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Functional Groups and Homologous Series in Nomenclature
A topic from the subject of Nomenclature in Chemistry.
Functional Groups and Homologous Series in Nomenclature
## Key Points
Functional group:A specific group of atoms within a molecule that determines its chemical properties. Homologous series: A series of organic compounds with similar structures and properties that differ by a repeating structural unit (-CH2-).
## Main Concepts
Functional Groups
Characterized by a specific group of atoms called an "-yl" suffix. Determine the physical and chemical properties of molecules.
Common functional groups include: Alkanes (-C-C-)
Alkenes (-C=C-) Alkynes (-C≡C-)
Alcohols (-OH) Ethers (-O-)
Aldehydes (-CHO) Ketones (-CO-)
Carboxylic acids (-COOH)Homologous Series Members have the same general structure and differ by a repeating structural unit.
Each member differs in molecular mass by CH2. Properties change gradually within a homologous series as the molecular mass increases.
Alkanes, alkenes, and alkynes form homologous series.Nomenclature Rules For hydrocarbons:
Use the suffix "-ane" for alkanes. Use the suffix "-ene" for alkenes.
Use the suffix "-yne" for alkynes. For functional groups:
Replace the "-ane" suffix with the functional group suffix. Indicate the location of the functional group using a number.
For homologous series: Use the Greek prefixes "mono-" to "penta-" to indicate the number of carbon atoms in the molecule.
For branched hydrocarbons: Use prefixes like "methyl-" and "ethyl-" to indicate the branching pattern.
## Key Points
Functional group:A specific group of atoms within a molecule that determines its chemical properties. Homologous series: A series of organic compounds with similar structures and properties that differ by a repeating structural unit (-CH2-).
## Main Concepts
Functional Groups
Characterized by a specific group of atoms called an "-yl" suffix. Determine the physical and chemical properties of molecules.
Common functional groups include: Alkanes (-C-C-)
Alkenes (-C=C-) Alkynes (-C≡C-)
Alcohols (-OH) Ethers (-O-)
Aldehydes (-CHO) Ketones (-CO-)
Carboxylic acids (-COOH)Homologous Series Members have the same general structure and differ by a repeating structural unit.
Each member differs in molecular mass by CH2. Properties change gradually within a homologous series as the molecular mass increases.
Alkanes, alkenes, and alkynes form homologous series.Nomenclature Rules For hydrocarbons:
Use the suffix "-ane" for alkanes. Use the suffix "-ene" for alkenes.
Use the suffix "-yne" for alkynes. For functional groups:
Replace the "-ane" suffix with the functional group suffix. Indicate the location of the functional group using a number.
For homologous series: Use the Greek prefixes "mono-" to "penta-" to indicate the number of carbon atoms in the molecule.
For branched hydrocarbons: Use prefixes like "methyl-" and "ethyl-" to indicate the branching pattern.
Experiment: Functional Groups and Homologous Series in Nomenclature
Objective:
To identify and classify organic compounds based on their functional groups and to observe the properties of homologous series.Materials:
- Ethanol- Methanol
- Butanol
- Hexanol
- Sodium metal
- Phenolphthalein solution
- Test tubes
- Graduated cylinder
- Bunsen burner
- Tongs
- Safety goggles
Procedure:
1. Place approximately 2 mL of each alcohol (ethanol, methanol, butanol, and hexanol) in separate test tubes.2. Add a small piece of sodium metal to each test tube.
3. Observe the reactions and record any observations.
4. Add 2 drops of phenolphthalein solution to each test tube.
5. Heat the test tubes gently over a Bunsen burner.
6. Record any changes in color and any other observations.
Key Procedures:
- Reaction with sodium metal: The reaction of alcohols with sodium metal is a classic test for the presence of an alcohol functional group. Alcohols react with sodium metal to produce hydrogen gas and an alkoxide salt.- Phenolphthalein test: Phenolphthalein is a pH indicator that turns pink in the presence of a base. The alkoxide salts produced in the reaction of alcohols with sodium metal are bases, so they will turn phenolphthalein solution pink.