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 -yl ie) ethanol would be ethyl. The second blank comes from the carboxylic acid -drop the -oic -add -oate ie) 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. 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.
Reactions: Esterification Neutralization/condensation reaction carboxylic 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 acidalcohol
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.htmlhttp://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 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 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.htmhttp://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.