Synthesis of corrosion preventive long-chain N-alkyl-2-(phenylthio)- acetohydrazides and 2-oxo-2-phenylethyl-2-alkanoylhydrazinecarbodithioates

Article abstract of DOI:10.1007/s00706-008-0933-1

Long-chain N-alkyl-2-(phenylthio)acetohydrazides were synthesized via the reactions of 2-(phenylthio)acetohydrazide with long-straight-chain aldehydes and then reduction with sodium borohydride. The reactions of long-straight-chain hydrazides with carbon disulfide in alkaline media give the corresponding carbodithioate salts. Heating of potassium 2-alkanoylhydrazinecarbodithioates with phenacyl bromide do not yield cyclization and failed to give the corresponding long-chain thiazolidine-2-thiones, but gave the corresponding 2-oxo-2-phenylethyl-2-alkanoylhydrazinecarbodithioates via nucleophilic substitution reaction. In addition, the synthesized compounds were tested for their corrosion prevention capabilities in acidic or in mineral oil media.

Full text of DOI:10.1007/s00706-008-0933-1

Monatsh Chem 139, 1279–1283 (2008)
DOI 10.1007/s00706-008-0933-1
Printed in The Netherlands
Synthesis of corrosion preventive long-chain N-alkyl-2-(phenylthio)-
acetohydrazides and 2-oxo-2-phenylethyl-2-alkanoylhydrazinecarbodithioates
Ayhan Yıldırım, Mehmet C°etin
ꢀ
Department of Chemistry, Faculty of Science and Arts, Uludag University, Bursa, Turkey
Received 21 February 2008; Accepted 16 March 2008; Published online 9 June 2008
# Springer-Verlag 2008
Abstract Long-chain N-alkyl-2-(phenylthio)acetohy-
drazides were synthesized via the reactions of 2-
(phenylthio)acetohydrazide with long-straight-chain
aldehydes and then reduction with sodium borohy-
dride. The reactions of long-straight-chain hydra-
zides with carbon disulfide in alkaline media give the
corresponding carbodithioate salts. Heating of potas-
sium 2-alkanoylhydrazinecarbodithioates with phena-
cyl bromide do not yield cyclization and failed to give
the corresponding long-chain thiazolidine-2-thiones,
but gave the corresponding 2-oxo-2-phenylethyl-
2-alkanoylhydrazinecarbodithioates via nucleophilic
substitution reaction. In addition, the synthesized
compounds were tested for their corrosion prevention
capabilities in acidic or in mineral oil media.
chemicals, derivatives using in metalworking fluids,
flotation, textiles, cosmetics, and toiletries are ex-
amples [1].
The largest use of N and=or S containing fatty
acids derivatives in oil field chemicals is in corrosion
inhibitors. The prior art has disclosed a wide variety
of chemical compounds which effectively reduce the
corrosion. Fatty diethanolamides [2], long-chain im-
idazolines [3], isoxazolines and isoxazolidines [4],
mercapto oxadiazoles and triazoles [5, 6], and thio-
semicarbazides [7] are well known compounds in
corrosion literature. In general, S-containing deriv-
atives are among the most effective inhibitors. This
is due to the fact that lone electron pairs at sulfur can
easily be polarized.
We report herein the synthesis of fatty N-alkyl-
2-(phenylthio)acetohydrazides 4a–4c and 2-oxo-
2-phenylethyl-2-alkanoylhydrazinecarbodithioates
7a–7d. It was found that under the reaction condi-
tions tested carbodithioates 6a–6d give the 2-oxo-
2-phenylethyl-2 alkanoylhydrazine carbodithioates
7a–7d and do not yield cyclization to afford thi-
azolidine-2-thiones 8a–8d. We also investigate the
corrosion prevention properties of the synthesized
compounds in 2 M HCl acidic media or paraffin
based mineral oil media.
Keywords Fatty acids; Surface; Corrosion inhibitors; Acidic;
Mineral oil media.
Introduction
Long-chain fatty acids and compounds derived
from them, especially, N, S, or P derivatives find
wide applications in every area of industrial activity
while many of them are products or constituents
of products. Fat-based emulsifiers, fabric soften-
ers and conditioners, synthetic lubricants, oil field
Results and discussion
Correspondence: Ayhan Yıldırım, Department of Chemistry,
There are many papers related to the reactions be-
tween a variety of substrates and the products
ꢀ
Faculty of Science and Arts, Uludag University, 16059 Bursa,
Turkey. E-mail: yildirim@uludag.edu.tr

obtained from carboxylic acid hydrazides and car-
bon disulfide in alcoholic alkaline media [8–11].
The starting material 1 was synthesized by first
reacting thiophenol with sodium chloroacetate in
alcoholic alkaline media to give the sodium salt of
2-(phenylthio)acetic acid, which provided the de-
sired acid after acidification [12]. Then this acid
was refluxed with methanol in the presence of a little
amount of sulfuric acid to give the methyl ester.
Treatment of this ester with hydrazine hydrate in
boiling methanol gave the corresponding hydra-
zide 1 in good yield. The IR spectrum shows the
characteristic bands for –NHNH2 at ꢀꢁ¼ 3290 cmꢀ1
and for –NC¼O at ꢀꢁ¼ 1649 cmꢀ1. Next, the treat-
ment of 1 with an equivalent of 2a–2c in methanol
yielded the corresponding N-alkylidene-2-(phenyl-
thio)acetohydrazides 3a–3c in moderate to good
yields (Scheme 1).
ꢀꢁ¼ 1665 cmꢀ1 due to the –N¼C group. The H
NMR spectrum showed a singlet at ꢁ ¼ 9.42 ppm
for the NH proton, a triplet at ꢁ ¼ 7.11 ppm for the
–N¼CH– proton and singlet at ꢁ ¼ 4.01 ppm for the
PhSCH2 protons. Compounds 3a–3c were reduced
with sodium borohydride in methanol to give the
corresponding hydrazides 4a–4c (Scheme 1). The
compound 4a–4c showed characteristic IR bands at
ꢀꢁ¼ 3287cmꢀ1 and at ꢀꢁ¼ 3215cmꢀ1 for the –NHNH2
group, at ꢀꢁ¼ 1650 cmꢀ1 for the –CONHNH2 car-
1280
A. Yıldırım, M. C°etin
Scheme 1
1
1
bonyl group. The H NMR spectrum showed a sin-
glet at ꢁ ¼ 3.65 ppm for the –SCH2– protons and a
triplet at ꢁ ¼ 2.71 ppm for the –NNCH2– protons.
The starting long-straight-chain carboxylic acid
hydrazides 5a–5d were simply prepared from the
corresponding methyl esters and hydrazine hydrate
in boiling methanol with good yields [13]. Treatment
of the obtained hydrazides 5a–5d with carbon disul-
fide and potassium hydroxide in ethanol gave the
salts of carbodithioates 6a–6d, which were used in
the next step without further purification (Scheme 2).
The IR spectra of 3a–3c showed absorption
bands at ꢀꢁ¼ 3222 cmꢀ1 due to the –NH group, and
at ꢀꢁ¼ 3080 cmꢀ1 due to the Ar¼C–H stretching, at
Scheme 2

Synthesis of corrosion preventives
1281
The IR spectrum of 6a–6d showed absorption bands
at ꢀꢁ¼ 3448 cmꢀ1 (br band) for the –NH groups and
at ꢀꢁ¼ 1647 cmꢀ1 for the C¼O group. Decomposi-
tion of these salts was observed upon heating to high
temperatures. Next, carbodithioates 6a–6d and phe-
nacyl bromide were heated in ethanol. They failed
to give the desired thiazolidine-2-thiones 8a–8d,
but the corresponding 2-oxo-2-phenylethyl-2-alka-
noylhydrazinecarbodithioates 7a–7d were obtained
(Scheme 2). The IR spectrum of compounds 7a–
7d showed absorption bands at ꢀꢁ¼ 3444 cmꢀ1 (br
band) for the –NH groups, and at ꢀꢁ¼ 1693 and
1682 cmꢀ1 for the C¼O groups. The 1H NMR spec-
trum does not exhibit a singlet signal for 8 thia-
zolidine H-5 proton, but showed a singlet at ꢁ ¼
4.91 ppm for two of the –SCSCH2– protons related
to 7a–7d. This result proves that the expected cycli-
zation shown in Scheme 2 not observed.
sible orientation of the acetohydrazides 4a–4c at the
metal-acidic solution interface is shown in Fig. 1.
For the corrosion inhibitors 7a–7d no visible rust
spots were observed on the metal stripe and it can be
concluded that the tested organic compounds may be
suitable inhibitors for such a corrosive medium.
Experimental
Melting points were recorded by Bu¨chi melting point B-540
apparatus. IR spectra were measured by Nicolet FTIR 6700
spectrometer. 1H NMR spectra were measured using a Varian
mercury plus spectrometer (400MHz) in CDCl3 using TMS
as an internal standard. All reagents and solvents were
purchased from either Merck or Fluka Chemie and used
without further purification. 2-(Phenylthio)acetic acid was
synthesized according to Ref. [12], and long-straight-chain
carboxylic acid hydrazides 5a–5d were prepared as described
in Ref. [13]. Phenacyl bromide was prepared by a literature
method [14].
2-(Phenylthio)acetohydrazide (1, C8H10N2OS)
Corrosion inhibition
To a solution of 20g 2-(phenylthio)acetic acid (118.9mmol)
in 300 cm3 methanol, 7 cm3 sulfuric acid were added cautious-
ly. The observed clear solution was refluxed for 3–3.5h at
65ꢁC. Solvent was removed by using a rotary evaporator
and ice water was added into the flask. Crude ester was
extracted with 3ꢂ50cm3 ether. The layers were separated
and the organic layer was washed successively with 10%
NaHCO3, water, and dried over Na2SO4. Ether was removed
by using a rotary evaporator to give 19.4g colorless oily liquid
methyl 2-(phenylthio)acetate which was dissolved in 50cm3
methanol, 5.33g hydrazine hydrate (106.5mmol) were added,
and the resulting mixture was refluxed for 3 h at 60–65ꢁC.
Methanol was removed by using a rotary evaporator. The
obtained white solid was crystallized from ethyl acetate=
petroleum ether and 14.6g white needles of 1 (67% for 2
steps) were collected. Mp 63–64ꢁC; IR (KBr): ꢀꢁ¼ 3290
In order to investigate corrosion preventive proper-
ties of the synthesized 4a–4c and 7a–7d, corrosion
tests were performed using 2 M HCl and mineral oil
media. All compounds exhibited corrosion preven-
tive capability (Table 1).
Inhibitor molecules bearing S atoms in their struc-
tures display improved efficiencies [4]. Inhibitor
molecules are adsorbed at the metal surface. A pos-
Table 1 Corrosion inhibition efficiencies for 4a–4c (inhibitor
concentration ꢁ ¼ 100 ppm) in 2 M HCl for 25 h at 30ꢁC
ꢃ
(NHNH2), 1649 (NC¼O) cmꢀ1
.
Inhibitors
Inhibition efficiencies
4a
4b
4c
95.4
97.0
97.5
N-Alkylidene-2-(phenylthio)acetohydrazides 3a–3c,
representative procedure for 3c
To a stirred solution of 1 g 2-(phenylthio)acetohydrazide (1)
(5.49 mmol) in 15 cm3 methanol, 1.01g of dodecanal (2c)
(5.48 mmol) were added and the resulting mixture was stirred
ꢃ
Duplicate experiments were performed in each case and the
mean value of the weight loss is reported
Fig. 1 Possible orientations of the inhibitor molecules 4c at the metal-acidic solution interface

1282
A. Yıldırım, M. C°etin
at room temperature for 30min. Then it was heated at 60ꢁC
for 2 h. Methanol was evaporated using a rotary evaporator to
give 1.60g of a white solid. If desired it can be recrystallized
from methanol to give 3c as a white crystalline solid.
(CDCl3): ꢁ ¼ 7.99 (s, –CONH), 7.31–7.28 (m, 4H, Ar), 7.24–
7.20 (m, 1H, Ar), 4.55 (s, NNH), 3.65 (s, –SCH2), 2.71 (t,
J ¼ 7.2 Hz, –NNCH2), 1.36–1.23 (m, 16H, –CH2–), 0.88 (t,
J ¼ 7.6 Hz, –CH3) ppm.
N-Octylidene-2-(phenylthio)acetohydrazide
(3a, C16H24N2OS)
N-Dodecyl-2-(phenylthio)acetohydrazide (4c, C20H34N2OS)
Yield 66% (0.95 g); mp 79–79.7ꢁC; IR (KBr): ꢀꢁ¼ 3288 (NH),
1
3215 (NH), 3014 (Ar, ¼CH), 1651 (C¼O) cmꢀ1; H NMR
Yield 69%; mp 54–55ꢁC; IR (KBr): ꢀꢁ¼ 3211 (NH), 3067
1
(Ar, ¼CH), 1665 (C¼O) cmꢀ1; H NMR (CDCl3): ꢁ ¼ 9.41
(CDCl3): ꢁ ¼ 7.98 (s, –CONH), 7.31–7.28 (m, 4H, Ar), 7.24–
7.20 (m, 1H, Ar), 4.54 (s, NNH), 3.65 (s, –SCH2), 2.71 (t,
J ¼ 7.2 Hz, –NNCH2), 1.36–1.23 (m, 20H, –CH2–), 0.88 (t,
J ¼ 7.2 Hz, –CH3) ppm.
(s, CONH), 7.46–7.43 (m, 1H, Ar), 7.37–7.17 (m, 4H,
Ar), 7.10 (t, J ¼ 5.2 Hz, –N¼CH), 4.01 (s, PhSCH2), 2.34
(m, –N¼CHCH2), 1.50 (quin, J ¼ 7.2 Hz, –N¼CHCH2CH2),
1.31–1.26 (m, 8H, –CH2–), 0.89 (t, J ¼ 7.2 Hz, –CH3) ppm.
Potassium 2-alkanoylhydrazinecarbodithioates 6a–6d;
representative procedure for 6a
N-Decylidene-2-(phenylthio)acetohydrazide
(3b, C18H28N2OS)
To a solution of 0.8 g dodecanehydrazide 5a (3.73 mmol) in
20cm3 ethanol, 0.3 g potassium hydroxide (5.36 mmol) and
0.3 cm3 carbon disulfide were added. The reaction mixture
was stirred under reflux for 6 h and for additional one night
at room temperature. Ethanol was evaporated by using a rotary
evaporator to give a white powder.
Yield 97%; mp 70–71ꢁC; IR (KBr): ꢀꢁ¼ 3213 (NH), 3067
1
(Ar, ¼CH), 1677 (C¼O) cmꢀ1; H NMR (CDCl3): ꢁ ¼ 9.40
(s, CONH), 7.46–7.44 (m, 1H, Ar), 7.37–7.17 (m, 4H,
Ar), 7.10 (t, J ¼ 5.2 Hz, –N¼CH), 4.01 (s, PhSCH2), 2.34
(m, –N¼CHCH2), 1.50 (quin, J ¼ 6.8 Hz, –N¼CHCH2CH2),
1.30–1.25 (m, 12H, –CH2–), 0.88 (t, J ¼ 7.2 Hz, –CH3) ppm.
Potassium 2-dodecanoylhydrazinecarbodithioate
(6a, C13H25KN2OS2)
N-Dodecylidene-2-(phenylthio)acetohydrazide
(3c, C20H32N2OS)
Yield 74% (0.91 g); mp (dec); IR (KBr): ꢀꢁ¼ 3448 (br, NH),
1647 (C¼O) cmꢀ1
.
Yield 75% (1.44 g); mp 72–73ꢁC; IR (KBr): ꢀꢁ¼ 3222 (NH),
3080 (Ar, ¼CH), 1665 (C¼O) cmꢀ1
;
1H NMR (CDCl3):
Yields of the 6b–6d were 66, 70, and 61% with mp and IR
data identical with those of 6a.
ꢁ ¼ 9.42 (s, CONH), 7.46–7.43 (m, 1H, Ar), 7.36–7.17 (m,
4H, Ar), 7.11 (t, J ¼ 5.2 Hz, –N¼CH), 4.01 (s, PhSCH2), 2.34
(m, –N¼CHCH2), 1.50 (quin, J ¼ 7.6 Hz, –N¼CHCH2CH2),
1.30–1.25 (m, 16H, –CH2–), 0.88 (t, J ¼ 7.2 Hz, –CH3) ppm.
2-Oxo-2-phenylethyl-2-alkanoylhydrazinecarbodithioates
7a–7d; representative procedure for 7a
To a solution of 0.9 g 6a (2.74 mmol) in 20 cm3 ethanol,
0.55 g phenacyl bromide (2.76 mmol) were added and the
resulting mixture was refluxed for 2 h. The mixture was
cooled to room temperature and then ice cold water was
added. The obtained yellow solid product was filtered under
vacuum and left to dry at room temperature for one night.
Solid material was crystallized from petroleum ether and
washed with cold petroleum ether to give 7a as a pale yellow
crystalline compound.
N-Alkyl-2-(phenylthio)acetohydrazides 4a–4c; representative
procedure for 4c
To a cooled and stirred solution of 1.44 g N-dodecylidene-
2-(phenylthio)acetohydrazide 3c (4.13 mmol) in tetrahy-
drofuran=methanol 10=10 cm3, 0.25 g sodium borohydride
(6.61 mmol) were added portionwise at 5–10ꢁC during
10min. It was stirred for 15min at this temperature and for
additional 1 h at room temperature. After 3c was consumed
(TLC control) the solvent was removed by using a rotary
evaporator to give a white solid. This solid product was
washed with cold water and dried overnight at room tem-
perature. Recrystallization from methanol afforded the title
compound 4c as a white solid.
2-Oxo-2-phenylethyl-2-dodecanoylhydrazinecarbodithioate
(7a, C21H32N2O2S2)
Yield 68% (0.76 g); mp 59–60ꢁC; IR (KBr): ꢀꢁ¼ 3444 (br,
NH), 3059 (Ar, ¼CH), 1693 (C¼O), 1682 (C¼O) cmꢀ1; 1H
NMR (CDCl3): ꢁ ¼ 8.05–8.02 (m, 2H, Ar), 7.66–7.62 (m,
1H, Ar), 7.53–7.50 (m, 2H, Ar), 4.91 (s, SCSCH2), 2.81 (t,
J ¼ 7.2 Hz, CH2CON), 1.76 (quin, J ¼ 7.6 Hz, –CH2–CH2–
CH2–), 1.39–1.26 (m, 16H, –CH2–), 0.88 (t, J ¼ 7.2 Hz,
–CH3) ppm.
N-Octyl-2-(phenylthio)acetohydrazide (4a, C16H26N2OS)
Yield 63%; mp 78ꢁC; IR (KBr): ꢀꢁ¼ 3286 (NH), 3214 (NH),
3012 (Ar, ¼CH), 1650 (C¼O) cmꢀ1
;
1H NMR (CDCl3):
ꢁ ¼ 7.99 (s, –CONH), 7.31–7.29 (m, 4H, Ar), 7.24–7.20 (m,
1H, Ar), 4.55 (s, NNH), 3.65 (s, –SCH2), 2.71 (t, J ¼
7.6 Hz, –NNCH2), 1.36–1.23 (m, 12H, –CH2–), 0.88 (t, J ¼
6.8 Hz, –CH3) ppm.
2-Oxo-2-phenylethyl-2-tetradecanoylhydrazine-
carbodithioate (7b, C23H36N2O2S2)
Yield 69%; mp 65–66ꢁC; IR (KBr): ꢀꢁ¼ 3469 (br, NH), 3058
(Ar, ¼CH), 1691 (C¼O), 1685 (C¼O) cmꢀ1
;
1H NMR
N-Decyl-2-(phenylthio)acetohydrazide (4b, C18H30N2OS)
Yield 63%; mp 78–78.7ꢁC; IR (KBr): ꢀꢁ¼ 3286 (NH), 3215
(CDCl3): ꢁ ¼ 8.05–8.03 (m, 2H, Ar), 7.66–7.62 (m, 1H, Ar),
7.54–7.50 (m, 2H, Ar), 4.91 (s, SCSCH2), 2.82 (t, J ¼ 7.6 Hz,
(NH), 3010 (Ar, ¼CH), 1649 (C¼O) cmꢀ1
;
1H NMR

Synthesis of corrosion preventives
1283
CH2CON), 1.76 (quin, J ¼ 8.0 Hz, –CH2–CH2–CH2–), 1.39–
1.26 (m, 20H, –CH2–), 0.88 (t, J ¼ 6.8 Hz, –CH3) ppm.
Acknowledgements
ꢀ
We are grateful to Uludag University Scientific Research
Projects Unit for providing financial support under the project
(No. 2004=44) during this study.
2-Oxo-2-phenylethyl-2-hexadecanoylhydrazine-
carbodithioate (7c, C25H40N2O2S2)
Yield 43%; mp 74–76ꢁC; IR (KBr): ꢀꢁ¼ 3471 (br, NH), 3058
(Ar, ¼CH), 1691 (C¼O), 1682 (C¼O) cmꢀ1
;
1H NMR
References
(CDCl3): ꢁ ¼ 8.05–8.03 (m, 2H, Ar), 7.66–7.62 (m, 1H, Ar),
7.54–7.50 (m, 2H, Ar), 4.91 (s, SCSCH2), 2.82 (t, J ¼ 7.6 Hz,
CH2CON), 1.76 (quin, J ¼ 7.2 Hz, –CH2–CH2–CH2–), 1.40–
1.26 (m, 24H, –CH2–), 0.88 (t, J ¼ 7.2 Hz, –CH3) ppm.
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(Ar, ¼CH), 1691 (C¼O), 1682 (C¼O) cmꢀ1
;
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CH2CON), 1.76 (quin, J ¼ 7.6 Hz, –CH2–CH2–CH2–), 1.38–
1.25 (m, 28H, –CH2–), 0.88 (t, J ¼ 7.2 Hz, –CH3) ppm.
Corrosion tests performed for acidic media
Selection of materials and chemicals used here was made
according to Ref. [4] and corrosion tests procedures were also
performed according to this Ref. except that the test period
and temperature were 25 h and 30ꢁC. The test conditions and
obtained results for the corrosion inhibitors 4a–4c are sum-
marized in Table 1.
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Soc 83:4019
Corrosion tests performed for mineral oil media
Test media and metal selection in additional corrosion tests
were according to Ref. [4] except that the period was 24h.
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