Alkanes, Alkenes, Alkynes

Alkanes

Saturated hydrocarbons with only single C-C bonds.

General formula of alkanes

CₙH₂ₙ₊₂

Alkenes

Unsaturated hydrocarbons with at least one C=C double bond.

General formula of alkenes

CₙH₂ₙ

Alkynes

Unsaturated hydrocarbons with at least one C≡C triple bond.

General formula of alkynes

CₙH₂ₙ₋₂

Homologous series

A group of compounds with the same functional group and similar chemical properties, differing by a CH₂ group.

Examples of homologous series

Alkanes, alkenes, alkynes

Structural isomers

Compounds with the same molecular formula but different structural arrangements.

How can structural isomers differ?

In chain branching, position of double/triple bonds, or position of functional groups.

Examples of butene isomers

1-butene: CH₂=CHCH₂CH₃; 2-butene: CH₃CH=CHCH₃

Functional group in alkanes

Single C-C bonds.

Functional group in alkenes

At least one C=C double bond.

Functional group in alkynes

At least one C≡C triple bond.

Structure of a methyl group

-CH₃

Structure of an ethyl group

-CH₂CH₃

Fluoro group

A halogen functional group: -F

Chloro group

A halogen functional group: -Cl

Bromo group

A halogen functional group: -Br

Iodo group

A halogen functional group: -I

Boiling point of hydrocarbons

Increases with chain length (more dispersion forces). Branched chains have lower boiling points than straight chains.

Melting point change in hydrocarbons

Increases with size, but more consistent for even-numbered chains (better packing).

Volatility change in hydrocarbons

Decreases as molar mass increases. Short chains are more volatile.

Viscosity change in hydrocarbons

Increases with chain length and branching.

Solubility of hydrocarbons in water

No. Hydrocarbons are nonpolar and insoluble in water (which is polar).

Solvents hydrocarbons dissolve in

Non-polar solvents like hexane or cyclohexane.

Density change of hydrocarbons

Hydrocarbons are less dense than water. Density increases with chain length.

First step in IUPAC naming of organic compounds

Find the longest carbon chain containing the functional group.

Second step in IUPAC naming of organic compounds

Number the chain to give branches/functional groups the lowest possible numbers.

Third step in IUPAC naming of organic compounds

Name branches: methyl, ethyl, etc.

Fourth step in IUPAC naming of organic compounds

Name halogens: fluoro, chloro, bromo, iodo.

Fifth step in IUPAC naming of organic compounds

Use the appropriate suffix: -ane, -ene, -yne.