Ninhydrin and its analogs give a brief idea of how the chemical reaction occurs while developing latent prints on different challenging surfaces.

1. Ninhydrin Analogs
Rituja R. Gharote
M.sc II
QD and Fingerprints

2. Ninhydrin
• Ninhydrin was first synthesized in 1910 by Siegfried Ruhemann, a
professor of chemistry at the University Chemical Laboratories at
Cambridge University.
• In an effort to synthesize dicarbonyl compounds by the reaction of
1-indanone with p-nitrosodimethylaniline, he isolated 1,2,3- indanetrione
(ninhydrin) instead of the desired 1,2-indanedione.
shorturl.at/tyBU9

3. Properties of Ninhydrin
• Ninhydrin is a crystalline solid.
• It is colorless to pale yellow in color.
• It is highly soluble in polar solvents such as water and methanol.
• When heated, the solid becomes pink to red in color.
• Boiling Point is approximately 125 0C.
• Melting Point is 130–140 0C.
• It decomposes at 241 0C.
• The compound is found as the stable hydrate in the presence of water but
will assume a triketone structure in anhydrous conditions.

4. Benzo(f)ninhydrin01
Thieno(f)ninhydrin02
5-Methylthioninhydrin03
ANALOGS

5. Benzo(f)ninhydrin01
• This compound had been synthesized by Almog in 1982.
1) Condense dimethyl naphthalene-2,3-dicarboxylate with dimethyl sulfoxide.
2) The intermediate sulfoxide is then treated with concentrated hydrochloric acid
to yield 2-chloro-2-(methylthio)-1,3-indanedione.
3) 2-chloro-2-(methylthio)-1,3-indanedione is hydrolyzed in boiling water to yield
benzo[f]ninhydrin.
http://shorturl.at/hmtK6
shorturl.at/tAFGI

6. Synthesis of Benzo(f)ninhydrin
Source: shorturl.at/tyBU9
19= dimethyl naphthalene-2,3-dicarboxylate 20= dimethyl sulfoxide
21= 2-chloro-2-(methylthio)-1,3-indanedione 22= benzo[f]ninhydrin

7. Advantages and Disadvantages:
• Prints developed with this reagent
provided marks with a
similar sensitivity to that of ninhydrin
and provided better contrast on a
variety of pink to purple backgrounds.
• The treatment of benzo(f)ninhydrin-
developed prints with zinc chloride
causes the formation of a complex that
exhibited luminescence properties.
• Benzo(f)ninhydrin has very
low solubility.
• It is so expensive.
• It is less effective in terms of
results as compared to
Ninhydrin.
• More usage of Reagents.

8. Thieno(f)ninhydrin02
1) Thiophene-1-carboxylic acid is deprotonated, then lithiated at the 2-position
and added to carbon dioxide to yield thiophene-2,3-dicarboxylic acid.
2) The diacid was reduced with lithium aluminium hydride to the diol, which was
converted to the dibromide.
3) Sonication of the dibromide with activated zinc provided the in situ generation
of a transient highly reactive diene which was subsequently trapped with 4-
cyclopentene-1,3-dione to provide intermediate in excellent yield.
4) Exposure to “Br” in pyridine resulted in aromatization of the 6-membered ring.
5) Oxidation of the 2-position followed by treatment with dimethyl sulfoxide
yielded thieno(f)ninhydrin.

9. Synthesis of Thieno(f)ninhydrin
Source: shorturl.at/tyBU9
32=Thiophene-1-carboxylic acid 33=thiophene-2,3-dicarboxylic acid 34=Thiophene-diol
35=Thiophene-dibromide 36= Intermediate
37= geminal dibromide 38=Thieno(f)ninhydrin

10. Advantages and Disadvantages:
• This compound displayed a
combination of good chromogenic
and fluorogenic properties after zinc
chloride treatment.
shorturl.at/oCGZ7
• Reagents are too expensive and
are required in great quantity.
• Results are not that effective as
these are one of the primarily
synthesized analogs.

11. 5-Methylthioninhydrin (5-MTN)03
• Lennard and co-workers have synthesized 5-methoxyninhydrin.
• The synthesis began with dimethyl 4-nitrophthalate.
• Reduction of the nitro group to the amine, was followed by diazotization
with nitrous acid in methanol to yield 4-methoxyphthalate.
• 4-methoxyphthalate mixed with ethyl acetate and sodium hydride and
treated with aqueous hydrochloric acid to yield the desired 1,3-diketone.
• Treatment with p-toluenesulfonyl azide in triethylamine delivered the 2-
diazo intermediate.
• 2-diazointermediate is hydrolyzed with refluxing aqueous tert-butyl
hypochlorite to yield 5-methoxyninhydrin.

12. Synthesis of (5-MTN)
Source: shorturl.at/tyBU9
23= 4-nitrophthalate 24= amine compond 25= 4-methoxyphthalate
26= 1,3-diketone 27= 2-diazo intermediate 28= 5-methoxyninhydrin

13. Advantages and Disadvantages:
• The reagent develops print with a
more intense fluorescence than
ninhydrin-developed prints.
• It gives more effective results than
Ninhydrin.
https://www.b
vda.com/en/5-
mtn
Fingerprint developed by (5-MTN)
• After treatment with zinc
chloride, 5-MTN-developed
prints do not become orange, but
a more reddish colored purple.
• The fluorescence of the
fingerprint is stronger than DFO.

14. Other Ninhydrin Analogs:
1
2
3
4
1,8-
Diazafluoren-9-
one (DFO)
1,2-
Indanedione
9-methyl
Anthracene
Naphtho(f)
ninhydrin

15. References:
ADD TITLE
• (2020). Retrieved 3 December 2020, from
https://www.researchgate.net/publication/7886048_The_Development_of_Novel_Ninhydrin
_Analogues/link/0deec530e46a87d7c8000000/download.
• (2020). Retrieved 3 December 2020, from
https://www.sciencedirect.com/science/article/abs/pii/S0015736888727991.
• (2020). Retrieved 3 December 2020, from
https://www.sciencedirect.com/science/article/abs/pii/S0015736886725103.
• (2020). Retrieved 3 December 2020, from https://www.ncjrs.gov/pdffiles1/nij/225327.pdf.
• (2020). Retrieved 3 December 2020, from
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_dat
a/file/143867/fsb-chap5-alt-development.pdf.