Notes – Anuja Sawant (Sarangdhar)

Safety during ultrasonication

James Bond in Casino Royale shoots a propane tank with a handgun. You didn’t miss that did you? If you did, do you at least remember what happens when a gas tank explodes after a crash in Terminator 2: Judgment Day? It’s okay if you don’t, because I’m going to tell you what happened when the famous ‘rainbow experiment’ went wrong in a lab. Not once but twice.

Chemicals are as nasty as they are shown in films. Chemicals are also very noxious in a chemical laboratory as much as they are at any place else. That’s why wherever you are, whatever you do, chemicals should be handled with care. (Girls, even the acetone that you use to remove nail polish from your nails can catch fire as soon as it comes in touch with an ignition source, i.e. fire.)

Coming to the rainbow experiment. It’s really fascinating to look at. What happens is, when elements such as Na, Sr, K, Li and Cu are mixed with methanol and ignited, they all burn in the colors of a rainbow. You can see its video here.

What went wrong with the rainbow experiment?

A teacher’s chemistry experiment exploded during a demonstration at Beacon High School in Manhattan on Thursday, creating a fireball that burned two 10th graders, one severely, according to Fire Department and school officials. – Chemjobber

It is better to be safe than sorry. As you can see, horrible things have happened, not only to grown-ups but also to children. This doesn’t meant you should avoid doing things that involve risks. Instead, you can do it in a safe way.

As students who had to work in a laboratory, we were told by our professor (Prof. Bhujle) to learn the safety aspects of our respective projects. For those who do not know me or what I was up to during my Masters degree, here’s what I did:

Process intensification using alternative energy source i.e. ultrasound irradiation (sonochemistry), which leads to decrease in energy consumption and waste reduction. Also investigated a Lewis acid catalyzed homogeneous organic condensation reaction and an ultrasound-assisted Pd-catalyzed heterogeneous transfer hydrogenation reaction.

Safety aspects associated with the project:

Ultrasound usage can be categorized as:

Low frequency, high power ultrasound (20–100 kHz)
High frequency, medium power ultrasound (100 kHz–1 MHz)
High frequency, low power ultrasound (1–10 MHz)

The equipment I used to generate ultrasound i.e. ultrasonic bath, runs on a 33 kHz frequency. Hence, it can be taken as low frequency, high power ultrasound.

Contact Exposures:

Contact exposure is exposure for which there is no intervening air gap between the transducer and the tissue. This may be via direct and intimate contact between the transducer and the tissue or it may be mediated by a solid or liquid. Contact exposure can in some cases provide nearly 100% energy transfer to tissue. [1] 33 kHz frequency ultrasonic bath can cause observable effects.

Airborne ultrasound:

The most plausible mechanisms for non-auditory effects of airborne ultrasound on a human are heating and cavitation. [1] An exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above). [2] The major effects of airborne ultrasound of concern in practice are the result of reception by the ear. To summarize, exposure to ultrasonic radiation, when sufficiently intense, appears to result in a syndrome involving manifestations of nausea, headache, tinnitus, pain, dizziness, and fatigue. The type of symptom and the degree of severity appear to vary depending upon the actual spectrum of the ultrasonic radiation and the individual susceptibility of the exposed persons, particularly their hearing acuity at high frequencies. A concise summary of the physiological effects of ultrasound with specific stated exposure conditions has been given by Acton.

Measures to be taken for safety:

Contact exposure to high-power ultrasound must be avoided at all times. [1]
Only operators qualified to use the equipment or persons under strict supervision should be allowed within the boundaries of the controlled area while the equipment is operating. [1]
Personnel using high-power ultrasound, and safety inspectors in industry should be knowledgeable about the possible harmful effects of ultrasound and necessary protective measures. [1]
Warning signs should be placed at the entrance to any area which contains high power ultrasound equipment or applied to each high power ultrasound device. Accompanying each warning sign there should also be a statement indicating the precautionary measures to be taken while the ultrasound power is on. [1]
Safety procedures for the protection of personnel are similar to those used for audible noise. The protection for ultrasonic frequencies is expected to be at least 14 dB for ear muffs and rubber ear plugs, and 24 dB for foam ear plugs. [1]

References:
1. Guidelines for the Safe Use of Ultrasound Part II – Industrial & Commercial
Applications – Safety Code 24. Health Canada. ISBN 0-660-13741-0, (1991).
2. AGNIR (2010). Health Effects of Exposure to Ultrasound and Infrasound. Health
Protection Agency, UK, 167–170.

I’ll discuss transfer hydrogenation in subsequent blog posts.

Stay safe. ;)

Green engineering, Notes, Separation processes

Separation processes in industry

No one is perfect… that’s why pencils have erasers.

separation The same is true for reactions. They are not perfect in the sense that we do not always get a 100% yield. The reasons for this are:

side reactions
excess raw material
loss of reactants through by-product formation/charring due to their sensitivity towards operating conditions
some of the reactants go unreacted

To solve these problems, one may use solvents. But then the product obtained would still be in a diluted state. This is why we need separation.

Various separation processes exist in an industry and depending on the applicability, one process is chosen over the rest. Some of these processes are:

Evaporation (e.g. recovering salts from solution)
Absorption (e.g. separation of NH3 from a mixture)
Crystallization (e.g. purification of solid compounds)
Distillation (e.g. separation of crude oil into fractions)
Chromatography (e.g. analysis in the lab)
Filtration (e.g. desalination)
Settling (e.g. waste-water treatment)
etc.

One can separate components of a mixture depending on the following properties:

Density (e.g. gravity separation)
Magnetic property/polarity (e.g. separation of minerals)
Boiling point/Melting point/Vapor pressure (e.g. distillation)
Viscosity/Solubility (e.g. separation of N2 and O2 can be done by absorption of N2 in a liquid as O2 leaves)
States of material (e.g. again – separation of N2 and O2 can be done by absorption of N2 in a liquid as O2 leaves)
etc.

Applications in water purification

With increase in the number of water-stressed regions such as India, the need for water purification is more than ever. Equally important are small scale and the large scale water purification systems. Small scale systems include the portable water purification systems such as SODIS that uses solar energy to disinfect disease causing biological agents or a homemade waterfilter. Disinfection is one of the many steps involved in the purification process. Large scale systems includes an array of processes such as pre-treatment, sedimentation, filtration, disinfection, desalination and many more that require bigger assemblies.

Recently, DOW Technology helped the Largest Desalination Plant in Spain operating with pressurized ultrafiltration to deliver freshwater for municipal use. Ultrafiltration is one of the advanced separation processes, which is a type of membrane filtration. Apart from water purification, such systems are used in industry was various reasons. Ultrafiltration is used for concentrating target molecules, clarification needed in wastewater treatment processes, desalination such as that used in the plant in Spain or for fractionation of peptides in dilute samples.

Chemical Industry

In a chemical industry or a chemical laboratory, separation processes are required before and after each stages. For example, before entering the system, the raw materials are purified. After reaction, the process may give out materials in different phases -gas/liquid/solid. These have to be separated so as to reach the recycle stream and the effluent stream. The effluent stream again has to undergo recovery of certain substances before it reaches the environment.

Treatment of industrial waste is growing evidently stringent as time passes by. This requires such separation processes which aid pollution prevention. In fact, the entire waste water treatment mechanism is based on physical separation of effluent entities.

Further reading:

Chemical process industry and pollution

Ways of treating waste

Chemical treatment of wastewater

Water filtration by tomato and apple peels

Fundamentals

Chemistry with glasses on

I’m going to take you back in time. Forget all the chemistry you know for the next few seconds – say three. Can you wonder how it must have been to think, ‘Hey, this material must have some structure.’? Sounds bizarre. As bizarre as Newton asking himself, “Why does anything fall?’

These three scientists wondered about chemical structures in the same bizarre way and are the founders of the theory of chemical structure.

Alexander Mikhaylovich Butlerov, a Russian chemist, one of the principal creators of the theory of chemical structure.
Archibald Scott Couper, a Scottish chemist who proposed an early theory of chemical structure and bonding.
August Kekulé, a German organic chemist. He was the principal founder of the theory of chemical structure.

First glass

In 1951, physicist Erwin Wilhelm Müller, a German physicist, was the first to see atoms. He did this using his own invention: the field ion microscope. Literature doesn’t have the photograph of what he saw but the following photograph is similar to what he observed: each dot is the image of an individual platinum atom.

Second glass

In 1931, Max Knoll and Ernst Ruska built the first TEM. In 2013, researchers put this to use by observing what happens inside a battery. The following image is a TEM image of the polio virus.

Third glass

The third glass quickly replaced the second in the year 1952 when the following photo was captured. But it was rather an indirect picture – Photo 51. Photo 51 is the nickname given to an X-ray diffraction image of DNA taken by Raymond Gosling in the lab of Rosalind Franklin, as her PhD student.

Fourth glass

The fourth glass was put on with the advent of scanning tunneling microscope. This gave rise to a technique called as scanning probe microscopy. Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very high-resolution type of scanning probe microscopy. In 2009, a single molecule was imaged for the very first time by IBM researchers. This was done by using a AFM. It is with AFM that for the very first time (2013) that scientists saw how hydrogen bonds looks like. The following is its picture.

Fifth glass

The fifth glass is our very own digital camera.

“A great deal of time is spent within synthetic chemistry laboratories on non-value-adding activities such as sample preparation and work-up operations, and labor intensive activities such as extended periods of continued data collection. Using digital cameras connected to computer vision algorithms, camera-enabled apparatus can perform some of these processes in an automated fashion, allowing skilled chemists to spend their time more productively. In this review we describe recent advances in this field of chemical synthesis and discuss how they will lead to advanced synthesis laboratories of the future.” – Abstract from an open-access paper ‘Camera-enabled techniques for organic synthesis‘ (Beilstein J. Org. Chem. 2013, 9, 1051–1072.)

Researchers from UCLA have developed a smartphone microscope to see single virus and synthetic nanoparticles. It produces images almost as good as a SEM.

Sixth glass

Last week, I attended a lecture by Prof. Prashant Jain (nanogold.org) from the University of Illinois, at ICT, Mumbai. It was called ‘Elucidating chemical reactions on the nanoscale’. He described how we can observe individual nanoparticles instead of observing the reaction in bulk. His research involves ‘Imaging Phase Transitions in Single Nanocrystals’. The following is a section from his profile describing this research work.

Phase transitions in solid-state materials often involve interesting dynamics. Since macroscopic solids are typically polycrystalline, such dynamics is smeared out in studies on bulk solids, due to ensemble averaging over different crystalline domains. By acquiring snapshots of a single nanocrystalline domain undergoing a phase transition, our lab is attempting to uncover the dynamic trajectory involved in the nucleation of a new phase. We are developing new optical and spectroscopic methods to acquire snapshots of model phase transitions and also using these techniques to learn new facts about fundamental phenomena such as crystal growth, impurity doping, and correlated electron systems.

We’ve come a long way observing chemistry, haven’t we? The more we see, we find how less we know.

Acknowledgment: Thanks to Dirk Schweitzer for introducing me to the paper – ‘Camera-enabled techniques for organic synthesis‘. You can find him on Google+.

Fundamentals, Notes

New in Green Chemistry: The Zipper approach

Many chemical products can be produced via different routes. One of these routes may be industrialized depending upon its cost-effectiveness, satisfaction of environmental constraints and ease of scale-up. As you may be aware, environmental constraints have become stringent due to the effects the chemical and allied industries have on our environment. Green Chemistry, with its 12 guiding principles has made the world look at conventional chemistry and its subsequent scale up with a fresh approach that is environmentally benign.

In 1990, Elias James “E.J.” Corey, an American organic chemist won the Nobel Prize in Chemistry for his development of the theory and methodology of organic synthesis, specifically retrosynthetic analysis. The most famous of all the restrosynthesis processes is the production of Ibuprofen, wherein 6 steps were reduced to just 3. This achieved one of the 12 principles of Green Chemistry that says, “Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.”

Synthesis Explorer by the Royal Society of Chemistry (RSC) helps students and teachers plan synthetic routes by choosing a starting compound, reacting it and viewing details of the reaction.

According to Warner, only 10 percent of current technologies are environmentally benign and 35 percent could be made benign relatively easy. The remaining 65 percent will need to be reinvented in more environmentally benign ways. A report by Lisa Lilleland, a sustainability advisor and environmental advocate.

Retrosynthesis is design of organic synthesis to find newer, simpler and benign ways to produce a compound. Technion Scientists have now developed a new method for selective synthesis of complex molecules. They call it the “Zipper Approach”. It is a one-of-a-kind stereochemistry for difficult transformations: allylic C-H (H=Hydrogen) and selective C-C bond activations. The paper is published in the journal Nature.

More and more companies are now offering services in upscaling and route scouting. Route scouting is the creation of sustainable synthesis routes. Some of the companies that provide such services are:

Notes, Safety & Health

Safety first with green chemistry

One of the most important parts of doing green chemistry is making the chemistry safe. Doing it safe comes in three parts: Firstly, the products that are made should be safe for the consumers. Secondly, and sadly, the neglected or less seriously taken part, is the safety of those who make these products, at any level of the production line – workers and their neighbors. Thirdly, researchers in a laboratory.

Let’s take an example. Let’s say you are an researcher in a lab, or may be just a college student. What will you do if sulfuric acid spills on the floor? Do you have any idea? Good if you do, but if you don’t here’s what you can do:

Put sand on it.
Collect it in a tray.
Add base: NaOH + H2SO4 = violent. So, we are not going to add NaOH. We’ll have to use another base, that is Na2CO3. Even better if you have CaCO3.

Safety education is very important, you see?

Who makes sure that workers are safe? Legislation and organizations do and every country has its own of doing it. Here’s a list of them:

European Union: European Agency for Safety and Health at Work (Read about REACH here.)
UK: Health and Safety Executive and local authorities (the local council) under theHealth and Safety at Work etc. Act 1974
Denmark: The Danish Working Environment Authority
US: National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA)
Canada: The Canadian Centre for Occupational Health and Safety (CCOHS)
Malaysia: Department of Occupational Safety and Health (DOSH)
People’s republic of China: Ministry of Health is responsible for occupational disease prevention and the State Administration of Work Safety
South Africa: Department of Labour
India: National Safety Council (NSC)

Although the NSC was set up in 1966, Bhopal disaster that occurred in the year 1984 brought even more attention to the importance of safety, not only in India but worldwide. Human loss is also accompanied by monetary loss for the plants involved. “A safe plant is a more profitable plant.” – Walt Boyes. One cannot ignore the financial risk that involves with every accident. In financial terms, these risks are known as ‘contingent costs’. Contingent costs include penalties, remediation, personal injury damages etc. Not to mention the damage that is caused to a company as its corporate image and relationships are at risk as well. Take the example of Hindustan Unilever, when its workers were exposed to mercury in the thermometer factory it owned in Kodaikanal. It shut down in 2001.

Now here we are looking at the bigger picture, to keep it all safe. ‘Life Cycle Analysis’ (LCA) gives us that bigger picture. There are softwares out there that can help a company and there are companies which are already at it.

LCA softwares include:

You will find some more here:

EPA‘s LCA resources

Companies involved in LCA:

Notes

E. coli, the green celebrity!

Escherichia coli or more commonly known as E. coli, according to me, happens to be the celebrity of the green world when it comes to biology in green chemistry. These are the friendly bacteria that live in our guts and help digest our food. Although, some of its strain do cause problems to us. It’s time to give it some positive attention. Scientists genetically engineer E. coli and greenify a chemical reaction.

Here are a few examples of how they did it:

Reduction of GO: Microbial reduction of graphene oxide by Escherichia coli: A green chemistry approach
Cleaner chemistry: Transplanting metabolic pathways into E. coli
Biofuels: Turning bacteria into butanol biofuel factories
Turning waste into fatty acids: Genetically Modified E. coli Bacteria Turn Waste Into Fat For Fuel!
Sugars into biofuels

The Presidential Green Chemistry Challenge Award Recipients included individuals/organizations who used E. coli. Here are some entries:

2012	Codexis, Inc.; Professor Yi Tang, University of California, Los Angeles	LovD, an acyltransferase from E. coli engineered by directed evolution, now performs regioselective acylation in the sysnthesis of the drug simvastatin (summary)
2011	BioAmber, Inc.	Genetically engineered E. coli strain licensed from the Department of Energy produces succinic acid from wheat-derived glucose on a commercial scale (summary)
2011	Genomatica	Genetically engineered E. coli strain produces 1,4-butanediol by fermentation of readily available sugars (summary)
2011	BioAmber,Inc.	Glucose is fermented on a commercial scale by a genetically engineered E. coli strain to make succinic acid, traditionally produced from petroleum (summary)
2011	Genomatica	Readily available sugars fermented by a genetically engineered E. colistrain produce 1,4-butanediol, a large-volume chemical usually made from petroleum (summary)

The world outside our guts is far harsher for these bacteria, especially in our reaction flasks. So what are scientists doing about it? They are making hospitable environments for these little celebrities. Making safer solvents for them is one way. But is E. coli losing its shine? Time will tell.

Read more:

How yeast replaced E. coli: BioAmber phases out E.coli use