Naming Alkanes m.keir @ SSHS

From Standard Grade Methane CH4 H - C - H H Ethane C2H6 H - C - C - H Propane C3H8 H - C - C -C - H H Butane C4H10 H - C - C -C - C - H H Isomer of Butane C4H10 H - C - C -C - H H C How do we name this isomer ?

From Standard Grade H Pentane C5H12 H - C - C -C - C - C - H H Hexane H - C - C -C - C - C - C- H H Heptane C7H16 H - C - C -C - C - C - C - C- H H Like Butane all these alkanes have isomers. How do we name them ? Octane C8H18 H - C - C -C - C - C - C - C - C- H H

Naming alkanes Follow a few basic rules H - C - C -C - H H C Isomer of Butane C4H10 1. Find the longest carbon to carbon chain (not always straight) 2 Name is based on propane name methyl propane ( no need for the 2 as the branch can only be on carbon 2 ) 2. Identify the side branch. As there is 1 carbon called methyl 3. Number the chain so that the branch has the lowest number possible. In this case both ends of the Carbon chain result in the number 2.

1. Find the longest carbon to carbon chain (not always straight) H - C - C -C - C- C - H H C This alkane is an isomer of heptane. 2 Name is based on pentane 2. Identify the side branches. Name 2,2 dimethyl pentane Both have one carbon so both are methyl groups 3. Number the chain so that the branch has the lowest number possible. The branches are both on carbon 2.

1. Find the longest carbon to carbon chain (not always straight) This alkane is an isomer of nonane H - C - C -C - C- C - H H C Name is based on hexane 2. Identify the side branches. As each branch has 1 carbon they are all methyl groups. 3. Number the chain so that the branch has the lowest number possible. 2 4 From the left hand side we get the lower numbers 2,4 which we use. Name 2,2,4 trimethyl hexane

If the branch has 1 carbon (CH3 )= methyl If the branch has 2 carbons (C2H5) = ethyl If the branch has 3 carbons(C3H7) = propyl If there are 2 groups of the same type = di If there are 3 groups of the same type = tri If there is more than one different branch, they are placed alphabetical within the name. Eg 2,2, dimethyl 3 ethylhexane