Question

Which of the following is not an example of green chemistry? (a) catalytic dehydrogenation of the diethanol amine without using cyanide and formaldehyde. (b) Replacement of $\mathrm{CFCs}$ by ${\mathrm{CO}}_2$ as a blowing agent in the manufacture of polystyrene foam sheets. (c) Reacting methyl amine and phosgene to produce methyl isocyanate. (d) Replacement of organotins by sea-nine as antifouling capound sea marines.

Short answer

The correct answer is (c) Reacting methyl amine and phosgene to produce methyl isocyanate.

Step-by-step solution

Understand What Green Chemistry is

Green chemistry involves designing products and processes that minimize the use and generation of hazardous substances. Look for practices that are safe for the environment and human health.

Analyze Option (a)

Option (a) describes catalytic dehydrogenation without using harmful chemicals like cyanide and formaldehyde. This aligns with green chemistry principles, as it avoids toxic substances.

Analyze Option (b)

Option (b) refers to replacing CFCs with CO2. CFCs are harmful to the ozone layer, while CO2 is less harmful, making this option part of green chemistry.

Analyze Option (c)

Option (c) involves reacting methyl amine with phosgene to produce methyl isocyanate. Phosgene is a highly toxic substance, making this process not compliant with green chemistry principles.

Analyze Option (d)

Option (d) discusses replacing organotins with sea-nine, a less harmful compound in marine applications. This replacement avoids toxic chemicals, aligning with green chemistry.

Determine the Outlier

By examining each option, identify the one that does not follow green chemistry principles. Option (c) uses a highly toxic substance, phosgene, indicating it is not an example of green chemistry.

Key concepts

catalytic dehydrogenation

Catalytic dehydrogenation is a process where hydrogen atoms are removed from a molecule with the help of a catalyst. This method is a key example of green chemistry, particularly when it avoids harmful substances.

For instance, the dehydrogenation of diethanol amine can be done without using cyanide or formaldehyde. Both are toxic and dangerous to the environment and human health.

When a catalyst is used in this reaction, it accelerates the process while reducing the need for harmful substances. This approach not only makes the process more efficient, but it also minimizes the generation of hazardous waste.

Key points to remember about catalytic dehydrogenation in green chemistry include:

• Use of non-toxic catalysts
• Minimization of by-products
• Enhanced reaction efficiency

environmentally friendly alternatives

Finding environmentally friendly alternatives is a core principle of green chemistry. This means replacing harmful chemicals with substances that have a reduced impact on the environment.

One example is the replacement of Chlorofluorocarbons (CFCs) with carbon dioxide (CO2) in the production of polystyrene foam sheets. CFCs are known to damage the ozone layer, leading to increased UV radiation reaching Earth. CO2, while not perfect, has a far smaller ozone-depleting potential.

Benefits of adopting environmentally friendly alternatives include:

• Reduced environmental impact
• Improved safety for humans and wildlife
• Increased sustainability of industrial processes

Implementing such alternatives helps industries comply with environmental regulations and improve their ecological footprint.

toxic substances reduction

Reducing the use of toxic substances is a fundamental aim of green chemistry. This involves identifying and minimizing the use of harmful chemicals in chemical processes.

An example is the reaction of methyl amine with phosgene to produce methyl isocyanate. Phosgene is an extremely toxic substance, posing significant health risks to workers and the environment.

Green chemistry promotes the development of processes that either eliminate the use of such dangerous chemicals or replace them with safer alternatives. Strategies to achieve this include:

• Substituting less hazardous raw materials
• Improving reaction selectivity to minimize waste
• Using safer reaction conditions

This approach not only protects human health but also reduces the environmental burden of chemical manufacturing.

hazardous chemicals avoidance

Avoiding hazardous chemicals altogether is a key objective in the practice of green chemistry. This entails designing chemical processes and products that do not involve substances known to cause harm to the environment or human health.

Replacing organotins with sea-nine as an antifouling compound in marine applications illustrates this point. Organotins are toxic and can accumulate in marine life, disrupting ecosystems. Sea-nine, on the other hand, is less harmful and provides a safer alternative.

Steps to avoid hazardous chemicals include:

• Identifying safer chemical alternatives
• Conducting thorough risk assessments
• Developing new technologies and methodologies

By prioritizing the avoidance of hazardous substances, green chemistry aims to create a safer and more sustainable world.