chemistry: chapter 16, pt. 1
Chapter 16: Organic Molecules (Hydrocarbons)
16.1 Learning Objectives
Understand properties and composition of organic vs inorganic compounds
Name and write formulas for alkanes
Recognize branched chains and isomers among alkanes
Write condensed and skeletal formulas for alkanes
Learn IUPAC naming conventions
Identify physical and chemical properties of alkanes
16.2 Organic vs Inorganic Chemistry
Organic Chemistry: Focuses on carbon compounds.
Inorganic Chemistry: Covers all other elements.
Key Characteristics:
Organic compounds typically contain carbon bonded to hydrogen.
Inorganic compounds may contain carbon in limited forms such as carbon dioxide or carbonates.
16.3 Types of Hydrocarbons
Alkanes: Only single bonds (saturated hydrocarbons).
Alkenes: Have at least one double bond.
Alkynes: Contain at least one triple bond.
Aromatic Compounds: Contain rings with alternating single and double bonds.
16.4 Structure of Alkanes
Alkanes are hydrocarbons with carbon atoms connected via single bonds.
Normal Alkanes: Straight-chain configurations.
16.5 Homologous Series
Each compound in a homologous series differs by one carbon and two hydrogens (CH2 unit).
Early members include methane (1C), ethane (2C), propane (3C).
16.6 Isomers
Isomers: Compounds with the same molecular formula but different structural forms and properties.
Example: Butane (C4H10) can be straight-chain or branched (isobutane).
16.7 IUPAC Naming Rules
Identify the parent chain (longest carbon chain).
Identify substituents (alkyl groups) attached to the parent chain.
Determine the point of attachment by numbering carbons.
Arrange substituents in alphabetical order in the name; use prefixes (di-, tri-, tetra-) for identical groups.
16.8 Common Alkyl Groups
1 Carbon:
Alone: Methane
Substituent: Methyl-
2 Carbons:
Alone: Ethane
Substituent: Ethyl-
3 Carbons:
Alone: Propane
Substituent: Propyl-
16.9 Physical Properties of Alkanes (Table 16.5)
Name | Formula | Melting Point (°C) | Boiling Point (°C) | Density (20°C) | State (at 20°C) |
|---|---|---|---|---|---|
Methane | CH4 | -182 | -164 | 0.668 g/L | Gas |
Ethane | C2H6 | -183 | -89 | 1.265 g/L | Gas |
Propane | C3H8 | -190 | -42 | 1.867 g/L | Gas |
Butane | C4H10 | -138 | -1 | 2.493 g/L | Gas |
Pentane | C5H12 | -130 | 36 | 0.626 g/mL | Liquid |
Hexane | C6H14 | -95 | 69 | 0.659 g/mL | Liquid |
Octane | C8H18 | -57 | 125 | 0.703 g/mL | Liquid |
Decane | C10H22 | -30 | 174 | 0.730 g/mL | Liquid |
16.10 Halogenated Hydrocarbons
Known as alkyl halides or haloalkanes.
Example Naming:
Common Name: Derived from the alkyl group plus halogen.
IUPAC: Use parent alkane name with halogen prefix.
16.11 Cycloalkanes
Cycloalkanes: Compounds where carbon atoms form a ring structure.
Examples: Cyclopropane, Cyclobutane, Cyclopentane, Cyclohexane.
16.12 Functional Groups
Recognize the significance of functional groups in organic chemistry (amines, alcohols, halides, etc.).
16.13 Simplified IUPAC Rules for Naming Alkanes
Identify longest chain (LCC).
Number chain ensuring lowest numbers to substituents.
Alphabetical arrangement of groups with Greek prefixes for multiple identical substituents.
16.14 Tips for Determining Hydrogen Atoms in Alkanes
Linear alkane formula: C_nH_(2n+2).
Cycloalkane formula: C_nH_(2n).