ChemistryChapter 8: Organic Chemistry
8.2.1 Naming Alkanes
**Alkanes:** Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds
Explanation level
Introduction
Every organic compound has a name that tells us important information about its structure. In organic chemistry, the IUPAC naming system is used to give each compound a unique and systematic name.
For alkanes, the name tells us:
- How many carbon atoms are in the chain (from the stem).
- What type of compound it is (from the suffix).
This section explains how to name alkanes using the stem and suffix system.
Definition
Alkanes: Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds.
Naming Alkanes: The names of alkanes are coded with the ending "-ane". Adding the stem before -ane gives the name of the alkane.
In simple words: Alkane names have two parts: a stem (which tells the number of carbon atoms) and a suffix (which tells the type of compound).
Main Idea
- The name of an alkane has two parts:
- For example:
- Meth- = 1 carbon atom → Methane (CH4)
- Eth- = 2 carbon atoms → Ethane (CH3CH3)
- Prop- = 3 carbon atoms → Propane (CH3CH2CH3)
- But- = 4 carbon atoms → Butane (CH3CH2CH2CH3)
Core Concept
The structure of an alkane name:
Stem + -ane = Name of alkane
Example: Meth + -ane = Methane
Key point: The stem tells you the number of carbon atoms; the suffix -ane tells you it is an alkane.
Detailed Explanation
What are Alkanes?
Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds.
Key features:
- They are saturated hydrocarbons (only single bonds).
- They have the general formula CnH2n+2.
- They are the simplest family of organic compounds.
The Naming System for Alkanes
Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds. Their names are coded with the ending "-ane". Adding the stem before -ane gives the name of the alkane.
For example:
- One carbon alkane is methane, CH4
- Two carbon alkane is ethane, CH3CH3
- Three carbon alkane is propane, CH3CH2CH3
- Four carbon alkane is butane, CH3CH2CH2CH3
Key point: The name of an alkane is determined by the number of carbon atoms in the chain.
Table 8.2: Stem Names
The source provides the following table of stem names:
| Stem | Number of C-atoms |
|---|---|
| Meth | 1 |
| Eth | 2 |
| Prop | 3 |
| But | 4 |
| Pent | 5 |
| Hex | 6 |
| Hept | 7 |
| Oct | 8 |
| Non | 9 |
| Dec | 10 |
Key point: The stem name tells you how many carbon atoms are in the chain.
Examples of Alkanes
| Name | Molecular Formula | Condensed Structural Formula | Number of Carbon Atoms |
|---|---|---|---|
| Methane | CH4 | CH4 | 1 |
| Ethane | C2H6 | CH3CH3 | 2 |
| Propane | C3H8 | CH3CH2CH3 | 3 |
| Butane | C4H10 | CH3CH2CH2CH3 | 4 |
| Pentane | C5H12 | CH3CH2CH2CH2CH3 | 5 |
| Hexane | C6H14 | CH3CH2CH2CH2CH2CH3 | 6 |
| Heptane | C7H16 | CH3CH2CH2CH2CH2CH2CH3 | 7 |
| Octane | C8H18 | CH3CH2CH2CH2CH2CH2CH2CH3 | 8 |
| Nonane | C9H20 | CH3CH2CH2CH2CH2CH2CH2CH2CH3 | 9 |
| Decane | C10H22 | CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 | 10 |
Key point: The name of the alkane is determined by the number of carbon atoms in the chain.
Summary Table
| Stem | Number of C-atoms | Alkane Name | Formula |
|---|---|---|---|
| Meth | 1 | Methane | CH4 |
| Eth | 2 | Ethane | CH3CH3 |
| Prop | 3 | Propane | CH3CH2CH3 |
| But | 4 | Butane | CH3CH2CH2CH3 |
| Pent | 5 | Pentane | CH3CH2CH2CH2CH3 |
| Hex | 6 | Hexane | CH3CH2CH2CH2CH2CH3 |
| Hept | 7 | Heptane | CH3CH2CH2CH2CH2CH2CH3 |
| Oct | 8 | Octane | CH3CH2CH2CH2CH2CH2CH2CH3 |
| Non | 9 | Nonane | CH3CH2CH2CH2CH2CH2CH2CH2CH3 |
| Dec | 10 | Decane | CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 |
Intermediate Level
Naming alkanes:
- Identify the number of carbon atoms in the chain.
- Choose the correct stem from the table.
- Add the suffix -ane to the stem.
- Write the name of the alkane.
Examples:
| Number of C-atoms | Stem | Name |
|---|---|---|
| 1 | Meth | Methane |
| 2 | Eth | Ethane |
| 3 | Prop | Propane |
| 4 | But | Butane |
| 5 | Pent | Pentane |
| 6 | Hex | Hexane |
| 7 | Hept | Heptane |
| 8 | Oct | Octane |
| 9 | Non | Nonane |
| 10 | Dec | Decane |
Key point: The name of an alkane is determined by the number of carbon atoms in the chain.
Important Points
- - Alkanes = hydrocarbons with only single bonds.
- - General formula: CnH2n+2.
- - The name of an alkane has two parts:
- 1. Stem — number of carbon atoms.
- 2. Suffix — -ane indicates an alkane.
- - Stem names:
- - Meth = 1 carbon
- - Eth = 2 carbons
- - Prop = 3 carbons
- - But = 4 carbons
- - Pent = 5 carbons
- - Hex = 6 carbons
- - Hept = 7 carbons
- - Oct = 8 carbons
- - Non = 9 carbons
- - Dec = 10 carbons
- - Examples:
- - Methane: CH4
- - Ethane: CH3CH3
- - Propane: CH3CH2CH3
- - Butane: CH3CH2CH2CH3
Remember
- - Alkanes = hydrocarbons with only single bonds.
- - Names have two parts: stem + suffix.
- - Suffix = **-ane**.
- - Stem names:
- - Meth = 1
- - Eth = 2
- - Prop = 3
- - But = 4
- - Pent = 5
- - Hex = 6
- - Hept = 7
- - Oct = 8
- - Non = 9
- - Dec = 10
- - Examples:
- - Methane: CH4
- - Ethane: CH3CH3
- - Propane: CH3CH2CH3
- - Butane: CH3CH2CH2CH3
Common Mistakes
| Mistake | Correction |
|---|---|
| Thinking the name of an alkane is random | The name is based on the number of carbon atoms and the type of bonds |
| Forgetting the suffix -ane | All alkanes end in -ane |
| Confusing the stem names | Meth = 1, Eth = 2, Prop = 3, But = 4, Pent = 5, Hex = 6, Hept = 7, Oct = 8, Non = 9, Dec = 10 |
| Thinking alkanes are unsaturated | Alkanes are saturated hydrocarbons (only single bonds) |
| Forgetting the general formula of alkanes | Alkanes: CnH2n+2 |
| Confusing alkanes with alkenes or alkynes | Alkanes: -ane; Alkenes: -ene; Alkynes: -yne |
| Thinking methane has more than one carbon atom | Methane has 1 carbon atom |
Quick Revision
Naming Alkanes:
Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds. Their names are coded with the ending "-ane". Adding stem before -ane gives the name of alkane. For example:
- One carbon alkane is methane, CH4
- Two carbon alkane is ethane, CH3CH3
- Three carbon alkanes are propane, CH3CH2CH3
- Four carbon alkane is butane, CH3CH2CH2CH3
Table 8.2: Shows stem names
| Stem | Number of C-atoms |
|---|---|
| Meth | 1 |
| Eth | 2 |
| Prop | 3 |
| But | 4 |
| Pent | 5 |
| Hex | 6 |
| Hept | 7 |
| Oct | 8 |
| Non | 9 |
| Dec | 10 |
- For example:
- Stem meth means one carbon atom and ending -ane indicates an alkane. So one carbon alkane is named as methane, CH4.
- The suffix indicates alkane.
- Stem indicates the number of carbon atoms.
8.2.1 Naming Alkanes:
Alkanes are hydrocarbons in which all the carbon atoms are joined to each other with single covalent bonds. Their names are coded with the ending "-ane". Adding stem before -ane gives the name of alkane. For example:
- One carbon alkane is methane, CH4
- Two carbon alkane is ethane, CH3CH3
- Three carbon alkanes are propane, CH3CH2CH3 and so on.
60-Second Revision
- Alkanes = hydrocarbons with only single bonds.
- Names = stem + suffix.
- Suffix = **-ane**.
- Stem names:
- Meth = 1
- Eth = 2
- Prop = 3
- But = 4
- Pent = 5
- Hex = 6
- Hept = 7
- Oct = 8
- Non = 9
- Dec = 10
- Examples:
- Methane: CH4
- Ethane: CH3CH3
- Propane: CH3CH2CH3
- Butane: CH3CH2CH2CH3
- General formula: CnH2n+2.
- ⚠️ Warning: the stem tells you the number of carbon atoms; the suffix -ane tells you it is an alkane.
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Quick revision
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Sticky Notes · Quick Revision
Key Point 1
- Alkanes = hydrocarbons with only single bonds.
Key Point 2
- Names = stem + suffix.
Key Point 3
- Suffix = **-ane**.
Key Point 4
- Stem names:
Key Point 5
- Meth = 1
Key Point 6
- Eth = 2
Key Point 7
- Prop = 3
Key Point 8
- But = 4
Key Point 9
- Pent = 5
Key Point 10
- Hex = 6
Key Point 11
- Hept = 7
Key Point 12
- Oct = 8
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