4-Hydroxy-5-methyl-3 furfural

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

Furfural identified in beef diffusate appears to be a prominent meat flavor intermediate. It is a dehydration product of pentoses similar to formation of hydroxy methyl furfural from hex-oses. These compounds are formed by dehydration of 1,2-enediols derived from deamination of Amadori compounds (51). 

Figure 2.1.5 Potential platform chemicals considered for the controlled chemical transformation into fuel compounds and possible approaches to obtain novel biofuel motifs (5-HMF, 5-hydroxy methyl furfural LA, levulinic acid IA, itaconic acid EtOH, ethanol).

The furanic aldehydes 5-(hydroxy-methyl)furfural and 2-furaldehyde, systematically present in the toasted wood, can be formed by the thermal degradation of 3-deoxyosone during sugar pyrolysis or Maillard reactions (27). They could also be formed from glyceraldehyde, coming from degradation of DDMP, by condensation with subsequent elimination of water or formaldehyde (24). 

Heating a solution of hexoses in a strong non-oxidising acidic conditions, hydroxy methyl furfural is formed. The hydroxymethyl furfural from hexose is usually oxidized further to other products When phenolic compounds such as resorcinol, a-naphthol or enthrone are added, mixture of coloured compounds are formed. ... 

This reaction follows the same theoretical principles in which there is formation of furfural from hexoses and hydroxy-methyl-furfural (HMF) and from aldopentoses by add dehydration (Fig. 1). These two products, singly are colorless, however, it is necessary a phenolic compoimd addition in the medium to develop a colored compound, in this case redness. This technique is firstly mentioned by Roe (1934), with some posterior modifications by Roe et al. (1949), becoming a quick reaction and with stable color. The reaction uses the hydrochloride acid (HCl) for carbohydrates dehydration and the resorcinol is the phenolic compoimd that reacts with furfural and HMF. 

Taking into account the specific properties of carbohydrates, only hydrophilic ILs can be used [Murugesan and Linhardt, 2005]. This means that only apolar solvents or scCCh may be used to extract reaction products. Unfortunately, 5-hydroxy methyl furfural (HMF) was found to have a larger affinity for the IL l-H-3-methyl imidazolium chloride than for the organic solvent (such as diethyl ether) or scCCh. For the dehydration of fructose, Moreau et al. (2006) showed that HMF could be completely extracted with diethyl ether in a continuous or stepwise manner. But, their paoliminary results using scCCb as extraction solvent do not seem to have better expected extraction properties. 

After the extraction of 5-hydroxy methyl furfural (HMF) with diethyl ether, the IL is recycled as such or after removal of the water formed during the course of the reaction (see Table 14). Such operation is rather important since three water molecules are produced during the course of the reaction. Under the operating conditions used, 5.55 mmol of fructose and 25.3 mmol of IL at 90 °C for 1 h, and although the amount of water formed after three cycles was twofold higher than that of the IL, the yield in HMF is not affected in a spectacular manner, but is more affected than after water removal where no significant loss in activity is observed within the experimental error [Moreau et al., 2006]. 

Table 14. Yield of 5-hydroxy methyl furfural (HMF) from fructose dehydration after recycling of IL l-H-3-methyl imidazolium chloride...

Further work by V an Ekenstein and Blanksma7 led to a revision of the formulation of hydroxymethylfurfural. It was found that chitose on dehydration gave hydroxymethylfurfural which when oxidized was converted into hydroxymethylpyromucic acid, identical with the compound obtained by Fischer and Andreae from chitonic and chitaric acids.8 The nature of chitose (a 2,5-anhydrohexose) was such that Kiermayer s original formulation of /J-hydroxy-S-methyl-furfural could not obtain and the accepted formulation, -hydroxymethylfurfural (5-hydroxymethyl-2-furaldehyde (IV)) was assigned to the compound. 

Decomposition with elimination of two water molecules, yielding the hydroxy-methyl- substituted furaldehyde (XVI) and then furfural by elimination of formaldehyde. 

The routes involved in the formation of the various furan sulphides and disulphides involve the interaction of hydrogen sulphide with dicarbonyls, furanones and furfurals. Possible pathways are shown in Scheme 12.8. Furanthiols have been found in heated model systems containing hydrogen sulphide or cysteine with pentoses [56-58]. 2-Methyl-3-furanthiol has also been found as a major product in the reaction of 4-hydroxy-5-methyl-3(2H)-furanone with hydrogen sulphide or cysteine [21, 59]. This furanone is formed in the Maillard reaction of pentoses alternatively it has been suggested that it may be produced by the dephosphorylation and dehydration of ribose phosphate, and that this may be a route to its formation in cooked meat [21, 60]. 

Adedeji et al. (1993) used a direct thermal desorption technique (220°C) to analyse the volatiles from beans that might cause the thermal degradation and transformation of sugar into common volatile compounds such as 3,5-dimethyl-2,4(3H,5H)-furandione and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one. This last compound was detected at a high concentration (3880 ppm) in Mexican vanilla, being the third most abundant compound after vanillin and 2-furfural, and far more abundant than vanillic acid, p-hydroxy-benzaldehyde or p-hydroxybenzoic acid. 

From the molecular beam MS of the pyrolysis products of the P/N fractions, a number of phenolic compounds were detected guaiacol (2-methoxyphenol) (m/z 124), catechols (m/z 110), isomers of substituted 2-methoxyphenols with alkyl groups such as methyl (m/z 138), vinyl (m/z 150), 3-hydroxy-propen(l)-yl (m/z 180), allyl (m/z 164), hydroxyethyl (m/z 168), and ethyl (152), most likely in the para position. In addition, a few carbohydrate-derived components are also present in this fraction such as furfuryl alcohol and other furfural derivatives. 

Figure 5.2.10. Cellulose pyrolysate obtained at 59CP C by Py-GC/MS. The separation was done on a Carbowax type column. 1 CO2, 2 acetaldehyde, 3 acetone, 4 2-butanone, 5 2,3-butandione, 6 toluene, 7 water, 8 cyclopentanone, 9 methylfuran, 10 3-hydroxy-2-butanone, 11 hydroxypropanone, 12 cyclopent-1-en-2-one, 13 2-methylcyclopentenone, 14 acetic acid, 15 acetic acid anhydride, 16 furancarboxaldehyde, 17 methylcyclopentenone, 18 dimethylcyclopentenone, 19 5-methylfurancarboxaldehyde, 20 2,3-dihydro-2-furanone, 21 furan-2-methanol, 22 3-methylfuran-2-one, 23 2(5H)-furanone, 24 hydroxycyclopentenone, 25 3,5-dimethylcyclopentan-1,2-dione, 26 2-hydroxy-3-methyl-2-cyclopenten-1-one, 27 2-hydroxy-3-ethyl-2-cyclopenten-1-one, 28 2,3-dimethyl-2-cyclopenten-1-one, 29 phenol, 30 dimethylphenol, 31 3 thyl-2,4(3H,5H)-furandione, 32 3-butenoic acid, 33 1,4 3,6-dianhydro-a-D-glucopyranose, 34 5-(hydroxymethyl)-furfural.

Figure 5.2.11. Cellulose pyrolysate obtained at 59(P C and separated on a methyl silicone with 5% phenyl silicone type column. 1 acetic anhydride, 2 pentanal, 3 2-hydroxybutanedialdehyde, 4 1,4-dioxadiene, 5 tetrahydro-2-furanmethanol, 6 2-(hydroxymethyl)-furan, 7 3-methyl-2-hexanone, 8 2-methoxy-2,3-dihydrofuran, 9 2(5H)-furanone, 10 1-acetyloxypropan-2-one, 11 hydroxycyclopentenone, 12 5-methylfurfural, 13 2,3-dihydro-5-methylfuran-2-one, 14 1-cyclopentylethanone, 15 2-hydroxy-3-methyl-2-cyclopenten-1-one, 16 3,5-dimethylcyclopentan-1,2-dione, 17 unknown, 18 3-ethyl-2,4(3H,5H)-furandione, 19 6-methyl-1,4-dioxaspiro[2,4]heptan-5-one, 20 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one, 21 1,4 3,6-dianhydro-a-D-glucopyranose, 22 5-(hydroxymethyl)-furfural, 23 4-cyclopenten-1,2,3-triol, 24 5-ethyl-3-hydroxy-4-methyl-tetrahydrofuran-2-one, 25 levoglucosan, 26 1,6-anhydro-p-D-glucofuranose.

Figure 7.1.1. Chromatogram for the pyrotysate ofgtucose obtained by on-line Py-GC/MS. The peak assignments are 1 furan, 2 2-melhylfuran, 3 2,5-dimethylfuran, 4 3-methyl-2-butanone, 5 water, 6 1-hydroxypropanone, 7 hydroxyacetaldehyde, 8 acetic acid, 9 oxopropanoic acid methyl ester, 10 furancarboxaldehyde, 11 1-(2-furanyl)-ethanone, 12 5-methyl-2-furfural, 13 2-hydroxycyclopent-2-en-1-one, 14 2-hydroxy-3-methyl-2-cyclopenten-1-one, 15 2,3-dihydro-5-hydroxy-6-methyl-4H-pyran-4-one, 16 2-methyl-1,3-benzendiol, 17 2,5-dimethyldioxane, 18 2-hydroxy-3-pentanone, 19 5-formyl-2-fufurylmethanoate, 20 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 21 1,4 3,6-dianhydro-a-D-glucopyranose, 22 5-(hydroxymethyl)-furancarboxaldehyde.

Furans furfural with its caramel, burnt, ethereal, almond character, is the most prominent sugar degradation product. 2-Methyl-5-ethyl-4-hydroxy-dihydro-furan-3(2H)-one has a strong, sweet, caramel, bread note. 

Within the GC detectable range, we identified the different composition of the liquid products from the various origins by using a GC-MS analysis. The liquid products from Kraft pine lignin contain mainly guaiacol and methyl dehydroabietate. The liquid products from oat hull, hardwood, and switchgrass contain acetic acid, 1-hydroxy-2-propanone, and/ or furfural, which are the products of hemicellulose and cellulose. This further confirms that these three materials contain hemicellulose and cellulose. The liquid products have only two to three component differences from one biomass species to another. But the composition distributions are quite different among species (Table 4). So the composition of liquid products depends on the type of raw materials. 

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