Fructose absorption spectrum

During the formation of colorant from D-fructose at pH 7.0,73 the first changes in the absorption spectrum occur at 210-240 mu and at 270-290 m/x. Judging by the data in Table II, these peaks are occasioned by a 2-furaldehyde derivative, possibly 5-(hydroxymethyl)-2-furaldehyde, or a compound of equivalent conjugation. Later, the absorption at 350-400 m/x increases. With further reaction, these peaks tend to be smoothed out to a hyperbolic curve, and absorption in the visible range appears and, still later, the solution becomes turbid as well as colored. If the process is continued, brown-to-black material is precipitated. 

Evidence has also been educed for the formation of two constituents, re-ductone and l,3-dihydroxy-2-propanone, by symmetrical scission of the D-fructose molecule these constituents are mainly responsible for the peak at 285-290 m/u in the ultraviolet absorption spectrum of the D-fructose solutions. 

A kinetic determination of 2-ketohexoses has been based on their reactions with the cysteine-sulphuric acid reagent sorbose gave a distinct absorption spectrum, whereas o-fructose, psicose, and tagatose were distinguished from each other by differences in the rate of increase of the absorbance at 412 nm. Procedures used in colorimetric ultramicroassays of reducing sugars, and... 

The extent to which the 4-thioaldoses are in the furanose forms is not certain. It has been claimed that 4-thio-L-ribose143 and 4-thio-D-glu-cose144 are completely in furanose forms, because they show no thiol absorption at 2550 cm-1 in their i.r. spectrum. This evidence is not convincing in the syrupy state, the composition may be different from that in dilute solution. The 13C-n.m.r. spectrum of a solution of 5-thio-D-fructose, however, shows141 only the signals of the two furanose forms, in the ratio of 11 89, at 25°. The -n.m.r. spectrum of a solution of... 

Oxidation of the o-fructose derivative (73) with lead tetraacetate gave a crystalline dialdehyde which showed no carbonyl absorption in the infrared spectrum, and to which structure (74) was assigned. Reaction with... 

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