HSC CHEMISTRY 2015​.

The Oxygen Free Radical       

 

 

Free Radical:

A neutral species that has an unpaired electron and which can be formed by splitting a molecule into two neutral fragments. 

Free radicals are generally very reactive due to their unpaired electron. This means they have a high tendency to react with other molecules, such as O2, CO, NO and SO in order to pair their free electron.

Eg)      

• Hydrogen peroxide can be split into two OH∙ fragments which have

an unpaired electron each thus it is a free radical. It is called a hydroxyl free radical.

 

• O∙ free radicals are formed in many ways. Including the

splitting of O2 into two O∙ free radicals and the splitting of NO2

into NO and an O∙ free radical

 

 

• HOCl also forms a free radical when split into a H atom and a ClO∙ free radical

 

 

 

Due to their high reactivity the concentrations of O∙ free radicals are very low as they recombine with molecules readily. In turn it is very difficult to collect concentrations of O∙ high enough to measure properties such as melting and boiling points.

 

Formation of O∙: In the troposphere O∙ free radicals form when high levels of NO2 is broken down by UV light to form NO and an O∙ free radical.

 

∙

 

In the stratosphere however O∙ is formed two ways. First when O2 molecules are broken down by short UV waves (<240nm). 

 

 

 

 

And also when O3 absorbs longer UV waves (200-300nm) decomposing to an O2 molecule and an O∙ free radical. 

 

 

 

Properties: