alkanes

What is the general formula for alkanes?

CₙH₂ₙ₊₂

What are the first 6 alkanes?

• Methane - CH4

• Ethane - C2H6

• Propane - C3H8

• Butane - C4H10

• Pentane - C5H12

• Hexane - C6H14

What are isomers?

Isomers have the same molecular formula but different structural arrangements

How many isomers does methane have?

1

How many isomers does ethane have?

1

How many isomers does propane have?

1

How many isomers does butane have?

2 isomers

• Butane

• Methylpropane

How many isomers does pentane have?

3 isomers

• Pentane

• (2) methyl butane

• (2,2) di methyl propane

How many isomers does hexane have?

5 isomers

• Hexane

• 2- methyl pentane

• 3- methyl pentane

• 2,2- dimethyl butane

• 2,3 - dimethyl butane

How many isomers does heptane have?

9 isomers

• Heptane

• 2 - methyl hexane

• 3 - methyl hexane

• 3,3 - dimethyl pentane

• 2,4 - dimethyl pentane

• 2,3 - dimethyl pentane

• 2,2 - dimethyl pentane

• (2,2,3) tri methyl butane

• (3) ethyl pentane

Methyl

CH3

Ethyl

C2H5

Propyl

C3H7

Formula for complete combustion of alkanes

CnH2n+2 + 3n+1 / 2 O2 goes to nCO2 + (n+1)H2O

Which chain of alkanes combust incompletely and why

Longer carbon chains are dirtier and this will combust incompletely.

What are exceptions to the rules of alkanes?

Cyclic molecules

How are cyclic molecules exceptions to the rules of alkanes?

• Cyclic alkanes are structured in a circle therefore there will always be two hydrogen atoms removed. For example for cyclohexane the formula will be C6H12

Formula of cycloalkanes?

CnH2n