#epoxides

Shrinking the carbon footprint of a chemical in everyday objects

New method for synthesizing the epoxides found in plastics, textiles, and pharmaceuticals

The biggest source of global energy consumption is the industrial manufacturing of products such as plastics, iron, and steel. Not only does manufacturing these materials require huge amounts of energy, but many of the reactions also directly emit carbon dioxide as a byproduct.

In an effort to help reduce this energy use and the related emissions, MIT chemical engineers have devised an alternative approach to synthesizing epoxides, a type of chemical that is used to manufacture diverse products, including plastics, pharmaceuticals, and textiles. Their new approach, which uses electricity to run the reaction, can be done at room temperature and atmospheric pressure while eliminating carbon dioxide as a byproduct.

"What isn't often realized is that industrial energy usage is far greater than transportation or residential usage. This is the elephant in the room, and there has been very little technical progress in terms of being able to reduce industrial energy consumption," says Karthish Manthiram, an assistant professor chemical engineering and the senior author of the new study.

Okay so I goofed this up twice now, but major props to dr4gon1te for the corrections! From what I can gather, weaker nucleophiles will exhibit a Sn1 ‘like’ reaction profile. (Source)

Once the epoxide has been protonated, the C-O bond begins to dissociate and the pair of electrons in the bond will migrate towards the O. As the bond dissociates, the carbon gains a carbocation character and is susceptible to attack from any weak nucleophile present. Since the nucleophilic attack occurs before the full carbocation is formed, the reaction only forms the trans product and the reaction is considered “Sn1 like”.

The Sn2 reaction with stronger nucleophiles will also only give the trans product. (Source)

Reaction: Darzens Reaction

Reagent: A strong base like tBuO-

Use in Chemistry: a- halo esters and carbonyl compounds condense in presence of a base produce a, b - epoxy esters that on decarboxylation gives substituted carbonyl compounds

Reaction Examples:

  Reaction Mechanism:

The reaction begins with the abstraction of the acidic hydrogen from the ester. The carbanion formed then acts as a nucleophile and gets added to the carbonyl compound to form a tetrahedral intermediate. In the next step an intramolecular nucleophilic substitution takes place in which the halide ion is eliminated to form the epoxide.

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