Carboxylic Acid and Derivatives

REPORT

EXPERIMENT 9 CARBOXYLIC ACID AND DERIVATIVES

Date: January 19, 2004

Objectives:

1. To understand the reactions of carboxylic compounds and derivatives.

2. To know the methods for preparing carboxylic acid derivatives.

3. To know the methods for testing the carboxylic acid derivatives.

Experimental Procedures:

9.1 Solubility

1. Prepare 3 test tubes with 3 ml of water in each.

2. Place 3 drops of acetic acid, benzoic acid, and oxalic acid in separate test tubes.

3. Shake and observe the solubility, then test the solution with litmus paper if soluble.

4. Repeat the experiment using ether and ethanol as the solvent.

9.2 Reactions with Bases

1. Prepare 3 test tubes with 3 drops of 5% NaOH.

2. Add 5 drops of 50 mg of acetic acid, benzoic acid and oxalic acid.

3. Shake and observe the changes.

4. Repeat the procedures using 5% NaHCO3.

9.3 Oxidation Reactions

9.3.1 Reaction with KMnO4

1. Prepare 4 test tubes with 2 ml of water and add 1 ml of conc. H2SO4 to each.

2. Place 4 drops (0.1 g) of formic acid, acetic acid, benzoic acid, and oxalic acid, each into a different test tube.

3. If the acid does not dissolve, place it in 50。C to heat until totally dissolved.

4. Add 3 drops of 5% KMnO4 to each, then shake and observe the reactions.

9.3.2 Reaction with Tollen's Reagent

1. Place 3 ml of Tollen's Reagent in 4 separate test tubes.

2. Add 3 drops of formic acid, acetic acid, benzoic acid, and oxalic acid each into a different test tube.

3. If the acid is a solid, dissolve 50 mg in 4-5 drops of ethanol before putting into the test tube.

4. Shake and let it stand, then observe the reactions.

5. If no reaction can be observed, warm the test tube in 50。C water bath for 5 minutes.

* Do not inhale the fumes occurring with oxalic acid, they are toxic to respiratory system.

9.4 Preparation of Ester from Halides

1. Place 0.5 ml of 1-butanol into a dry test tube, and add 0.5 ml of benzol chloride.

2. Warm for 2-3 minutes in a hot water bath, and then soak it in ice.

3. Pour the content into a 10 ml cold beaker, then stir and smell the oil-like compound.

9.5 Hydrolysis Reaction Using Sodium Acetate

1. Dissolve 0.2 g of NaOOCCH3 in 5 ml of water then test with litmus paper.

9.6 Hydrolysis Reaction of Amides

1. Place 0.2 g of acetamide and 2 drops of 10% NaOH in a test tube.

2. Boil and smell the gas regenerated, and test the gas with litmus paper.

3. Repeat the experiment using 0.4 g of acetamide mixing with 10% H2SO4.

Results & Discussions:

9.1 Solubility

Compound Water Litmus Paper Ether Ethanol

Acetic acid Soluble Red (acid) Soluble Soluble

Benzoic acid Insoluble X Soluble Soluble

Oxalic acid Insoluble X Insoluble Insoluble

Since carboxylic acids are polar molecules, they can dissolve fairly well in polar solvents such as water, especially those with less than 5 carbon atoms. Another name for acetic acid is methanoic acid. It contains only one carbon, therefore, its solubility in water is very good, and the acidic characteristic is clearly shown in the solution.

As for benzoic acid, it contains more than 5 carbon atoms in its benzene ring, thus its solubility in water is not good. However, since like-dissolves-like, it is soluble in ether and ethanol.

Oxalic acid contains two -COOH groups joined together, causing to have an unusual polarity, therefore, it is insoluble in water, ether and ethanol.

9.2 Reactions with Bases

Compound 5% NaOH 5% NaHCO3

Acetic acid Soluble Soluble, oily

Benzoic acid Turbid, opaque Clear solution with white precipitate on top

Oxalic acid Turbid, opaque Clear solution with white precipitate at bottom

The rather strong acetic acid reacted with the strong base NaOH to form a salt, and this salt was soluble in water. This was why the result of this part was a clear solution. As for the 5% NaHCO3, a weak base, carbon dioxide gas was produces, thus the solution seemed oily with all the little bubbles in the liquid. However, the salt produced was still soluble in water.

Benzoic acid was a rather weak acid, therefore its reaction with NaOH was not so clear, causing a turbid liquid. When reacted with NaHCO3, the salt was not soluble in water; instead, it turned into white precipitate.

The oxalic acid was different from the common carboxylic acids as mentioned in 9.1. Therefore, the result was also negative, that was the salt produce was not soluble in water.

Equation: R-C-O-H + NaOH  R-C-O-Na+ + H2O