γ-Valerolactone (GVL) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

with the formula C₅H₈O₂. This colourless liquid is one of the more common

lactone Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the co ...

s. GVL is chiral but is usually used as the

racemate In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

. It is readily obtained from cellulosic biomass and is a potential fuel and

green solvent Green chemistry, also called sustainable chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances. While environmental che ...

. GVL behaves as a prodrug to γ-hydroxyvaleric acid (GHV), a drug with similar effects to those of

γ-hydroxybutyric acid ''gamma''-Hydroxybutyric acid (or γ-hydroxybutyric acid (GHB), also known as 4-hydroxybutanoic acid) is a naturally occurring neurotransmitter and a depressant drug. It is a precursor to GABA, glutamate, and glycine in certain brain areas. ...

(GHB), albeit with less potency in comparison. Because GHB is controlled in many parts of the world, while GVL is not, GVL has gained popularity as a legal substitute for GHB.

Synthesis

GVL is produced from

levulinic acid Levulinic acid, or 4-oxopentanoic acid, is an organic compound with the formula CH3C(O)CH2CH2CO2H. It is classified as a keto acid. This white crystalline solid is soluble in water and polar organic solvents. It is derived from degradation of cel ...

, which is obtained from

hexose In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily convert ...

s. In a typical process, cellulosic biomasses, such as corn stover, sawgrass, or wood, is hydrolysed into

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

and other sugars using acid catalysts. The resulting glucose can then be dehydrated via hydroxymethylfurfural to yield formic acid and

, which cyclises to intermediate unsaturated ring compounds, which can then be

hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...

to ''gamma''-valerolactone, which has potential applications as a liquid fuel. :

Potential applications

GVL has been identified as a potential green solvent. Because of its herbal odor, it is used in the perfume and flavor industries. It is a structural isomer of δ-valerolactone.

Potential fuel

Since it is readily obtained from glucose, GVL has long been identified as a potential "green fuel." GVL retains 97% of the energy of glucose and can be blended by itself in gasoline where it performs comparably to

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

/gasoline mixtures. However, due to blending limits for use in conventional combustion engines, it may be more efficient to convert GVL into liquid

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

s (or alkanes). The first step in this process is the ring-opening of GVL to yield a mixture of pentenoic acids. These acids can then be decarboxylated to produce

butene Butene, also known as butylene, is an alkene with the formula . The word ''butene'' may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for ...

and CO₂. These conversions can be performed with

zeolite Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...

catalysts. After this stream is dehydrated, the products can be oligomerized at elevated pressures in the presence of a common acid-catalyst to yield alkenes with higher

molecular weights The molecular mass (''m'') is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quanti ...

, targeted for gasoline and other fuel applications. One of the main advantages that allows GVL to be a practical biofuel is that it is relatively inexpensive to produce. Using a cheap feedstock, this biofuel can be produced at prices between 2-3 US$/gallon. The conversion of GVL to transportation fuel capable alkenes only requires a system containing two flow reactors, two phase separators, and a simple pumping arrangement for the delivery of an aqueous GVL feed. Since the use of precious metal catalysts is not required, this also decreases the total price of fuel production.

Potential production of biomass-derived fuels

Apart from its value as a potential fuel in its own right, gamma-valerolactone has shown promise in laboratory-scale thermocatalytic production of soluble carbohydrates from corn stover and wood at high yields. The biomass reacts in a solvent mixture of water, dilute sulfuric acid, and gamma-valerolactone, itself derived from biomass. The gamma-valerolactone promotes thermocatalytic hydrolysis into monosaccharides by complete solubilization of the raw material, including lignins. The saccharide products can be recovered from the lactone into water solution by antisolvent addition of salt or liquid carbon dioxide. The product can be used as feedstock for producing furans or ethanol at high yield, while the gamma-valerolactone is returned to the catalytic cycle.

Membrane Fabrication

Gamma-Valerolactone has been studied and shown the potential to prepare dope solutions for the fabrication of polymeric membranes. Due to the toxicity of the traditional solvents, green solvents were investigated in recent years. Due to its environmentally friendly profile, Gamma-Valerolactone showed the potential to fabricate polysulfone membranes as a co-solvent.

References

External links

; General Safety Information
gamma-Valerolactone MSDS by Sciencelab.com
{{DEFAULTSORT:Valerolactone, gamma- Gamma-lactones GABAB receptor agonists GHB receptor agonists Designer drugs Hypnotics Prodrugs Solvents