# Upcycling Waste Polycarbonate into N,N'-Diphenylethylurea: A Hands-On Experiment for Undergraduate Chemistry Laboratories

S. Chowdhary, N. Kumar, Natacha Henry, Pascal Roussel, K. Demertzis, S.

Singh, V. Kumar

► To cite this version:

S. Chowdhary, N. Kumar, Natacha Henry, Pascal Roussel, K. Demertzis, et al., Upcycling Waste Polycarbonate into N,N'-Diphenylethylurea: A Hands-On Experiment for Undergraduate Chemistry Laboratories. Journal of Chemical Education, 2025, J. Chem. Educ., 102 (5), pp.1737-1744. 10.1021/acs.jchemed.4c01130. [https://doi.org/10.1021/acs.jchemed.4c01130](https://doi.org/10.1021/acs.jchemed.4c01130)

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# Upcycling Waste Polycarbonate into N,N'-Diphenylethylurea: A Hands-On Experiment for Undergraduate Chemistry Laboratories

Shefali Chowdhary, Nitish Kumar, Natacha Henry, Pascal Roussel, Konstantinos Demertzis, Sukhdeep Singh,* and Vipan Kumar*

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Cite This: *J. Chem. Educ.* 2025, 102, 1737–1744

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Supporting Information

**ABSTRACT:** The urgent challenge of climate change drives the need for sustainable and environmentally friendly practices, such as recycling, upcycling, and sustainable chemistry. Despite their importance, these practices are rarely integrated into undergraduate chemistry laboratories. Here, we describe a hands-on approach suitable for a second-semester organic chemistry lab that incorporates waste management principles, guiding students to recognize the value of repurposing chemical waste. The precursors for this experiment are discarded CDs and DVDs, which are readily available in most households. This not only helps reduce waste but also demonstrates how everyday materials can be transformed into high-value chemicals (HVCs). In this lab,

students extract a carbonyl group from old CDs and DVDs, using a process called “carbonyl harvesting,” to show how waste can be turned into valuable materials. The recycled bisphenol A (BPA) is monitored using thin layer chromatography (TLC) and collected separately, while the N,N'-diphenylethylurea is purified by simple filtration and characterized using ¹H, ¹³C NMR, IR, XRD, and melting point analysis. This approach not only reinforces fundamental organic lab techniques but also provides hands-on training in sustainability lab practices, showing students how to integrate waste management, resource recovery, and sustainability into their experimental work. Its versatility allows it to be integrated into chemical engineering, general chemistry, and biotechnology curricula. It serves as a valuable learning tool by demonstrating sustainable process design, functional group preservation, and selective chemical transformations.

**KEYWORDS:** Hands-On Learning, Laboratory Instruction, Organic Synthesis, Plastic Recycling, Sustainable Chemistry, Undergraduate Experiment

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## INTRODUCTION

In today's world, where people are more aware of environmental issues, there's a growing need to reduce plastic waste and use eco-friendly methods.¹⁻³ At the same time, the pursuit of sustainable methodologies in chemical synthesis has emerged as a pressing priority, driven by the imperative to reduce carbon footprints and promote circular economies.⁴⁻⁶ One promising innovation lies in the conversion of waste plastic into high-value chemicals (HVCs), a concept gaining significant attention in the field of sustainable chemistry.⁷ This aligns with the broader global agenda outlined in the 2030 Agenda for Sustainable Development, adopted by all of the UN Member States in 2015. The 17 Sustainable Development Goals (SDGs) at the heart of this agenda call for urgent action across various sectors, including environmental protection, climate change mitigation, and sustainable economic growth.⁸ Significant progress has been made in health, education, economic growth, and gender equality.⁹ Teaching sustainable practices to students, the leaders of tomorrow, can accelerate this progress. With the intensification of climate change and

disaster risks, educating students on sustainable technologies is key to preparing them for global challenges. Strengthened global partnerships and funding emphasize the importance of equipping future generations with the skills to advance these efforts.

This laboratory promotes sustainability by incorporating waste management and resource recovery into the chemistry curriculum. By repurposing discarded plastic to extract valuable chemicals, it aligns with Green Chemistry Principle 1: waste prevention. Rather than relying on traditional methods that generate waste, this experiment demonstrates how everyday materials can be upcycled into HVCs, reducing environmental impact and promoting a circular economy.

Received: September 14, 2024

Revised: April 7, 2025

Accepted: April 18, 2025

Published: April 28, 2025

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Students also gain hands-on experience in sustainable lab techniques, helping them develop responsible chemical practices. As climate change and environmental risks grow, teaching practical sustainability skills prepares students to address global challenges. By combining waste management with Green Chemistry, this approach not only tackles environmental issues but also encourages innovation in sustainable solutions.

Urea derivatives, considered high-value chemicals due to their versatile functional groups, play a pivotal role in various sectors such as agriculture and medicinal chemistry.¹⁰ Traditionally, these compounds have been synthesized by using hazardous reagents such as phosgene. However, as environmental concerns grow and the demand for cleaner synthetic methods rises, several alternative approaches have emerged to replace these toxic reagents.¹¹,¹² Despite this progress, many of these alternatives still depend on expensive metal catalysts such as gold, rhodium, or ruthenium, which increase production costs (Figure 1). Furthermore, many

methods require high temperatures, up to 150 °C, and must maintain specific pressure conditions, which complicates the reaction setup. Some processes also involve carbon oxides, like carbon dioxide or carbon monoxide, which necessitate specialized equipment for safe handling. While these alternative methods offer some advantages, the reliance on costly catalysts, high temperatures, and complex reaction conditions remains a significant barrier to their broader adoption.¹³⁻¹⁵

Urea derivatives exhibit a remarkable spectrum of biological activities, making them invaluable assets in pharmaceutical research and development. These derivatives boast anti-HIV, antibacterial, antiviral, analgesic, HDL elevating,¹⁶ and anti-Alzheimer properties.¹⁷ Of particular interest to researchers are urea containing alkylaromatic moieties, as they often showcase potent anticancer activity.¹⁸ Recently, a report highlighted the therapeutic potential of incorporating phenethylamine into urea-based derivatives.¹⁹ These compounds have shown promise as cardiac myosin activators, offering innovative avenues for treating systolic heart failure-a significant cardiovascular condition with limited treatment options.²⁰ Another study revealed that symmetrical urea compounds, such as N,N'-diphenethylurea, containing the phenethylamine ring, possess the ability to promote adipocyte differentiation, a process crucial in understanding and addressing metabolic disorders such as obesity,²¹ and has been reported to have an antidepressant effect.²²

<figure><img src="image_9.png" /><figcaption>**Figure 1.** Traditional synthesis routes for urea derivatives, involving hazardous reagents such as isocyanates and triphosgene with amines, often require high temperatures and costly catalysts.</figcaption></figure>

The study employs the “carbonyl harvesting” method to transform polycarbonate (PC) waste into N,N'-diphenethylurea. PC is a durable plastic used in products like CDs, automotive optical parts, and electronics due to its optical clarity, impact resistance, excellent thermoformability and stability in various environmental conditions.²³ Its production has steadily grown over the years. However, despite its broad applications, most PC waste has been discarded in landfills or incinerated. While some PC is mechanically recycled, the material often degrades in quality and ultimately goes to waste.²⁴

PC recycling occurs through three primary methods: mechanical recycling, chemical recycling, and thermochemical recycling. Mechanical recycling degrades PC's quality, reducing properties like impact resistance. Blending recycled PC with other materials can improve its durability, but it does not fully restore the original quality.²⁵ Chemical recycling, which can break PC down into high-quality monomers, faces challenges due to complex separation processes and the use of toxic organic solvents, posing environmental and safety risks. This method has seen limited exploration, mostly with organocatalysts. Examples include TBD- and DBU-catalyzed methanalysis as reported by Do et al.²⁶ and Quaranta et al.²⁷

This study falls under chemical recycling as it introduces a method for transforming PC waste into valuable compounds by reacting it with phenylethylamine without using any catalyst. Unlike mechanical recycling, which only reprocesses the material, or thermochemical recycling, which typically involves high-temperature decomposition, this method chemically breaks down polycarbonate into useful organic scaffolds. This straightforward, eco-friendly approach effectively upcycles PC, promoting a circular plastics economy, reducing waste, and lowering environmental impact. Through this innovative process, students gain hands-on experience in green chemistry and circular economy principles. Integrating this method into laboratory courses offers benefits such as improved lab safety, reduced hazardous waste, and optimized facility costs. These concepts not only provide a tangible link between classroom learning and real-world applications but also serve as inspiring examples of how academia can drive positive environmental and societal change.

Additionally, the study explores a sustainable approach to synthesizing a urea derivative using waste PCs. This method addresses the pressing issue of plastic waste accumulation by repurposing discarded CDs. This method demonstrates the potential of circular economy principles in HVC manufacturing.

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## BACKGROUND AND GOALS

Using waste PC from discarded CDs and DVDs as a starting material, this laboratory experiment provides students with hands-on experience in synthesizing key organic scaffolds by using sustainable methods. CDs and DVDs are inexpensive, widely available, and often discarded in large quantities, making them ideal feedstock for recycling. By transforming these discarded plastic materials into valuable compounds, the exercise highlights the environmental challenges posed by plastic waste and connects these issues to broader pollution and sustainability concerns. This aligns with SDG 12: Responsible Consumption and Production, by promoting waste prevention, resource recovery, and plastic upcycling, and SDG 13: Climate Action, by equipping students with skills to mitigate climate change and reduce environmental impact.
**Extracted from biological species**

Extracted from
Streptomyces bacteria
and Marine organism

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<figure><img src="image_13.png" /><figcaption>N,N'-diphenethylurea</figcaption></figure>

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**Traditional synthetic preparation**

Use of
phosgene

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Use of CDI or
metal catalysts
at high
temperature

<figure><img src="image_16.png" /></figure>

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**This work**

Catalyst free
reaction

Easy isolation
of product

Promotes
sustainability

Upcycling
plastic waste

<figure><img src="image_18.png" /><figcaption>**Figure 2.** Comparison of N,N'-diphenethylurea extraction from biological species, traditional synthetic preparation, and the approach demonstrated in this work.</figcaption></figure>

The experiment introduces students to microwave-mediated
reactions, highlighting their role in improving the reaction
efficiency, sustainability, and safety in organic synthesis.
Microwave-assisted synthesis, which heats the reaction mixture
directly, offers rapid heating, shorter reaction times, and higher
yields compared to conventional methods minimizing energy
use and waste.<sup>28-30</sup>

In this lab, students use microwave heating to synthesize N,N'-diphenethylurea from waste polycarbonate, demonstrat- ing the upcycling of waste into valuable products. They will also investigate how adjustments to reaction conditions influence the overall sustainability of the process, fostering an understanding of the broader effects of these modifications on environmental and economic outcomes. Additionally, students will develop skills in the purification and isolation of organic compounds. By utilizing discarded materials, this approach significantly lowers production costs compared to commercial sources, highlighting both its financial and environmental benefits.<sup>31</sup>

This approach tackles the environmental problems caused
by plastic waste, connecting polymer studies to real-world
pollution issues and waste reduction. The primary goals of this
experiment are to

* Demonstrate hands-on recycling by transforming waste PC into valuable chemical products.

* Practice waste management and resource recovery techniques by transforming discarded materials into valuable products, highlighting the practical benefits of upcycling and sustainable resource utilization.

* Explore energy-efficient conversion through microwave-assisted reactions.

* Review common techniques in synthesizing, purifying, and characterizing organic compounds, reinforcing previously taught methods.

Student assessment will be based on laboratory reports,
instructor observations of lab skill development, postlab
questions focused on spectral analysis and reaction mecha-
nisms, and exam questions (see Supporting Information).

■ EXPERIMENTAL OVERVIEW

N,N'-Diphenethylurea can be acquired *via* distinct pathways (Figure 2). The first pathway involves extraction from natural sources, including *Streptomyces* sp. No. Am-2498<sup>22</sup> and marine ascidians *Didemnum ternatanum*,<sup>32</sup> such as the Okinawan ascidian *Didemnum mole* sp.<sup>21</sup> This method harnesses the biosynthetic pathways of these organisms that produce N,N'-diphenethylurea. Conversely, there are various synthetic routes in the laboratory that allow for controlled production of N,N'-diphenethylurea. These methods involve the use of 1,1-carbonyldiimidazole (CDI), phosgene and catalysts like 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and Pd(OAc)<sub>2</sub>.<sup>11,33,34</sup> These can result in carcinogenic byproducts and difficulty in the isolation of the desired product. In contrast, this work introduces an innovative, cost-effective method that mitigates these drawbacks, emphasizing an efficient pathway for N,N'-diphenethylurea synthesis. The method theoretically achieves 100% incorporation of reactant atoms into valuable products, as reflected in the atom economy calculation, thereby maximizing both sustainability and resource efficiency. Detailed calculations are provided in the *Supporting Information*.

Reaction Conditions for Urea Synthesis

The initial optimization for carbonyl harvesting explored various solvents and heating methods to maximize efficiency and yield, ultimately favoring microwave heating for its shorter reaction times and higher yields, as shown in Table S1. After the reaction, N,N'-diphenethylurea was isolated by cooling and filtration, while the byproduct Bisphenol A was extracted from the filtrate using water with purity confirmed by TLC and melting point analysis. This detailed optimization and procedural data are provided in the Supporting Information.

■ HAZARDS

All experiments are to be conducted in an efficient fume hood,
with students wearing safety goggles, gloves, and appropriate
protective clothing. Proper disposal of all chemicals in
designated waste containers is essential. Methanol, ethanol,
and 2-propanol (IPA) are flammable and harmful if inhaled,
<figure><img src="image_19.png" /><figcaption>Figure 3. Procedure for PC extraction from compact discs and reaction follow up.</figcaption></figure>

<figure><img src="image_20.png" /><figcaption>Figure 4. Representative parts of (A) FTIR spectrum; (B) ¹H NMR spectrum of N,N'-diphenethylurea; (C) crystal packed structure; and (D) structure with the atomic labeling confirmed using single crystal XRD analysis.</figcaption></figure>

causing eye irritation. Acetonitrile is flammable and harmful if swallowed, in contact with skin, or inhaled and can also cause

eye irritation. Phenylethylamine is a skin irritant.³⁵ Microwave vessels must be capped and sealed according to the reactor
instructions. Importantly, there are no known hazards associated with N,N'-diphenethylurea, ensuring the safety of handling this compound under standard laboratory conditions.³⁶

## Toxicity and Hazards Related to Bisphenol A

BPA, which is often coextracted in this process, poses health risks and should be handled with strict safety protocols. Direct skin contact and inhalation must be avoided, and appropriate protective equipment, such as gloves, lab coats, and eye protection, should be worn when working with BPA.³⁷ Handle BPA in a well-ventilated area, such as a fume hood, to minimize inhalation risks. Use only the amount of BPA needed for the procedure to limit the potential exposure. In the case of a spill, contain it immediately using suitable absorbent materials and dispose of it as hazardous waste, keeping contaminated items separate to avoid harming the environment.

## ■ RESULTS AND DISCUSSION

### PC Extraction

The detailed protocol for PC extraction, along with an interactive student handout with details about the experiment, is provided in the Supporting Information (SI).

The process for extracting PC from discarded compact discs is carried out in multiple steps, as illustrated in Figure 3. First, the CD is broken into 2–3 pieces and subjected to ultrasonication for 40 min. This step helps to loosen the upper thin layer, which is then peeled off, and CD pieces are washed with ethanol. After this, the CD pieces are washed again with acetone, and the surface is then scratched to facilitate further processing.

Next, the CD pieces are ground into a fine powder using a pestle and mortar. This powdered PC can be directly used as a starting material for further chemical reactions. This protocol not only emphasizes the practical aspects of polymer recycling but also reinforces the principles of green chemistry and waste reduction by repurposing discarded materials for educational and research purposes.

### Spectral Analysis

To confirm the structure of synthesized urea, FTIR was performed (Figure 4A). The spectrum showed an absorption band at 3334 cm⁻¹, indicating N–H stretching vibrations. Peaks observed at 3027 cm⁻¹ and 2880 cm⁻¹ correspond to aromatic and aliphatic C–H stretching, respectively. The C=O stretching band appeared at 1609 cm⁻¹. The absorption peak at 1570 cm⁻¹ was attributed to aromatic C=C stretching vibrations. The peak corresponding to C–N stretching appeared at 1474 cm⁻¹.

The synthesized urea was characterized by using the ¹H NMR spectrum. The analysis of the ¹H NMR spectrum allows the consolidation of concepts such as chemical shifts and multiplicity. For example, in the ¹H NMR spectrum of N,N'-diphenethylurea (Figure 4B), it is possible to identify the presence of signals corresponding to alkyl protons appearing at 2.76 and 3.37 ppm as a (t) and b (dd), respectively. The signal corresponding to –NH protons appeared at 4.38 ppm as a triplet. The structure of the product obtained was also confirmed by using single crystal XRD (Figure 4 C,D).

### Laboratory Implementation

This laboratory experiment provides an introduction to sustainable chemistry and plastic upcycling. The experiment

is suitable for any undergraduate or postgraduate curriculum and can be easily conducted over a one laboratory period. Every student can perform the experiment individually or in a group of two or three.

Using the experimental handouts, we successfully performed this lab experiment of our second semester undergraduate organic chemistry laboratory course with students working in pairs (10 total student groups, 30 students total).

Students began by extracting PC from discarded CDs, following the detailed instructions provided in the handouts. Once the extraction of PC was successfully completed, the subsequent reaction step was conducted in sealed glass vials using a microwave synthesizer at 80 °C for 10 min (Scheme 1). Acetonitrile was chosen as the solvent due to its ability to yield the highest product amounts (as shown in Table S1).

<figure><img src="image_21.png" /><figcaption>Scheme 1. Optimized Reaction Condition for the Synthesis of N,N'-Diphenethylurea</figcaption></figure>

The microwave-assisted reaction allowed students to synthesize N,N'-diphenethylurea in yields ranging from 44% to 78%. The students typically isolated the final product as white, shiny, flaky solids. After purification, the purity of synthesized N,N'-diphenethylurea was confirmed through melting point analysis.

In addition to synthesizing N,N'-diphenethylurea, students also extracted BPA from the residual filtrate. Given the low solubility of BPA in water, it was extracted by adding water to the filtrate. The collected BPA was then checked for its purity by using TLC and melting point analysis. The extraction of BPA was incorporated into the students' assessments, along with the synthesis of N,N'-diphenethylurea.

The entire process can be effectively completed within a 3 h lab session, with the time distribution outlined in Table S3 (see Supporting Information).

### Student Outcomes or Student Assessment

We asked students to provide feedback on their experiences with the experiment. This experiment provided them with hands-on experience in green chemistry and sustainable practices. They learned not only about efficient microwave-assisted synthesis but also about the recycling and purification of valuable chemicals from waste materials. By focusing on synthesizing N,N'-diphenethylurea and extracting BPA, the experiment highlighted the importance of sustainability and waste management in chemical processes.

Engaging in these activities provided students with a deeper understanding of sustainable chemistry principles, equipping them for future challenges in the field. The experiment effectively combined theory and practice, reinforcing concepts of green chemistry, waste recycling, and sustainable practices. Hands-on experience improved their understanding, while working with microwave-assisted synthesis introduced them to
<figure><img src="image_22.png" /><figcaption>**Figure 5.** Student feedback on the experiment highlighting their engagement, understanding of sustainable chemistry, appreciation for recycling practices, fascination with the microwave reactor, and ease of following instructions.</figcaption></figure>

modern, eco-friendly methods. For future opportunities, this
process can be adapted to synthesize a wider range of high-
value chemicals (HVCs). Additionally, various plastic sources
could be explored for upcycling, further expanding the
sustainability impact of the experiment.

Survey results indicated that 25 out of 30 students found the experiment engaging and enjoyable, 23 out of 30 were fascinated by the microwave reactor, and 22 out of 30 felt it improved their understanding of sustainable chemistry (Figure 5). Additionally, 20 out of 30 students acknowledged the value of recycling and waste management in chemistry, and 24 out of 30 students found the instructions easy to follow. These findings emphasize the experiment's success in enhancing learning outcomes and aligning with sustainability goals.

The lab reports included assessment tasks that evaluated the
synthesized molecule using TLC, melting point analysis, and
IR spectral analysis (Supporting Information). These tasks
reinforced students' understanding of experimental techniques
and their ability to apply theoretical knowledge to practical
laboratory situations.

■ CONCLUSION

The pressing challenge of climate change highlights the
importance of adopting sustainable practices, such as recycling,
upcycling, and resource recovery, in education. However, such
concepts are often missing from undergraduate chemistry
laboratories. To address this, we developed a 3 h module for
chemistry laboratory course that integrates principles of green
chemistry and waste management. The use of inexpensive,
nontoxic starting materials not only reduces costs but also
highlights the importance of transforming waste into useful
resources. Students found the experiment fun, engaging, and
educational, gaining insight into sustainability practices and
innovative techniques such as microwave-assisted reactions.
The activity achieved significant financial impact, reducing
costs by 99% compared to commercial sources.³¹ This
experiment effectively engaged students in meaningful
scientific work with significant environmental and financial
impact. By combining fundamental laboratory techniques with
sustainability principles, this experiment not only educates

students on the environmental and economic benefits of
sustainable chemistry but also engages them in meaningful
scientific work. Its versatility allows its integration into the
curricula of chemical engineering, general chemistry, and
biotechnology courses, making it a valuable tool for fostering a
sustainable mindset in future scientists.

■ ASSOCIATED CONTENT

SI Supporting Information

The Supporting Information is available at https://pubs.ac-
s.org/doi/10.1021/acs.jchemed.4c01130.

Detailed experimental procedures (PDF, DOCX)

Student's manual (PDF, DOCX)

Teacher's manual (PDF, DOCX)

Accession Codes

Crystallographic data for this study have been deposited with the Cambridge Crystallographic Data Centre under CCDC 2379852. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures.

■ AUTHOR INFORMATION

Corresponding Authors

Vipan Kumar - Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India; orcid.org/0000-0002-6164-7161; Email: vipan_org@yahoo.com

Sukhdeep Singh - Research Group Bioorganic Chemistry of Bioactive Surfaces, Institute of Chemistry and Biotechnology, 98693 Ilmenau, Germany; orcid.org/0000-0001-6871-4294; Email: sukhdeep.singh@tu-ilmenau.de

Authors

Shefali Chowdhary - Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India

Nitish Kumar - Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India

Natacha Henry - Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS), Lille F-59000, France
Pascal Roussel – Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS), Lille F-59000, France; orcid.org/0000-0001-7243-7293

Konstantinos Demertzis – Research Group Bioorganic Chemistry of Bioactive Surfaces, Institute of Chemistry and Biotechnology, 98693 Ilmenau, Germany

Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.jchemed.4c01130

## Notes

The authors declare no competing financial interest.

## ACKNOWLEDGMENTS

We acknowledge the University Grants Commission (UGC), India for awarding Senior Research Fellowships (ref No. 1594/CSIR-UGC NET DEC 2018). We also acknowledge Council of Scientific & Industrial Research (CSIR), India (grant no. 02(0400)/21/EMR-II). This work has been partially funded by the Carl Zeiss Foundation in the “Ilmenau School of Green Electronics” (CZS: P2022-00-135). Open access funding enabled and organized by agreement with Technische Universität Ilmenau is highly appreciated.

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