Manuale di laboratorio JoVE

Hydrolysis of an Ester

Hydrolysis of an Ester

CONCETTI

PREPARAZIONE ISTRUTTORI

Student Protocol

Lab Manual
Chimica

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Lab Manual Chimica

Hydrolysis of an Ester

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Learning Objectives

What is a triglyceride?

A triglyceride is a molecule possessing three fatty acid molecules connected to a glycerol molecule through ester bonds.

What is the difference between a saturated fatty acid and an unsaturated fatty acid?

A saturated fatty acid has only single bonds in the carbon chain, whereas unsaturated fatty acids possess one or more double bonds in the carbon chain. The presence of double bonds affects the structure of the fatty acid.

What occurs during a hydrolysis reaction?

In a hydrolysis reaction, water acts as a nucleophile to break a bond. In the case of an ester, the water molecule attacks the carbonyl carbon. One fragment of the ester gains the hydrogen ion from water to form an alcohol, and the other fragment gains the hydroxide group to form a carboxylate salt.

Why is a strong base usually added to a hydrolysis reaction?

Very few hydrolysis reactions occur spontaneously under normal conditions; thus, a strong base is added to act as a catalyst to speed up the reaction.

How do soap molecules behave in water?

A soap molecule has a long hydrophobic carbon chain with a hydrophilic carboxylate anion at one end. Due to the differing solubility properties of the molecule, soap molecules cluster together to form micelles. The hydrophobic tails of the soap are at the center of the micelle, and the hydrophilic heads are oriented outwards and in contact with water.

List of Materials

Stirring hotplate

5
Stir bar

5
Package of pH paper

5
pH meter

5
250-mL wash bottle filled with DI water

5
50-mL volumetric flask

10
100-mL graduated cylinder

10
50-mL graduated cylinder

30
50-mL glass beaker

5
400-mL glass beaker

10
10-mL graduated cylinder

5
10-mL glass vials

10
Labeling tape

5 rolls
Glass stirring rod

5
Small spoon/scoopula

5
Spatula

5
Silicone soap mold

5
Small rubber stopper (3 cm)

5
Commercial liquid soap (at least 1 bottle)

1
Solid coconut oil

750 g
Sodium hydroxide

200 g
Calcium chloride

150 g
3 M Hydrochloric acid

1 L
Powder soap dye (variety of colors)

5
Fragrance oil (5 different kinds)

5
Deionized water

3 L
1-L volumetric flask

2
1-L glass bottle with cap

2
Glass funnel

2
Large stir bar

2
Top-loading balance (at least 1)

-1
Analytical balance (at least 1)

-1 Dependent on lab size
Lab wipes

-1 Dependent on lab size
Weighing boats

-1 Dependent on lab size

Lab Prep

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

Preparation of Laboratory

Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

Before you get started, put on a lab coat, safety glasses, and nitrile gloves. Ensure that the lab is equipped with enough lab coats, splash goggles, and gloves for all of the students.
Prepare 1 L of 3 M NaOH. Measure 120 g of NaOH pellets, and transfer the pellets to a 1-L volumetric flask. Add deionized water to the 1-L line. Place a stir bar in the flask and mix the solution until the pellets are fully dissolved.
Once the solution is homogeneous, transfer the solution to a glass bottle, cap it, and label it. Place the bottle in a central hood so that students have access to it.
Prepare 1 L of 1 M CaCl₂ solution. Weigh 110.98 g of CaCl₂, and transfer it to a 1-L volumetric flask. Fill the flask to the marked line with deionized water, add a stir bar, and mix the solution on a stir plate until the CaCl₂ is fully dissolved.
Once the solution is homogeneous, transfer it to a clean glass bottle, cap it, and label it. Store the solution in a central hood.
Prepare at least 1 L of 3 M HCl, which will be used to neutralize any excess sodium hydroxide at the end of the experiment.
Obtain 5 silicone soap molds and leave them in a common area. Obtain at least five different fragrance oils and five powder soap dyes in a variety of colors, and set them near the molds.
Place a container of commercial liquid soap in a common area. Set coconut oil next to the balance making sure there are clean spatulas and weighing boats.

Set out the following glassware and equipment at each student lab station (we suggest that students work in pairs):

1 Stir bar

1 Hotplate

1 Package of pH paper

1 pH meter

1 250-mL plastic squeeze bottle of DI water

2 50-mL volumetric flasks

2 100-mL glass graduated cylinders

6 50-mL glass graduated cylinders

1 50-mL beaker

2 400-mL beaker

2 Glass vials

1 Glass stirring rod

1 Small spoon

1 Small spatula

Tags

JoVE Lab Chem Lab: 59 Prep