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 cellulose and is a potential precursor to biofuels, such as ethyl levulinate.

Synthesis
Levulinic acid was first prepared in 1840 by Dutch chemist Gerardus Johannes Mulder by heating fructose with hydrochloric acid. The first commercial production of levulinic acid began as a batchwise process in an autoclave by starch manufacturer A. E. Staley in the 1940s. In 1953 Quaker Oats developed a continuous process for the production of levulinic acid. In 1956 it was identified as a platform chemical with high potential. and in 2004 the US Department of Energy (U.S. DoE) identified levulinic acid as one of the 12 potential platform chemicals in the biorefinery concept.

The synthesis of levulinic acid from hexoses (glucose, fructose) or starch in dilute hydrochloric acid or sulfuric acid. In addition to formic acid further, partly insoluble, by-products are produced. These are deeply colored and their complete removal is a challenge for most technologies. Many concepts for the commercial production of levulinic acid are based on a strong acid technology. The processes are conducted in a continuous manner at high pressures and temperatures. Lignocellulose is an inexpensive starting material. Levulinic acid is separated from the mineral acid catalyst by extraction. Levulinic acid is purified by distillation.

Reactions and applications
Levulinic acid is used as a precursor for pharmaceuticals, plasticizers, and various other additives. The largest application of levulinic acid is its use in the production of aminolevulinic acid, a biodegradable herbicide used in South Asia. Another key application is the use of levulinic acid in cosmetics. Ethyl levulinate, a primary derivative of levulinic acid, is extensively used in fragrances and perfumes. Levulinic acid is a chemical building block or starting material for a wide variety of other compounds including γ-valerolactone and 2-methyl-THF.



Other occurrence and niche uses
Levulinic acid is used in cigarettes to increase nicotine delivery in smoke and binding of nicotine to neural receptors.

Levulinic acid, in its cyclic alternate structure, was the first pseudoacid to be described as such.

Etymology
The former term “levulose” for fructose gave levulinic acid its name.

Safety
Levulinic acid is relatively nontoxic, with an of 1850 mg/kg.