Synthesis and characterization of new aromatic hydroxy acid compounds

Article abstract of DOI:10.4314/bcse.v32i3.11

Four novel aromatic hydroxy acid (HA) compounds N-(4-hydroxyphenyl)-4’-trimellitimide, N-(3-hydroxyphenyl)-4’-trimellitimide, N-(5-hydroxynaphthyl)-4’-trimellitimide and N-{4’-[2-(4-hydroxyphenyl) isopropyl phenyl]}-4’’-trimellitimide are synthesized thro

Full text of DOI:10.4314/bcse.v32i3.11

Bull. Chem. Soc. Ethiop. 2018, 32(3), 523-530.
 2018 Chemical Society of Ethiopia and The Authors
DOI: https://dx.doi.org/10.4314/bcse.v32i3.11
ISSN 1011-3924
Printed in Ethiopia
SYNTHESIS AND CHARACTERIZATION OF NEW AROMATIC HYDROXY ACID
COMPOUNDS
P. Thiruvasagam*
School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur-613401,
India
(Received June 23, 2017; Revised June 27, 2018; Accepted July 12, 2018)
ABSTRACT. Four novel aromatic hydroxy acid (HA) compounds N-(4-hydroxyphenyl)-4’-trimellitimide,
N-(3-hydroxyphenyl)-4’-trimellitimide, N-(5-hydroxynaphthyl)-4’-trimellitimide and
N-{4’-[2-(4-hydroxyph-
enyl) isopropyl phenyl]}-4’’-trimellitimide are synthesized through nucleophilic substitution reaction of trimelitic
dianhydrides with the corresponding aminophenol/aminonaphthol using polar aprotic solvents. The hydroxy acid
compounds are characterized by FT-IR and 1H-NMR spectroscopy.
KEY WORDS: Bifunctional molecule, Hydroxy acid, AB-molecule, Imide ring, Nucleophilic substitution
reaction
INTRODUCTION
Bifunctional molecule has properties of two different types of functional groups. Some common
functional groups are –COOH (carboxylic acids), –CHO (aldehyde), –CONH2 (amide), –CN
(nitrile), –OH (alcohol), –NH2 (amino), –X (halo), etc. The functional groups determine the
chemical and biological behavior of the compounds. Many of bifunctional molecules are used to
produce medicine, catalysts and also used in condensation polymerization to synthesize
polyester, polyamide, etc. [1-3]. Biological molecules such as proteins are made up of
bifunctional amino acids. Bifunctional molecules having –COOH and –NH2 are used to
synthesize polyamides by self polycondenzation reaction [4, 5] and the molecules having active
–NO2 and –OH group are used to make polyether by nucleophilic displacement reaction [6, 7].
Bifunctional molecules having the combination of –COOH and –F, –CHO and –F, –CONH2 and
–F, –CN and –F, –COOH and –NO2, –CHO and –NO2, –CONH2 and –NO2, –COOH and –Cl,
–CHO and –Cl, –CONH2 and –Cl, etc. are used to synthesize numerous organic compounds that
are used to prepare medicines, polymers, etc. [8, 9]. Among the bifunctional molecules, hydroxy
acids (HAs) represent a class of compounds which have been widely used in a number of
cosmetic, therapeutic formulations and polymer synthesis. Salicylic acid, a most important
hydroxy acid is used as a starting material for synthesizing drugs etc. Even though the hydroxy
acids are commercially important, the available compounds are less, particularly aromatic
hydroxy acids are very limited. This prompted me to synthesize stable imide containing hydroxy
acid. In this research work four novel imide containing hydroxy acid compounds are synthesized
through two step process and the structures are characterized by spectroscopic analysis.
EXPERIMENTAL
Materials and instruments
1H-NMR spectra were recorded in DMSO-d6 solution using Bruker 300 MHz instrument and
FT-IR spectra were obtained on spectrum one (Perkin Elmer, USA). Aniline, bisphenol-A, 4-
aminophenol, 3-aminophenol, 5-amino-1-naphthol and trimellitic anhydride were purchased
__________
*Corresponding author. E-mail: thiru_mek@yahoo.com
This work is licensed under the Creative Commons Attribution 4.0 International License

524
P. Thiruvasagam
from Sigma-Aldrich Chemicals India and they were used without further purification. N-methyl
pyrolidone (NMP) was distilled under reduced pressure before using. All the reagents used were
analytical grade. The compound 2-(4-aminophenyl)-2-(4’-hydroxyphenyl) propane was
prepared in the laboratory starting from bisphenol-A and aniline as per the procedure reported in
our previous publications [10-12].
Synthesis of aromatic hydroxy acid
N-(4-hydroxyphenyl)-4’-trimellitimide (IIIa). The stable aromatic hydroxy acids (IIIa-IIId)
were prepared by the nucleophilic substitution reaction of trimellitic anhydride with aromatic
amino phenol/amino naphthol [13-19]. The typical procedure adopted for the synthesis of the
compound IIIa was as follows: in the first step, trimellitic anhydride (I) (0.02 mol) was added
slowly under nitrogen atmosphere into the solution of 4-aminophenol (IIa) (0.04 mol) in polar
aprotic solvent NMP (25 mL), and was stirred at room temperature for 6 h to form amic acid
intermediate. In the second step, toluene (15 mL) was added into the amic acid intermediate and
o
the resulting mixture was refluxed at 120 C for 10 h to afford the cyclic diiimide IIIa. The
water formed during this conversion was removed azeotropically using Dean-Stark trap
(Scheme 1). After removing the water, the temperature of the reaction mixture was raised to
distilled off the residual toluene. The reaction mixture was cooled, poured into water and the
precipitated hydroxy acid compound IIIa was filtered, washed with excess of dil. HCl to
remove the unreached 4-aminophenol and washed with excess of water, finally dried in vacuum
o
oven at 80 C. Yield: 93%, FT-IR (KBr): 3600-2500 cm-1 (–COOH and –OH), 1779 cm-1
(imide C=O symmetrical stretching), 1724 cm-1 (imide C=O asymmetrical stretching), 728 cm-1
(imide ring deformation) and 1371 cm-1 (imide C–N stretching). 1H-NMR (300 MHz, DMSO-d6,
ppm): δ 9.81 (s, –OH, Ar ), δ 8.41–8.38(d, J = 9.0 Hz, H, Ar), δ 8.28 (s, H, Ar), δ 8.06–8.03 (d, J
= 9.0 Hz, H, Ar), δ 7.23–7.20 (d, J = 9.0 Hz, 2H, Ar) and δ 6.89–6.86 (d, J = 9.0 Hz, 2H, Ar).
N-(3-hydroxyphenyl)-4’-trimellitimide (IIIb). The hydroxy acid compound IIIb was
synthesised using trimellitic anhydride and 3-aminophenol using the same procedure as adopted
for the synthesize of IIIa. Yield: 95%, FT-IR (KBr): 3400–2550 cm-1 (–COOH and –OH), 1780
cm-1 (imide C=O symmetrical stretching), 1722 cm-1 (imide C=O asymmetrical stretching), 725
1
cm-1 (imide ring deformation) and 1373 cm-1 (imide C-N stretching). H-NMR (300 MHz,
DMSO-d6, ppm): δ 9.82 (s,–OH, Ar), δ 8.42–8.39 (d, J = 9.0 HzH, Ar), δ 8.30(s, H, Ar), δ 8.08–
8.05(d, J = 9.0 Hz, H, Ar), δ 7.34–7.28(t, H, Ar) and δ 6.87–6.84(m, 3H, Ar).
N-(5-hydroxynaphthyl)-4’-trimellitimide (IIIc). The hydroxy acid compound IIIc was
synthesised using trimellitic anhydride and 5-amino-1-nahthol using the same procedure as
adopted for the synthesize of IIIa. Yield: 95%, FT-IR (KBr): 3450–2850 cm-1 (–COOH and
–OH), 1782 cm-1 (imide C=O symmetrical stretching),1724 cm-1 (imide C=O asymmetrical
1
stretching), 726 cm-1 (imide ring deformation and 1375 cm-1 (imide C-N stretching). H-NMR
(300 MHz, DMSO-d6, ppm), δ 10.45 (s, –OH,Ar), δ 8.47–8.44 (d, J = 9.0 Hz, H,Ar), δ 8.36 (s,
H, Ar), δ 8.32–8.29 (d, J = 9.0 Hz, H, Ar), δ 8.14–8.11 (d, J = 9.0 Hz, H, Ar), δ 7.64–7.55 (m,
2H, Ar), δ 7.34–7.20 (t, H, Ar), δ 7.20–7.17 (d, J = 9.0 Hz, H, Ar) and δ 6.95–6.92 (d, J = 9.0
Hz, H, Ar).
N-{4’-[2-(4-hydroxyphenyl) isopropylphenyl]}-4’’-trimellitimide (IIId). The hydroxy acid
compound IIId, was synthesised using trimellitic anhydride and 2-(4-aminophenyl)-2-(4’-
hydroxyphenyl)propane using the same procedure as adopted for the synthesize of IIIa. Yield:
97%, FT-IR (KBr): 3400–2800 cm-1 (–COOH and –OH), 1780 cm-1 (imide C=O symmetrical
stretching), 1723 cm-1 (imide C=O asymmetrical stretching), 726 cm-1 (imide ring deformation)
1
and 1380 cm-1 (imide C–N stretching). H-NMR (300 MHz, DMSO-d6, ppm) δ 9.26 (s, H,
-OH), δ 8.42–8.39 (d, J = 9.0 Hz, H, Ar), δ 8.30 (s, H, Ar), δ 8.08–8.05 (d, J = 9.0 Hz, H, Ar), δ
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Synthesis and characterization of new aromatic hydroxy acid compounds
525
7.34 (s, 4H, Ar), δ 7.08–7.05 (d, J = 9.0 Hz, 2H, Ar), δ 6.70–6.67 (d, J = 9.0 Hz, 2H, Ar) and δ
1.6 3 (s, 6H, –CH3).
Scheme 1. Synthesis of hydroxyl acid.
RESULT AND DISCUSSION
Structural characterization of hydroxy acid compounds by FT-IR spectroscopy
The hydroxy acid compounds were prepared by the nucleophilic substitution reaction of
trimelitic dianhydrides with the corresponding aminophenol/aminonaphthol under nitrogen
atmosphere using NMP as solvent in a two step process. In the first step intermediate amic acid
was prepared through the nucleophilic attack of the amino group on the carbonyl carbon of the
anhydride group. In the second step, the imidization was accompanied through nucleophilic
attack of the amide nitrogen on the acid carbonyl carbon with the elimination of water. The
complete cyclisation of the intermediate amic acid was achieved by toluene-water azeotropic
distillation (Scheme 1). The FT-IR spectrum of the monomer IIIa (Figure 1) showed a
characteristic absorption band for the imide ring at 1779 cm-1 (imides C=O symmetrical
stretching), 1724 cm-1 (imides C=O asymmetrical stretching), 728 cm-1 (imide ring
deformation). The stretching of –COOH group merged with penolic –OH stretching and showed
a broad and strong absorption band at 3600–2500 cm-1. The C-H (sp2) absorption band (at 3330
cm-1) merged into the absorption band of –COOH and –OH group. The FT-IR spectrum of the
compound IIIa confirmed the formation of imide ring between the trimellitic anhydride and 4-
aminophenol. Similarly the FT-IR spectral data of the hydroxy acid compounds IIIb, IIIc and
IIId (Figure 2) supported the proposed structures.
Bull. Chem. Soc. Ethiop. 2018, 32(3)

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P. Thiruvasagam
Figure 1. FT-IR- spectrum of N-(4-hydroxyphenyl)-4-trimellitimide (IIIa).
Figure 2. IR spectrum of NN-{4’-[2-(4-hydroxyphenyl) isopropylphenyl]}-4’’’-trimellittimide
(IIId).
Structural characterization of hydroxyl acid compounds by 1H-NMR spectroscopy
1
The H-NMR spectrum of N
-
rr
(4-hydroxyphenyl)-4’-nitrophthalimide (IIIa) is shown in
ed as a singlet at 9.81 δ ppm. The two aromatic protons orrtho to
s a doublet at 6.89–6.86 δ ppm and the two aromatic protonss meta
to the hydroxyl group appeareed as a doublet at 7.23–7.20 δ ppm. The two aromatic protonn meta
and ortho to the carboxylic g oup and flanked between by imide carbonyl and carboxyl group
appeared as a doublet at 8.0 –8.03 δ ppm and 8.41–8.38 δ ppm, respectively. The aroomatic
proton flanked by imide carb nyl and carboxyl group appeared as a singlet at 8.28 δ pp . The
FFigure
3. The phenolic proton appea
the hydroxyl group appeared
aa
r
r
6
oo
mm
protons designated in Figure 3 as “d”, “e” and “f” appeared in the farthest downfield in the
range 8.41–8.03 δ ppm because of the electron withdrawing –COOH and imide groupps. The
1
peaks at 2.5 δ ppm and at 3.
NMR spectrum of the hydr
(Figure 6) supported the prop
4
4
δ ppm are due to DMSO and water in DMSO. Similarly t
hh
e H-
ooxyl acid compounds IIIb (Figure 4), IIIc (Figure 5) and IIId
oo
sed structures.
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Synthesis and ch
a
a
racterization of new aromatic hydroxy acid compounds
527
Figure 3. 1H-NMR spectrum of N-(4-hydroxyphenyl)-4’-trimellitimide (IIIa).
Figure 4. 1H-NMR spectrum
oof N-(3-hydroxyphenyl)- 4’-trimellitimide (IIIb).
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P. Thiruvasagam
Figure 5. 1H-NMR spectrum of N-(5-hydroxynaphthyl)-4’-trimellitimide (IIIc).
Figure 6. 1H-NMR spectrum of N-{4’-[2-(4-hydroxyphenyl) isopropylphenyl]}4’’-tri
mmellit-
imide (IIId).
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Synthesis and characterization of new aromatic hydroxy acid compounds
529
CONCLUSION
We have successfully synthesised four imide containing hydroxyl acid (HA) compounds
through two step process with high yield. The structures of the compounds are confirmed by FT-
IR and 1H-NMR spectroscopy analysis. These compounds can be used as a starting material for
synthesize of new organic compounds and also can be used to synthesise polyesters, polyether,
polyamides, etc. Thus, these HAs are considered to be more useful compounds for further
applications.
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