2-Methyltetrahydrofuran
Encyclopedia
2-Methyltetrahydrofuran is an organic compound
with the molecular formula CH3C4H7O. It is a highly flammable mobile liquid. It is mainly used as a replacement for THF
in specialized applications for its better performance, such as to obtain higher reaction temperatures, or easier separations due to the solubility of 2-methyltetrahydrofuran. It is derived from furfural
and is usable as a biofuel
.
.
Furfural is produced by the acid-catalyzed digestion of pentosan sugars, C5 polysaccharide
s, in biomass
. Thus, the raw materials of 2-methyltetrahydrofuran are renewable biomass rich with cellulose
, hemicellulose
s, and lignin
, such as corncobs or bagasse
and other plant and agricultural waste.
2-Methyltetrahydrofuran can also be produced starting from levulinic acid
. Cyclization and reduction gives γ-valerolactone
:
This lactone
can be hydrogenated to 1,4-pentanediol, which can then be dehydrated to give 2-methyltetrahydrofuran:
2-Methyltetrahydrofuran has one stereocenter, so it exists in two enantiomer
ic forms. The commercial processes involving hydrogenation gives a racemic
mixture of the two. The asymmetric synthesis of (S)-(+)-2-methyltetrahydrofuran can achieved by using a wool
–rhodium
complex as a chiral catalyst for hydrogenation of methyl furan.
. It also is used in the electrolyte
formulation for secondary lithium
electrode
s and as a component in alternative fuel
s. It is a valued solvent for low temperature reactions. 2-Methyltetrahydrofuran forms a glass, which does not crystallize, and is frequently used as a solvent for spectroscopic studies at -196 °C.
Other common uses of 2-methyltetrahydrofuran is as a solvent for Grignard reagents
used in organometallic and biphasic chemical process
es, because of the oxygen
atom's ability to coordinate to the magnesium
ion component of the Grignard reagent, or to azeotropically dry products. The use of 2-methyltetrahydrofuran provides very clean organic-water phase separations. It is a popular, but costlier substitute for tetrahydrofuran.
2-Methyltetrahydrofuran is approved by the United States Department of Energy
as an additive to gasoline. Furfural and other partially hydrogenated/reduced furyl compounds between it and 2-methyltetrahydrofuran (furfuryl alcohol, methylfuran, tetrahydrofural alcohol) have a tendency to polymerize and are quite volatile. 2-Methyltetrahydrofuran itself, however, is more stable and less volatile, and thus is suitable for use as a motor fuel.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the molecular formula CH3C4H7O. It is a highly flammable mobile liquid. It is mainly used as a replacement for THF
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
in specialized applications for its better performance, such as to obtain higher reaction temperatures, or easier separations due to the solubility of 2-methyltetrahydrofuran. It is derived from furfural
Furfural
Furfural is an organic compound derived from a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. The name furfural comes from the Latin word , meaning bran, referring to its usual source....
and is usable as a biofuel
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...
.
Structures and properties
2-Methyltetrahydrofuran is “inversely soluble” in water. That is, its solubility decreases with increasing temperature, which is a rare property. 2-Methyltetrahydrofuran behaves like tetrahydrofuran as a Lewis base in organometallic reactions.Preparation
2-Methyltetrahydrofuran is usually synthesized by catalytic hydrogenation of furfuralFurfural
Furfural is an organic compound derived from a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. The name furfural comes from the Latin word , meaning bran, referring to its usual source....
.
- OC4H3CHO + 4 H2 → OC4H7CH3 + H2O
Furfural is produced by the acid-catalyzed digestion of pentosan sugars, C5 polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s, in biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
. Thus, the raw materials of 2-methyltetrahydrofuran are renewable biomass rich with cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
, hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
s, and lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
, such as corncobs or bagasse
Bagasse
Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials....
and other plant and agricultural waste.
2-Methyltetrahydrofuran can also be produced starting from levulinic acid
Levulinic acid
Levulinic acid, or 4-oxopentanoic acid, is an organic compound with the formula CH3CCH2CH2CO2H. It is a keto acid. This white crystalline is soluble in water, ethanol, and diethyl ether.-Synthesis and uses:...
. Cyclization and reduction gives γ-valerolactone
Gamma-Valerolactone
gamma-Valerolactone is an organic compound with the formula C5H8O2. This clear liquid is one of the more common lactones. It is a structural isomer of delta-valerolactone. Because of its herbal odor, it is used in the perfume and flavor industries....
:
This lactone
Lactone
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule...
can be hydrogenated to 1,4-pentanediol, which can then be dehydrated to give 2-methyltetrahydrofuran:
2-Methyltetrahydrofuran has one stereocenter, so it exists in two enantiomer
Enantiomer
In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable , much as one's left and right hands are the same except for opposite orientation. It can be clearly understood if you try to place your hands one over the other without...
ic forms. The commercial processes involving hydrogenation gives a racemic
Racemic
In chemistry, a racemic mixture, or racemate , is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was "racemic acid", which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid.- Nomenclature :A...
mixture of the two. The asymmetric synthesis of (S)-(+)-2-methyltetrahydrofuran can achieved by using a wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
–rhodium
Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...
complex as a chiral catalyst for hydrogenation of methyl furan.
Applications
2-Methyltetrahydrofuran is mainly used as a higher boiling substitute for tetrahydrofuran as specialty solventSolvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
. It also is used in the electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
formulation for secondary lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s and as a component in alternative fuel
Alternative fuel
Alternative fuels, known as non-conventional or advanced fuels, are any materials or substances that can be used as fuels, other than conventional fuels...
s. It is a valued solvent for low temperature reactions. 2-Methyltetrahydrofuran forms a glass, which does not crystallize, and is frequently used as a solvent for spectroscopic studies at -196 °C.
Other common uses of 2-methyltetrahydrofuran is as a solvent for Grignard reagents
Grignard reaction
The Grignard reaction is an organometallic chemical reaction in which alkyl- or aryl-magnesium halides add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon–carbon bonds...
used in organometallic and biphasic chemical process
Chemical process
In a "scientific" sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by somebody. Such a chemical process commonly involves a chemical reaction of some sort...
es, because of the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atom's ability to coordinate to the magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
ion component of the Grignard reagent, or to azeotropically dry products. The use of 2-methyltetrahydrofuran provides very clean organic-water phase separations. It is a popular, but costlier substitute for tetrahydrofuran.
2-Methyltetrahydrofuran is approved by the United States Department of Energy
United States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
as an additive to gasoline. Furfural and other partially hydrogenated/reduced furyl compounds between it and 2-methyltetrahydrofuran (furfuryl alcohol, methylfuran, tetrahydrofural alcohol) have a tendency to polymerize and are quite volatile. 2-Methyltetrahydrofuran itself, however, is more stable and less volatile, and thus is suitable for use as a motor fuel.