Advances in Fingerprint Technology.pdf

Figure 5.1 2,2-Dihydroxy-1,3-indanedione (ninhydrin).
and other aromatic vicinal dicarboxaldehydes, 9,10 7-chloro-4-nitrobenzo-
2-oxa-1,3-diazole (NBD-chloride) and its derivatives, 12-14 together with a
long list of ninhydrin analogues, particularly 1,8-diazafluorenone (DFO) and
most recently also 1,2-indanedione (see text); but from the forensic scientist’s
perspective, ninhydrin is undoubtedly the most important. 1,3,7,15,16
Ninhydrin: The Universal Reagent for Fingerprints on Paper
History and General Properties of Ninhydrin
Ninhydrin (Figure 5.1) was first prepared by Ruhemann 17 in an attempt to
oxidize 1-hydrindone (II) to 1,2-diketohydrindene (III, Figure 5.2)*. Instead
of the expected product, he obtained another compound, triketohydrindene
hydrate, known today as ninhydrin. On the basis of his experimental work,
Ruhemann proposed the structure of the new substance as 2,2-dihydroxy-
1,3-indanedione (Figure 5.1). 17,18
It is interesting that Kaufmann had previously reported the preparation
of a compound with the same structure, but his compound did not have
ninhydrin properties. 19
Ninhydrin is a crystalline solid that is soluble in water and other polar
solvents. It crystallizes from ethanol as pale yellow prisms. When the solid is
heated to 125–130°C, it changes to pink, red, or reddish brown. At 130–140°C,
* The more common names for these compounds are 1-indanone and 1,2-indanedione,
accordingly. These names will prevail throughout this chapter.
O
O
I
OH
OH