Alkanes: Saturated Hydrocarbons
• Aliphatic
– Also know as paraffins
• General formula CnH2n+2 for chains
• Very unreactive; nonpolar compounds
• Structures
– Can form chains or/and rings
• CH3 groups at ends of chains, CH2 groups in the middle

– Branched or unbranched
• Saturated compounds
– All carbon atoms form single bonds with other atoms

Physical Properties of Aliphatic Hydrocarbons
•

Boiling points and melting points increase as the size of the molecule increases.

• Nonpolar molecules
– Main attractive forces are dispersion forces.

• Less dense than water
– They are insoluble in water.

Naming of Organic Compounds in General for Aliphatic
Hydrocarbons
Each name consists of three parts:
• Prefix
– Indicates position, number, and type of branches
– Indicates position, number, and type of each functional group

• Parent
– Indicates the length of the longest carbon chain or ring

• Suffix
– Indicates the type of hydrocarbon
• -ane, -ene, -yne

– Indicates certain functional groups

Naming Alkanes
1. Find the longest continuous carbon chain. 2. Number the chain from end closest to a branch.
If first branches are at equal distance, use next substituent.

3. Name branches as alkyl groups.
Locate each branch by preceding its name with the carbon number on the chain.

4. List branches alphabetically.
Do not count n-, sec-, t-; count iso.

5. Use prefix if more than one of same group present.
Di-, tri-, tetra-, penta-, hexaDo not count in alphabetizing.

Alkanes

Alkanes continued

Alkyl Groups

Unsaturated Hydrocarbons

• Unsaturated hydrocarbons have one or more
C=C double bonds or C≡C triple bonds.
• Unsaturated aliphatic hydrocarbons that contain double bonds
(C=C) are called alkenes.
– The general formula of a monounsaturated chain alkene is CnH2n.
– Remove two more H for each additional double bond.

• Unsaturated aliphatic hydrocarbons that contain triple bonds
(C≡C) are called alkynes.
– The general formula of an alkyne with one triple bond is CnH2n−2.
– Remove four more H for each additional triple bond.

Alkenes (Double Bonds)
• Alkenes are the following:
– Aliphatic

• Also known as olefins

– Hydrocarbons that contain double bonds
• C=C double bonds

– Unsaturated components

• The formula for one double bond is CnH2n.

– Subtract 2 H from alkane for each double bond.

• Geometry around the carbon atom
– Trigonal shape around C
– Flat

• Polyunsaturated = many double bonds

Table of Alkenes

Alkynes (Triple Bonds)
• Alkynes are the following:
– Aliphatic
• Also known as acetylenes

– Hydrocarbons that contain at least on triple bond
• C≡C triple bond

– Unsaturated compounds

• The formula for one triple bond is CnH2n−2.
– Subtract 4 H from alkane for each triple bond.

• Geometry around the carbon atom
– Linear shape

• Internal alkynes have both triple-bond carbons attached to C.
• Terminal alkynes have one carbon attached to H.

Table of Alkynes

Naming Alkenes and Alkynes
• Change suffix on main name from -ane to -ene for the base name of alkene, or to -yne for the base name of the alkyne.
• Number chain from end closest to