EstersKaitlyn Picavet, Natalie Williamson, Sidney

Wittman, Vivian Ly

General Structure

O R – C – O – R’

• The general formula of an ester is written as RCOOR’

Where RCO = carboxylic acid And where OR’= alcohol

||

Nomenclature

• Esters are made up of 2 alkyl groups and 2 oxygen atoms.

• The alkyl groups and oxygen come from the carboxylic acid and alcohol used in esterification (the formation of esters).

Ethanol + Butanoic Acid Ethyl Butanoate + Water Alcohol Carboxylic Acid Ester

The name follows the pattern ____yl ____oate

• The first blank comes from the alcohol-drop the -anol-add -ylie) ethanol would be ethyl.

• The second blank comes from the carboxylic acid-drop the -oic-add -oateie) butanoic acid would become butanoate

• (drawings on white board)

Drawing Rules

• Drawing esters combines drawing Alcohols and drawing Carboxylic Acids.

• The alkyl with the –oate is double bonded to an oxygen atom. The alkyl with the –yl has an oxygen atom incorporated in it.

OH

O

Butanoic Acid

OH

Ethanol

O

O

H-OH

Ethyl Butanoate

+ +

Physical and Chemical Properties

• Low polarity• Not as polar as alcohols• Dipole-Dipole, London dispersion• In Hydrogen bond, esters can only act as

Hydrogen acceptors, not donors• Unsaturated fats/oils always have at least one

C=C double bond

• Similar boiling points to ketones and Aldehydes

• As chain length increases, solubility in water decreases

• Solid form: Fat• Liquid form: Oil• Fats have a higher boiling point

Uses

• Esters are known for the odours of fruits, flowers, cosmetics and perfumes.

• Esters are also used in fats and oils.• Synthetic esters are added as flavourings to

processed foods. • They are good compounds for polar organic

compounds like; printing ink and cement.

Examples

• Apple- methyl butanoateCH3CH2CH2COOCH3 • Banana- 3-methylbutyl ethanoate

CH3

|CH3COOCH2CH2CHCH3

• Cherry- ethyl benzoateC6H5COOC2H5

• Pineapple- ethyl butanoateCH3CH2CH2COOCH2CH3

• Rum- ethyl methanoate CH3CH22CH2CH2CH2CH2COOCH2CH3

Reactions: Esterification

• Neutralization/condensation reactioncarboxylic acid + alcohol ----------> ester + water O|| – OH + R–OH --------> RC–O–R + HOH RC

heat

catalyst

heat

catalyst

O ||

organic base organic salt

Reactions: Hydrolysis

• Ester treated with acid or base: reversal of esterification occurs (split into acid & alcohol)

• Products: sodium salt of acid + alcohol

RC–O–R + NaOH- ------> RC–O- + Na+ + R–OH

O ||

O||

ester base acid alcohol

Reactions: Saponification

• Fats and oils are esters of long-chain acids: • When heated with a strong base,

saponification occurs & produces soap.

References

AUS-e-TUTE. (n.d.) Chemistry Tutorial: Esters and Esterification. Retrieved from the Web 29/09/11. http://www.ausetute.com.au/esters.html

Clark, J. (2004). Introducing Esters. Retrieved from the Web 22/09/11. http://www.chemguide.co.uk/organicprops/esters/background.html

Kimble, M.G. (2008). Esterification Reactions. Retrieved from the Web 29/09/11. http://www.ipfw.edu/chem/112/kimble/5-Synthesis%20of%20Esters.pdf

Snelling, C.R. (2002). Synthesis of an Ester: Fischer Esterification. Retrieved from the Web 29/09/11. http://www2.volstate.edu/msd/CHE/242/Labs/Ester.htm

van Kessel, H., Jenkins, F., Davies, L., Plumb, D., Di Giuseppe, M., Lantz, O., & Tompkins, D. (2003). Nelson Chemistry 12. Toronto: Nelson Thomson Canada Limited.