Mr. Bouyer
Day 1 | Day 2 | Day 3 | Lab | Skills Test

Write formulas of alkenes. Name alkenes. Draw structural formulas for normal and branched alkenes. Write formulas of alkynes. Name alkynes. Draw structural formulas for normal and branched alkynes. Write the chemical and structural formula for benzene. Describe the characteristics of the each group formed when oxygen is added to a hydrocarbon.

Classes of Organic Compounds

• Alkanes - C_nH_2n+2
  • Saturated hydrocarbons with only single bonds.
  • Rules for naming branched alkanes:

• Alkenes - C_nH_2n
  • Unsaturated hydrocarbons with at least one double bond.
  • Ethene (C₂H₄), commonly called ethylene, is the #1 industrial organic chemical. It is used in making plastics, antifreeze, synthetic fibers, and solvents.

Rules for naming alkenes: A position number is given to the carbon on which the double bond begins. Begin at the end that will make this position number the lowest. This position number is always placed just before the name of the parent compound. The parent compound is named for the longest chain containing the double bond. If the molecule has more than one double bond, the -ene ending must be preceded by a prefix indicating the number of double bonds. Any branches in the parent chain are named as in alkanes.

Practice Problems: name the following alkenes from their condensed structural formulas. 1. 2. 3. 4. 5.

• Alkynes - C_nH_2n-2  (chem lab 314)
  • Hydrocarbons with at least one triple bond.
  • Ethyne (C₂H₂), commonly called acetylene, is an important industrial gas produced by the reaction of calcium carbide with water.

Rules for naming alkynes: The numbering system for locating the triple bond and other groups are exactly the same as in Alkenes. If a compound contains both double bonds and triple bonds, the double bond is given the lower position number and is named first.

Practice Problems: Write the condensed structural formula for the following hydrocarbons: 1.   2, 3-dimethylpentane   2.   2-methyl-2-propene   3.   1, 2-pentadiene   4.   acetylene   5.   1, 3-butadiene This molecule is the monomer in natural rubber. 6.   2-methylbutadiene This molecule is an "elastomer" in synthetic rubber.

Day 2

One of the most important industrial hydrocarbons is composed of a cyclic ring.

Aromatic Hydrocarbons
• Aromatic hydrocarbons contain benzene - C₆H₆
  

  The complete structural formula for benzene is almost never drawn. It is shown here to indicate the position numbers of each of the carbon atoms. This shorthand diagram is used with a carbon and a hydrogen atom "understood" to be at each corner.

• The electrons in benzene, as well as many inorganic radicals, form what is known as a resonance structure. This is a complex sharing of electrons giving greater stability to the molecule than does nonresonant bonding. The arrangement of electrons does not fluctuate as the term seems to indicate. There are several possible ways for the atoms to be linked. What can be observed experimentally is actually an "average" of the possibilities.

  The diagram below represents resonance. There are three possible places for the double bond. Since all possibilities are present, an average structure is observed.

  

• This diagram is used to represent the resonance structure of benzene.
• Other hydrocarbons form a cyclic ring:
  • Gasolines are given an octane rating. The higher the octane rating, the less "knocking" as the fuel burns. Knocking occurs when some of the fuel explodes suddenly instead of evenly, causing the pistons in the engine to move out of sequence. High-octane gasolines contain more "ring" compounds and highly branched hydrocarbons than do low-octane gasolines. Normal heptane is assigned an octane rating of 0, and 2,3,4-trimethylpentane (an isomer of octane) is assigned an octane rating of 100. Gasolines are rated based on the blend of these two substances.

    Tetraethyl lead was the first substance used to increase the octane rating of gasoline. It was replaced because of dangerous levels of lead pollution in the atmosphere - giving rise to the term "unleaded gasoline". The major octane-enhancing additive used today is 2-methoxy-2-methylpropane.

Atoms other than carbon and hydrogen can be substituted for part of a hydrocarbon molecule. The non-hydrocarbon part of the molecule is called a functional group and usually increases the reactivity of the molecule.

• Halogen Derivatives
  • In the group, an atom of the halogen family replaces a hydrogen atom.
  • The compounds are named as derivatives of the hydrocarbon.
  • CHCl₃, trichloromethane, is better known as chloroform.
  • CCl₄, tetrachloromethane, is better known as carbon tetrachloride.

In-class Assignment 332:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

Name the following organic molecules.

1.		2.
3.

4.   Use the Internet to find the structural formula for the explosive known as TNT.

Day 3

During this chemistry class you have learned to write chemical formulas using oxidation numbers. Valence electrons in organic compounds follow a different set of rules. When you take more advanced courses in organic chemistry, you will have to understand the l (Lambda) Convention.

When oxygen is added to a hydrocarbon, the following groups are formed:

• Alcohols
  • Contain the hydroxyl group - OH, but are not bases.
  • Alcohols with four or more carbon atoms are not soluble in water.
  • Methanol, CH₃OH is used in making plastics and fibers.
  • Rubbing alcohol is a mixture of 2-Propanol, CH₃CHOHCH₃ and water.
  

• Ketones
  • Contain the carbonyl group C=O
  • Acetone, CH₃COCH₃, is an important ketone.

• Organic Acids
  • Contain the carboxyl group - COOH
  • The strength of organic acids depends on the other atoms in the molecule.
  • Acetic acid, CH₃COOH, is a common organic acid.

Organic compounds containing nitrogen are important to the biology of life.

• Amines and Amides
  • Amines are derived from ammonia.
  • Amides have an amine group along with a carbonyl group.
  • Amino acids are probably the most important organic compounds containing nitrogen and oxygen because they are the building blocks of proteins.

In-class Assignment 333:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

Draw the complete structural formulas for the following organic compounds:

1. Rubbing alcohol
2. Acetone
3. Acetic acid

Research Links:

• Glossary of Class Names of Organic Compounds - Internation Union of Pure and Applied Chemistry
• Nomenclature of Organic Chemistry - Advanced Chemistry Development, Inc.
• Organic Chemistry - HordeNet, The University of Akron
• The Plastics Industry - Polymers . com
• Plastics and More - Dow Chemical
• The Chemistry of Tires - Goodyear
• The Gasoline Industry - Mobil Oil

Alkene Practice Problem Answers:

1. ethene
2. propene
3. 1-butene
4. 3-heptene
5. 4-methyl-2-hexene