Overview
This lecture explains the properties, structures, and common uses of alcohols, aldehydes, and ketones—three important groups of organic compounds.
Properties and Structure of Carbon
- Carbon atoms have four valence electrons, allowing four covalent bonds.
- Carbon forms single, double, and triple bonds, creating various chain structures in organic compounds.
Alcohols: Structure, Properties, and Uses
- Alcohols contain an alkyl group and a hydroxyl group (-OH).
- The boiling point of alcohols increases with the number of carbon atoms due to stronger hydrogen bonding.
- Alcohols are soluble in water; solubility decreases as the hydrocarbon chain length increases.
- Viscosity of alcohols rises as molecule size increases.
- Flammability of alcohols decreases as size and mass increase.
- Methanol is used as fuel and a solvent; produced from wood chips.
- Ethanol, produced by fermentation, is used as fuel and in beverages.
- Isopropyl alcohol is used as a solvent and disinfectant.
- Ethylene glycol is used in antifreeze and hydraulic fluids.
- Glycerol is used in explosives, moisturizers, and as a solvent.
Aldehydes and Ketones: Structure, Properties, and Uses
- Both contain a carbonyl group (C=O).
- In aldehydes, the carbonyl group is at the end; in ketones, it is located between two carbons.
- Aldehydes have one hydrogen and a second group attached to the carbonyl carbon.
- Ketones have two hydrocarbon groups attached to the carbonyl carbon.
- The simplest aldehyde is formaldehyde; simplest ketone is acetone.
- Boiling points rise as molecule size increases.
- Lower aldehydes and ketones are miscible with water; solubility decreases with longer chains.
- Aldehydes' odors become less pungent and more fragrant as size increases.
- Formaldehyde is used in preservation and sterilization.
- Acetaldehyde occurs naturally in foods; used in acetic acid production.
- Propionaldehyde is used as a flavoring agent.
- Acetone is a solvent in various industries.
- Butanone and cyclohexanone are used in plastics, textiles, and nylon production.
Key Terms & Definitions
- Alkyl group — a hydrocarbon chain attached to a molecule.
- Hydroxyl group — the functional group -OH found in alcohols.
- Carbonyl group — a carbon atom double-bonded to oxygen (C=O), found in aldehydes and ketones.
- Viscosity — a fluid’s resistance to flow.
- Flammability — ease with which a substance can ignite and burn.
- Miscible — capable of being mixed in any ratio without separating.
- Saponification — a process to make soap, producing glycerol as a byproduct.
Action Items / Next Steps
- Review the structure and properties of alcohols, aldehydes, and ketones.
- Prepare for the next lesson on the mole concept and expressing mass of substances.