Synthesis and application of phenyl Nitrone derivatives as acidic and microbial corrosion inhibitors

Article abstract of DOI:10.1155/2015/201259

Nitrone has drawn great attention due to its wide applications as a 1,3-dipole in heterocyclic compounds synthesis and the bioactivities. With the special structure, nitrone can also be used as ligand in inorganic chemistry. Based on the current research,

Full text of DOI:10.1155/2015/201259

Hindawi Publishing Corporation
Journal of Chemistry
Volume 2015, Article ID 201259, 6 pages
http://dx.doi.org/10.1155/2015/201259
Research Article
Synthesis and Application of Phenyl Nitrone Derivatives as
Acidic and Microbial Corrosion Inhibitors
Shijun Chen,1,2 Kang Zhao,1 and Gang Chen2
1Department of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China
2College of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an, Shaanxi 710065, China
Correspondence should be addressed to Kang Zhao; 158737534@qq.com and Gang Chen; gangchen@xsyu.edu.cn
Received 17 February 2015; Revised 15 April 2015; Accepted 3 June 2015
Academic Editor: Gre´gory Durand
Copyright © 2015 Shijun Chen et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nitrone has drawn great attention due to its wide applications as a 1,3-dipole in heterocyclic compounds synthesis and the
bioactivities. With the special structure, nitrone can also be used as ligand in inorganic chemistry. Based on the current research,
the nitrones are anticipated to be effective inhibitors against acidic and microbial corrosion. e aim of this work is to investigate
the inhibitory action of nitrones. In this work, a series of phenyl nitrone derivatives (PN) was synthesized and used as acidic and
microbial corrosion inhibitors. e results indicate that several compounds show moderate to high inhibition efficiency (IE) in 3%
HCl. Accompanied with HMTA or BOZ, the IEs greatly increase, and the highest efficiency of 98.5% was obtained by using PN4 +
BOZ. Investigation of the antibacterial activity against oilfield microorganism shows that the nitrone derivatives can inhibit SRB,
IB, and TGB with moderate to high efficiency under 1,000 mg/L, which makes them potential to be used as bifunctional oilfield
chemicals.
1. Introduction
N-diphenyl nitrones have been used as corrosion inhibitors
for mild steel in organic acid media, and they were found to
be with moderate to high inhibition in 20% formic acid/acetic
acid under the concentration of 50 to 150 ppm [11]. It should
be noticed that, for most corrosion, the microbiologically
influenced corrosion (MIC) cannot be avoided especially in
oilfield, so it will be an interesting work to develop inhibitors
against acidic corrosion and MIC.
ese compounds are generally prepared by two main
methods: condensation of carbonyl compounds with N-
monosubstituted hydroxylamines [12] and oxidation of sec-
ondary amines or hydroxylamines [13]. In particular, the
oxidative approach provides the most direct and gen-
eral method for preparing nitrones. Based on the current
research, the nitrones are anticipated to be effective inhibitors
against acidic and microbial corrosion. e aim of this work
is to investigate the inhibitory action of nitrones.
e nitrone is an N-oxide of an amine, which is a 1,3-
dipole and is used in 1,3-dipolar cycloadditions and formal
[3 + 3] cycloadditions in the synthesis of many natural
products of biological interest with the remarkable region,
and stereo selectivity along with efficient incorporation of
multiple stereocenters [1]. Many nitrone derivatives are found
to possess pharmacological activity and form an essential
part of the molecular structure of important drugs [2–4].
Nitrones are generated most ofen either by the oxidation
of hydroxylamines or condensation of aldehyde/ketone and
monosubstituted hydroxylamines [5–7]. Recently, some new
methods were developed, such as addition reaction of highly
reactive allenyl acetates with oximes and a novel Baylis-
Hillman reaction [8, 9]. Due to the unique moiety, nitrones
have been a fascinating and challenging topic for inorganic
chemistry as well. It has been reported that some nitrone
compounds can form stable complexes with Cu(II), Ni(II),
Co(II), and Cr(III) ions [10], which is useful during the acidic
corrosion inhibition for the inhibitors interacting with the
metal, so they may be potential corrosion inhibitors. Some
2. Experimental
2.1. Materials. e corrosion tests were performed on Q235A
steel with a composition (in wt%) C: 0.20, P: 0.015, Si: 1.45, S:

2
Journal of Chemistry
-
0.15, Mn: 0.020, and Fe balance. A small hole of about 3 mm
diameter near the upper edge of the coupons was made to
help hold them with cotton cords and suspend them into
the corrosive medium. Before all measurements, the steel
samples were mechanically abraded with increasing grades
of emery papers (100, 600, and 1000 grit size) to remove rust
particles. e treated coupons were then rinsed by petroleum
ether, degreased by ethanol, and dried in air. Finally, the
coupons were treated through a procedure that consisted of
measuring the length, width, thickness, and diameter and
kept in moisture-free desiccators before their immersion in
experimental solution. e weights of the specimens were
noted before immersion.
CH3
OH
O
N+
K2CO3
O
+
HN
HCl
R
R
Scheme 1: Synthesis of phenyl nitrone derivatives.
100
80
60
40
20
0
2.2. Synthesis of Phenyl Nitrone Derivatives. Benzaldehyde
derivative (1 mmol), N-methylhydroxylamine hydrochloride
(1.1 mmol), and K CO (5 mmol) were mixed in methanol
2
3
(50 ml). e mixture was refluxed until the disappearance
of benzaldehyde derivative, as evidenced by thin-layer chro-
matography. It was cooled to room temperature and the
insoluble residue was filtrated. e solvent was removed in
vacuo and the residue was separated by column chromatogra-
phy (silica gel, petroleum ether/ethyl acetate = 1–3 : 1), giving
the target compound. NMR spectra were recorded using
a Bruker Drx-400 spectrometer operating at 400 MHz for
1H in CD OD-CDCl . Mass spectra were recorded on a
0
200
400
600
800
1000
1200
Concentration (mg/L)
Figure 1: IE of PN4 for Q235A steel dissolution in 3% HCl at
different concentrations.
high yield. And most substituted benzaldehydes with electric
withdrawing group, such as –NO and –Cl, provide higher
2
3
3
yield than that with electric donating groups, such as –CH
Micromass Platform spectrometer using a direct-inlet system
operating in the electron impact (EI) mode at 75 eV.
3
and –OH. o-Hydroxy-benzaldehyde gives a relatively higher
yield that can be due to the activation of the carbonyl group
by o-OH group through the intramolecular hydrogen bond.
2.3. Weight Loss Determination. e corrosion tests were
performed on Q235A steel with a composition (in wt%) C:
0.22, P: 0.045, Si: 0.35, S: 0.05, Mn: 1.40, and Fe balance. e
electrolyte solution was 1 M HCl, prepared from analytical
grade 38% HCl and distilled water. All tests have been
performed in water solutions and at 333 0.5∘C for 5 h. e
gravimetric tests were carried out according to the Standard
of Petroleum and Natural Gas Industry of China (Evaluation
method for behavior of corrosion inhibitor for produced
water of oilfield, SY/T5273-2000) with a few modifications.
Each test was done with three specimens at the same time to
give reproducible results.
3.2. Gravimetric Measurements. Corrosion inhibition of
Q235A steel by using corrosion inhibitors in 3% HCl solution
containing various phenyl nitrone was investigated afer
immersion at 333 0.5∘C for 5 h. Table 2 summarizes the
inhibition efficiency (IE) from the weight-loss measurements.
e results reveal that the structure affects the IE which
varies with the substituted groups of phenyl nitrone, and
PN4 displays the highest IE of 85.2% compared to PN8 with
the lowest IE of 56.3%. Concerning the structures, most
of the molecules with electrodonating groups, such as –
OH, –CH , and –OCH , display relatively high inhibition
efficiency, while, with two –OH groups, PN10 and PN11
display relatively low inhibition efficiency, which may be
due to the intramolecular and/or intermolecular hydrogen
bonding weakening the interaction with the steel.
e correlativity between concentration of PN4 and
inhibition efficiency was shown in Figure 1. e corrosion
inhibition efficiency increases sharply as the concentration
rising from 100 mg/L to 500 gm/L. As the concentration
rising to over 500 mg/L, the efficiency does not rise obviously.
e highest IE, 92.3%, is obtained in our study under the
concentration of 1000 mg/L.
3
3
2.4. Microbiological Monitoring. Viable counts of sulfate
reducing bacteria (SRB), iron bacteria (IB), and total general
bacteria (TGB) were determined with the “most probable
number” method (China Standard of Petroleum and Natural
Gas Industry, the national method of the bactericidal agent’s
performance, SY/T 5890-1993). e produced water contain-
ing the three kinds of bacteria was gathered from Zichang
Oilfield Factory, Yanchang Oilfield.
3. Results and Discussion
3.1. Synthesis. Phenyl nitrone derivatives were synthesized
as shown in Scheme 1. e different substitutes are listed in
Table 1. e NMR, MS, yield, and the name of the synthesized
compounds were also included in Table 1. From the results,
it can be found that the phenyl nitrone derivatives are all in
3.3. Enhancement by Additives. Hexamethylenetetramine
(HMTA) has a symmetric tetrahedral cage-like structure, as
shown in Figure 2, whose four “corners” are nitrogen atoms
and “edges” are methylene groups. e molecule behaves like

Journal of Chemistry
3
Table 1: e yield, NMR, and MS of phenyl nitrone derivatives.
R
Yield (%)
83.4
Name
NMR, MS
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.2 (m, 2H), 7.4 (m, 3H), 7.3
(s, 1H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 130.9,
H
PN1
PN2
PN3
PN4
129.9, 129.8, 129.7, 128.8, 128.6, 128.0, 51.0; MS (EI) ꢁꢂ/: 135 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.1 (m, 2H), 7.2 (m, 3H), 7.1
(s, 1H), 3.7 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 152.2,
o-OH
m-OH
p-OH
89.5
80.0
83.2
132.0, 131.8, 129.6, 121.8, 118.6, 118.0, 51.2; MS (EI) ꢁꢂ/: 151 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.0 (m, 2H), 7.2 (m, 3H), 7.0
(s, 1H), 3.7 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 153.4,
132.1, 131.9, 129.9, 122.0, 117.8, 117.5, 51.0; MS (EI) ꢁꢂ/: 151 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.0 (s, 1H), 7.2–7.3 (m, 4H),
7.0 (s, 1H), 3.7 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 142.2,
130.1, 129.9, 129.6, 122.8, 118.2, 118.0, 51.1; MS (EI) ꢁꢂ/: 151 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.1 (m, 1H), 7.4 (m, 3H), 7.3
(s, 1H), 4.2 (s, 3H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz),
ꢀ: 138.5, 129.0, 128.8, 128.6, 127.8, 126.6, 126.5, 51.3, 24.6; MS (EI) ꢁꢂ/:
149 (M+)
p-CH3
79.5
PN5
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.3 (m, 2H), 7.3 (m, 3H), 7.1
(s, 1H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 133.9,
o-Cl
p-Cl
90.5
92.0
PN6
PN7
129.9, 129.8, 129.6, 128.6, 128.5, 126.0, 51.4; MS (EI) ꢁꢂ/: 169 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.2 (m, 2H), 7.4 (m, 3H), 7.3
(s, 1H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 134.2,
132.1, 131.9, 129.9, 128.8, 128.1, 128.0, 51.3; MS (EI) ꢁꢂ/: 169 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 9.2 (s, 1H), 8.1 (m, 2H), 7.8
(m, 2H), 7.6 (m, 1H), 3.9 (s, 3H); 13C NMR (CD3OD-CDCl3,
o-NO2
p-NO2
96.5
93.2
PN8
PN9
100 MHz), ꢀ: 150.1, 134.9, 130.2, 129.7, 129.6, 122.4, 121.8, 51.4; MS (EI)
ꢁꢂ/: 180 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 9.1 (s, 1H), 8.1 (m, 2H), 7.7
(m, 2H), 7.6 (m, 1H), 3.9 (s, 3H); 13C NMR (CD3OD-CDCl3,
100 MHz), ꢀ: 150.9, 139.0, 129.9, 129.4, 129.4, 122.4, 122.2, 51.4; MS (EI)
ꢁꢂ/: 180 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.2 (m, 2H), 7.3 (m, 3H), 7.1
(s, 1H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 160.5,
2,4-OH
3,5-OH
92.6
88.7
PN10
PN11
157.8, 131.8, 129.9, 110.2, 109.6, 108.1, 51.2; MS (EI) ꢁꢂ/: 167 (M+)
1H NMR (CD3OD-CDCl3, 400 MHz), ꢀ: 8.1 (m, 2H), 7.2 (m, 3H), 7.1
(s, 1H), 3.8 (s, 3H); 13C NMR (CD3OD-CDCl3, 100 MHz), ꢀ: 159.9,
159.2, 132.9, 129.5, 108.4, 108.3, 103.6, 51.3; MS (EI) ꢁꢂ/: 167 (M+)
Table 2: Inhibition efficiency of phenyl nitrone for Q235A steel in
3% HCl solution.
an amine base, undergoing protonation and N-alkylation.
With these features, it has been used as corrosion inhibitor.
1,4-Dihydroxy-2-butyne (BOZ), as shown in Figure 2 con-
taining hydroxyl groups and p-electrons in triple bonds, is
also used as a corrosion inhibitor in many conditions, but
it was found that the inhibition efficiency is relatively low;
moreover much quantity is needed to obtain high inhibition
efficiency (about 1–3%), so both are only used as additives
in some combined corrosion inhibitors [14]. So HMTA and
BOZ were investigated as synergists for the PN4, and the
results were shown in Figure 3.
From Figure 3, it was found that HMTA and BOZ are
not efficient inhibitors with the IE of 23.8% and 35.7%,
respectively, while they can enhance the IE of PN4 from
85.2% to 95.6% and 98.5%, respectively. e reason should be
due to the fruitful p-electrons of N, O and triple bond, which
Inhibitor
PN1
PN2
PN3
PN4
PN5
PN6
PN7
PN8
PN9
PN10
PN11
Concentration (mg/L)
IE (%)
75.0
67.8
500
500
500
500
500
500
500
500
500
500
500
80.5
85.2
80.5
66.7
65.7
56.3
83.7
65.2
69.6

4
Journal of Chemistry
N
−0.25
−0.35
−0.45
−0.55
HO
N
N
N
OH
1,4-Dihydroxy-2-butyne
Hexamethylenetetramine
Figure 2: e structure of hexamethylenetetramine and 1,4-
dihydroxy-2-butyne.
100
80
60
40
20
0
10−9
10−8
10−7
10−6
I (A/cm2)
10−5
10−4
10−3
Blank
200 ppm
500ppm
1000 ppm
50ppm
100 ppm
Figure 4: Typical polarization curves for corrosion of Q235A steel
in 1 M HCl in the absence and presence of different concentrations
of PN4.
conjugated double bonds in the organic structures makes the
formation of p–d bonds resulting from overlap of p-electrons
to the 3d vacant orbital of iron atoms, which enhances the
adsorption of the inhibitors on the metal surface [18].
Inhibitor
Figure 3: e IE of PN4 companied with HMTA or DHBY.
e steady conformation of PN4 was expressed in
Figure 5, which was simulated by a minimized energy of
MM2 in Chem 3D, and the p-electrons of the hydroxyl groups
were colored in pink. e inhibition efficiency afforded by
PN4 may be attributed to the presence of electron-rich
nitrone group, phenol group, and phenyl group. e possible
reaction centers are unshared electron pair of heteroatoms
and p-electrons of phenyl group. e schematic illustration of
different modes of adsorption on metal is shown in Figure 6.
can form covalent bonds between the molecules and the ion
surface, capture H+ to release the acidity, and even link PN4
molecules as “bridges” to enhance the protective film on the
ion surface.
3.4. Electrochemical Impedance Spectroscopy. e potentio-
dynamic polarization curves for mild steel in acid solution
in the absence and presence of various concentrations of
PN4 are shown in Figure 4. Extracts at different concen-
trations lead to different anodic, cathodic Tafel slopes, and
3.6. Antibacterial Activity against Oilfield Microorganism.
Microbiologically influenced corrosion (MIC) is metal dete-
rioration as a result of the metabolic activity of various
microorganisms. is type of corrosion applies to nonmetal-
lic objects as well as metals. For instance, aerobic bacteria
such as Acidithiobacillus thiooxidans can cause significant
corrosion as they serve as a factor in biogenic sulfide corro-
sion. As MIC bacteria grow, consumption of the metal in the
pipe occurs and sometimes tubercles are formed. Pitting is
a likely effect and the walls of the pipe may be penetrated,
but the flow characteristics of the pipes are degraded and the
loose scale or rust can plug sprinklers and valves. MIC can be
prevented through periodic mechanical cleaning, chemical
treatment using biocides to prevent bacteria population, and
dry storage and total drainage.
In oilfield, the MIC is mainly caused by the growth of
such microorganism as sulfate reducing bacteria (SRB), iron
bacteria (IB), and total general bacteria (TGB) in oil pipelines,
which is considered as a major problem for water treatment
in the oilfield [19]. MIC can result in different types of
attack, such as pitting, crevices, dealloying, and erosion in
the ꢃ
values, suggesting that these compounds behave
corr
as mixed-type (anodic/cathodic) inhibitors [15]. Increasing
inhibition efficiencies with increasing concentration shows
that the inhibition occurs because of adsorption on the
steel surface [16]. e inhibition efficiencies obtained from
potentiodynamic polarization were different from those cal-
culated from weight-loss measurements; the reason is that
weight-loss method gives average corrosion rate whereas the
electrochemical method gives instantaneous corrosion rates.
ese variations may also arise because of the different times
required to form the adsorbed layer of the inhibitors on metal
surface that inhibit corrosion [17].
3.5. Mechanism. It is well known that organic inhibitors
establish inhibition by adsorption onto the metal surface, and
the adsorption of the organic compounds can be described
by two main types of interaction: physical adsorption and
chemisorption that are influenced by the nature and charge
of the metal, the chemical structure of the inhibitor, and the
type of electrolyte. e presence of N, O, and S atoms and

Journal of Chemistry
5
Figure 5: e steady conformation of PN4.
Fe
Fe
Fe
Fe
Fe
Fe
+
+
+
+
+
+
+
Interaction with the p-electrons
Interaction with the aromatic ꢀ-electrons
Figure 6: e absorption of PN4 on the steel surface by coordination.
Table 3: e antifungal activity of PN against oilfield waterborne
different treatment systems to inhibit corrosion should be
considered, among which using bactericide has received the
greatest acceptance. Currently, oxidizer, aldehyde, quaternary
bacteria.
Microbiotic concentration/mL
Concentration
mg/L
MGLE
ammonium salt, and heterocycle compounds, such as Cl ,
2
TGB
IB
SIB
ClO , formaldehyde, pentane-1,5-dial, trichloroisocyanuric
2
4
3
4
3
1
1
2
4
1
2
1
4
4
2
1
1
0
0
0
3
0
0
1
0
4
2
2
2
0
1
2
1
1
2.5 × 10
2.5 × 10
2.5 × 10
7.0 × 10
0.9 × 10
0.9 × 10
0.9 × 10
2.5 × 10
0.9 × 10
2.5 × 10
2.5 × 10
0.9 × 10
2.5 × 10
7.0 × 10
2.5 × 10
1.1 × 10
2.5 × 10
1.1 × 10
7.0 × 10
2.5 × 10
2.5 × 10
0.9 × 10
7.0 × 10
2.5 × 10
2.5 × 10
2.5 × 10
2.5 × 10
2.5 × 10
2.5 × 10
2.5 × 10
1.1 × 10
2.5 × 10
2.5 × 10
—
acid (TCCA), Schiff base, and some natural products, have
been used as bactericides [21–23], but the toxicity and
oxidation tests have been conducted on a limited selection.
Since the researches have shown nitrone derivatives to
be antibacterial active [2–5], the PNs are anticipated to be
bactericides for oilfield microorganism. e inhibition of PNs
against oilfield microorganism was investigated under the
concentrations of 1,000 mg/L, and the results are summarized
in Table 3. e results show that the some of the PNs are active
against the three microorganisms. For TGB, PN4, PN5, PN6,
PN8, and PN10 are very active, for IB almost all PNs are active
except PN1 and PN7, and for SRB all PNs display inhibitions,
in which PN4, PN9, and PN11 are the top active ones.
PN1
1,000
1,000
1,000
1,000
1,000
1,000
1,000
1,000
1,000
1,000
1,000
PN2
PN3
PN4
PN5
PN6
PN7
PN8
PN9
PN10
PN11
0
0 × 10
2
2.5 × 10
2.5 × 10
0
4. Conclusion
pipelines [20]. In addition, microbial degradation of crude
oil can lead to increased acidity in the oil phase, and the
high-acid-contained oil is a problem concerning corrosion
of pipelines. Even more serious, the interaction of IB, SRB,
and TGB can accelerate the corrosion rate; in other words,
the corrosion in the mixture of IB, SRB, and TGB was more
serious than in a single microbial system. Based on this case,
In this work, a series of phenyl nitrone derivatives (PN) was
synthesized and characterized. en the corrosion inhibition
efficiency and the mechanism of these nitrone derivatives
were investigated. e results indicate that several com-
pounds show high IE of over 80% in 3% HCl. Accompanied
with HMTA or BOZ, the IEs greatly increase, and the

6
Journal of Chemistry
highest efficiency of 98.5% was obtained by using PN4
+ BOZ. Investigation of the antibacterial activity against
oilfield microorganism shows that the nitrone derivatives can
inhibit SRB, IB, and TGB with moderate to high efficiency
under 1,000 mg/L, which makes them potential to be used as
bifunctional oilfield chemicals.
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Conflict of Interests
e authors declare that there is no conflict of interests
regarding the publication of this paper.
Acknowledgments
is work was financially supported by the grants from
National Science Foundation of China (21376189), Tech-
nological Plan Projects of Shaanxi Province of China
(2012KJXX-40), and Scientific Research Plan Projects of
Shaanxi Education Department (2013JK0647).
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