Overview
This lecture introduces the main classes of organic compounds, focusing on functional groups, alcohols, alkyl halides, and ethers, their properties, naming rules, and real-world uses.
Functional Groups and Classes of Organic Compounds
- Functional groups are specific atoms or groups responsible for the characteristic properties and reactions of organic compounds.
- Compounds with the same functional group have similar physical and chemical properties.
- The general formula is R–(functional group), where R is the hydrocarbon chain.
Alcohols: Structure, Naming, and Properties
- Alcohols contain the hydroxy group (–OH) as their functional group.
- General formula: R–OH, where R is a hydrocarbon chain.
- To name alcohols, select the longest chain containing all hydroxy groups, and use the “-ol” suffix (e.g., methanol, ethanol).
- Number the chain so hydroxy groups get the lowest possible numbers; for multiple hydroxyls, use "diol," "triol," etc.
- Cyclic alcohols follow similar naming rules (e.g., cyclopentanol).
- Alcohols have higher boiling points than alkanes due to hydrogen bonding.
- Increasing hydroxy groups raises both boiling point and water solubility; larger hydrocarbon chains reduce water solubility.
- Alcohols like ethanol are used as fuels and solvents; glycerol (a triol) is used in cosmetics.
Toxicity and Biotransformation of Alcohols
- All simple alcohols (methanol, ethanol, propanol) are toxic.
- Ethanol is metabolized by alcohol dehydrogenase to acetaldehyde, then to acetic acid by aldehyde dehydrogenase.
- Methanol is more toxic than ethanol, forming toxic formaldehyde and formic acid, leading to nerve damage, coma, or death.
Alkyl Halides: Structure, Naming, and Properties
- Alkyl halides have one or more halogen atoms substituting hydrogens in a hydrocarbon (general formula: R–X, X = F, Cl, Br, I).
- Name by identifying the longest chain containing the halogen, then prefixing positions and names of halogens in alphabetical order.
- Use prefixes di-, tri-, tetra- for multiple identical halogens.
- Freons (e.g., Freon-11 CCl3F, Freon-12 CCl2F2) are stable, nonflammable alkyl halides used as refrigerants, but they deplete the ozone layer.
- Teflon (polytetrafluoroethylene, PTFE) is a polymer made from tetrafluoroethene, valued for its nonstick and heat-resistant properties.
Ethers: Structure, Naming, and Properties
- Ethers have the general structure R–O–R', where R and R' are alkyl groups.
- Name ethers by listing the alkyl groups in alphabetical order followed by "ether" (e.g., ethyl methyl ether).
- Polymers and cyclic ethers are named similarly, identifying each alkyl or cyclic group.
- Ethers and alcohols have similar water solubility, but ethers have lower boiling points than alcohols.
- Ethers are less reactive (like alkanes) and are used as solvents and octane enhancers (e.g., MTBE).
Key Terms & Definitions
- Functional Group — Atom/group giving specific properties to organic compounds.
- Alcohol — Organic compound with a hydroxy (–OH) group.
- Alkyl Halide — Hydrocarbon with one or more halogen atoms replacing hydrogen.
- Ether — Compound with two alkyl groups bonded to the same oxygen atom.
- Freons (CFCs) — Chlorofluorocarbons used as refrigerants, harmful to the ozone layer.
- Teflon (PTFE) — Nonstick, heat-resistant polymer made from tetrafluoroethene.
Action Items / Next Steps
- Practice naming and drawing structures for alcohols, alkyl halides, and ethers.
- Review boiling point and solubility trends for alcohols and ethers.
- Read the next section on additional organic compound classes and organic reactions.