Synthesis of benzoic acid (Oxidation of toluene)

Summary

In this captivating video from Random Experiments Int., viewers are guided through the chemical synthesis of benzoic acid via the oxidation of toluene, utilizing potassium permanganate as the oxidizing agent. The process, detailed by the video narrator, involves setting up a complex reaction apparatus with safety precautions due to the hazardous nature of the chemicals involved. The video provides a thorough walkthrough of the experiment procedure, highlighting crucial steps such as the azeotropic behavior of toluene, its interaction with potassium permanganate, and the challenges faced during the synthesis, like bumping and ensuring complete reaction. By the end, the experiment successfully yields a significant amount of crystal-clear benzoic acid.

Highlights

• Toluene is flammable and toxic. Caution is advised! ⚠️
• Experiment setup involves a magnetic stirrer, hot plate, and oil bath. 🛠️
• Potassium permanganate solution acts as the oxidizer in this reaction. 🔄
• Watch out for azeotropic behavior of toluene, relevant for water removal. 💧
• Post-reaction cooling helps in crystallizing the benzoic acid effectively. ❄️

Key Takeaways

• Safety first! Handle toluene and potassium permanganate with care as they can be hazardous to health. 🧪
• An oil bath and magnetic stirrer setup ensures even heating throughout the experiment. 🔥
• Azeotropes play a key role in separating toluene and water during the reaction. 🌡️
• After synthesis, cool the mixture in a freezer for improved crystallization. ❄️
• Achieved a 71% yield of benzoic acid, demonstrating efficient conversion without a phase transfer catalyst. 🚀

Overview

The video kicks off with a word of caution regarding the chemical hazards of toluene and potassium permanganate. We are introduced to a sophisticated setup involving a magnetic stirrer, oil bath, and a series of glassware crucial for conducting the oxidation reaction safely. The narrator clearly explains each step, ensuring that viewers are aware of the precautions needed to handle the toxic and flammable substances involved.

Following the initial setup, we dive into the chemical journey of synthesizing benzoic acid. The reaction involves a precise addition of potassium permanganate to the toluene under controlled conditions. This section of the video fascinatingly showcases the detailed chemical interactions and the importance of maintaining the right temperature to promote the completion of the reaction and separation of products.

As the experiment reaches its culmination, we see the process of cooling and crystallization of benzoic acid. The video thoughtfully illustrates how minor tweaks, such as cooling the solution in a freezer, can largely impact the yield and purity of the final product. The synthesis concludes with an impressive 71% yield, underscoring the efficiency of the process without the need for a phase transfer catalyst.

Chapters

• 00:00 - 01:00: Safety Precautions and Setup In the chapter titled 'Safety Precautions and Setup,' the synthesis of benzoic acid is discussed, emphasizing the importance of safety. It highlights that toluene is flammable, can be fatal if swallowed, and poses risks to respiratory health, organs, and skin. Potassium permanganate is noted as an oxidizing agent that is toxic if ingested and can cause severe chemical burns and eye damage. Potassium hydroxide is identified as corrosive, and benzoic acid itself is capable of causing skin irritation and severe eye damage.
• 01:00 - 02:30: Initial Ingredients and Heating This chapter covers the initial setup and ingredients required for an experiment involving magnetic stirring and heating. It details the equipment used, including a magnetic stirrer with a hot plate, an oil bath, a three-neck round-bottom flask, a stirring bar, a thermometer, a pressure equalizing dropping funnel, and a Dimroth condenser. It emphasizes safety and disclaims responsibility for any damage caused by recreating the experiment.
• 02:30 - 04:30: Permanganate Solution Preparation The chapter titled 'Permanganate Solution Preparation' describes the initial steps in preparing a solution. It begins with the addition of five milliliters of a 20% potassium hydroxide (KOH) solution to a flask. This is followed by the addition of 45 milliliters of distilled water. After these steps, 5.1 grams of toluene are introduced into the mixture.
• 04:30 - 06:30: Addition and Reaction Process The chapter titled 'Addition and Reaction Process' explains a chemical procedure involving heating a flask to 85°C and dissolving 17.5 grams of potassium permanganate in a solution.
• 06:30 - 08:00: Reaction Monitoring and Ethanol Addition This chapter discusses the process of reaction monitoring and the addition of ethanol in a chemical synthesis. It starts by heating distilled water to 70 degrees Celsius. The use of toluene and water to form an azeotrope that boils at 85 degrees Celsius is introduced. This azeotrope is utilized to remove water from a reaction mixture, which is a common step in many syntheses. Once both solutions (distilled water and permanganate) reach the desired temperatures, monitoring and further synthesis steps are implied.
• 08:00 - 10:00: Filtration and Washing The chapter discusses a laboratory process involving the filtration and washing of substances. A particular focus is given to the handling of the stopcock which, despite not sealing properly, did not pose a problem for the procedure. The solution was added drop-wise to the boiling mixture over the course of 15 minutes.
• 10:00 - 13:00: Final Processing and Filtration The chapter discusses the final processing and filtration involving chemical reactions where toluene is oxidized by permanganate to form benzoic acid. This acid undergoes deprotonation in a basic solution to create a water-soluble salt. Additionally, the reduction of permanganate leads to the formation of manganese dioxide. The chapter also touches on using the azeotrope's cooling and separation into toluene and water as a method to detect significant amounts remaining.
• 13:00 - 15:00: Final Yield and Conclusion The chapter titled 'Final Yield and Conclusion' discusses the process of adding a substance to toluene and the subsequent reaction required to achieve the final yield. The procedure involves boiling the mixture under reflux for an hour and a half. However, an unexpected situation arises when the mixture starts to bump immediately after the addition of the substance. This forces the removal of the flask from the oil bath to prevent further issues. The narrator likens this situation to a familiar one discussed in previous content, particularly in a video about alt tags, highlighting the challenges in managing reactions that don't proceed as expected.

Synthesis of benzoic acid (Oxidation of toluene) Transcription

• 00:00 - 00:30 the synthesis of benzoic acid atención toluene is flammable and can cause death when it's swallowed by enters the respiratory tract it can cause damage of the organs dizziness of rosiness and irritation of the skin potassium permanganate is an oxidizing agent and toxic of swallowed it can cause severe chemical burns on the skin and eyes and is toxic to aquatic life with non lasting effects potassium hydroxide is corrosive benzoic acid can cause irritation of the skin severe damage of the eyes and damage of
• 00:30 - 01:00 the organs are repeated along exposure I don't take any responsibility for damage done to persons or property caused by the recreation of this experiment the set up is a magnetic stirrer with a hot plate and an oil bath in the oil bath for three Necron bottom flask is placed with a stirring bar on top is a thermometer a pressure equalizing grouping funnel and a dimmer off condenser
• 01:00 - 01:30 at first five milliliters of 20% potassium hydroxide solution were added to the flask then 45 milliliters of distilled water were added and 5.1 grams of toluene
• 01:30 - 02:00 that makes John the flask was then heated to 85 degrees C [Music] in the meantime 17.5 grams of potassium permanganate were dissolved a 150
• 02:00 - 02:30 milliliters of distilled water and heated up to 70 degrees C toluene and water do form an azeotrope which boils at 85 degrees C which is also used to remove water from the reaction mixture and some synthesis when both solutions had reached the temperature the permanganate solution
• 02:30 - 03:00 was added to the dripping follow it could be seen that the stopcock was not sealing properly but this was not a problem then the solution was edit drop-wise to the boiling mixture within 15 minutes
• 03:00 - 03:30 the following reaction takes place the toluene is oxidized by the permanganate to form benzoic acid which is then deprotonated in the basic solution a water soluble salt of the acid is formed the permanganate is reduced and manganese dioxide is formed when the azeotrope cools it separates into toluene and water again this can be used to see if there are still large amounts
• 03:30 - 04:00 of toluene present after the addition it should be boiled under reflux for 1.5 hours but immediately after the addition the mixture began to bump and the flask was removed from the oil bath those who have seen my video about the alt tags know what this situation reminds me of due to the bumping staying at a constant
• 04:00 - 04:30 rate the flask was added back to the oil bath after a short while after 1.5 hours that could be seen that the condensate did contain significant amounts of toluene to check if commanded was also still present the flask was removed from the oil bath the manganese dioxide settled at the bottom and it could be seen that permanganate was still present so it was heated for another hour after
• 04:30 - 05:00 20 minutes it could already be seen that the condensate contained way less toluene in the progress of the reaction the temperature of the mixture had risen to almost 100 degrees C which is also an indicator that most of the toluene had reacted at the end some ethanol was added and the mixture was stirred again to reduce the residual permanganate then it was left to sit until it reached 50 degrees C in the mean time 70
• 05:00 - 05:30 milliliters of distilled water were heated to 70 degrees C after cooling down the manganese dioxide had settled at the bottom then it was filtered off and residues were washed out of the flask with a bit of water the smell of toluene was still present
• 05:30 - 06:00 usually some manganese dioxide passes through the filter which is why the filtrate had a slightly brownish color next they was washed two times with ten milliliters of distilled water which were taken from the 17 millilitres this should wash out residues of the benzoic acid salt [Music] after that the manganese dioxide was
• 06:00 - 06:30 added to the residual 50 milliliters of the distilled water the mixture was then left to sit for 10 minutes at 70 degrees C this helps to remove last traces of product the manganese dioxide was filtered off again and the second filtrate was added directly to the first one while morph the dioxide did passed through the filter to the filtrate a small amount of sodium metabisulfite was added sodium sulphite could also be used
• 06:30 - 07:00 this is able to reduce the manganese dioxide and soluble manganese 2 salts are formed which happens when the solution is acidified to get the benzoic acid out of the solution and reduce the manganese dioxide 45 milliliters of one more loss of uric acid were added this protonates the benzoic acid which is wholly soluble in this form and precipitate the acid was added in
• 07:00 - 07:30 portions so the manganese dioxide was reduced before the benzoic acid did precipitate otherwise inclusions might be present in the product the pH was tested to make sure the solution was acidic if it had not been more acid should have been added then the mixture was cooled in the freezer to 6 degrees C and the benzoic acid was filtered off
• 07:30 - 08:00 the benzoic acid was washed with water and sucked dry for a few minutes then it could be removed from the filter quite easily 5.21 grams of raw product were obtained which was not right completely because it had to be recrystallized water is recommended for the recrystallization but it has to be taken care that a dozen boiled benzoic acid is
• 08:00 - 08:30 steam volatile when it cooled down could be seen that it's good that the beak is covered above the solution small crystals could be observed which would otherwise spread around the beaker benzoic acid forms colorless needle
• 08:30 - 09:00 shaped crystals as it can be seen here then the mixture was cooled in the freezer to 3 degrees C after that it was filtered again
• 09:00 - 09:30 the product was washed with water and sucked dry for 10 minutes after drying it on air four point eight one grams of benzoic acid were obtained which corresponds to a yield of 71% this synthesis was done out of curiosity because usually when a reaction with two phases is done a phase transfer catalyst is added this speeds up the reaction now makes it possible at all but obviously it wasn't needed
• 09:30 - 10:00 this was the synthesis of benzoic acid I hope you enjoyed please rate and comment if you want to see more synthesis you can watch my playlist about it here or you can watch my latest video here you