E06 - Esterification

Organic compounds

composed of carbon and hydrogen atoms along with heteroatoms such as oxygen, nitrogen, sulfur, and the halogens

Functional groups

• because of the vast number of organic compounds that exist in nature and that can be synthesized in the laboratory, they are place in this

• depends on structural features present in the molecules

Alcohols

• functional group

• contain hydroxyl (OH) group

Carboxylic acid

• functional group

• contain a carboxyl group (COOH)

Esters

• formed by combining alcohols and carboxylic acids

• characterized by the presence of a carbonyl group with an alkoxy group attached to the carbonyl carbon- volatile substances that have lower boiling points than alcohols and carboxylic acids

Alcohols and carboxylic acids

occur naturally and are synthesized in the laboratory as scents of flowers and fruits

Fischer esterification

a process that can synthesize esters from an alcohol and carboxylic acid in the presence of an acid catalyst and heat

Phenolphthalein

• common acid-base indicator

• test that characterizes esters synthesized in test tubes from different alcohols and carboxylic acids

Objectives

• synthesize esters from alcohols and carboxylic acids;

• describe the conditions required for the synthesis and hydrolysis of esters;

• observe the changes in the physical and chemical properties of alcohols, carboxylic acids, as they are combined into esters; and

• distinguish alcohols, carboxylic acids, and esters based on their physical, chemical, and structural properties

Reagents

• ethanol

• methanol

• glacial acetic acid

• benzoic acid

• salicylic acid

• concentrated sulfuric acid

• sodium hydroxide

• phenolphthalein

Instrument

electric stove or electric water bath

To borrow

• beaker (600 mL)

• beaker (100 mL)

• test tube holder

• test tube

Safety reminders

• Wear your complete PPE!

• Highly volatile and flammable solvents should be placed under the fume hood

• Make sure no excess amount of the solvents will be left in the droppers and beakers

• Use the correct droppers to avoid contamination

• Have a tissue paper on your pockets for spills.

Water disposal

• Dispose all organic wastes in their respective bottles: Non-Halogenated Waste Bottle and Halogenated Waste Bottle

• Diluted aqueous solutions can be disposed directly to the sink with running water

• Acid wastes can be diluted with water then flushed down to the sink.

Synthesis of ester 

• Prepare a hot water bath by filling up a 500-mL halfway with tap water and placing it on top of a stove

• Before mixing the alcohol and the carboxylic acid, try to waft and take note of their individual smell. Add 10 drops of alcohol, 10 drops (if liquid) or a pinch (if solid) of carboxylic acid into a test tube

• Add 2 drops of concentrated sulfuric acid into the test tube with the alcohol and carboxylic acid

• Place the test tube into the hot water bath for ten (10) minutes or until a scent is detected coming from the test tube

• Transfer the test tube into a 100-mL beaker filled halfway with tap water to cool down. Observe any changes in the appearance of the contents of the test tube

• After cooling, carefully waft the scent coming out of the test tube and describe the scent. B. Charac

Examples of alcohols

• isoamyl alcohol

• ethanol

• methanol

Types of carboxylic acids

• glacial acetic acids

• salicylic acid

Characterization of Prepared Ester

• Add 5 drops of sodium hydroxide into the test tube followed by 2 drops of phenolphthalein indicator. Take note of any changes

• Place the test tube back into the hot water bath for ten (10) minutes or until changes are observed. Take note of your observations.