Green Chemistry

Green chemistry is an approach that focuses on designing products and processes to minimize their environmental impact. It involves using the principles of chemistry and other sciences to reduce pollution and environmental deterioration.

1.0Introduction

Ongoing environmental degradation and pollution have spurred the development of green chemistry. In simple terms, green chemistry, also known as sustainable chemistry, is a field of chemistry focused on designing products and processes that reduce the use and production of hazardous substances. It provides a foundation for developing alternative green and sustainable technologies.

Green chemistry aims to create a more sustainable and less polluting chemical industry by integrating environmental considerations into the design and execution of chemical processes. This approach benefits the environment and enhances economic and social sustainability.

Byproducts generated during a chemical process contribute to environmental pollution if not utilized effectively.  Such processes are not only harmful to the environment but also economically inefficient. Waste generation and disposal are both costly and unsustainable. Green chemistry aims to reduce chemical hazards by using existing knowledge and developing new methods.

2.0Features of Green Chemistry

1. Minimizing Waste: Byproducts should be managed and utilized effectively to prevent environmental pollution. This approach is both environmentally friendly and cost-effective.
2. Safe Chemicals: Organic solvents like benzene, toluene, and carbon tetrachloride are highly toxic, and their use should be minimized. Safer alternatives should be considered.
3. Reaction Efficiency: Chemical reactions involve reactants, attacking reagents, and the reaction medium. The efficiency of a reaction depends on parameters like temperature, pressure, and the use of catalysts.
4. Optimal Conditions: Choosing starting materials that convert to end products with nearly 100% yield under optimal conditions reduces waste and improves efficiency.
5. Environmentally Friendly Mediums: Conducting reactions in water can be beneficial as water is cost-effective, non-flammable, and non-carcinogenic. It has a high specific heat and low volatility, making it an excellent medium for many reactions.

3.0Green Chemistry Practices

• Utilize Non-Toxic Solvents: Avoid toxic solvents and opt for safer alternatives whenever possible.
• Optimize Reaction Conditions: Strive for conditions that maximize yield and minimize waste.
• Choose Safer Reagents and Catalysts: Select reagents and catalysts that reduce hazardous byproducts.
• Embrace Aqueous Mediums: Water can be used as a reaction medium to leverage its environmental and safety benefits.

4.0Benefits of Green Chemistry

• Economic Efficiency: Reducing waste and using safer materials lowers the costs associated with disposal and health risks.
• Environmental Protection: Minimizes the release of hazardous substances into the environment.
• Health and Safety: minimize workers' and consumers' exposure to toxic chemicals.

Green chemistry aims to create processes where reactants are fully converted into useful, environmentally friendly products, eliminating chemical pollutants. This approach benefits the environment and enhances economic viability by reducing waste and improving efficiency.

5.0Green Chemistry in day-to-day Life

• Dry Cleaning of Clothes

Tetrachloroethene (Cl₂C=CCl₂) was previously used as a solvent for dry cleaning. However, this compound contaminates groundwater and is a suspected carcinogen. To address these issues, the industry is shifting to using liquefied carbon dioxide (CO₂) with a suitable detergent. This replacement significantly reduces the risk to groundwater compared to halogenated solvents.

Hydrogen peroxide (H₂O₂) is now commonly used for bleaching clothes in laundry processes. Compared to traditional methods, it provides better results and requires less water. This approach is more environmentally friendly and efficient.

• Bleaching of Paper

Chlorine gas was previously used for bleaching paper. Nowadays, hydrogen peroxide (H₂O₂), with a suitable catalyst that enhances its bleaching action, is preferred. This shift to hydrogen peroxide is due to its lower environmental impact than chlorine gas, which can produce harmful byproducts. Hydrogen peroxide, when used with a suitable catalyst, provides effective bleaching while minimizing environmental concerns.

• Synthesis of Chemicals

Ethanal (CH₃CHO), commonly known as acetaldehyde, is now synthesized commercially through a one-step oxidation process of ethene. This oxidation takes place in the presence of an ionic catalyst in an aqueous medium, achieving a high yield of 90%.

The reaction can be represented as:

${\mathrm{CH}}_2={\mathrm{CH}}_2+{\mathrm{O}}_2\underset{\text{ Pd (II)/Cu(II) (In water) }}{\overset{\text{ Catalyst }}{\to }}{\mathrm{CH}}_3\mathrm{CHO}(90\%\text{ yield })$

• ‘Green Solution’ to Clean Turbid Water

Powder made from tamarind seed kernels has been discovered to be an effective material for cleaning municipal and industrial wastewater. This material is non-toxic, biodegradable, and cost-effective. Typically discarded as agricultural waste, tamarind seed powder offers a sustainable alternative to conventional treatments.

Currently, alum is commonly used to treat such water. However, alum increases the concentration of toxic ions in the treated water, which can lead to health issues. By contrast, using tamarind seed powder avoids these problems and syncs with the principles of green chemistry.

NOTE: In 2005, Yves Chauvin de Institut Français du Pétrole (Rueil-Malmaison, France), Robert H. Grubbs of the California Institute of Technology (Caltech, Pasadena, CA, USA), and Richard R. Schrock of the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA) were awarded the Nobel Prize in Chemistry. Their work significantly reduced hazardous waste by creating new chemicals.  The award was given for their development of the metathesis method in organic synthesis, a technique that rearranges groups of atoms within molecules.