Safer Solvents for Purifying Polar Reaction Mixtures

DCM Alternatives to Normal-Phase Flash Chromatography

For many organic chemists purifying polar reaction mixtures, normal-phase flash chromatography is the go-to method. However, these polar reactions can often result in compounds eluting too early or too late in the separation or not separating at all.

This study utilizes Hansen Solubility Parameter theory and TLC testing to identify safer solvents or solvent blends that are capable of replacing DCM for reaction mixture purification. The solvents and solvent blends identified are then evaluated using chemical hazard classification approaches.

1. Dioxane

A colorless, flammable liquid, 1,4-dioxane is found in the environment at sites where it has been released by industrial discharges or from petroleum distillation. 1,4-Dioxane is persistent in the environment, bioaccumulates and can be toxic when ingested or inhaled.

It also is a skin irritant and has been linked to several health problems, including liver damage, kidney disease and nervous system damage. The Environmental Working Group (EWG) has called on the EPA to set a federal limit for the chemical.

Researchers have developed green solvents such as tert-butyl acetate, sec-butyl acetate, ethyl isobutyrate and methyl pivalate that are safer, more sustainable alternatives to DCM in TLC mobile phases analysing common, small drug molecules [6]. They were selected because they lie below the less polar zone of the Kamlet-Taft solubility parameter diagram (Fig. 2) and are predicted to have similar or improved Rf values than DCM. A statistical thermodynamic framework enabled chemists to interpret chromatographic results in ways not possible with interpretation using traditional solubility parameters alone.

2. Methyl acetate

Methyl acetate is a clear liquid that has an ester odor similar to glues and nail polish remover. It is a low toxicity solvent used in early drying paints and wood coatings, industrial applications, perfumes and lubricants. It is also an intermediate in the manufacture of chlorophacinone, diphacinone, fenfluramine and o-methoxyphenyl acetone and an acidic reagent for the preparation of cellulose adhesives.

It is miscible with most organic solvents (alcohols, ketones and esters) but it is only sparingly soluble in water at elevated temperatures. It can be disposed of in a chemical incinerator equipped with an afterburner and scrubber.

Methyl acetate is toxic if swallowed and can cause drowsiness or dizziness. Following oral exposure, it is rapidly cleaved by esterases in the digestive tract and blood to form methanol and acetic acid. It is readily absorbed through the skin and may cause eye irritation. It is also a moderate hazard to the environment with an estimated BCF of 3 (SRC). Methyl acetate can be released to the environment through various waste streams and may biodegrade in soil.

3. Ethyl acetate/acetone

Ethyl acetate is a clear, colorless liquid solvent that has a light fruity odor and is soluble in many organic compounds. It is used in chemical synthesis and for extracting organic compounds from plant material. It is also used as an industrial paint and varnish thinner and for removing casual stains and grease from surfaces.

It can be absorbed into the body via inhalation, but only at low doses (2000 ppm). Chronic exposure may cause eye irritation, lung damage, and liver & kidney damage. Ethyl acetate is metabolized to acetic acid & ethanol in the liver and blood.

A method was developed to identify nonhazardous replacements for DCM using thin-layer chromatography (TLC) and Hansen Solubility Parameter theory. A number of safer solvent blends were identified and down-selected based on their dissolution properties and safety. The final selections were then evaluated by three separate chemical hazard classification approaches to determine the best nonhazardous DCM replacement. The resulting four solvent blend combinations were then compared to DCM in TLC performance testing.

4. Chloroform

Chloroform (CHCl) is a volatile liquid, a colourless and odourless compound. It is a useful solvent for manufacturing pesticides, film, lacquers, floor polishes, alkaloids and resins. It is also used as an anaesthetic during medical procedures.

Chronic exposure to chloroform can cause headaches, dizziness and fatigue. It can also damage the liver and kidneys. If it comes in contact with the skin, it can cause sores and blisters.

It enters the environment mainly through industrial effluent, waste from paper mills and chlorination of drinking water. It evaporates quickly from lakes and rivers and can seep into groundwater. On prolonged heating, it decomposes to formic acid, carbon monoxide and hydrogen chloride.

This is a dangerous chemical that can be found in many different places in the environment. It is often contaminated with other chemicals such as petroleum, ammonia and chloride. It can be difficult to identify because it has similar physical characteristics to other substances like ether and methyl acetate. The best way to identify chloroform is by chemical analysis.

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Chemical Engineers: Industries, Salary, and Career Progression

How Many Chemical Engineers Are There?

Chemical engineers work in the oil and gas, manufacturing, design, pulp and paper and petrochemicals industries. They also develop and direct facility operations.

They help to create greener, low-carbon industrial processes, upcycling and more at a scale that will change our world.

Five-year veterans often get their first taste of managerial work and more responsibility in their jobs. Many also start to focus more on people skills.

1. About 1.6 million

Chemical engineers are employed in the oil and gas, manufacturing, pharmaceuticals, paper, petrochemicals and food industries. Demand for these engineers largely mirrors the demand for the products produced by manufacturing industries. This field also offers opportunities in alternative energy research, nanotechnology and biotechnology.

Chemical engineering jobs involve designing, testing and supervising industrial processes and production. Other duties include calculating costs and schedules for projects. They may also test product quality and conduct forensic analysis of equipment problems.

Those with five years of experience can specialize in design, production or technical sales. They may become supervisors or take on leadership positions. Those with ten or more years in the field have gained considerable experience and are capable of managing projects from start to finish. They can also help train and supervise new engineers.

2. About 31,700

Chemical engineers conceive and design large-scale manufacturing processes for creating chemicals, fuels, pharmaceuticals, food, paper, clothing and more. Many of these mass-produced items that ordinary people use daily – from electronics and fuel to plastics, medicine and processed foods – wouldn’t exist without their efforts.

Entry-level chemical engineers work under more experienced engineers and must complete on-the-job training as they build their skills and experience. Over time they can advance to supervisory and technical sales positions.

Those who’ve been in the field for five years have become “senior” engineers and are likely involved in research, production, or development. They have gained considerable managerial experience and are largely in charge of operations, management, and personnel. They also have a significant input in product development and engineering decisions.

3. About ten-year veterans

Chemical engineers earn a very competitive salary. Their salaries far exceed the national average for all occupations, according to 2020 data from the Bureau of Labor Statistics. Those who choose to move into management will find themselves with even higher salaries.

A comparatively small group of chemical engineers make up the CEOs of major companies, including 3M, Du Pont, Union Carbide, Exxon, Dow Chemical and BF Goodrich. They also have made the news as military leaders, political figures and sportspeople.

These skills are requested frequently by employers in job postings for Chemical Engineer positions. They are considered Hot Technologies. These are the skills that distinguish a professional from their peers. Click on a skill to see how it rates against other skills. The percentage of jobs that request a skill is shown as well.

4. Five-year veterans

Chemical engineers can work in many different industries, including pharmaceuticals and medicine, oil & gas, design and construction, manufacturing, pulp and paper and the chemicals, petrochemicals, plastics and synthetic rubber subsectors. They can also find positions in the military.

They have a reputation for being able to take on any project and make it work. They often have to be creative, however.

A career in chemical engineering requires a high level of technical understanding. A bachelor’s degree is usually sufficient, though a graduate program can be beneficial. If you want to be licensed as a professional engineer, you need to complete four years of work experience and pass an exam. A great way to get first-hand knowledge of a specific industry is through an industrial placement that is available as part of your studies or as an internship.

5. Ten-year veterans

Chemical engineers say that the profession’s job satisfaction ratings are high, partly because they are able to solve big problems. It also requires creativity and the ability to think outside of the box, as the field is highly technical.

By five years into their careers, many chemical engineers have specialized in research, production or development and gained significant management responsibility. They enjoy good salaries, but often wish they could spend more time with family and friends.

Some leave the profession altogether, choosing tangential jobs in fields like finance, data or software development. Others opt for postgraduate study in the areas of science or design, and even medicine. But most continue to thrive in the largely male-dominated field.

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