M.I. Velasco et al. / Dyes and Pigments 90 (2011) 259e264
263
Table 3
Green metrics calculated for the synthetic reactions of azo compounds.a
Acknowledgements
This research was supported in part by the Consejo Nacional de
Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional
de Promoción Científica y Técnica (FONCYT), the Secretaría de
Ciencia y Técnica (SECyT) of Universidad Nacional de Córdoba,
Ministerio de Ciencia y Tecnología de Córdoba (MINCyT), Argentina.
M.I.V and C.O.K. are grateful recipients of fellowships from CONICET.
Product
Synthetic methods
% RME
% CE
% AE
83.49
42.73
84.93
84.93
b
1
1
1
1
NaNO2/HCl(aq)
8.41
23.7
23.4
28.7
14.9
34.2
38.5
43.6
c
Fe(NO3)3/HCl(aq)
d
HNO3 (aq)/HCl(aq)
e
HNO3 (aq)/HCl(g)
b
2
2
NaNO2/HCl(aq)
12.6
17.7
22.3
25.5
81.06
38.72
c
Fe(NO3)3/HCl(aq)
3
3
3
3
NaNO2/HCl(aq)
Fe(NO3)3/HCl(aq)
HNO3 (aq)/HCl(aq)
HNO3 (aq)/HCl(g)
8.5
9.6
13.4
13.0
13.0
12.7
20.0
18.0
83.72
43.15
85.15
85.15
c
d
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e
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% RME: percentage reaction mass efficiency. % CE: percentage carbon efficiency.
% AE: percentage atom economy.
b
Classical synthesis [35], aqueous media.
Solvent acetonitrile, nitrosonium ion source Fe(NO3)3$9H2O/HCl(aq)
Solvent acetonitrile, nitrosonium ion source HNO3(aq)/HCl(aq)
Solvent acetonitrile, nitrosonium ion source HNO3(aq)/HCl(g)
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In the Table 3, the green metrics calculated for our alternative
method and traditional synthesis are summarized. The results
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cases, better than the classical synthesis. In addition, the other
values show the same tendency.
4. Conclusions
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It can be concluded that the new proposed methods are excel-
lent synthetic alternative procedures to obtain known azo
compounds and they would permit to synthesize new azo
compounds. The nitrosonium ion source HNO3(ac)/HCl(g) is the best
because it gave very good yields in most of the cases. Except for the
synthesis of Ice Bordeaux, no by-products were formed which is
very important because there are no washed material and the
purification of the desired azo dye is easier.
Our reaction conditions are agreement with some the Green
Chemistry principles and they gave very good values of the green
metrics.
In summary, we report herein efficient and greenner methods
for the synthesis of azo compounds with good yields and excellent
prospect to obtain new azo compounds.
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