Cyclopentyl methyl ether

Cyclopentyl methyl ether (CPME), also known as methoxycyclopentane, is hydrophobic ether solvent. A high boiling point of 106 °C (223 °F) and preferable characteristics such as low formation of peroxides, relative stability under acidic and basic conditions, formation of azeotropes with water coupled with a narrow explosion range render CPME an attractive alternative to other ethereal solvents such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), dioxane, and 1,2-dimethoxyethane (DME).

Synthesis

The synthesis of this compound can be done in two different ways:

(1) by methylation of the cyclopentanol.

(2) by the addition of methanol to the cyclopentene. This second method is better from the point of view of sustainable chemistry as it does not produce by-products.

Applications

Cyclopentyl methyl ether is used in organic synthesis, mainly as a solvent. However it is also useful in extraction, polymerization, crystallization and surface coating.

Some examples of reactions where it acts as a solvent are:

• Reactions involving alkali agents: nucleophilic substitutions of heteroatoms (alcohols and amines)
• Lewis acids-mediated reactions: Beckmann Reaction, Friedel-Crafts Reaction etc.
• Reactions using Organometallic reagents or basic agents: Claisen condensation, formation of enolates or Grignard reaction.
• Reduction and oxidation.
• Reactions with transition metal catalysts.
• Reactions with azeotropical removal of water: acetalization, etc.

Cyclopentyl methyl ether possesses characteristics that make it a potential alternate for other ethers. According to an evaluation of three chemistry journals from 2020, ethereal solvents have a share of 22–25% of all solvents employed.

In contrast to water-soluble ethers like tetrahydrofuran and 1,4-dioxane, cyclopentyl methyl ether (CPME) - being hydrophobic - acts suitably as an extractant. In aqueous phases, only trace amounts of CPME remain due to its low solubility. CPME also exhibits stability at both low and high pH levels, even under elevated temperatures and extended contact times. It can form an azeotrope with water in a ratio of 83.7% CPME to 16.3% water at an azeotropic end temperature of 83 °C. These properties enable CPME to function effectively as an entrainer during esterification processes and acetalizations.

Recently, investigations into the use of cyclopentyl methyl ether as an eco-friendly solvent in a wide range of chemical reactions, such as reductions, oxidations, and Grignard reactions, have been conducted.

At present, however, the production of cyclopentyl methyl ether, which in multiple respects fulfills the criteria of a "green" chemical, still depends on cyclopentene derived from non-renewable, fossil-fuel sources. The platform chemical furfural can yield cyclopentanol in high yields through catalytic hydrogenation using a copper contact or a nickelcobalt contact. The resulting cyclopentanol can then be easily dehydrated to cyclopentene.

References