Alcohols
When a hydrogen of an alkane is replaced by Hydroxyl (-OH) group , we get Alcohol
- Alkane - (Hydrogen Atom) + Hydroxyl (-OH) Atom = Alcohol
- For alcohol, we use the suffix ‘ol’.
Eg. Methanol , ethanol etc.
Example:
- We know that Methane (CH 4 ) is an alkane.
- It has 1 Carbon atom and 4 Hydrogen Atoms.
- If we replace 1 of Hydrogen Atom with Hydroxyl (-OH) ,
- We get CH 3 OH (Methanol).
- This Methanol is an alcohol.
CH 4 - H + H 2 O = CH 3 OH + H 2
Similarly,
- If we replace 1 of Hydrogen Atom with Hydroxyl (-OH) in Ethane,
- We get C 2 H 5 OH (Ethanol)
Ethanol is an alcohol.
Naming of Alcohols:
Step 1
We take Parent alkane by seeing number of carbon atoms in the longest chain.
(If 1 Carbon Atom, we use Methane, if 2 carbon atoms ,we use ethane)
Step 2
We use the suffix ‘ol’ for Alcohols, added to the parent chain name.
Example:
CH 3 OH is called Methanol for its 1 Carbon Atom , and 1 Hydroxyl ion in the structure.
General Formula for Alkanes and Alcohols:
|
Alkane |
Alcohol |
|
C n H 2n+2 |
C n H 2n+1 OH |
Different Alkanes and their Alcohols of Hydroxyl (-OH)
|
Number of Carbon Atoms |
Alkane Name |
HaloAlkane Name ( IUPAC) |
General Name |
|
1 |
Methane |
Methanol |
Methyl Alcohol |
|
|
CH 4 |
CH 3 OH |
|
|
2 |
Ethane |
Ethanol |
Ethyl Alcohol |
|
|
C 2 H 6 |
C 2 H 5 OH |
|
|
3 |
Propane |
Propanol |
Propyl Alcohol |
|
|
C 3 H 8 |
C 3 H 7 OH |
|
|
4 |
Butane |
Butanol |
Butyl Alcohol |
|
|
C 4 H 10 |
C 4 H 9 OH |
Note :
- Methanol, Ethanol and Butanol all have same functional group OH
- Hence all these have the same chemical properties.
- The presence of a functional group such as alcohol decides the properties of the carbon compound, regardless of the length of the carbon chain .
