Chemists Develop a Practical Toolbox for Predicting the Solubility of Small Molecules in Different Solvents
Solvents are a vital part of the manufacturing and chemical industry, as they often make up the bulk of a chemical product, and dramatically affect how it works. For example, solvents influence how pesticides stay longer on leaves, how paints and inks dry faster, and how cosmetics are applied more easily.
One of the biggest challenges facing solvent manufacturers when developing new chemical products is predicting the solubility of small molecules in different solvents. But this task is about to become a lot easier as research chemists have created a ‘practical toolbox’ to aid solvent developers and chemical raw material suppliers in predicting how molecules will react in solvents.
Up until now, solubility has been predicted using the, so-called, Hansen Solubility Parameters: dispersion (D), polar interactions (P), and hydrogen bonding (H). Currently, this is used to great effect in the coatings and polymers industry for predicting the solubility of polymers.
However, the parameters have two major limitations that prevent them being used effectively in other industries, such as pharmaceuticals and cosmetics:
1. Drugs and cosmetics typically have more varied functional groups.
2. The original Hansen parameters exclude thermodynamic considerations regarding mixing, melting and dissolution. This is acceptable for polymers (where the thermodynamics cancel out) but not for small molecules.
Working with a team based at Solvay (headed by Dr Bernard Roux), Dr Manuel Louwerse and Prof. Gadi Rothenberg, have now improved Hansen’s model and adapted it to handle small-molecule solutes by including the thermodynamics of mixing, melting and dissolution.
As the online scientific journal Phys.org explains, “The improvements are based on a better description of both the entropy and the enthalpy terms. When a compound dissolves, molecules leave the crystal and mix into the solvent. This increases the entropy, but usually costs some enthalpy. The key issue here is that the amount of entropy gained by mixing determines how much enthalpy can be lost while keeping a negative ∆G (in other words, maintaining the driving force for the dissolution). Since the entropy effect depends on the concentration, the temperature, and the size of the molecules, these should all be included.”
The research team have now published their results in the journal ChemPhysChem, where they write, “The most important corrections include accounting for the solvent molecules’ size, the destruction of the solid’s crystal structure, and the specificity of hydrogen bonding interactions, as well as opportunities to predict the solubility at extrapolated temperatures.” Adding that, so far, “Testing the original and the improved methods on a large industrial dataset including solvent blends, fit qualities improved from 0.89 to 0.97 and the percentage of correct predictions rose from 54% to 78%.”
This is a significant improvement, as simply guessing the solubility of blends would give 50% correct predictions. The new model also enables predictions at extrapolated temperatures.
Furthermore, the research team has made access to the models and a full description of the theory publicly accessible, with the ‘full and annotated Matlab routines’ available. This has allowed other researchers to begin making adjustments to the HSPiP software.
The decision to share the ‘toolbox’ with everyone is based on a desire to bring academics and industry closer together. As Prof. Rothenberg notes, “Industrial partners need to keep their data confidential, but most of them realise that open-access publishing of the methods and tools creates goodwill and enables further developments by both collaborators and competitors. By sharing methods and tools, companies can benefit from each other’s knowledge without sacrificing data.”
How far this ‘goodwill’ goes in the business world is uncertain, but what is clear is that the ‘toolbox’ for predicting small molecule solubility in solvents will shorten the time and lower the cost for developing improved chemical products. By sharing the information, the researchers are helping the entire chemical industry.
Research chemists from Berkeley Lab in California have unlocked a class of polymers that they claim are cleaner and cheaper to produce than polycarbonate plastics. They also believe that the manufacturing processes will be easy to upscale, and will make less waste by-product.
Such is the excitement over this new range of polymers, that many are wondering if this class of plastics could replace polycarbonates as the ‘go-to material’ for the modern world.
The story begins in 2001, with the introduction of ‘click chemistry’ by the Nobel laureate K. Barry Sharpless. ‘Click chemistry’ is a concept in organic chemistry that describes a range of highly reactive, yet controllable reactions that have high yields, with little to no purification required.
As the Berkeley Lab website describes, “Following nature’s example, click reactions follow simple protocols, use readily available starting materials, and work under mild reaction conditions with benign starting reagents. Click chemistry has become a valuable tool for generating large libraries of potentially useful compounds as industries look to discover new drugs and materials.”
“Click chemistry is a powerful tool for materials discovery,” explains Yi Liu, director of the Organic Synthesis facility at the Molecular Foundry at Lawrence Berkeley National Laboratory, “but synthetic chemists are often not well-equipped to characterize the polymers they create. [Here at the Foundry] we can provide a broad spectrum of expertise and instrumentation that can expand the scope and impact of their research.”
Publishing their results in the journal Nature, the chemists report that, “Polysulfates and polysulfonates possess exceptional mechanical properties making them potentially valuable engineering polymers. However, they have been little explored due to a lack of reliable synthetic access.”
By using the Molecular Foundry, a facility that specializes in nanoscale science, a team led by Sharpless and Peng Wu were able to create long chains of linked sulfur-containing molecules, termed polysulfates and polysulfonates, using a SuFEx click reaction.
As the Berkeley Lab website explains, “Polymers are assembled from smaller molecules – like stringing a repeating pattern of beads on a necklace. In creating a polysulfonate ‘necklace’ with SuFEx, the researchers identified ethenesulfonyl fluoride-amine/aniline and bisphenol ether as good ‘beads’ to use and found that using bifluoride salt as a catalyst made the previously slow reaction ‘click’ into action.”
A newly developed chemical technique could make polysulfate plastics more competitive with polycarbonates.
The research team have now published their results explaining how the new SuFEx catalyst was able to produce a high quality and durable polymer, with little waste. Stating, “Bifluoride salts are significantly more active in catalysing the SuFEx reaction compared to organosuperbases.”
Adding that, “Using this chemistry, we are able to prepare polysulfates and polysulfonates with high molecular weight, narrow polydispersity and excellent functional group tolerance. The process is practical with regard to the reduced cost of catalyst, polymer purification and by-product recycling. We have also observed that the process is not sensitive to scale-up, which is essential for its future translation from laboratory research to industrial applications.”
Similar results were published in the scientific journal Angewandte Chemie, where the catalyst’s high rate of effectiveness was noted. The report stating that, “The SuFEx-based polysulfonate formation reaction exhibited excellent efficiency and functional group tolerance, producing polysulfonates with a variety of side chain functionalities in >99 % conversion within 10 min to 1 h.”
The research team also found that the 99% efficiency rate of the catalyst meant that as much as 100 to 1,000 times less was needed, resulting in the production of significantly less hazardous waste. As Berkeley Lab notes, “Bifluoride salts are also much less corrosive than previously used catalysts, allowing for a wider range of starting substrate ‘beads,’ which researchers said they hope could lead to its adoption for a range of industrial processes.”
Given the wide-ranging use of polycarbonate polymers in making everything from goggles, to frames for glasses, drinks bottles, syringes, and even bulletproof glass, then a cleaner, cheaper polymer replacement could have a huge impact on the plastics industry. With the research team claiming that the manufacturer of polysulfates is efficiently up-scalable, then it might not be long before plastic manufacturers begin to change their products.
In fact, given the success of the work being done at Berkeley, it is possible that ‘Click Chemistry’ will lead to the development of even more new polymers, and other ground-breaking material discoveries. As Liu observes, “There are many new polymers that haven’t been widely used by industry before. By reducing waste and improving product purity, we can lower costs and make reactions much more industry friendly.”
Photo credit: Chinaperfectroof
Photo credit: Berkeley Lab
The World Food Prize has been won by a man who may have many in the fertilizer industry rethinking their fertilizer sales strategies. This is because the 2017 award was recently presented to Akinwumi Adesina, president of the African Development Bank.
The reason that the prize giving may cause many to rethink their approach to fertilizer sales is best answered by Adesina himself. When collecting his award, he said, “You know, you can find Coca-Cola or Pepsi anywhere in rural Africa, so why can’t you find fertilizers?” He continues to explain that, “It is because the model that was used to distribute those farm inputs were old models based on government distribution systems, which are very, very inefficient.”
Fertilizer Distribution Challenges
He began to realize the cause of the poor quality of agriproduct distribution in Africa during his time as Nigerian Minister of Agriculture and Rural Development. As he writes on LinkedIn, “When I came on board as minister of agriculture in July of 2011, I found a corrupt and totally inefficient fertilizer sector. The government was spending huge amounts of money on direct procurement and distribution of subsidized fertilizer, but less than 11% of farmers got the fertilizers. Some of the fertilizers paid for by government were never delivered to the warehouses. Some of the fertilizer delivered contained more sand than fertilizer while a large portion of the fertilizer subsidized by government found its way across our borders to neighboring countries where it was sold at prevailing market prices.”
This is a problem highlighted by a recent report by the UN operated organization Africa Renewal, which states that, “Heavy reliance on imported fertilizers, combined with high transportation costs and the absence of suppliers in the countryside, has meant that African farmers pay between two and six times the average world price for fertilizer — when they can find it at all. An International Fertilizer Development Centre (IFDC) study estimated that it costs more to move a kilogram of fertilizer from an African port to a farm 100 kilometres inland than it costs to move it from a factory in the US to the port. With millions of African family farmers surviving on less than a dollar a day, imported fertilizer is simply unaffordable.”
Organic vs Chemical Fertilizer Use in Africa
This has left many African farmers relying on organic fertilizer alone to replenish soil that has been intensively farmed for years. As Natasha Gilbert, a reporter for the Guardian newspaper recently observed, “Organic fertilizer can help freshen up Africa’s ailing, rusty-red soils, but there is not enough land available to produce manure in sufficient quantities, says Professor Ken Giller, a soil scientist at Wageningen University in the Netherlands. One cow can produce about 15kg of nitrogen in manure annually. But a healthy maize crop needs up to 100kg of nitrogen a hectare, Giller says.”
This has created incredibly low farm productivity, and an environment which is crying out for agriproduct manufacturers to begin distributing farm products to Africa. As Giller points out, “Harvests have stagnated on the continent since the 1960s, according to data from the World Bank. On average, farmers in Africa harvest about one ton of maize (corn) a hectare, whereas their American counterparts reap up to 12 tons.”
Effective Fertilizer Distribution
So, the question becomes, how to get the chemical fertilizer that African farmers need to the rural communities. Which is where prize winning Adesina may have the answer, when he said, “I thought the best way to [provide fertilizer and agriproducts to Africa farmers] is to support rural entrepreneurs to have their own small shops to sell seeds and fertilizers to farmers.”
He continues by outlining how, “We started these agro-dealer networks and they spread over Africa. It brought farm inputs closer to farmers and it encouraged the private sector into the rural space.”
Now that many networks have been established, more and more agriproduct sales teams and fertilizer manufacturers are starting to join the trend. The need for more farming products is evident, but the challenge for fertilizer distributors is in proving the value of their fertilizer products.
It is important for African farmers to understand the benefits of soil nutrition, and how applying the right amount of fertilizer, at the right time will more than pay back the money invested. To continue to farm without replenishing the soil will lead to diminishing productivity and hunger. It is the fertilizer supplier’s task to provide the correct product and information to allow African farmers to make smart decisions.
Meanwhile, Adesina and the African Development Bank will continue to support fertilizer distributors who are willing to take on the challenge of selling agrichemicals in Africa. As he says, “The award is not just about recognition for me, it is also about putting the wind behind the sails of what still needs to be done in African agriculture.”
A wind which also blows in the sails and sales of the fertilizer industry.
“The World Food Prize was founded in 1986 by Dr. Norman E Borlaug, recipient of the 1970 Nobel Peace Prize.” the BBC reports, “Dr Adesina will receive the US $250,000 prize at the Borlaug Dialogue international symposium, which is held in the US to “help further the discussion on cutting-edge global food security issues and inspire the next generation to end hunger.”
If you want to learn more about agrichemical distribution in Africa, then you can read more via this link; Tips in Trading Chemicals in Africa.
Photo credit: goodhabaritanzania