Alkane Foundations

Alkane

A saturated hydrocarbon containing only carbon–carbon (C–C) single bonds and carbon–hydrogen (C–H) bonds.

Hydrocarbon

A compound composed only of carbon and hydrogen atoms.

Saturated Hydrocarbon

A hydrocarbon containing only single bonds between its carbon atoms and therefore having the maximum possible number of hydrogens for its carbon skeleton.

General Formula of an Acyclic Alkane

CₙH₂ₙ₊₂, where n is the number of carbon atoms.

Why are alkanes called saturated?

Because their carbon atoms are connected only by single bonds and carry the maximum possible number of hydrogen atoms for an acyclic carbon skeleton.

What types of bonds occur in alkanes?

C–C single bonds and C–H single bonds.

Carbon–Carbon Bond in an Alkane

A single σ bond between two sp³-hybridized carbon atoms.

Hybridization of Carbon in an Alkane

sp³

Aliphatic Compound

A term traditionally used for nonaromatic organic compounds; alkanes are members of the aliphatic family.

Methane

The simplest alkane, containing one carbon atom and having the molecular formula CH₄.

Ethane

The two-carbon alkane, with molecular formula C₂H₆.

Propane

The three-carbon alkane, with molecular formula C₃H₈.

Butane

The four-carbon alkane, with molecular formula C₄H₁₀.

Relationship Between Carbon Number and Hydrogen Number in an Acyclic Alkane

An acyclic alkane containing n carbon atoms contains 2n + 2 hydrogen atoms.

Why does methane have the formula CH₄?

A single carbon atom forms four bonds, so four hydrogen atoms are required to satisfy carbon's valence of four.

Why does ethane have the formula C₂H₆?

The two carbon atoms form one C–C single bond with each other, leaving each carbon able to form three C–H bonds, giving six hydrogens total.

Why does propane have the formula C₃H₈?

Applying the alkane formula CₙH₂ₙ₊₂ with n = 3 gives C₃H₈.

Why does butane have the formula C₄H₁₀?

Applying the alkane formula CₙH₂ₙ₊₂ with n = 4 gives C₄H₁₀.

Acyclic Alkane

An alkane whose carbon atoms form an open chain rather than a ring.

Carbon Chain

A sequence of carbon atoms connected to one another by carbon–carbon bonds.

Straight-Chain Alkane

An alkane whose carbon skeleton forms one continuous unbranched chain.

Branched-Chain Alkane

An alkane whose carbon skeleton contains one or more branches from the main carbon chain.

Normal Alkane

A traditional term for a straight-chain, unbranched alkane.

Meaning of n- in an Alkane Name

The prefix n- means normal and indicates the straight-chain form of an alkane, such as n-butane.

Can the same alkane molecular formula sometimes produce more than one structure?

Yes. Beginning with C₄H₁₀, the same molecular formula can correspond to different carbon connectivities.

Smallest Alkane That Can Have More Than One Carbon Skeleton

Butane, C₄H₁₀.