Synthesis and structural elucidation of sulfonated naphthalene-formaldehyde

Article abstract of DOI:10.1080/10426500802211585

The synthesis, characterization, structural elucidation, and application of the dispersant obtained from the condensation of -naphthalene sulfonic acid and formaldehyde are reported. The one-pot synthesis from naphthalene, sulfuric acid, and formaldehyde leads to reproducible polymers with 13 and 14 naphthalene nuclei. The 1H and 13C NMR spectra in D2O (representative spherical shape) and DMSO (representative rod-like shape) are reported. The belching technique led to excellent super pure material.

Full text of DOI:10.1080/10426500802211585

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Phosphorus, Sulfur, and Silicon
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Synthesis and Structural
Elucidation of Sulfonated
Naphthalene-Formaldehyde
S. Moradian a , N. O. Mahmoodi b & R. Shemshadi a
a Polymer Engineering, Department of Dye
Technology , Amirkabir University of Technology ,
Tehran, Iran
b Department of Chemistry, Faculty of Science ,
University of Guilan , Rasht, Iran
Published online: 19 Feb 2009.
To cite this article: S. Moradian , N. O. Mahmoodi & R. Shemshadi (2009)
Synthesis and Structural Elucidation of Sulfonated Naphthalene-Formaldehyde,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:3, 578-584, DOI:
10.1080/10426500802211585
To link to this article: http://dx.doi.org/10.1080/10426500802211585
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Phosphorus, Sulfur, and Silicon, 184:578–584, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802211585
Synthesis and Structural Elucidation of Sulfonated
Naphthalene-Formaldehyde
S. Moradian,1 N. O. Mahmoodi,2 and R. Shemshadi1
1Polymer Engineering, Department of Dye Technology, Amirkabir
University of Technology, Tehran, Iran
2Department of Chemistry, Faculty of Science, University of Guilan,
Rasht, Iran
The synthesis, characterization, structural elucidation, and application of the
dispersant obtained from the condensation of β-naphthalene sulfonic acid and
formaldehyde are reported. The one-pot synthesis from naphthalene, sulfuric acid,
and formaldehyde leads to reproducible polymers with 13 and 14 naphthalene nu-
clei. The 1 H and 13 C NMR spectra in D2 O (representative spherical shape) and
DMSO (representative rod-like shape) are reported. The belching technique led to
excellent super pure material.
Keywords Auxiliaries dispersing; belching technique; dispersing agent; β-naphthalene
sulfonic acid; polymer with formaldehyde (NSC)
INTRODUCTION
During the past few years, commercial applications of water-soluble
macromolecules, particularly as dispersing agents and surface mod-
ifiers, have been introduced in the textile, pharmaceutical, and other
related industries.1–10 The use of insoluble dyestuffs in textile processes
has become a common practice in recent years. Due to the lack of the
solubility of such compounds in aqueous systems, dispersing agents
often are used to increase the dispersion of such suspensions.
Formaldehyde condensate of β-naphthalene sulfonate first appeared
in the industry in 1913 in a patent of BASF.11 Since then, it has been
widely used for different purposes such as effective dispersant for dyes
and pigments, as an emulsifier for synthetic rubbers, as leather tan-
ning agents, or pulp rheology on the grindability of coals.12 A detailed
Received 31 March 2008; accepted 19 May 2008.
Address correspondence to Professor Dr. Nosrat O. Mahmoodi, Department of Chem-
istry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht, Iran. E-mail:
nosmahmoodi@gmail.com
578

Sulfonated Naphthalene-Formaldehyde
579
H
S
S
n-1
n = number of nuclei
s = sulfonate group
FIGURE 1 Structure formula proposed for the commercially available
formaldehyde condensate with β-naphthalene sulfonic acid.
investigation on the composition and physicochemical properties of this
compound confirmed that it is a polynuclear macromolecule, with prop-
erties in aqueous solutions that vary depending on the number of naph-
thalene nuclei in the molecule. Although these products, which became
known as the Tamol types, have been in use for a very long time, their
constitution is not yet completely known. The formula in Figure 1 in-
dicates schematically the assumed structure.
RESULTS AND DISCUSSION
The degree of condensation of the commercial products presumably
ranges between 2 and 10 naphthalene nuclei. The quantitative dis-
tribution of the condensates, however, varies depending on the con-
densation during manufacture. However, the yield of conversion for
the crude mixture published in the patenting process is less than 75
%. Recently, analysis of sulfonated naphthalene-formaldehyde conden-
sates by ion-pair chromatography and their quantitative determina-
tion from aqueous environmental samples were reported.13 In recent
articles, Wolf et al.13 described the development of an ion-pair solid-
phase extraction (IPE) and an ion-pair chromatography (IPC) proce-
dure with fluorescence detection for the quantitative analysis of sul-
fonated naphthalene-formaldehyde condensates (SNF), which provides
full resolution of SNF up to a degree of condensation n = 5 and partial
resolution up to n = 15.14 In this context, here we present two clear
routes for the reproducible synthesis of this auxiliary dispersing agent.
The first route involves sulfonation of naphthalene under strong acidic
conditions fallowed by the condensation of the resulting product with
formaldehyde (Figure 3). A different approach is provided by the re-
action of β-naphthalene sulfonic acid with formaldehyde under weak
or neutral conditions. The FT-IR spectra of the product synthesized by
us were identical to that of commercial standard NSC, which has been
prepared by the patent procedure of BASF.11 In our hands, the yield

580
S. Moradian et al.
SO3H
conc. H2SO4
150-155 oC
5 h reflx
3
4
H
95-100 oC
12 h ref
3
+
CH2O
n-1
SO3H
H
SO3H
2
1) NaOH
2
12 h reflx
2) NaOCl
n-1
SO3Na
SO3Na
1
FIGURE 2 Synthetic sequences for the formation of formaldehyde condensate
of β-naphthalene sulfonate 1.
of conversion for pure NSC with n = 13 has been increased to 93.5 %.
Examination of a model of NSC by MM2 calculations indicated the dot
surface, shown in Figure 2.
To the best of our knowledge, there is no literature report on the
1
1H and 13C NMR spectra of NSC. The H NMR spectra of NSC were
recorded in two different solvents: D2O and DMSO. However, these
two spectra are not identical. The solubility of the condensates in wa-
1
ter increases sharply as the number of nuclei increases. The H NMR
spectrum obtained in D2O suggests a spherical shape of the molecules
in water. However the 1H NMR spectrum of similar condensate in
DMSO suggest a random rod-like shape (Figure 3 and Table I). Al-
though formaldehyde condensates of naphthalene sulfonate belong to
a relatively old generation of surfactants, they may find new fields of
industrial application in the future, e.g., as precipitants for cationic sub-
stances, caking agents for basic dyes, anticaking agents for fertilizers
that contain ammonium nitrate in the gypsum industry, for manufac-
turing of fire bricks, for agricultural formulations, and in the ceramic
industry.

Sulfonated Naphthalene-Formaldehyde
581
FIGURE 3 Dot surface MM2 models of synthesized NSF (CS Chem 3D Ultra).
EXPERIMENTAL
Products were characterized by comparison of their physical data with
those of authentic samples (IR, FT-IR, VPO, DSC, and CHNO elemental
analysis). IR spectra were obtained either on a Shimadzu IR-470 or with
a FT-IR–Domem instrument. NMR data were recorded in D2O and
1
DMSOwith a Bruker Avance 500 spectrometer. H and 13C chemical
shifts are reported in ppm (δ)using TMS as internal reference. The
UV/VIS and diffuse reflectance spectra (DRS) were recorded either on
a Shimadzu UV-2100 instrument equipped with an integrated sphere
assembly or with a DuPont-910 instrument. Vapor phase osmometry
(VPO) data were obtained with a KNAUER instrument.
Sulfonation of Naphthalene in Strong Acidic Media
and Condensation with Formaldehyde; Preparation of NFC
To a 250 mL three-neck round-bottom flask equipped with a reflux
condenser and a dropping funnel was added 42.5 g of naphthalene. The
flask was heated to 150–155◦C, and from the dropping funnel at this
temperature was added dropwise 44 g of concentrated H2SO4 over a
period of 30 min. The reaction mixture was allowed to stay at 150–
155◦C during addition of H2SO4. The resulting solution was refluxed at
this temperature for 5 h. After this time, the temperature of the reaction
mixture was adjusted to 90◦C. To the mixture was added 24 mL of

582
S. Moradian et al.
TABLE I Physical Properties of Synthesized NSC
V.P.O MW
found 3200 g/mol, for synthesized NSC, calcd. n = 13;
found 3440 g/mol for NSC, calcd. n = 14
n = 13 found 22.5; n = 14 found 27.3
Sulfonation degree, %
CHN-O
n = 13, found N: 0 %, C: 36.43 %, H: 2.77 %
n = 14, found N: 0 %, C: 39.39 %, H: 3.11 %
n = 13: 3433, 3066, 3003, 2921, 2851, 2345, 1738, 1624,
1501, 1447, 1384, 1352, 1118 (S = O), 1119, 1036,
890, 821, 745, 669, 620, 561, 473
FT-IR cm−1
NSC n = 14: 3435, 3056, 3013, 2912, 2849, 1597, 1504,
1443, 1357, 1488, 1118 (S=O), 1037, 895, 829, 751,
681, 620, 566, 477
DSC
n = 13: >325◦C [dec.]; n = 14: >325◦C [dec.]
Yield
1H NMR (500 MHz)
n = 13: 93.5 %; n = 14: <75 %
n = 13: (DMSO) δ = 9.17 (s, 1H), 8.7 (d, J = 4.5 Hz,
2H), 8.48 (s, 7H), 8.27–8.17 (m, 8H), 7.98 (m, 10H),
7.89 (s, 6H), 7.77 (s, 14H), 7.54 (s, 3H), 7.48 (s, 2H),
7.39 (d, J = 7 Hz, 3H), 6.96 (d, J = 2.2 Hz, 11H), 4.86
(s, 22H)
n = 13: (D2O) δ = 9.35 (s, 2H), 9.0 (s, 2H), 8.8 (s, 2H)
8.76 (s, 1H), 8.70 (d, J = 4.5 Hz, 2H), 8.61 (s, 4H),
8.54 (s, 2H), 8.39 (d, 3H), 8.28 (s, 6H), 8.24 (s, 4H),
8.00 (s, 6H), 8.04 (s, 4H), 7.99 (s, 3H), 7. 84 (s, 6H ),
7.72 (t, J = 7 Hz, 4H), 7.53 (t, J = 7 Hz, 3H), 7.45 (d,
J = 5 Hz, 5H), 7.00 (s, 3H), 6.70 (d, J = 7 Hz, 5H),
4.71 (s, 22H)
13C NMR (125 MHz), DMSO
n = 13: δ = 146.9, 146.2, 145.6, 145.3, 134.2, 132.8,
131.6, 128.3, 128.0, 126.5, 125.6, 124.8, 122.2, 122.0,
49.3, 50.2
CH2O over a period of 30 min. Then the reaction mixture was refluxed
at 95–100◦C for an additional 12 h. After this time, the pH of the
resulting mixture was adjusted to 8–8.5 diluting with H2O and with
50% aqueous NaOH solution. To the resulting solution was added 50 mL
of commercial sodium hypochlorite (6–14% active chlorine) for belching,
and the reaction mixture was allowed to stay at 60◦C for 1 h. The
solution was then spread on the glass plate and stored in the oven at
90–100◦C for 2 h when 94 g of solid was obtained. The product contains
18–20% of Na2SO4. For the preparation of dispersions with a lower
amount of Na2SO4, it is required that the temperature of solution while
stirring is kept below 23◦C. At this stage, the amount of Na2SO4was
found 0.5 % at 22◦C; 2.4% at 15◦C, and 1.6 % at 10◦C.

Sulfonated Naphthalene-Formaldehyde
583
Utilizing Methanol for Decreasing the Amount of Na2SO4
A similar procedure as used for NFC was applied, but instead of diluting
to 53% concentration of the solid material, 50% concentration of the
solid material was diluted with water and then 3% MeOH was added.
The solution was cooled, and the precipitated Na2SO4 was removed.
At this stage, the amount of Na2SO4was found to be 2.5% at 16◦C and
2.2% at 10◦C. Alternatively, instead of 3 mL MeOH, 5 mL of MeOH was
added. Then after cooling and filtration, the filtrate contained 2.2%
Na2SO4 at 10◦C.
Condensation of β-Naphthalene Sulfonic Acid
with Formaldehyde in Weakly Acidic Media
To a 250 mL three-neck round-bottom flask equipped with a reflux
condenser and a dropping funnel was added 13.8 g naphthalene sulfonic
acid and 37% aqueous solution of formaldehyde (3 mol, 24.3 g) over a
period of 68 h at 98–100◦C. During reflux, water was continuously
added to make certain that the reaction mixture was still homogenous.
After this time, the crude reaction mixture was neutralized with an
appropriate amount of CaCO3. The viscosity of the reaction mixture
was adjusted to 6.1 cpoise (ca. 12% solution). At this stage, the pH of
the mixture was adjusted to 6.5 at 75◦C by adding 3.5 mL of hot water
and neutralizing with sufficient solid CaO. The product was converted
to its water soluble calcium salt. The excess of H2SO4 resulting from
the sulfonation reaction was precipitated as CaSO4. At this stage, to
remove the Na2SO4, the reaction mixture was filtrated, and the filtrate
was dried to yield a brown powder.
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