to visualize what molecules actually look like. Use one black ball with four holes drilled in it to represent a carbon atom, and four light-blue balls to represent hydrogen atoms; the short straight rods will represent carbon-hydrogen bonds. The four light-blue balls are at the four corners of a tetrahedron. Compare your model to the figure of methane in the LibreText. Appreciating the geometry of a tetrahedron is fundamental to understanding some of the stereochemistry covered later in the course.

1.5  The Nature of Chemical Bonds: Valence Bond Theory

Objectives

After completing this section, you should be able to

  1. explain how covalent bonds are formed as a result of the ability of atoms to share electrons.
  2. draw Lewis structures (also known as Lewis formulas or electron-dot formulas) of simple species, such as CH4, H2O, H3O+, CH3OH and NH3, without the aid of a periodic table.
  3. draw structural formulas (i.e., Kekulé structures or line-bond structures) of simple species without the aid of a periodic table.
  4. describe the formation of covalent bonds in terms of the overlapping of atomic orbitals.

Learning Activities

Read 1.5 The Nature of Chemical Bonds: Valence Bond Theory and do any associated exercises.

1.6  sp3 Hybrid Orbitals and the Structure of Methane

Objective

After completing this section, you should be able to describe the structure of methane in terms of the sp3 hybridization of the central carbon atom.

Learning Activities

Read 1.6 sp3 Hybrid Orbitals and the Structure of Methane and do any associated exercises.

1.7  sp3 Hybrid Orbitals and the Structure of Ethane

Objective

After completing this section, you should be able to describe the structure of ethane in terms of the sp3 hybridization of the two carbon atoms present in the molecule.

Learning Activities

  1. Read 1.7 sp3 Hybrid Orbitals and the Structure of Ethane.
  2. Make a molecular model of ethane using two of the four-hole black polyhedra, six of the light-blue balls, six of the short straight bonds $\ce{\sf{(C-H)}}$ and one of the longer straight bonds $\ce{\sf{(C-C)}}$. Connect the two carbon atoms with the longer straight bond. Insert the shorter straight bonds into the remaining carbon atom holes and attach a hydrogen (light-blue ball) to the end of each of the six bonds. Compare your model to that shown in the Libretext. Note that all of the bond angles are identical, and that it is easy to rotate the two carbon atoms about the $\ce{\sf{C-C}}$ bond.

1.8  sp2 Hybrid Orbitals and the Structure of Ethylene

Objectives

After completing this section, you should be able to

  1. account for the formation of carbon-carbon double bonds using the concept of sp2 hybridization.
  2. describe a carbon-carbon double bond as consisting of one σ bond and one π bond.
  3. explain the difference between a σ bond and a π bond in terms of the way in which p orbitals overlap.

Learning Activities

  1. Read 1.8 sp2 Hybrid Orbitals and the Structure of Ethylene.
  2. The construction of a molecular model will help you to understand the geometry of the ethylene molecule. First, take out two of the large, black, four-hole carbon atoms and join the two carbon atoms with two curved rods. Insert straight bonds into the remaining carbon atom holes. At the end of each straight bond attach a hydrogen atom (light-blue ball). Compare your model to that shown in the LibreText; the curved rods represent the double bonds. Note that this model illustrates that all of the atoms in the ethylene molecule are in the same plane, and that the double bond makes it impossible to rotate either of the carbon atoms.

1.9  sp Hybrid Orbitals and the Structure of Acetylene

Objectives

After completing this section, you should be able to

  1. use the concept of sp hybridization to account for the formation of carbon-carbon triple bonds, and describe a carbon-carbon triple bond as consisting of one σ bond and two π bonds.
  2. list the approximate bond lengths associated with typical carbon-carbon single bonds, double bonds and triple bonds. (You may need to review Sections 1.7 and 1.8.)
  3. list the approximate bond angles associated with sp3-, sp2- and sp‑hybridized carbon atoms, and hence, predict the bond angles to be expected in given organic compounds. (If necessary, review Sections 1.6, 1.7 and 1.8.)
  4. account for the differences in bond length, bond strength and bond angles found in compounds containing sp3-, sp2- and sp‑hybridized carbon atoms, such as ethane, ethylene and acetylene.

Learning Activities

  1. Read 1.9 sp Hybrid Orbitals and the Structure of Acetylene and do associated exercises.
  2. Construct a molecular model of acetylene to appreciate the geometry of molecules containing an sp‑hybridized carbon atom. Use the black four-holed atoms to represent carbon. Insert a straight bond into one of the square faces of the black atom, and insert three curved bonds into the other three holes on the opposite side. Attach a hydrogen atom (round ball) to the end of the straight bond. Next, insert the ends of the three curved bonds into three holes of another carbon atom. Finally, insert another straight bond into the fourth hole of the second carbon, and attach a hydrogen atom to the end of that bond. Compare your model to the structure of acetylene shown in the LibreText.

1.10  Hybridization of Nitrogen, Oxygen, Phosphorus and Sulfur

Objective

After completing this section, you should be able to apply the concept of hybridization to atoms such as N, O, P and S to explain the structures of simple species containing these atoms.

Learning Activities

  1. Read 1.10 Hybridization of Nitrogen, Oxygen, Phosphorus and Sulfur.
  2. Construct a model of methylamine $\ce{\sf{(CH3-NH2)}}$, compare your model to the structure of methylamine shown in the LibreText.

1.11  The Nature of Chemical Bonds: Molecular Orbital Theory

Objectives

After completing this section, you should be able to

  1. describe the formation of covalent bonds in terms of molecular orbitals.
  2. account for differences in bond length and strength in terms of the efficiency with which atomic orbitals overlap.
  3. draw simple molecular orbital diagrams (e.g., for the H2 molecule) showing the formation of bonding and antibonding orbitals.

Learning Activities

Read 1.11 The Nature of Chemical Bonds: Molecular Orbital Theory and do any associated exercises.

1.12  Drawing Chemical Structures

Objectives

After completing this section, you should be able to

  1. propose one or more acceptable Kekulé structures (structural formulas) for any given molecular formula.
  2. write the molecular formula of a compound, given its Kekulé structure.
  3. draw the shorthand structure of a compound, given its Kekulé structure.
  4. interpret shorthand structures and convert them to Kekulé structures.
  5. write the molecular formula of a compound, given its shorthand structure.

Learning Activities

Read 1.12 Drawing Chemical Structures and do any associated exercises.