Orgo 1 Experiment 11 PDF

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Experiment 11: Synthesis of Biodiesel and Soap

23 June 2020 CHM2210L.007

Introduction: In organic chemistry a reaction that produces an ester is considered an esterification reaction. This type of reaction can be seen in the first step of glycolysis (2). Esterification reactions will often involve an alcohol and a Bronsted acid (2). In the event a R group of an ester is switched with a R group of an alcohol, it is referred to as transesterification. These two mechanisms differ, the alcohol is changed during transesterification. This process is used in the synthesis of biodiesel. A catalyst is typically involved during this process, either a strong acid or base along with heat. Transesterification is a completely reversible reaction (3). During the preparation of biodiesel vegetable oil acts as the ester and is also referred to as triglyceride. While the methanol acts as the alcohol. Biodiesel provides a green alternative to fossil fuels. Vegetable oil is a renewable resource unlike petroleum; therefore, it can be sustained for centuries. Biodiesel when used does not release any harmful chemicals into the atmosphere. When biodiesel is synthesized by vegetable oil glycerol is produced as a byproduct and can be used to feed livestock. When vegetable oil reacts with sodium hydroxide, soap and glycerol is produced, this process is known as saponification. Saponification and transesterification are very similar; however, saponification does not require the help of an acid or base catalyst (2). Both of these reactions depend on temperature and are considered second order reactions. These reactions are also unable to take place without the use of an external heat source, which means they are endothermic.

Figure 1: Transesterification

The reaction above displays transesterification, sodium methoxide is used as the catalyst. During the first step Na is disassociated, and the carbon double bond is attacked by the methoxy group. Once the double bond is broken electrons are then transferred to the oxygen. During the second step the ether group is pushed out by the double bond formed by the oxygen and carbon. The triglyceride then pronates and produces glycerol. In the even the equipment used is not completely dry, residual H2O can give rise to an unwanted side reaction. Figure 2: Possible side reactions of Triglyceride

Figure 3: Saponification

The reaction above displays saponification, this process can be used to make soap. Triglyceride reacts with H2O and sodium hydroxide; soap and glycerol are the products of this reaction. Figure 4: Possible side reaction of saponification

Experimental Section: -Part A: Synthesis of Biodiesel from Vegetable OilAdd 300 mg of potassium hydroxide and 8.5 mL of methanol to an Erlenmeyer flask. Then, cover the flask with parafilm and use a stir rod to mix until fully dissolved.

Use a separatory funnel to separate the mixture, allow to sit for 30min. Once the two layers are visible, the top layer should contain the biodiesel and the bottom layer should be glycerol.

Next, heat up 32 mL of vegetable oil to 60oC and add it to the flask mixture. Cover the flask once again and allow to stir for an hour at 60oC.

The 27/3 Methanol Test should then be performed to determine for certain the contents of the top layer. Pipette 3mL of the top layer to 27mL of methanol. If the solution is miscible then it is biodiesel.

Determine the mass of the biodiesel and calculate the percentage yield. -Part B: Saponification of Coconut OilAdd 50 g of coconut oil to a beaker with a stir bar. Place on a heating stir plate to 100oC, and allow for the oil to completely liquefy.

Allow the molten soap to cool in a watch glass. Then shape the soap to form a bar. Record the mass of the produced soap along with the smell.

Then, add 24mL of 30% w/w sodium hydroxide solution. Continue to heat and stir the mixture for 1 hour.

Table of Chemicals: Properties Molecular formula

Triglyceride C55H98O6

Sodium Hydroxide NaOH

Methanol CH3OH

305-307 °C 122-125 ℃

1388 °C 318 ℃

64.7 °C -97.6 ℃

Structural formula

Boiling point Melting point Molecular weight Density Flammability Appearance

872 g/mol

39.997 g/mol

32.04 g/mol

0.915 g/mL

2.13 g/mL

0.792 g/mL

Flammable Solid

Non-flammable White solid

Flammable Colorless liquid

Results: Mass of biodiesel prepared: 27.05 g Color and appearance of biodiesel: Yellowish homogeneous mixture Mass of soap prepared: 53.67 g Odor of soap prepared: Odorless -Percent Yield of Biodiesel-

32 mL vegetable oil x

0.93 g 1 mL

x

1mol 872 g

= 0.0341 mol vegetable oil

0.0341 mol vegetable oil x

0.102 mol biodiesel x

% yield =

( 3 mol fatty acid methylester ( biodiesel )) 1 mol vegetable oil

= 0.102 mol biodiesel

292.2 g ( molar mass of biodiesel ) = 29.92g biodiesel 1mol biodiesel

actual yield theoretical yield

=

27,05 g 29.92 g

x 100 = 90%

Discussion: During this experiment biodiesel was produced via transesterification, by utilizing vegetable oil and methanol. Potassium hydroxide acted as the catalyst. This reaction is considered a green one due to the environmental benefits of biodiesel. Unlike petrol, biodiesel does not release any harmful or unwanted chemicals into the atmosphere. It is also a renewable resource that can continue to be reused. The percent yield of biodiesel during this experiment was 90%, the experiment was a success. During the second part of the experiment soap was produced via saponification. The amount of soap produced, weighed 53.67 g. During saponification, the cleaning, hardness, and aroma are determined by the fatty acids. The soap produced in this experiment was odorless. This process provides a renewable and green nature to soap making. Some soaps are produced with harmful chemicals that may not pose risks to us directly, however, they affect the earth we live on Conclusion: The aim of this experiment was to use vegetable oil to produce biodiesel and soap, by utilizing transesterification and saponification. During the production of biodiesel, an alcohol and base catalyst are used along with vegetable oil. During the production of soap, sodium hydroxide and water as well as heat is used. A byproduct of this experiment is glycerol. The experiment was

concluded as a success due to the percent yield of biodiesel as well as the properties of the produced soap. This experiment provides a green alternative to two major everyday needs, like fuel and soap. Every day people are using soap for multiple different things, like washing their hands to washing their bodies. It is important to look for greener alternatives to every day needs in science. Biodiesel provides a cleaner and greener alternative to petrol. It can also be reused and is a renewable resource. Petrol is a major contributor to global warming, while the use of biodiesel is not. In countries around the world, including the United States, biodiesel is mixed in with gasoline in an attempt to reduce the ecological footprint left by us and our ancestors (1).

References (1) “Biofuels: The Benefits and Drawbacks.” Biofuel Facts and Information | National Geographic, 27 Feb. 2017. (2) “Illustrated Glossary of Organic Chemistry.” Illustrated Glossary of Organic Chemistry -

Esterification, www.chem.ucla.edu/~harding/IGOC/E/esterification.html. (3) Weldegirma S. Laboratory Manual: CHM2210L and CHM2211L Fall 2019, Spring 2020, and Summer 2020; Pro-Copy: E. Fowler Ave. Tampa FL, 2019...