Fundamentals of Organic Chemistry and Hydrocarbon Naming

Organic Chemistry Fundamentals

Organic compounds are defined by containing carbon atoms, often forming complex structures. They can sometimes be synthesized from inorganic sources.

Exceptions to the Organic Definition

Compounds traditionally classified as inorganic, despite containing carbon, include:

• Carbon dioxide (CO₂)
• Carbon monoxide (CO)
• Carbonic acid (H₂CO₃)
• Carbonates (CO₃²⁻), such as Sodium Carbonate (Na₂CO₃)

General Properties of Organic Compounds

Organic compounds typically exhibit the following characteristics:

• They have low melting points.
• They are generally insoluble in water (H₂O) but soluble in organic solvents.
• They are often flammable.
• Their bonding is predominantly covalent.

Saturated Hydrocarbons: Alkanes and Cycloalkanes

Saturated hydrocarbons include alkanes and cycloalkanes.

Alkanes

Alkanes are characterized by single bonds. The bond angle in alkanes is 109.5° (tetrahedral geometry).

Compounds that share the same molecular formula but possess different structural arrangements are known as structural isomers.

The general formula for alkanes is CₙH₂ₙ₊₂.

Physical Properties of Alkanes

Physical properties (such as melting point, boiling point, and density) increase regularly as the number of carbon atoms increases:

• C₁ to C₄: Gases
• C₅ to C₁₅: Liquids
• C₁₆ and above: Solids

Chemical Properties of Alkanes

Alkanes are generally less reactive than other organic compounds, but they readily undergo combustion.

Nomenclature of Alkanes (IUPAC Rules)

1. For unbranched chains, the name ends in the suffix -ane, often preceded by the letter n- (e.g., n-butane).
2. The name of a branched chain consists of two parts: the final part names the longest continuous carbon chain (the parent chain).
3. The first part of the name uses prefixes to indicate the groups attached to the principal chain.
4. The location of substituent groups (alkyl groups) on the longest chain is designated by numbers.
5. When two or more identical groups are attached to the main chain, the location number for each substituent must be specified. Prefixes such as di- (2), tri- (3), and tetra- (4) are used to indicate the number of identical groups attached.

Cycloalkanes

Cycloalkanes are characterized by having a closed structure (a ring or cycle), which may or may not have alkyl radicals attached.

The general formula for cycloalkanes is CₙH₂ₙ. They are structural isomers of alkenes.

Unsaturated Hydrocarbons: Alkenes and Alkynes

Unsaturated hydrocarbons include alkenes (containing double bonds) and alkynes (containing triple bonds).

Nomenclature of Alkenes

1. Alkene names end in the suffix -ene. If two double bonds are present, the suffix -diene is used.
2. The longest carbon chain selected must contain the double bond(s) present in the compound.
3. Carbon atoms are numbered starting from the chain end nearest to the double bond. The location of the double bond is designated by the number of the first carbon atom involved in the double bond.
4. Substituent groups are named according to the methods used for alkanes, ensuring the double bond receives the lowest possible number.