Kinetic studies of hydrazine and 2-hydroxyethylhydrazine alkylation by 2-chloroethanol: influence of a strong base in the medium

Article abstract of DOI:10.1002/kin.20409

To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N ₂H₄ by 2-chloroethanol (CletOH) was carried out with and without sodium hydroxide. In both cases, the main reaction of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or dialkylation of N₂H₄), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkylations followed SN₂ reactions triggered directly by CletOH or indirectly in the presence of a strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the influence of a strong base present in the medium on the reaction mechanisms were established. A global mathematical treatment was applied for each alternative. It allowed modeling the reactions as a function of reagent concentrations and temperature. In the case of direct alkylation by CletOH, simulation was established for semi-batch and batch syntheses and was confirmed in experiments for concentrated mediums (1.0 M≤[CletOH]0 ≤3.2 M and 15.7 M≤[N₂H₄]0 ≤18.8 M). Simulation therefore permits the prediction of the instantaneous concentration of reagents and products, in particular ethylene oxide concentration in the case of indirect alkylation, which must be as weak as possible.

Full text of DOI:10.1002/kin.20409

Kinetic Studies of
Hydrazine and
2
-Hydroxyethylhydrazine
Alkylation by
-Chloroethanol:
2
Influence of a Strong Base
in the Medium
V. GOUTELLE, V. PASQUET, J. STEPHAN, A. J. BOUGRINE, H. DELALU
◦
Laboratoire Hydrazines et Proc e´ d e´ s, UMR n 5179 CNRS-ISOCHEM (groupe SNPE), Universit e´ Claude Bernard Lyon 1,
B aˆ timent Berthollet, 22 Avenue Gaston Berger, F-69622 Villeurbanne Cedex, France
Received 5 June 2008; revised 7 October 2008, 18 November 2008; accepted 25 November 2008
DOI 10.1002/kin.20409
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: To optimize yields, the study of reaction kinetics related to the synthesis of
2
-hydroxyethylhydrazine (HEH) obtained from the alkylation of N2H4 by 2-chloroethanol
(CletOH) was carried out with and without sodium hydroxide. In both cases, the main re-
action of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or
dialkylation of N2H4), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine
and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkyla-
tions followed SN2 reactions triggered directly by CletOH or indirectly in the presence of a
strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted
mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography
coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the
influence of a strong base present in the medium on the reaction mechanisms were estab-
lished. A global mathematical treatment was applied for each alternative. It allowed modeling
the reactions as a function of reagent concentrations and temperature. In the case of di-
rect alkylation by CletOH, simulation was established for semi-batch and batch syntheses
and was confirmed in experiments for concentrated mediums (1.0 M ≤ [CletOH]0 ≤ 3.2 M and
1
5.7 M ≤ [N2H4]0 ≤ 18.8 M). Simulation therefore permits the prediction of the instantaneous
concentration of reagents and products, in particular ethylene oxide concentration in the case
of indirect alkylation, which must be as weak as possible. ꢀC 2009 Wiley Periodicals, Inc. Int J
Chem Kinet 41: 382–393, 2009
INTRODUCTION
Correspondence to: V. Pasquet; e-mail: veronique.pasquet@
univ-lyon1.fr.
c 2009 Wiley Periodicals, Inc.
2
-Hydroxyethylhydrazine (HEH) is currently used in
ꢀ
the aerospace industry and as a precursor in the

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
383
pharmaceutical and cosmetics industries [1–7]. At
present, HEH is prepared by the alkylation of N2H4 by
using one of two methods. The first method, described
under laboratory conditions, consists in the reaction of
For the two processes (with and without a strong
base) described, this work also includes the kinetic
study of the secondary alkylation reactions of HEH and
the global mathematical modeling of all the reaction
phenomena.
2-chloroethanol (CletOH) on hydrazine hydrate in the
presence of an equimolecular quantity of sodium hy-
droxide [8]. A molar ratio of 5 is found for the initial
concentrations of the reagents. Sodium hydroxide pel-
EXPERIMENTAL
◦
lets are first added to hydrazine hydrate at 80 C until
Reagents and Apparatus
complete dissolution, after which the solution is cooled
at ambient temperature. 2-Chloroethanol is then added
gradually. Since the reaction is exothermic, the mixture
All the reagents and salts used were reagent-grade
products from Aldrich and Prolabo RP. Water was
passed through an ion-exchange resin, then distilled
twice, deoxygenated, and stored under nitrogen.
The apparatus consisted of two thermostated ves-
sels, one on top of the other and joined by a conical
◦
is cooled so that its temperature does not exceed 35 C.
When the reaction is complete, the excess hydrazine
is distilled under vacuum. Absolute ethanol is added
to the residue to facilitate the precipitation of sodium
chloride and its filtration. The filtrate is then distilled
under vacuum to obtain pure HEH.
The second method, described in three patents, con-
sists in using ethylene oxide as an alkylating reagent.
The first patent proposes a batch synthesis of HEH,
starting with diluted or nondiluted hydrazine hydrate
into which a gas flow of ethylene oxide is introduced.
Injection is progressive and carried out in a closed
reactor under a controlled positive pressure of ap-
proximately 2.7 kPa [9]. The second and third patents
3
fitting. The lower reactor (500 cm ) contained a mag-
netic stirrer and had inlets to allow temperature mea-
surement, the influx of circulating nitrogen, and the
removal of aliquots for analysis. The upper cylindri-
3
cal vessel (200 cm ) had a temperature sensor. It was
blocked at its base by a large-diameter needle valve in-
tegrated in the thermostated jacket. This setup allowed
rapid introduction of the ampoule’s contents into the
reactor, and therefore precise definition of the onset
of reaction. The temperatures of the two vessels were
[10,11] innovate by proposing the continuous synthe-
◦
defined to ± 0.1 C.
sis of HEH in a column reactor or at low temperature
◦
◦
(
−10 C to 10 C), allowing the use of ethylene oxide
Procedure and Analysis
in liquid state.
All these methods use excess hydrazine (between
and 12) to obtain good yields of HEH (molar ra-
The kinetic study of hydrazine alkylation by
◦
◦
4
chloroethanol was carried out between 35 C and 75 C
and reagents’ concentration varying from 0.3 to 5 M.
The hydrazine and hydroxyethylhydrazine solu-
tio hydrazine hydrate/2-chloroethanol or ethylene ox-
ide between 4 and 12). Nevertheless, the experimental
protocols described in the literature and the patents are
complex and empirical. Until now, no kinetic data have
been established. Ethylene oxide is a toxic, odorless,
colorless, and flammable gas at ambient temperature
and atmospheric pressure, which is why its use in an
anhydrous state requires synthesis under pressure or at
very low temperatures.
The first part of this work describes a process with-
out ethylene oxide. It consists in reacting chloroethanol
with hydrazine hydrate without a strong base. The
objective is to establish relations between the yields
and characteristics of reaction flows (concentration
and temperature) in the case of batch and semi-batch
syntheses.
3
tions (V = 100 cm ) were introduced under nitrogen
into the reactor. A solution of chloroethanol of the
same volume was introduced in the upper vessel. When
the temperature setting was reached, the reagents were
3
mixed (V total = 200 cm ) and systematic samplings
were carried out.
The alkylation reaction products were directly iden-
tified by gas chromatography (GC) (6890 N model
from Agilent Technologies) by using a flame ioniza-
tion detector coupled, and uncoupled, with a mass spec-
trometer (GC-MS) (MS 5970 from Agilent Technolo-
gies). The GC-MS analyses were performed by using
an HP-5 MS trace analysis column (30 m, 250 μm,
df = 0.25 μm). Chloroethanol concentrations were de-
termined, after dilution by 50 times the initial volume
in methanol, by GC-MS by using the same column but
by focusing on the ionic fragment m/z = 44 (“SIM”
method). The internal standard, n-octanol, was quanti-
fied with the fragment m/z = 56. For HEH quantifica-
tion, a sample of 5 ml was taken, diluted in methanol
The second part describes a general study performed
to determine the activation parameters of hydrazine
alkylation reaction by ethylene oxide to control the
reaction, starting from the in situ generation of ethylene
oxide. This entailed carrying out hydrazine alkylation
by CletOH in the presence of a strong base.
International Journal of Chemical Kinetics DOI 10.1002/kin

3
84
GOUTELLE ET AL.
by 10 times the initial volume, and then neutralized by
N sodium hydroxide solution. It was then analyzed
monoalkylated product as much as possible. Measure-
◦
◦
1
ments were performed from 35 C to 75 C and for
reagent concentrations varying from 0.3 to 5 M.
Because of the partial protonation of hydrazine,
the kinetic treatment of the reaction involves a global
order between the reagents different from molecular-
ity. Since the yields were quasi-quantitative (94% for
by GC-FID by using triglyme as the internal standard.
The dilution of the samples was sufficient to block any
evolution of the reaction during analytical treatments.
Separation was done on a CHROMPACK CpSil 19 CB
column (30 m, 250 μm, df = 0.25 μm).
◦
T = 70 C and [N2H4]0/[CletOH]0 = 15.3), we could
consider only the monoalkylation (reaction (I)) and
protonation of hydrazine (reaction (IV)) reactions. In
these conditions, we can write the equations:
RESULTS AND DISCUSSION
Direct Alkylation of Hydrazine by CletOH
−
d[Cl(CH2)2OH]
The action of CletOH on hydrazine hydrate without a
strong base in the medium involved the following main
reactions:
=
k1[Cl(CH ) OH][N H4]
2 2
2
dt
−d[N H ]
2
4
=
k1[Cl(CH ) OH][N H4]
2 2
2
dt
Cl(CH2)2OH + N2H4
+
+
+
k3[N2H4][H ] − k−3[N2H5 ]
k1
→ HO(CH2)2NHNH2 + H + Cl−
+
(I)
+
−
d[H ]
=
k1[Cl(CH2)2OH][N2H4]
dt
Cl(CH2)2OH + HO(CH2)2NHNH2
+
+
ꢁ
k
2
− k3[N2H4][H ] + k−3[N2H5 ] = 0
+
−
−→ [HO(CH2)2]2NNH2 + H + Cl
(II)
with
Cl(CH2)2OH + HO(CH2)2NHNH2
ꢁ
ꢁ
k
2
+
−
k−3
N2H4
−→ HO(CH2)2NHNH(CH2)2OH + H + Cl
= Ka
k3
(
III)
N
H
4
Ka
2
+
−
+
−
The hydrogen ions produced by reaction (I) are im-
mediately neutralized by N2H4. Thus, we can consider
that their concentration is very low after an induction
period and becomes almost constant as a result of the
acid-base balance. In these conditions, we can consider
N2H4 + H + Cl ←− −−−−→− [N2H5] Cl
(IV)
(V)
+
−
HO(CH2)2NHNH2 + H + Cl
HEH
Ka
←
+
3
−
−
−−→ [HO(CH ) NHNH ] Cl
−−−
2 2
+
d[H ]/dt = 0, which leads to the following equation:
Reactions (I)–(III) were consecutive and parallel,
whereas reactions (IV) and (V) were concurrent.
The first alkylation led to hydroxyethylhydrazine,
whereas the second led to a mixture of dihydrox-
yalkylhydrazine: 1,1-di(hydroxyethyl)hydrazine and
+
+
k1[CletOH][N2H4] = k3[H ][N2H4] − k−3[N2H5 ]
Consequently,
d [N2H4] 2d [CletOH]
1,2-di(hydroxyethyl)hydrazine (unsymmetrical).
=
= − 2k1 [CletOH] [N2H4]
1)
After integrating Eq. (I), we obtain the expression
F([CletOH], [N2H4]) = f (t), which makes it possible
to determine k1 as a function of time and confirm the
partial orders and molecularity of the reaction:
dt
dt
The second-order reaction mechanisms (SN2) that
govern alkylation reactions involve the elimination of
a proton that reacts with the strongest base: hydrazine
(
(
pKa (N2H4) = 8.1 > pKa (HEH) = 7.3). The value of
pH was controlled as a function of time by the instan-
taneous formation of a buffer mixture N2H4/N2H5 .
+
1
Molecular hydrazine was then consumed not only by
its reaction with chloroethanol but also by protonation.
This contributed toward reducing the rate of the first
process (I) and was to appear during kinetic treatments.
F = (
[N H ] − 2 [CletOH] )
2
4 0
0
[CletOH] [N H ]
2
4
0
ln
= k1t
N2H4] [CletOH]
0
(2)
[
Kinetic Study of Hydrazine Alkylation. Kinetic pa-
rameters were determined in the presence of ex-
cess hydrazine ([N2H4]0 ꢂ [CletOH]0) to isolate the
with [N2H4] = [N2H4]0 − 2 ([CletOH]0 − [CletOH]).
Taking into account the conditions of the previous
experiments ([N2H4]0 ꢂ [CletOH]0), the first member
International Journal of Chemical Kinetics DOI 10.1002/kin

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
385
Table I Determination of the Rate Constant for 2-Hydroxyethylhydrazine Formation for Different Molar Ratios (p)
and Temperatures
◦
k1 (×10−3
−1
−1
2
T ( C)
[N2H4]0 (M)
[CletOH]0 (M)
p = [N2H4]0/[CletOH]0
M
min
)
R
60
60
60
60
75
70
50
35
5.04
5.04
1.69
0.67
5.04
5.04
5.04
5.04
0.31
0.47
0.32
0.31
0.30
0.33
0.33
0.32
16.2
10.6
5.3
3.9
3.9
3.9
4.1
16.5
10.9
1.6
0.998
0.994
0.997
0.997
0.988
0.998
0.996
0.992
2.2
16.8
15.3
15.3
15.7
0.4
⎧
of Eq. (2) is linear as a function of time until the term
of the reaction with a good correlation coefficient (R
2 2 2 2
[HO(CH ) ] NNH
⎨
2
k2
+
−
−→
+
+ H + Cl (VI)
⎩
>
0.994).
2 2 2 2
HO(CH ) NHNH(CH ) OH
To confirm the invariability of k1 for a constant tem-
◦
perature (T = 60 C), a similar treatment was carried
However, there are two differences compared with the
monoalkylation reaction of N2H4:
out on a series of mixtures (Table I) of different com-
−
1
positions in reagents (3.0 × 10 ≤ [CletOH]0 ≤ 4.7 ×
−1
Hydrogen ions produced by alkylation (VI) react
with HEH. Consequently, the stoichiometry is
given by the formula
10
M and 0.67 ≤ [N2H4]0 ≤ 5.04). The influence of
◦
◦
temperature was studied from 35 C to 75 C for a con-
stant [N2H4]0/[CletOH]0 ratio (p = 16) (Table I). The
evaluation of plot ln k1 = F(1/T ) led to the following
activation parameters:
d [HEH]
2d [CletOH]
=
=
ꢀ
ꢁ
dt
dt
8
1.4
8
k1 = 4.04 × 10 exp −
−2k2 [HEH] [CletOH]
RT
(
k1 in M 1
−
s
−1
, Ea1 in kJ mol
−1
)
The reaction products of HEH/CletOH were two
isomers of dihydroxyethylhydrazine.
0
#
= 79.0 kJ mol−1; ꢀS 10 # = −89 J K−1 mol−1
ꢀ
H
1
We limited ourselves to the kinetic study of the
HEH/CletOH reaction. The results are presented in
Table II.
Kinetic Study of Hydrazine Dihydroxyalkylation
HEH Alkylation). To discriminate HEH from other
derivatives and model the whole reaction system, a
similar study of hydroxyethylhydrazine alkylation re-
action (VI) was carried out.
(
Modeling and Optimization. The concentrations of
chloroethanol, hydrazine, and hydroxyethylhydrazine
and the sum of the two dihydroxyalkylhydrazines
are respectively x, u, u1, and u2. For a constant
temperature, the synthesis is then described by the
HO(CH2)2NHNH2 + Cl(CH2)2OH
Table II Determination of the Rate Constant for 2-Hydroxyethylhydrazine Alkylation for Different Molar Ratios (p)
and Temperatures
◦
k2 (×10−3
−1
−1
2
T ( C)
[HEH]0 (M)
[CletOH]0 (M)
p = [HEH]0/[CletOH]0
M
min
)
R
60
60
60
60
73
50
35
5.05
2.56
1.67
0.48
5.05
5.00
5.00
0.30
0.20
0.24
0.33
0.28
0.31
0.28
16.8
12.8
6.8
2.31
1.97
1.99
1.92
8.66
1.07
0.29
0.993
0.987
0.989
0.983
0.993
0.997
0.994
1.5
18.0
16.1
17.7
International Journal of Chemical Kinetics DOI 10.1002/kin

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86
GOUTELLE ET AL.
Figure 1 Kinetics of HEH formation. Variation of the concentrations of chloroethanol (x), HEH (u1), and the sum of dialkyl
◦
derivatives (u2) as a function of time (T = 70 C, [x]0 = 0.33 M, [u1]0 = 5.04 M).
following system of differential equations (with t = 0:
x = x0, u = u0, u1 = u2 = 0):
Figure 1 shows, by way of example, the simulation re-
◦
sults for a molar ratio p = 15.3 and T = 70 C. There
is good agreement between the experimental and cal-
culated data.
dx
−
−
= k1xu + k2xu1
= 2k1xu + k2xu1
dt
du
dt
Transfer in a Concentrated Medium: Influences of
the Molar Ratio and the Temperature. The applica-
tion of the kinetic model for concentrated mediums
requires prior access to all the extensive parameters
to predict the evolution of the system starting from
moment t = 0.
du1
dt
=
=
k1xu − k2xu1
k2xu1
du2
dt
◦
A series of tests carried out at 60 C with various
volumes of anhydrous CletOH and hydrazine hydrate
made it possible to study the influence of p on the HEH
yield defined by the following relation:
Because of the buffer effect of hydrazine, this system
simulates all the reaction phenomena until the com-
plete consumption of N2H4. For the experiments with
p = [N2H4]0/[CletOH]0 < 2, the limiting reagent is
hydrazine. Consequently, only the dialkylation pro-
cess still continues, involving the partial protonation
of HEH. The continuity of the reaction system is then
controlled by the same equations with u = 0 and by
taking into account the following equation:
[HEH]∞
[CletOH]0
ρHEH =
× 100
The concentrations of the reagents, the volumes in-
troduced (V CletOH and VN2H4 ), the molar composition
in the mixture at t = 0 and t = ∞, and the yield of
HEH (ρN), are indicated in Table III. The yield in-
creases by 85.2% to 96.6% for molar ratios from 4.9 to
d [HEH]
2d [CletOH]
=
19.5 (Fig. 2). Obtaining an HEH yield higher than 95%
dt
dt
International Journal of Chemical Kinetics DOI 10.1002/kin

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
387
◦
Table III Influence of the Molar Ratio (p) on the Yield in a Concentrated Medium (T = 60 C)
Volumes Injected
Concentrations
t = 0
Yield ρN (%)
t = ∞
p
VCletOH (mL)
VN H (mL)
[CletOH]0 (M)
[N2H4]∞ (M)
[HEH]∞ (M)
Exp.
Calc.
2
4
2
3
4
9
1
1
.2
.4
.9
.7
5.2
9.5
15.5
10.0
7
7
4.5
3.5
25
25
25
50
50
50
5.65
4.23
3.23
1.81
1.22
0.97
12.4
14.4
15.7
17.7
18.5
18.8
3.3
3.2
2.87
1.65
1.16
0.92
58.0
75.1
88.9
91.2
95.1
94.9
60.1
77.5
85.2
93.0
95.6
96.6
requires the injection of large quantities of hydrazine, at
least equal to 15 equivalents of the halogenous deriva-
tive. In addition, it is necessary to extract hydrazine
and to recycle it.
stant volume of hydrazine hydrate. It is necessary to
distinguish two phases:
An initial phase (τ ), during which the global
1
The influence of the temperature was studied from
volume increases due to the injection of the chlo-
rinated derivative.
◦
◦
1
0 C to 90 C for reagent ratio p = 6 (Table IV). In-
creased temperature is a parameter that favors better
yields but is insufficient to completely discriminate
the dialkylhydrazine derivatives. However, its influ-
ence is limited because the values of the activation
A second period (τ ) with constant volume, dur-
2
ing which the initial concentrations correspond
to those obtained at the end of the first phase (end
of reagent addition). During this time segment,
the reactions continue until the total consumption
of the limiting reagent.
0
#
−1
parameters are rather close (ꢀH = 79 kJ mol and
1
0
#
−1
ꢀ
H
= 75.7 kJ mol ).
2
Kinetic Profile in the Case of Batch/Semi-Batch
Reactors. In the case of a semi-batch reactor,
chloroethanol is injected with a constant flow in a con-
To simulate the variation of the concentrations during
the two periods and estimate τ , the flow of injec-
2
tion and the initial concentration of the solution of
chloroethanol are, respectively, Dx and Qx:
dVx
Dx =
(L s 1); Qx (mol L−1
−
)
100
dt
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
During τ2, the instantaneous volume of the mixture,
V t , is expressed by the formula in which V 0 and t are
the initial volume of the hydrazine solution and time,
Calculated plot
Experimental points
Table IV Calculated Influence of the Temperature on
Both the Yield and the Half-Time Reaction for Molar
Ratio p = 6
T
k1
k2
min )
Yield
(%) Reaction (min)
Half-Time
◦
−1
−1
−1
−1
(
C) (M min ) (M
−5
−5
−5
−4
−4
−3
−3
−3
−2
−2
1
2
3
40
50
60
0
0
0
2.3 × 10
1.8 × 10
5.7 × 10
1.6 × 10
4.4 × 10
1.1 × 10
2.7 × 10
6.1 × 10
1.3 × 10
2.7 × 10
86.2
86.5
87.0
87.4
87.9
88.2
88.6
88.9
89.2
1950
598
200
71
27
11
5
−5
7.5 ×10
2.3 × 10
6.3 × 10
1.7 × 10
4.1 × 10
9.7 × 10
2.2 × 10
4.7 × 10
−
4
4
3
3
3
2
2
−
−
−
−
−
−
0
5
10
15
20
2 4 0 0
p = [N H ] /[CletOH]
70
80
90
Figure 2 Variation of the yield of HEH for different molar
2
1
◦
ratios p (T = 60 C, 1.0 M ≤ [CletOH]0 ≤ 3.2 M and 15.7 M
≤
[N2H4]0 ≤ 18.8 M).
International Journal of Chemical Kinetics DOI 10.1002/kin

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88
GOUTELLE ET AL.
respectively:
resolution of Eqs. (3)–(7) by using the fourth-order
Runge-Kutta method:
Vt = V0 + Dxt
The quantity of chloroethanol in the system per unit of
time and volume is then deduced:
dx
=
−k1xu − k2xu1
dt
du
dt
x0Dx
x0Dx
=
−
= 2k1xu + k2xu1
V0 + Dxt
Vt
+
Under these conditions, for an unspecified reagent (i),
the number of moles of reagents (ni) that disappears
per unit of time and volume is
du
=
=
k1xu + k2xu1
k1xu − k2xu1
dt
du1
dt
ꢀ
ꢁ
d
ni
1 dni
+ V
Vt dt
t
ni dVt
vi = −
= −
2
dt Vt
dt
du2
dt
ꢀ
ꢁ
= k2xu1
d
ni
ni 1 dVt
+
Vt Vt dt
=
−
dt Vt
Figure 3 presents a simulation for a semi-batch reactor
under industrial concentration conditions. The reagents
used were 23 ml of anhydrous CletOH (purity 99%)
and 100 ml of hydrazine hydrate (purity 98%). The
flow was fixed at 1 ml/min so that the temperature
dxi
xi dVt
Vt dt
or vi = −
+
dt
The first term of the second member of the previous
equation relates to the effect of the chemical reaction,
whereas the second term relates to the volume effect
due to the dilution of the reagents. In what follows,
we consider the additivity of volumes. Consequently,
time segments τ1 and τ2 are controlled by two sys-
tems of differential equations. If the concentration in
◦
does not exceed 60 C.
The CletOH concentration curve presents a break
point at t1 = 23 min, indicating the end of injection.
At this time, half of the introduced quantities was con-
verted to HEH. The reaction had terminated completely
at the end of the second phase (t2 = 80 min). The evo-
+
hydrazinium ions is u , the evolution of the various
+
lution of concentrations of HEH and N2H5 as a func-
entities during injection period (τ1) is controlled by
the following system:
tion of time each shows a point of inflection due to
a reagent injection rate higher than its consumption.
Initially confounded during the first moments of the
reaction, the two curves separated thereafter because
of the dialkylation process. The calculated yield of
HEH was established at about 88%. The same opera-
tion carried out in a batch reactor led to the same final
state. However, the heat exchange was more efficient
due to the higher reaction rate.
A product containing 98.1% HEH (GC) was ob-
tained by semi-batch synthesis and two successive dis-
tillations under low pressure (10 kPa), the first one
permitting the extraction of water and then the extrac-
tion of hydrazine hydrate, the second one leading to
HEH after NaCl filtration.
dx
dt
DxQx
Vt
xDx
Vt
=
− k1xu − k2xu1 −
(3)
(4)
(5)
(6)
(7)
du
uDx
−
= 2k1xu + k2xu1 +
dt
Vt
+
+
du
u Dx
Vt
=
=
=
k1xu + k2xu1 −
k1xu − k2xu1 −
dt
du1
dt
u1D
Vt
du2
dt
u2D
k2xu1 −
Vt
with the following initial concentrations at t = 0:
+
Alkylation of Hydrazine with a Strong Base
u = u0; x = u = u1 = u2 = 0; and V t = V 0.
This system controls the reactions until the end of
τ1, represented as t1 and defined by the relation
The kinetics was studied initially at constant temper-
ature by mixing a volume of chloroethanol solution
with the same volume of a solution of hydrazine hy-
drate and sodium hydroxide. Chloroethanol and hy-
droxyethylhydrazine were quantified as previously by
GC-MS and GC-FID.
0
Vx
t1 =
Dx
0
x
where V is the volume of chloroethanol.
After t1, the second system is deduced by making
Dx = 0 and by initializing it to start from values x(t1),
Contrary to the process without a strong base,
the curve of HEH concentration as a function of
time shows a point of inflection. Correlatively, the
+
u(t1), u (t1), and u2(t1), resulting from the numerical
International Journal of Chemical Kinetics DOI 10.1002/kin

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
389
[
(
Concentration] (M)
a), (c), (d)
[Concentration] (M)
(b)
6
20
5
1
5
1
2
4
3
2
1
0
(u)
+
10
(
u )
(u )
1
5
(
x)
(u )
2
0
0
20
40
60
80
100
120
140
Time (min)
Figure 3 Evolution of the concentrations of reagents and products as a function of time. (x) CletOH, (u) N2H4, (u ) N2H
+
+
,
5
◦
−1
(
u1) HEH, and (u2) dialkyl compounds (T = 60 C, Dx = 1 ml min ). [Color figure can be viewed in the online issue, which
is available at www.interscience.wiley.com.]
plot representing the stoichiometry of the reaction
The authors determined a first-order reaction and a
reaction rate equal to
(
δ[CletOH] = f ([HEH])) is not linear. These results
are interpreted by considering the existence of an inter-
mediate product, ethylene oxide, which reaches a max-
imum concentration during the reaction. Under these
conditions, the main reactions are as follows:
ꢀ
ꢁ
75.2
RT
11
k4 = 1.23 × 10 exp −
(
k4 in s 1, Ea4 in kJ mol−1
−
)
k
1
(VII)
Cl(CH
2
)
2
OH + NaOH
+ NaCl
+
H
2
O
Kinetics of Ethylene Oxide Formation: Rate Law
(Determination of k1). The mechanism of ethylene
oxide formation has been the subject of several works
O
k2
(
VIII)
+
+
N
2
H
4
HO(CH
2
)
2
NHNH
2
O
O
[13–16]. It comprises a first fast acid-base reaction,
k
3
(HO(CH ) ) NNH
2 2 2 2
followed by a slow intramolecular rearrangement.
HO(CH
2
)
2
NHNH
2
+
(IX)
2 2 2 2
HO-(CH ) NHNH(CH ) OH
k
−
−
−
→
Cl(CH2)2OH + OH ←− Cl(CH2)2O + H2O (fast)
X)
In addition to these reactions, the hydrolysis of ethy-
lene oxide occurs in the alkaline medium. This reaction
was studied by Lichtenstein and Twigg [12]. It leads to
the formation of ethylene glycol by a catalytic process.
(
k
′
1
Cl(CH
2
)
2
O
+ Cl (slow)
(XI)
k′′
O
1
k
4
OH
+
H
2
O
Because of the nature of mechanisms (X) and (XI),
reaction (VII) is bimolecular and independent of the
HO
O
OH
International Journal of Chemical Kinetics DOI 10.1002/kin

3
90
GOUTELLE ET AL.
other interactions. Under this condition, it is pos-
sible to determine k1 from the experimental curve
compared with the others. We chose to separate k2 and
k3 from k1 physically by mixing a volume of ethy-
lene oxide solution, prepared at the moment of reac-
tion, with the same volume of hydrazine solution. The
two solutions were at the same temperature and had
the same concentration in sodium hydroxide. Under
these conditions, the hydrolysis of ethylene oxide (k4)
[
CletOH] = f (T ) and the integration of the following
differential equation:
dx
dt
−
= k1xz
(8)
−3
−1 −1
min ). Conse-
was negligible (k4 = 1.36 × 10
M
If the initial and instantaneous concentrations in
chloroethanol and sodium hydroxide are respectively
quently, the reactional system was limited to two reac-
tions (VIII) and (IX). By using the same formalism as
in the case of alkylation without sodium hydroxide, the
system of differential equations that manages simulta-
neous reactions (VIII) and (IX) is the following:
(
x0, x) and (z0, z), the integration of Eq. (8) (z0
ꢃ
leads to
1
x0z
F = (
ln
= k1t with z = z0 − (x0 − x)
z − x )
z x
0
0
0
dy
=
=
=
=
−k2yu − k3u1y
−k2yu
(9)
(10)
(11)
(12)
dt
du
Curves F = f (t) were established with a constant con-
centration of chloroethanol (≈0.2 M) and various con-
centrations of sodium hydroxide (0.3 M ≤ [NaOH]0
dt
du1
◦ ◦
0.8 M) at temperatures ranging from 10 C to 22 C.
≤
k2yu − k3yu1
k3yu1
They are linear until the end of the reaction, which
confirms that the chlorinated derivative is not involved
in other secondary reactions. The results are shown
in Table V. The values of k1 determined by other au-
thors are also mentioned, as are the corresponding tem-
peratures. On the whole, they are consistent with the
experimental data.
dt
du2
dt
with y = [ethylene oxide], u = [N2H4], u1 = [HEH],
and u2 = [dialkyl derivatives].
Mathematical treatment permits direct access to the
k3/k2 ratio, starting from the final concentration of
HEH. To achieve this, t is removed from Eqs. (9) and
(10):
k1 is then deduced as follows:
ꢀ
ꢁ
9
7.3
15
k1 = 1.11 × 10 exp −
RT
ꢀ
ꢁ
ꢂ
ꢃ
dy
du
k3
k2
u1
k1 in M−1
−1
−1
= 1 +
(13)
(
s , Ea1 in kJ mol )
u
The k3/k2 ratio depends only on the ionic force of
the medium and temperature. Equation (13) can be
integrated if u1 is expressed as a function of u. To do
this, Eq. (11) is divided by Eq. (10):
Kinetics of the Mono/Dihydroxyalkylation: Rate
Laws (Determination of k2 and k3). The determina-
tion of mono- and dialkylation rate constants (k2 and
k3) would imply the degeneration of the first reaction.
The isolation method requires a very high NaOH con-
centration so that the first reaction is instantaneous
du1
du
ru1
k3
k2
=
−1 +
,
with r =
u
Table V Rate Constant (k1) of Ethylene Oxide Formation at Various Temperatures
◦
1/T (×10−3
−1
k1 (×10−3
−1 −1
−1
−1
−1
min )
T ( C)
T (K)
K
)
M
s
)
k1 (10
M
−ln k1
a
2
1
3
2
1
0
2
0
5
5
295
283
308
298
288
273
3.4
3.5
3.2
3.4
3.5
3.7
7.8
4.70
0.76
21.70
6.00
1.53
0.17
4.85
6.68
3.32
4.61
5.97
8.19
a
b
b
b
1.3
36.2
10.0
2.6
5
c
0.3
a
Experimental results.
From references [13] and [15].
b
International Journal of Chemical Kinetics DOI 10.1002/kin

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
391
Table VI Determination of Rate Constants of 2-Hydroxyethylhydrazine (HEH) Formation and Alkylation (with Sodium
Hydroxide in the Medium)
−
2
−2
−1
T
[N2H4]0
(M)
[CletOH]0
(M)
p = [N2H4]0/
k2 (×10
k3 (×10
ρN HEH
(%)
◦
−1
−1
−1
(
C)
[CletOH]0
r = k3/k2
M
min
)
M
min
)
1
1
1
2
2
3
0
2.43
1.20
0.60
1.22
1.20
1.20
0.20
0.20
0.20
0.21
0.20
0.21
12.1
6.0
3.0
5.9
5.9
5.8
0.74
0.68
0.66
0.67
0.67
0.68
2.6
3.3
3.3
5.5
10.0
20.9
1.9
2.2
2.2
3.7
6.7
88.8
84.7
74.5
81.6
82.4
80.9
0
0
0
5
5
14.3
By calling auxiliary variable u1 = ϕ(t)u, a differential
equation is obtained in which variables u1 and ϕ(t) can
be separated:
u∞ is easily deduced from the final experimental con-
∞
centration of HEH (u ), starting from the assessment
1
(y = 0, t = ∞):
ꢈ
ꢈ
ꢈ
u1
y
u
dϕ
d ln u = −[
du −
1
dy = −2
du
1 − ϕ(r − 1)]
U10
y0
u0
ꢉ
ꢊ
∞
with u∞ = u0 − 0.5 u + y0 .
By integration at t = 0: u = u0, u1 = 0, and ϕ = 0:
1
u
1
k2 and k3 are obtained by r and using curve u1 = f (t). It
is identified with the slope of the chart of the following
equation, F = f (t):
ln
=
ln [1 − ϕ (r − 1)]
u0
(r − 1)
Indeed,
1
y0(u0 − u1)
ꢄ
ꢅ
ꢀ
ꢁr−1
F =
ln
(u0 − y0) u0(y0 − u1)
= k2t avec k3 = rk2
(15)
u
u
u1 =
1 −
(
r − 1)
u
0
u1 = 0 is confirmed when u = u0 (t = 0). The substi-
tution of this expression in (13) makes it possible to
obtain a differential equation that depends only on vari-
ables y and u:
The experimental results are given in Table VI:
The rate constants and activation parameters are as
follows:
ꢀ
ꢁ
5
3.3
6
ꢄ
r−1ꢅ
k = 3.74 × 10 exp −
ꢀ
ꢁ
2
RT
dy
dt
r
u
=
1 +
1 −
−1
−1
−1
(r − 1)
u0
(
k2 in M
s , Ea2 in kJ mol )
For t = 0, y = y0, and u = u0, then
0
#
= 50.8 kJ mol−1; ꢀS 20 # = −127 J K−1 mol−1
ꢀ
H
ꢀ
ꢁ
ꢀ
2
2
r − 1
y0 − y = (u0 − u)
r − 1
and
ꢀ
ꢁ ꢆ
ꢁ ꢇ
r
ꢀ
ꢁ
u0
u
5
4.1
−
1 −
6
k3 = 3.46 × 10 exp −
r − 1
u0
RT
−1
−1
−1
When ethylene oxide is completely consumed (y = 0)
3
(k in M
s
, E in kJ mol
)
a3
∞
and if the final concentration of hydrazine, u , can be
0#
= 51.6 kJ mol−1; ꢀS 30 # = −128 J K−1 mol−1
ꢀ
H
3
measured, the ratio of rate constants r is obtained by
the resolution of implicit Eq. (14):
Generalization: Integration of all the Reactions. The
rate laws relating to the alkylation reactions have now
been established, the system must then be general-
ized by introducing the synthesis of ethylene oxide.
In this new configuration, ethylene oxide is a transi-
tion product that leads to an initial induction period,
ꢀ
ꢁ
2
r − 1
y0 − (u0 − u∞)
r − 1
ꢀ
ꢁ ꢆ
ꢀ
ꢁ ꢇ
r
u0
u∞
u0
+
1 −
= 0
(14)
r − 1
International Journal of Chemical Kinetics DOI 10.1002/kin

3
92
GOUTELLE ET AL.
Figure 4 Simulation and experimental results for the alkylation of hydrazine in the presence of a strong base in the medium.
◦
(
[CletOH]0 = 0.20 M, [N2H4]0 = 0.60 M, [NaOH]0 = 0.29 M, T = 10 C). (x) CletOH, (u) N2H4, (u1) HEH, (u2) dialkyl
compounds, (y) ethylene oxide, and (z) NaOH. [Color figure can be viewed in the online issue, which is available at
www.interscience.wiley.com.]
as well as second acceleration period concentration-
time curves of HEH and its derivatives. The accumu-
lation of ethylene oxide in the medium, and conse-
quently its maximum concentration, is related to its
rates of formation and decomposition and thus to the
initial parameters. Modeling is essential to simulate all
the phenomena. If we add the equations relating to the
consumption of reagents CletOH and CH2OCH2 to the
previous system (9)–(12), and modify the term dy/dt,
it is then possible to predict the evolution of all the
du1
dt
=
k2yu − k3u1y
du2
dt
= k3u1y
with initial concentrations: x = x0; z = z0; u = u0; and
y = u1 = u2 = 0.
The integration of this new system is numerical. It
was solved by the Runge-Kutta method. The results
of the mathematical treatment are in good agreement
with the experimental values (Fig. 4). This model also
permits the prediction of the evolution of the concentra-
tions of entities not easily quantifiable by experiments.
The synthesis of HEH by the in situ generation
of ethylene oxide requires knowledge of all the ki-
netic parameters of activation and control of heat ex-
change. For an industrial application, the injection flow
of chloroethanol will have to be controlled as a function
of internal reaction rates and the temperature setting of
the reactor. The ethylene oxide concentration must be
−
entities (x = [CletOH], z = [OH ], y = [CH2OCH2],
u = [N2H4], u1 = [HEH], and u2 = [sum of the dialkyl
derivatives]) as a function of time:
dx
dt
dz
= dt = −k1xz
dy
dt
=
=
k1xz − k2yu − k3u1y − k4y
−k2yu
du
dt
International Journal of Chemical Kinetics DOI 10.1002/kin

ALKYLATION OF HYDRAZINE AND 2-HYDROXYETHYLHYDRAZINE BY 2-CHLOROETHANOL
393
quasi-stationary and as weak as possible to maintain it
in a single-phase medium.
them by those difficult to achieve through experimen-
tation. The operating conditions and yields obtained
are similar to those resulting from alkylation without
a strong base. This result is related to the similarity
of the successive mechanisms of mono- and dialkyla-
tions for each process, confirmed by the activation en-
thalpy and entropy values. However, the global reaction
rate is faster with ethylene oxide as the intermediate
compound.
CONCLUSION
The kinetic study of mono- and dihydroxyalkylation of
hydrazine by chloroethanol (CletOH) was carried out
with and without a strong base. For each experiment,
concentrations in CletOH and HEH were analyzed,
respectively, by GC-MS and GC-FID.
Without sodium hydroxide, the global kinetic model
established takes into account the variations of sto-
ichiometry related to the successive protonation of
N2H4 and HEH. The transfer in concentrated medium
was studied starting from hydrazine hydrate and an-
hydrous chloroethanol. A numerical simulation rep-
resenting the kinetic profiles of the compounds for
batch and semi-batch processes was established, and
the optimal conditions were determined and vali-
dated in a batch reactor as a function of molar ratio
BIBLIOGRAPHY
1. Olin Corporation, US Patent 5 433 802, 1995.
2. Atlantic Research Corporation, WO Patent 0 109 063,
2001.
3. USA–Air Force, US Patent 6 218 577, 2001.
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46, 8009.
5. Pfizer, US Patent 0 020 012, 2006.
6. L’Oreal, US Patent 5 769 903, 1998.
7. Eastmann Chemical Company, US Patent 6 452 019,
[
N2H4]/[CletOH] and temperature. The mechanisms
2
002.
. Lespagnol, A.; Deprey, J. Bull Soc Chim France 1962,
117.
. Gever, G., US Patent 2 660 607, 1953.
of HEH formation and its derivatives are equivalent
because enthalpy and entropy activation are very close
to each other. An yield of 80% HEH was obtained for
8
1
9
◦
a small molar ratio p = 3 and temperature T = 60 C.
1
0. Tsenyuga, V. S.; Malushina, C. I.; Nadezhina, N. A.;
Petrov, N. A.; Ovchinnikov, P. N.; Abramov, I. A.;
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K. A.; Tigane, V. G.; Trofimov, V. N., SU Patent
1 027 153, 1983.
On the other hand, it will be difficult to completely dis-
criminate HEH during synthesis without injecting large
quantities of hydrazine hydrate. An increase of temper-
ature is advantageous but insufficient. A product con-
taining 98.1% HEH (GC) was obtained by distillation.
Contrary to the results obtained by direct alkyla-
tion, the formation of HEH in the presence of a strong
base implies the formation of an intermediary com-
pound (ethylene oxide). A coherent kinetic model was
established in order to control heating effects due to
the injection of CletOH in an alkalized solution of hy-
drazine hydrate, while maintaining the concentration
of ethylene oxide as weak as possible.
11. Olin Mathieson Chemical Corporation, GB Patent
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1
1
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1
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6
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The resolution of the system permits identifying the
shape of the experimental curves and supplementing
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International Journal of Chemical Kinetics DOI 10.1002/kin