The Pyrolysis of Sugars

Ever since the work of Cemiani in 1951, the pyrolysis of sugars has been studied at temperatures ranging from 200 to 1000°. Above 200°, or 250°, deep changes occur in sugars, and a great variety of products is formed, such as carbon mon-, and di-oxide, hydrocarbons (among them alkanes, alkenes, and aromatic hydrocarbons), alcohols, aldehydes, ketones, and several furan derivatives. The number, and character, of the products depend, at least, on both the temperature and the time of reaction. Controversy exists in respect to the influence of the atmosphere in which the pyrolysis takes place. 

Percentage Composition of Gases from the Pyrolysis of Some Sugars  

Pyrolyzate obtained under nitrogen at 400°, as well as at 1000°, is entirely free from alcohols. Again, butanedione is formed only under nitrogen at 400°, and not under hydrogen (see Table X). (Pyrolysis of D-glucose, and of sucrose, at 270-300° appeared to be uninfluenced by the oxides of aluminum, chromium, and zinc ). 

who pyrolyzed a-D-glucose and maltose, showed that, as the temperature of the process is raised from 300 to 1000°, the volume of gases 

—The Course of Total Gas Evolution from o-Glucose (Points), Lactose (Dashes), and Sucrose (Solid Line) Heated from 200 to 500°. 

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Acetone was originally observed about 1595 as a product of the distillation of sugar of lead (lead acetate). In the nineteenth century it was obtained by the destmctive distillation of metal acetates, wood, and carbohydrates with lime, and pyrolysis of citric acid. Its composition was determined by Liebig and Dumas in 1832. 

A recent study extensively investigated the pyrolysis of polysaccharide binders, with and without a silylating agent [56]. Some of the main results relative to the pyrolysis silylation of sugars and polysaccharide binders can be summarised as follows [56 59] ... 

J-Hydroxyamino acids under pyrolysis conditions (250 °C) can give rise to a-hydroxyaldehydes and a-aminoalcohols, which can enrich the pool of sugar fragmentation products.59... 

Pyrrole and N-substituted pyrroles are formed by a reaction analogous to the conversion of sugars to furan aldehydes. Ammonium and substituted ammonium salts of mucic acid, H02C(CH0H)4C0jH, are cyclized and de-carboxylated by pyrolysis. The yields of pyrrole and its N-phenyl and N-methyl derivatives are about 40%. Tetrahydropyrroles (pyrrolidines) are formed from various 4-substituted amines by elimination of water, ammonia, or hydrogen halide. ... 

Other reactions may take place with elimination of water and other small molecules such as formaldehyde and the formation of furancarboxaldehyde, which is very abundant in the pyrolysis of most sugars ... 

Pyrolysis products of the proline/fructose Maillard polymer show typical products for the pyrolysis of proline and of peptides containing proline. The sugar moiety is also shown by the presence of cyclopentenone derivatives (e.g. 2-hydroxy-3-methyl-2-cyclopenten-... 

The association of Maillard polymer pyrolysis with the formation of these compounds is based on the correlation of the level of sugars and amino acids with the level of mutagen formation. Also, it was shown that the presence of creatinine (common in animals) may play an important role in the formation of these compounds, and a reaction path as shown below was proposed [19] ... 

Quantitative estimations of the yield of levoglucosan from the pyrolysis of cellulose have been made. Schwenker and Pacsu found that, at 350-375°, some 12.5% of levoglucosan was produced when various cellulose samples were pyrolyzed in a limited supply of air. Madorsky and cowork-ers 2 found a 52% yield of anhydro sugar from cotton heated at 280° under vacuum. This proportion was dramatically diminished to about 5%, when the pyrolysis was conducted in the presence of such salts as sodium chloride or sodium carbonate. Comparable results have been obtained by Holmes and coworkers. ... 

Pyrrole and the simple alkyl-pyrroles are colourless liquids, with relatively weak odours rather like that of aniline, which, also like the anilines, darken by autoxidation. Pyrrole itself is readily available commercially, and is manufactured by alumina-catalysed gas-phase interaction of furan and ammonia. Pyrrole was first isolated from coal tar in 1834 and then in 1857 from the pyrolysate of bone, the chemistry of which is similar to an early laboratory method for the preparation of pyrrole - the pyrolysis of the ammonium salt of the sugar acid, mucic acid. The word pyrrole is derived from the Greek for red, which refers to the bright red colour which pyrrole imparts to a pinewood shaving moistened with concentrated hydrochloric acid. 

It is formed in the pyrolysis of alanine (Merritt et al., 1970) and in the reaction of alanine with a polyphenol oxidase (Motoda, 1979). In coffee, it comes from sugar pyrolysis (Liardon et al., 1984). 

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