Alcohols - What are Alcohols?
Alcohols are organic compunds (compounds containing carbon).
They contain the functional group (an atom or group of an atom responsible for most of the chemical reactions for that compund). -OH.
Many different alcohols together form a homologous series which is a family of compunds with the same general formula. The general formula for an alcohol is:
C n H 2n+1 OH.
The first three alcohols are methanol, ethanol, propanol. The '-ol' at the end shows its an alcohol and the beginning bit represents the number of carbons in the molecule 'methan' = 1.
Alcohols - Properties and Uses
Properties and Uses
The simplest alcohols are colourless and dissolve in water to more a neutral solution.
They are good solvents and dissolve in substances water does not, therefore can be used in medicines, perfumes and cosmetics.
They react with sodium to form hydrogen gas like water but the reaction isn't as vigorous.
They burn well and form carbon dioxide an water.
Unfortunately, alcohols are also dangerous and toxic, causing death in large doses.
It is good that alcohols burn well as they can be used as a renewable fuel made from crops. Petrol contains 5% of ethanol. This method is also carbon neutral.
Carboxylic acids are a homologous series of organic compounds containing the functional group -COOH.
They contain 'oic' (ex. methanoic) to show that it is a carboxylic acid and has the general formula of:
C n H n+1 COOH.
Carboxylic acids are formed when alcohols are mildly oxidised.
Once diluted, carboxylic acids can be used as vinegar. It is also used in the pain killing drug aspirin. Vitimin C is also a carboxylic acid.
Carboxylic acids are weak acids. All acids dissolve in water to give off hydrogen ions.
So carboxylic acidshave an unpleasant taste or smell, butanboic acid is found in sweat and methanoic acid is found in ant stings.
Esters are organic compaounds containing the functional group of - COO - . The general formula is more complex. There are two sides to the - COO - .
The first end with an 'yl' (ex. methyl, ethyl) meaning C n H 2n+1. The other side of the - COO - ends with 'oate' (ex. propanoate, ehtanoate) and the general formula for that side is the same.
Examples of this are methyl methanoate and ethyl propanoate.
Esters are made by reacting alcohols with carboxylic acids.
For example, mixing methanol with ethanoic acid would make methyl ethanoate.
Esters are responsible for the smells of fruits and can therefore be extracted from fruits.
Their smell is also used for perfumes.
Esters can also be used for food flavouring.
Esters are volatile, meaning they have low boiling points and readily evapourate.