CHAPTER 14: Unit 7.Chemical Reactions of esters
Hydrolysis of Esters
Esters can be converted back to carboxylic acids and alcohols under either acidic or basic conditions. Under acidic conditions, the process sis called hydrolysis and the products are the acid and alcohol. Under basic conditions, the process is called saponification and the products are acid salts and alcohol.
| Base hydrolysis or saponification reaction: It is a hydrolysis of an organic compound under basic condition in which a carboxylic acid salt is one of the products. In ester saponification reaction, NaoH or KOH is used as a base. |
| Acid Hydrolysis: Ester hydrolysis requires the presence of a strong acid-catalyst or enzymes. ester hydrolysis is the reverse of esterification reaction, the formation of an alcohol and carboxylic acid. |
| Example: |
| https://www.youtube.com/watch?v=2kU5ytsrQgo |
| https://www.youtube.com/watch?v=iMHRf83TZTo |
| Example
Write an equation for the acidic hydrolysis of ethyl butyrate (CH3CH2CH2COOCH2CH3) and name the products.SolutionRemember that in acidic hydrolysis, water (HOH) splits the ester bond. The H of HOH joins to the oxygen atom in the OR part of the original ester, and the OH of HOH joins to the carbonyl carbon atom: HOMEWORK EXERCISE 1. How do acidic hydrolysis and basic hydrolysis of an ester differ in terms of 2. What is saponification? 2. the basic hydrolysis of an ester |
| Thioesters & Phosphoesters: Thioesters are sulfur-containing analogs of esters in which an -SR group has replaced the -OR group. |
| They are known for irritating distinct odor(skunk odor). |
| Inorganic esters are manly formed by reacting an alcohol with phosphoric acid called phosphate ester. |
| Phosphate esters of simple sugars or monosaccharides are very important in the energy harvesting biochemical pathways. |
| Glucose-6-phosphate |
| Polyesters: Polyesters are polymers in which the monomers ( diacids and dialcohols) are joined through ester linkages. Polyesters constitute a second major class of condensation polymers. The most common polyester is polyethylene terephthalate (PET). Plastic soft drink bottles are made of PET. They can be also used in clothing, films, tires even in artificial heart valves and substitute blood vessels. |
| Terephthalic acid Polyethylene Terephthalate(PET) |
| Isomerism of carboxylic Acids and Esters: Constitutional isomers are produced based on different carbon skeletons and on different positions for the functional group are possible for carboxylic acid, esters and acid derivatives. carboxylic acid skeletal isomers: Ester positional isomers: |
The products are butyric acid (butanoic acid) and ethanol.
b.
6. Complete each equation.a. 
b. CH3COOCH(CH3)2 + KOH(aq) →Answers3.
5.