120-year-old reaction turned on its head with environment-friendly, paste-based method

Date:
November 18, 2021
Source:
Hokkaido University
Summary:
A new method for creating one of chemistry's most widely used
class of compounds could revolutionize industrial processes,
making them cheaper, simpler and more environmentally friendly.



FULL STORY ==========================================================================
A new method for creating one of chemistry's most widely used class of compounds could revolutionize industrial processes, making them cheaper, simpler and more environmentally friendly.


==========================================================================
A group of researchers led by scientists at Hokkaido University have
developed a simpler, greener method for producing Grignard reagents --
one of the most important and widely used type of reagents in the chemical industry -- that drastically cuts down on the use of hazardous organic
solvents and could lead to reduced production costs. This new process
was reported in Nature Communications.

Grignard reagents are an essential ingredient in a common method
for creating carbon-carbon bonds, the building blocks of organic
molecules. These reagents were discovered 120 years ago, but due
to their instability, the conventional production method still used
today is carried out in toxic organic solvents and with no exposure
to moisture and oxygen. This results in a complicated, delicate, and
expensive process that produces environmentally hazardous waste.

Researchers sidestepped these problems by minimizing the amount of
organic solvent used and by employing a mechanochemical technique called ball-milling to produce Grignard reagents. The reactants, magnesium
metal and organohalides, were loaded into a metal chamber along with a stainless-steel ball. In a key step, a small amount of organic solvent --
about one-tenth the amount used in conventional methods -- was added to
the solid reactants. The chamber was then spun for one hour, causing the
ball to tumble around and slam into the solid- state reactants, helping
them to mix thoroughly and react, forming a paste-like Grignard reagent.

Researchers even succeeded in creating new Grignard reagents using organohalides that have poor solubility in organic solvents, which
can't typically be made by the conventional method. Avoiding heavy
use of organic solvents allowed the researchers to overcome solubility problems, which opens up a world of new reactions with Grignard reagents prepared from insoluble compounds. It also leads to a major reduction
in hazardous waste.

Additionally, it is more difficult for water or oxygen to affect the
Grignard reagents when less organic solvent is used. This means that
removing water and oxygen from the surrounding air is not required,
making the process easier to perform and less costly. Given the potential economic and environmental benefits, this discovery could have a huge
effect on chemical industries.

"With a growing need to address environmental concerns and reduce
CO2 emissions, it is important to develop chemical reactions
that don't require organic solvents," commented Associate
Professor Koji Kubota. "Grignard reagents are arguably the most
well-known, commonly used reagents in industry, and so our work could fundamentally change the way a vast number of chemicals are produced
at scale, leading to significantly reduced impact on the environment." ========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Rina Takahashi, Anqi Hu, Pan Gao, Yunpeng Gao, Yadong Pang,
Tamae Seo,
Julong Jiang, Satoshi Maeda, Hikaru Takaya, Koji Kubota, Hajime Ito.

Mechanochemical synthesis of magnesium-based carbon nucleophiles
in air and their use in organic synthesis. Nature Communications,
2021; 12 (1) DOI: 10.1038/s41467-021-26962-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211118061319.htm

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