Ethanol (CH3CH2OH) Oxidation Number
Ethanol (CH3CH2OH) lewis structure should be drawn to find oxidation numbers of elements. Then, you need electronegativity values each atoms to determine oxidation numbers of elements.
Oxidation numbers of carbon, hydrogen and oxygen atoms in ethanol
Now, we are going to look oxidation numbers of each element and you can see the following figure with oxidation numbers.
Oxidation number of two carbon atoms
There are two carbon atoms in ethanol molecule and they are in different oxidation states. One carbon atom is at -3 oxidation state and other carbon atom is at -1 oxidation state.
Oxidation number of hydrogen atoms
Oxidation number of each hydrogen atom is +1.
Oxidation number of oxygen atom
Oxygen atom is at -2 oxidation state.
How to find oxidation numbers in ethanol molecule
Electronegativity values of atoms are used to determine oxidation numbers. When electronegativity of one atom is higher than another atom, electrons of the bond (between those two atoms) are attracted to the higher electronegativity atom.
| Element | Electronegativity |
|---|---|
| Hydrogen | 2.1 |
| Carbon | 2.5 |
| Oxygen | 3.5 |
Now, we can mark how electrons of bonds are attracted toward some atoms as below.
When an atom attract an electron from a bond, that atom gets -1 oxidation state and other atom in that bond gets +1 oxidation state. We can mark this as below.
After marking individual oxidation numbers, add them all for a relevant atom to find the oxidation number. As an example, carbon atom which has three hydrogen atoms, have -1 individual oxidation numbers. Then get the sum of -1 + (-1) + (-1) = -3
Questions
There are two carbon atoms in ethanol molecule. Are they in same oxidation state?
Those two carbon atoms are at different oxidation states. One carbon atom is at -1 oxidation state and other one is at -3.
How oxidation number of carbon atoms are changed when ethanol is oxidized to ethanoic acid?
The carbon atom which is joint with -OH bond in ethanol molecule is oxidized to ethanoic acid in the presence of a strong oxidizing agent in an acidic medium. That carbon atom is at -1 oxidation state in ethanol molecule and at +3 oxidation state in acetic acid molecule. So, oxidation number of carbon atom is increased from 4.
Can ethanol be oxidized by looking oxidation states of carbon atoms in ethanol
In ethanol molecule there are two carbon atoms and their oxidation states are -3 and -1. Carbon atom can show oxidation numbers from -4 to +4. Therefore, carbon atoms of ethanol can be oxidized to higher oxidation states. As an example, in the presence of acidic potassium permanganate, ethanol is oxidized to acetic acid (ethanoic acid).