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Esters: Preparation - Nomenclature - Properties

 

Esters

Esters have got the same functional group with carboxylic acids.

The structural formula of esters is

 

 

Esters: Preparation - Nomenclature - Properties

General formula is CnH2nO2. Here R´=R or R´≠R.

Besides, R can never be a hydrogen atom as in carboxylic acids.

 

Esters: Preparation - Nomenclature - Properties


 

 

Nomenclature of Esters

As esters are made up of two groups, one is from carboxylic acid and the other is from alcohol, so they are named after they are di- vided into two groups as follows:

 

1.      The first name of ester belongs to the alkyl group bonded to the oxygen atom in alcohol group.

2.     The remaining name is written by adding –oate suffix to the alkane part of the carboxylic acid.

 

Nomenclature of Esters


Do you know that

Esters which are found in fruits and vegetables have pleasant odors and therefore they are used as sweetener in foods, perfumes and kids’ foods?

 

 

Preparation of Esters

Esters can be synthesized through many methods such as the reaction of alcohols and carboxylic acids. Besides, by adding pyridine to produce HCl, carboxylic acid chloride is obtained and with its reaction with alcohol, esters are prepared.

 

Preparation of Esters

 

 

Physical Properties of Esters

Esters can ionize. They don’t form hydrogen bonds between their molecules. Therefore, their boiling points are lower than those of carboxylic acids with the same number of carbons. Most esters don’t dissolve in water but dissolve in many organic solvents. Besides, these substances are used as good solvents for many organic compounds.

 

Physical Properties of Esters


 

 

Chemical Properties of Esters

Esters undergo following reactions.

 

a) Reaction of Esters with Water in Acidic Solution

This reaction is the opposite of esterification reaction which is synthesis of esters from alcohols and carboxylic acids. Here H2SO4 and HCl are used as catalysts. Esters react with water and form carboxylic acids and alcohols.

 

a) Reaction of Esters with Water in Acidic Solution


 

b) Reaction of Esters with Water in Basic Medium

Esters react with water molecules in basic solution such as NaOH. At the end of the reaction, sodium salt of carboxylic acid and alcohol are formed. This reaction is very important as it is used in soap production. Therefore, it is also known as saponification reaction. Besides, it is used to differentiate esters as shown in the following reaction:

 

b) Reaction of Esters with Water in Basic Medium


 

Apples and beeswax contains esters.

Apples and beeswax contains esters.

 

  

 

See also

1.      Alcohols: nomenclature – synthesis - Properties

2.     Alkyl halides: nomenclature - synthesis - Properties

 

 

References

1.      K. J. Denniston c J. J.Topping c and R. L.Caretc “General Organic and Biochemistry”c Mc-Graw- Hillc New York   (2004).

2.     K.W. Whittenc R.E. Davis  and L. M. Peckc “General Chemistry” 7th ed. Holt Rinehart and Winstonc New York (2010).

3.     Clayden, J.; Greeves, N. and Warren, S. (2012) Organic Chemistry. Oxford University Press. pp. 1–15. ISBN 0-19-927029-5.

4.     Streitwieser, Andrew; Heathcock, Clayton H.; Kosower, Edward M. (2017). Introduction to Organic Chemistry. New Delhipages=3–4: Medtech (Scientific International, reprint of revised 4th edition, Macmillan, 1998). ISBN 978-93-85998-89-8.


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