AN ester is simply an oxygen bonded between two hydrocarbon atoms. ESTERS AN ester is simply an oxygen bonded between two hydrocarbon atoms. {

{ O R-C O-R’ GENERAL FORMULA Carbonyl Group Alkyl Group or Aryl Group The R groups can be short-chain or long –chain aliphatic (alkyl) or aromatic (aryl) groups, saturated or unsaturated.

WHAT ARE ESTERS Esters are derivatives of carboxylic acids in which the –OH of the carboxyl group has been replaced by an –OR from an alcohol. Esters contain a carbonyl group and an ether link to the carbonyl carbon.

MORE ABOUT ESTERS Although the molecules are polar, they cannot form hydrogen bonds with one another because they do not contain hydrogen attached to oxygen or another electronegative atom.

R–C O O + RO H R–C + H - OH OH OR ESTERIFICATION H+ Carboxylic Alcohol Carboxylate Water Acid Ester Esters mainly result from the condensation (water producing reaction) of a carboxylic acid and an alcohol. The process is called esterification. This reaction can be catalyzed by the presence of H+ ions. Sulphuric acid, (H2SO4) is often used as a catalyst for this reaction.

PROPERTIES They have much lower boiling points than the strongly hydrogen-bonded carboxylic acids from which they are derived from. The low formula-mass esters are somewhat soluble in water, but esters containing more than four or five carbons have very limited solubility.

NAMING The format is as follows: (alkane further from carbonyl) (alkane closest to carbonyl) (parent chain)

Step 1: Identify the alkyl group attached to the oxygen atom. General Formula In this case, it is methyl attached to the oxygen because there is only one carbon.

Step 2: Determine the acid present, and change the stem name from –oic to –oate. Methyl Methanoate The acid attached is methanol, only have one carbon. Creating methanoate.

EXAMPLE #1 Ethyl Ethanoate First you identify the alkyl group attached to the oxygen. Identify the alkane that attaches the carbon atoms. Replace the –oic ending with an –oate ending NOTE: You name the structure backwards from how its written. Ethyl Ethanoate

EXAMPLE #2 Methyl Ethanoate 1) Name the alkane farthest from the Carbonyl group first (Methyl) 2) Name the alkane attaching the Carbons (or carbonyl group) (Ethyl) 3) Change the ending to –oate. Methyl Ethanoate

MORE EXAMPLES

Many Esters give blueberries, pineapples, apples, pears, bananas and many other fruits there characteristic aromas.

Raspberries HCOOCH2CH3 ethyl methanoate (IUPAC) ethyl formate (common) Pineapples CH3CH2CH2COOCH2CH3 ethyl butanoate (IUPAC) ethyl butyrate (common)