Organic Chemistry: Comprehensive Notes

Organic Chemistry Targets

• Define terms: organic chemistry, hydrocarbon, alkanes, alkenes, alkynes, saturated/unsaturated hydrocarbons, hydrogenation, petroleum, fractional distillation, cracking, combustion, polymerization.
• Identify carbon's significance in chemistry.
• Identify different hydrocarbons (alkanes, alkenes, alkynes), including names and structural formulas.
• Describe differences between saturated and unsaturated hydrocarbons.
• Explain properties of hydrocarbons (melting/boiling points, reactivity, solutions) and how they are affected by size and makeup.
• Describe petroleum refining, including fractional distillation and cracking.
• Analyze hydrocarbon combustion reactions.
• Identify societal impacts of plastic stability.

Topic Overview: Organic Chemistry

• Organic Chemistry:
  • Carbon-based compounds.
  • Most molecules and all living things on Earth are carbon-based.
  • Fats, proteins, and sugars are carbon chains.
• Why carbon?
  • Carbon is most stable when its outer energy level is full.
  • Carbon has 4 valence electrons and 4 empty spots in its outer energy level.
  • Carbon forms 4 bonds to become stable; hydrogen needs 1 electron.
  • Hydrogen bonds with only one other atom to be stable.
  • Carbon forms many bonds, producing a large variety of compounds.
  • Adding one carbon to the chain creates a new compound with different properties.
  • Carbon chains in plastics consist of thousands of atoms.

The Simplest Carbon Compounds - Hydrocarbons

• Hydrocarbons:
  • Hydrocarbons are compounds containing only carbon and hydrogen.
  • Alkanes: hydrocarbons with only carbon-carbon single bonds.
  • Alkenes: hydrocarbons with at least one carbon-carbon double bond.
  • Alkynes: hydrocarbons with at least one carbon-carbon triple bond.

Alkanes

• Each carbon is bonded to 4 other atoms.
• Only single bonds between carbon atoms.
• The number of hydrogen atoms follows the formula CnH{2n+2}, where n is the number of carbon atoms.
• Alkanes are called continuous chain alkanes when carbon atoms form one chain.

Representing Continuous Chain Hydrocarbons

• Represent continuous chain hydrocarbons using chemical formulas, complete structural diagrams, or condensed structural diagrams.
• Line Diagrams

Naming Continuous Chain Alkanes

• IUPAC (International Union of Pure and Applied Chemistry) developed a system for naming organic compounds.
  • Uses prefixes to indicate number of carbons and suffixes to indicate the molecule family.
  • Different families have different molecular structures.

• To name an alkane, match the prefix to the number of carbons in the longest continuous chain and add the suffix "-ane".
• Alkanes have single bonds and use the suffix "-ane."

Branched Alkanes

• IUPAC system for naming branched alkanes:
  • Step 1: Find and circle the longest continuous chain (parent chain) and name it as a continuous-chain alkane.
  • Step 2: Find and circle all branches (alkyl groups). Name each alkyl group, using the prefix corresponding to the number of carbons in the group, and end the name with "-yl".
  • Step 3: Number the carbons on the parent chain starting closest to the branch. Assign each branch the appropriate number.
  • Step 4: Use prefixes (di-, tri-, tetra-, etc.) to indicate how many of each branch type exists in the molecule.

• Step 5: Put the name together, starting with the alkyl groups in alphabetical order (NOT number order!), and ending with the parent chain.
  • Example Problem 3.1 (page 118).

The Importance of the IUPAC System

• Carbon can form four single bonds, resulting in many arrangements for a given number of carbon and hydrogen atoms.
  • One chemical formula can have multiple arrangements.
• Review Topic 3.1 Summary – Page 121
• Topic 3.1 Questions - #1 through 7

Topic 3.2 Saturated and Unsaturated Hydrocarbons

Fatty Acids

• Fats and oils are organic molecules rich in carbon and hydrogen.
• Greasy snack foods contain significant amounts of fat.
• Gram for gram, fat contains more energy than any other type of nutrient.

Saturated vs. Unsaturated Hydrocarbons

• Each carbon atom requires 4 bonds to be stable.
  • Ethane has 3 hydrogen bonds and a single bond to another carbon (total: 4 bonds per carbon).
• Saturated hydrocarbon: contains only single covalent bonds between carbon atoms.
• Carbon atoms can form double or triple bonds.
  • Ethene
  • If each carbon atom loses an additional hydrogen, a triple bond can form.
• Unsaturated hydrocarbons have double or triple bonds.
  • They are missing their maximum number of bonds to hydrogen atoms.
  • More reactive than saturated hydrocarbons.

The Difference Between Animal Fats and Plant Oils

• Foods containing animal fats and oils are a rich source of food energy.
  • Provide flavour, texture, aroma and help one feel full
• To determine if oils are healthy or unhealthy, look at the shape of the molecules.
• Fats and oils in foods consist of three connected chains of fatty acids.
  • Fatty acid: organic molecule with a long carbon chain, a carboxyl group at one end (acid end), and a methyl group at the other end (non-acid end).
• The properties are determined by the particular fatty acids in chains.
• Stearic acid is a saturated hydrocarbon.
• Oleic acid is an unsaturated hydrocarbon, containing a carbon-carbon double bond.

Shape of Fatty Acids

• Unsaturated fatty acids have a crooked twig shape due to the two missing carbon atoms on each side of the double bond.
• Unsaturated fats cannot pack as closely as saturated fats because of this shape.
• Unsaturated fat molecules are further apart and require less energy to separate and melt (oil).
• Saturated fats pack closely together, resulting in greater forces of attraction, they form solid fats at room temperature.
• Oleic acid is an omega-9 fatty acid.
  • The double bond is on the ninth carbon from the methyl group end.
  • Small amounts of omega-9 can be made in your body, or obtained through olive oil, canola oil, and other vegetable oils.
• In general, unsaturated fats are healthier than saturated fats.
• Unsaturated fats and oils:
  • Monounsaturated fats: have only one double bond.
  • Polyunsaturated fats: have more than one double bond.

Essential Fatty Acids

• Not all fats are unhealthy; some are essential for good health.
• Sufficient intake of essential fatty acids is necessary for formation of healthy cell membranes, proper development of the brain and nervous system, and the production of hormone-like substances (regulate blood pressure).
• The essential fatty acids are omega-3 and omega-6 fatty acids.
  • Most people get enough omega-6, but many have trouble getting enough omega-3.
  • Omega-3 sources: fish, flaxseed, walnuts.

Naming Hydrocarbons with Multiple Bonds

• Alkane: hydrocarbon containing only single bonds.
• Alkene: hydrocarbon containing at least one double bond.
• Alkyne: hydrocarbon containing at least one triple bond.
• Rules for naming alkenes and alkynes are similar to alkanes, but the suffix "-ene" is used for alkenes, and "-yne" is used for alkynes.
• The double or triple bond must appear in the longest continuous chain of the carbon atoms
• Number the chain so that the carbons with the double or triple bond receive the smallest possible number
• The location of the double or triple bond is communicated by a number, placed before the name of the parent chain
• Example Problems 3.2 through 3.5

Saturated and Unsaturated Compounds in Food

• Types of hydrocarbons: alkanes, alkenes, and alkynes.
• Butter is made of saturated fats (alkanes).
• Margarine is produced from oils containing primarily unsaturated carbon chains, and has properties more like an oil.
• Physical properties: characteristics that you can observe without changing the substance’s chemical identity.
• Chemical properties explain how reactive something is

The Melting Points and Boiling Points of Hydrocarbons

• Boiling and melting points of hydrocarbons increase as the number of atoms in the molecule increases.
  • Attraction between molecules increases with the number of atoms.
  • Stronger attraction requires more energy (heat) to break.
  • More energy is required to move something with greater mass. If the molecule is larger, more energy (or heat) is required to make it move
• Therefore, a greater number of carbons in a molecule results in higher melting and boiling points for the compounds because of stronger attractions between the molecules and greater mass
  • Ethane, Octane, Wax
• The reactivity of hydrocarbons depends on other molecules around them
• Unsaturated hydrocarbons are more reactive than saturated hydrocarbons because of the double or triple bond between carbons
• Carbon atoms joined by a double or triple bond have a greater number of electrons between the carbons than singly bonded carbon atoms
  • The larger the number of electrons results in a greater negative charge between them
• Hydrocarbons with double or triple bonds (unsaturated) are more reactive than those with single bonds (saturated).
• Many plastics and artificial rubbers are produced from chemical reactions involving unsaturated hydrocarbons.

The Origins of Industrially Produced Trans Fatty Acids

• Margarine is made by bubbling hydrogen through hot vegetable oils under pressure.
• This breaks the double bonds and adds hydrogen to carbon atoms.
  • Hydrogenation
  • Two more hydrogen atoms are added to the molecule for every double bond that is broken
• Hydrogenation is complete when all of the double bonds are broken
• Partial hydrogenation produces a soft, spreadable fat called shortening.
• The high temperatures seem to have unintended effects on some of the unsaturated molecules
• After being subjected to high temperatures and pressures, elaidic acid is transformed into trans fatty acids
• Position of hydrogen atoms makes the molecule trans fatty acids
• Trans fatty acids by this process can combine with other fatty acids to make an unhealthy fat
• This industrial hydrogenation process generates a family of trans fatty acids that are completely different than what tends to be produced naturally by plants and animals
• Biochemists and nutritionists are concerned that the molecules of trans fatty acids are dissimilar from the essential fatty acids that our bodies need to stay healthy
• Trans fatty acids have a straight chain of carbon atoms, giving them properties similar to saturated fatty acids in beef, cheese, and coconut oil.
• Trans fatty acid – either in your sink or your arteries!
  • Fat deposits develop inside arteries and lead to heart and brain problems
  • Cholesterol also contributes to the buildup of fat deposits in blood vessels
• Trans fats pose a greater risk for heart disease than saturated fats!

Making Healthy Food Choices

• Fats and oils are a major energy source and play key roles in the operation of the nervous system and other essential body functions
• However, it is important to choose foods that have moderate amounts of monounsaturated fatty acids, such as olive oil, canola oil, nuts and avocados, and polyunsaturated fatty acids such as fish, corn oil, soybean oil and flaxseed.
• Saturated fats, industrially produced trans fats, and dietary cholesterol can increase the risk of heart disease, and should be avoided.
• Review Topic 3.2 Summary – Page 135
• Topic 3.2 Questions - #1 through 7

Topic 3.3 Petroleum Is the Source

Petroleum

• Scientists suspect that atoms in plastics were once part of microscopic plants and animals that lived in shallow tropical seas
• Petroleum is the connection between organisms from millions of years ago and plastic item.
• Petroleum contains a large variety of hydrocarbons
  • Like a “soup” of hydrocarbons
• After locating the resource, the petroleum is pumped from below and is separated into different components( fractions). Each component is a mixture of smaller molecules called fractions
• Fraction = a mixture of hydrocarbons with a similar number of carbon atoms.
• The process of separating and processing petroleum into different fractions is called petroleum refining.

Separating Petroleum

• Each fraction of petroleum has unique properties and can be used for different purposes.
• The refining industry uses the unique boiling point for each group of hydrocarbons to separate.

Fractional Distillation

• Petroleum is a mixture of many hydrocarbons which must be separated into its different fractions for useable products
• Refineries use the different boiling points of each fraction to accomplish this separation.
• The process of separating the different sizes of molecules in petroleum is called fractional distillation.
• Fractional distillation occurs when each fraction is heated to become a gas and can rise to different levels in the tower.
• Recall (from Lesson 3.2) that the boiling point of a hydrocarbon increases as the number of carbons within the hydrocarbon increases.
• Summary of fractional distillation:
  • Step 1: The petroleum is heated
  • Step 2: The petroleum vapor is placed at the bottom of a distillation column
  • Step 3: The temperature decreases inside the column. The vapor cools as it moves away from the heat source
  • Step 4: As the vapor cools, it drops in temperature, and the molecules condense into liquids at different places in the tower. This allows the fractions to be collected separately.
  • Step 5: Fractions with high boiling points (the largest molecules in the mixture) will condense first at the bottom of the column. Fractions with lower boiling points (the smallest molecules in the mixture) condense higher up in the column.
    • Fractions with the lowest boiling points are gases and are collected at the top

Processing Hydrocarbons

• Smaller hydrocarbons are more useful because they can easily combine to create substances that can be used to make products.
• Smaller hydrocarbons are easier to control in a chemical reaction.
• It is easier to use smaller molecules as a structural component
• Larger hydrocarbon molecules are often used as a source of smaller molecules.
• Production of Ethene
  • Naptha fraction is used again in Step 3 to separate the ethene from other products
• Ethene produced from Naphtha is used to make Polyethylene plastic
  • Approximately 50 million tones of polyethylene are produced worldwide every year.
  • Mostly used to manufacture thin plastic used in grocery bags, freezer bags, and cling wrap
  • Also used to make plastic food containers and electrical cable and wire insulation

Cracking

• The cracking reaction results in short hydrocarbon chains
• When a single, large saturated hydrocarbon chain is cracked there are a wide range of products that can be produced
• This process also produces unsaturated hydrocarbons
• There is an insufficient number of hydrogen atoms to completely saturate the products of the reaction

Topic 3.4 Everyday Use of Hydrocarbons

Petrochemicals

• Virtually every human activity in modern society is somehow dependent upon - petrochemicals.
• Using fractional distillation, the petroleum is heated, and the individual hydrocarbons are separated from the large mixture of other hydrocarbons
• There are two possible outcomes for hydrocarbons once they have been refined:
  • They may be burned to provide heat or energy
  • They may become the building blocks (eg. Plastics, synthetic fabrics, fertilizers, medicines, etc.)

Hydrocarbons as Fuel

• Consumers use hydrocarbons as fuel.
  • Ride in a car, bus, cook on the barbeque, turning up the furnace in your house
• The energy is from the burning of hydrocarbons.
• Hydrocarbons make excellent fuels because they:
  • Are liquids that are easily transported
  • Have bonds that contain a large amount of energy
  • Are readily available (petroleum deposits)
• When something burns, it is reacting with oxygen.
  • Combustion
• When hydrocarbons are combusted, carbon dioxide and water are the most common oxides formed
• During a hydrocarbon combustion reaction, hydrocarbon reacts with the oxygen to produce carbon dioxide and water
  • CH4 + 2O2 → CO2 + 2H2O
• Combustion of methane in furnace
• In order for the methane molecules to react, energy has to be added to break the carbon-hydrogen single bonds and the oxygen-oxygen double bonds
• With this input energy, the bonds are broken, and the individual atoms temporarily move into an excited and unstable state
• When the atoms recombine to form carbon dioxide and water, they become more stable, and energy is released
• The overall effect of this reaction is to release energy into the environment
  • The output energy from forming bonds of carbon dioxide and water is greater than the input energy to break the bonds of methane and oxygen a furnace captures as much of this energy as possible
• Impurities – such as hydrogen sulfide are also may be present
  • These impurities are removed before the natural gas is delivered to homes in Alberta
  • This helps make natural gas one of the cleanest carbon fuels

Comparing Combustion Reactions

• The concepts that explained the combustion of methane (natural gas) can also be applied to the combustion of gasoline.
• Longer hydrocarbon chains have more bonds than shorter hydrocarbon chains. Therefore, longer hydrocarbon chains:
  • Contain more energy than shorter hydrocarbon chains
  • Require greater amounts of energy to be broken than shorter hydrocarbon chains
  • Will produce a greater amount of energy, carbon dioxide and water when combusted than shorter hydrocarbon chains

Environmental Impact

• Combustion of hydrocarbons has increased in the last 200 years.
• The products of combustion are carbon dioxide and water.
• When carbon dioxide is present in the atmosphere, it helps trap energy near Earth’s surface, contributing to global warming.
• Increased levels of carbon dioxide are increasing the greenhouse effect, warming Earth and rising sea levels.
• Increasing levels of carbon dioxide will eventually result in global climate change.

From Hydrocarbons to Polymers

• Many products that are purchased result from polymerization
• The process of joining many short, unsaturated hydrocarbon molecules is called polymerisation
• The resulting plastic is called a polymer (poly = many, mer = units).

Exploring Polymers

• There are many different polymers, each with their own unique properties and different uses
• The properties of polymers are a result of their molecular structure
• Rubbers and plastics are often used either as materials for products or as a coating to protect products from other compounds in the environment
  • These are inertsubstances, which means that they do not react readily with compounds that they are exposed to on a daily basis
• The greatest problem with polymers is that they take a long time to decompose or decay
• Carbon atoms become locked in polymers for hundreds of years because polymers are resistant to natural processes that decomposes or break down matter. As a result, society is facing problems with the accumulation of discarded polymers