Herbicidal ionic liquid with dual-function

Article abstract of DOI:10.1016/j.tet.2013.07.053

Herbicidal ionic liquid with dual functions has been synthesized and characterized (properties, chemical stability and biological activity). 2-Chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)acetate prepared in an alkaline environment undergoes the reaction of dehydrochlorination by the E2 mechanism. This may be described as a specific instance of providing third generation ILs with high potential of application, which preserve both pesticidal properties: the herbicidal activity due to their anions and plant growth inhibition effect due to their cations.

Full text of DOI:10.1016/j.tet.2013.07.053

Tetrahedron 69 (2013) 8132e8136
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Tetrahedron
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Herbicidal ionic liquid with dual-function
,
a
b
b
Juliusz Pernak a , Micha1 Niemczak , Katarzyna Zakrocka , Tadeusz Praczyk
*
a Department of Chemical Technology, Poznan University of Technology, Poznan 60-965, Poland
b Institute of Plant ProtectiondNational Research Institute, Poznan 60-318, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 May 2013
Received in revised form 27 June 2013
Accepted 15 July 2013
Available online 20 July 2013
Herbicidal ionic liquid with dual functions has been synthesized and characterized (properties, chemical
stability and biological activity). 2-Chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)acetate
prepared in an alkaline environment undergoes the reaction of dehydrochlorination by the E2 mecha-
nism. This may be described as a specific instance of providing third generation ILs with high potential of
application, which preserve both pesticidal properties: the herbicidal activity due to their anions and
plant growth inhibition effect due to their cations.
Keywords:
Herbicidal ionic liquids
Herbicide
Ó 2013 Elsevier Ltd. All rights reserved.
Plant growth regulator
1. Introduction
broad-leaved plants. 2,4-D as the high volatile ester has been
banned in some countries to reduce the risk of crop damage.13
Herbicidal ionic liquids (HILs)1e4 represent a group of ionic
liquids (ILs) with targeted herbicidal properties combined with
specific physical and chemical properties. They are new phyto-
pharmaceuticals representing the third generation of ILs.5e8 Re-
cently, also in the field of agrochemistry, novel hydrophobic
fungicide forms of the active thiabendazole and imazalil have been
suggested to be used as ILs.9
Various formulations of MCPA also differ in their volatility,14 thus,
the search for its new non-volatile forms carries practical
importance.
The study presented here demonstrates reactivity, stability and
biological activity of 2-chloroethyltrimethylammonium (4-chloro-
2-methylphenoxy)acetate.
Much of the interest in ILs has been focused on their possible use
as ‘green’ alternatives to volatile organic compounds. This claim
usually rests on the fact that under ambient conditions ILs are
generally non-volatile.10e12 ILs are also known as ‘designer sol-
vents’. The physical, chemical and biological properties of these
salts can be tuned to their particular function. Depending on the
appropriate combination of cation and anion, they can be thermally
and electrochemically highly stable, be liquid over a wide range of
temperatures, and have a negligible vapour pressure. The different
combinations of cation and anion correspond to the dual-functional
nature of ILs, as exemplified by the earlier described by us 2-
2. Materials and methods
2-Chloroethyltrimethylammonium chloride (CCC) was pur-
chased from SigmaeAldrich and had a purity of 98% while
97.5% pure MCPA was obtained from Organika Sarzyna SA. 2-
Chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)ace-
tate [CC][MCPA] was synthesized by anion exchange reaction using
the earlier described technique.1
2.1. Dehydrochlorination of CCC or [CC][MCPA]
chloroethyltrimethylammonium
(2,4-dichlorophenoxy)acetate,
In a round-bottom flask CCC (7.90 g, 50.0 mmol) or [CC][MCPA]
(16.11 g, 50.0 mmol) was dissolved in distilled water (25 mL). Then,
a solution of potassium hydroxide (2.81 g, 50.0 mmol) in distilled
water, was added and the mixture was stirred for 24 h at 50 ꢀC.
Then, water was evaporated using a rotary evaporator and the
residue was dissolved in isopropanol. The inorganic by-pro-
ductdpotassium chloride (3.73 g, 50.0 mmol) precipitated as
a white solid and was separated carefully from the solution. After
removal of isopropanol the product was dried under reduced
pressure at 50 ꢀC for 24 h. The reaction yield was 95% for
manifesting a very good herbicidal activity and also used as a plant
growth regulator.4 (2,4-Dichlorophenoxy)acetic acid (2,4-D) is one
of the earliest to be designed and a widely used herbicide in agri-
culture, but high volatility manifested by some of its formulations is
a factor that limits the use due to high risk of damage off target
* Corresponding author. Tel./fax: þ48 61 6653649; e-mail address: juliusz.pernak@
put.poznan.pl (J. Pernak).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.053

J. Pernak et al. / Tetrahedron 69 (2013) 8132e8136
8133
trimethylvinylammonium chloride and 96% for trimethylviny-
lammonium (4-chloro-2-methylphenoxy)acetate.
performed both in water or methanol. Activation energy (Ea) and
entropy (
s) were calculated from the equation of Arrhenius
and Eyring.
D
S
2.1.1. Trimethylvinylammonium chloride. 1H NMR (DMSO-d6, 298 K,
400 MHz)
d
ppm¼3.40 (s, 9H, (CH3)3Nþ), 5.54e5.57 (m, 1H, NþCH]
2.4. Greenhouse experiments
CHH), 5.84 (d, J¼15.3 Hz, 1H, NþCH]CHH), 6.83e6.91 (m, 1H,
NþCH]CH2); 13C NMR (DMSO-d6, 298 K, 100 MHz)
d
ppm¼53.2,
The seeds of common lambsquarters (Chenopodium album)
were sown into soil-filled plastic pots to the depth of 0.5 cm. After
emergence, the plants were thinned to five plants in each pot. The
treatments were applied at fourth leaf stage using a spray
chamber with Tee Jet 1102 flat-fan nozzles delivering 200 L of
spray solution per 1 ha at 0.2 MPa pressure. The sprayer was
moving above the plants at a constant speed of 3.1 m sꢁ1. The
distance from nozzles to the tips of the plant was 40 cm. The
plants were treated once with a water solution of tested herbi-
cides and they were placed in a greenhouse at the temperature of
20 ꢀC, humidity of 60% and photoperiod (day/night hours) of 16/8.
The tank mixture of commercial products, containing MCPA as
sodiumepotassium salt (Chwastox Extra 300 SLd300 g MCPA per
1 L) and plant growth regulator, Antywylegacz 725 SL (725 g of
chlormequat chloridedCCC per 1 L) were used as the comparable
treatments. The study was carried out in four replications in
a completely randomized setup. After 2 weeks, the plants were
cut to soil level and weighed (at 0.1 g accuracy). The reduction of
plant fresh weight was measured, as compared to control (not
sprayed plants).
111.3, 143.1. Elemental analysis calcd (%) for C5H12ClN (M¼121.61) C
49.38, H 9.95, N 11.52; found: C 49.55, H 10.13, N 11.26. IR (KBr)
nmax: 3429, 3085, 3018, 1658, 1634, 1603, 1491, 1473, 1414, 1401,
1071, 952, 895, 713, 543 cmꢁ1. Decomposition temperature of 5%
sample, Tonset5%¼185 ꢀC and decomposition temperature of 50%
sample, Tonset¼228 ꢀC (TG analysis).
2.2. Preparation of trimethylvinylammonium (4-chloro-2-
methylphenoxy)acetate [TMVA][MCPA]
In a round-bottom flask MCPA as acid (10.03 g, 50.0 mmol) was
added. Then, a solution of potassium hydroxide (2.81 g, 50.0 mmol)
in distilled water (30 mL) was added dropwise and the mixture was
stirred at room temperature until the solution became homoge-
neous. Subsequently, a trimethylvinylammonium chloride (6.08 g,
50.0 mmol) was added and the mixture was stirred vigorously.
After 24 h the water was evaporated using a rotary evaporator and
the residue was dissolved in acetonitrile. The inorganic by-pro-
ductdpotassium chloride (3.73 g, 50.0 mmol) precipitated as
a white solid and was separated carefully from solution. After re-
moval of solvent the product was dried under reduced pressure at
50 ꢀC for 24 h. The reaction yield was 97%. After recrystallization
from acetone the product had a melting point of 120e122 ꢀC.
2.5. Field experiments
The field trials were carried out in winter wheat in 2010 and
2011 at the Experimental Station in Winna Gora, western Poland
(the E: 17ꢀ 260, N: 52ꢀ 120). Winter wheat was cultivated according
to the local agricultural practice. The plot size was 16.5 m2. The
experimental design involved a randomized block with four repli-
cations. Water solutions of the tested herbicides were applied at the
growth stage of first detectable node (BBCH 31) using a small plot
spraying equipment with XR 11003 flat-fan nozzles with a water
volume of 200 L haꢁ1 and an operating pressure of 0.3 MPa. The
standard treatments were the same as mentioned above in
greenhouse experiments. The doses used in the field trial are pre-
sented in Tables 2 and 3. Weed control was evaluated visually 4
weeks after herbicide application using a scale of 0 (no control) to
100% (a complete weed destruction).
2.2.1. Trimethylvinylammonium
(4-chloro-2-methylphenoxy)
ppm¼2.17 (s, 3H,
acetate. 1H NMR (DMSO-d6, 298 K, 400 MHz)
d
CH3C]CCO), 3.30 (s, 9H, (CH3)3Nþ), 4.69 (s, 2H, OCH2COOꢁ),
5.50e5.53 (m, 1H, NþCH]CHH), 5.78 (d, J¼15.1 Hz, 1H, NþCH]
CHH), 6.67e6.75 (m, 1H, NþCH]CH2), 6.82 (d, J¼8.7 Hz,1H, ClCCH]
CHC), 7.16 (dd, 1,2J¼8.7 Hz, 1,3J¼2.5 Hz, 1H, ClCCH]CHC), 7.21 (d,
J¼2.7 Hz, 1H, CCH3CCH]CCl); 13C NMR (DMSO-d6, 298K, 100 MHz)
d
ppm¼15.8, 53.4, 65.1, 111.4, 112.9, 124.1, 126.3, 128.4, 130.0, 143.1,
154.9, 170.0. Elemental analysis calcd (%) for
C14H20ClNO3
(M¼285.77) C 58.84, H 7.05, N 4.90; found: C 58.69, H 7.22, N 4.72. IR
(KBr) nmax: 3418, 3108, 3018, 2988, 2907,1657,1635,1603,1492,1478,
1447, 1432, 1426, 1412, 1404,1343, 1291, 1275, 1239, 1192,1140, 1063,
954, 943, 893, 877, 801, 759, 710, 696, 620, 577, 554 cmꢁ1. De-
composition temperature of 5% sample, Tonset5%¼144 ꢀC and de-
composition temperature of 50% sample, Tonset¼227 ꢀC (TG analysis).
2.6. Statistical analyses
The data from field trials were analysed by ANOVA. Tukey’s test
was used for the comparison of averages and the lowest significant
difference (LSD) was determined at the level of 5%. All calculations
were performed using Agriculture Research Manager (ARM)
software.
2.3. Analysis of dehydrochlorination kinetics
The temperature was maintained with an accuracy of 0.1 ꢀC. The
concentration of substrates in water or methanol was determined
using semi-automated reactor system for the laboratory synthesis
(EasyMaxÔ, Mettler, Toledo). The temperature of the reactor con-
tents was controlled with an accuracy of 0.01 ꢀC, using a Pt100
sensor. Connecting SevenMulti Mettler Toledo instrument, equip-
ped with a suitable electrode, allowed for precise measurement of
decrease in pH of the mixture as a result of the proceeding reaction.
The reaction order of n was calculated by the Ostwald-Zawicki
method, using the equation:
3. Results and discussion
Thermal analysis (DSC and TG) demonstrated that 2-
chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)ace-
tate [CC][MCPA] was thermally stable. Decomposition temperature of
5% sample, Tonset5% was 198 ꢀC and decomposition temperature of
50% sample, Tonset amounted to 238 ꢀC, the glass transition temper-
ature was ꢁ5 ꢀC. The compound involved a white salt, forming a hy-
drate manifesting melting temperature of 94e96 ꢀC.1 Thus, [CC]
[MCPA] represented an IL. In DSC analysis neither melting tempera-
ture nor crystallization could be noted. However, the compound
was chemically unstable: in presence of strong bases, such as KOH,
NaOH or CH3ONa [CC][MCPA] underwent dehydrochlorination. The
product of bimolecular dehydrochlorination of [CC][MCPA] involved
ꢀ
ꢁ
s1=2;I
log
s1=2;II
ꢀ
ꢁ
n ¼ 1 þ
Cm0;I
Cm0;II
log
where s1/2 is the reaction half-life time, and Cm0 is the initial
concentration of reactants. Measurements of s1/2 were

8134
J. Pernak et al. / Tetrahedron 69 (2013) 8132e8136
Table 1
Summary of calculated kinetic parameters
Substrate
CCC
Solvent
Water
Temp [K]
k [dm3 molꢁ1 minꢁ1
]
s1/2 [min]
Ea [kJ molꢁ1
]
D
Hs[kJ molꢁ1
]
D
Ss [J molꢁ1 Kꢁ1
]
D ]
Gs [kJ molꢁ1
293.2
303.2
313.2
323.2
333.2
293.2
303.2
313.2
323.2
333.2
0.011
0.034
0.105
0.261
0.734
0.010
0.027
0.080
0.206
0.528
952.4
295.0
95.5
38.3
13.6
1041.7
377.4
125.5
48.6
85.6
83.2
83.1
83.0
82.9
82.8
79.3
79.2
79.1
79.0
79.0
ꢁ33.0
ꢁ33.1
ꢁ33.1
ꢁ34.2
ꢁ33.8
ꢁ47.0
ꢁ48.0
ꢁ47.7
ꢁ48.2
ꢁ48.2
92.8
93.1
93.4
94.0
94.1
93.1
93.8
94.1
94.6
95.0
[CC][MCPA]
81.7
18.9
CCC
Methanol
298.2
303.2
308.2
313.2
318.2
298.2
303.2
308.2
313.2
318.2
0.215
0.476
1.156
2.308
5.061
0.227
0.413
0.819
1.570
2.794
46.5
21.0
8.6
4.3
2.0
44.0
24.2
12.2
6.4
124.6
100.2
122.1
122.1
122.0
121.9
121.8
97.8
97.7
97.6
97.6
97.5
117.9
117.4
117.8
116.8
116.6
36.8
35.9
36.0
35.9
35.4
87.6
86.5
85.1
84.1
83.0
87.0
86.8
86.4
85.9
85.7
[CC][MCPA]
3.6
Table 2
Efficacy of MCPA applied in winter wheat (average from 2010 to 2011)
trimethylvinylammonium (4-chloro-2-methylphenoxy)acetate [TM
VA][MCPA], as presented in Scheme 1.
Dose (g haꢁ1
CCC
)
CENCY
Weed control (%)
BRSNW
MATIN
[TMVA][MCPA] was also obtained with a 97% yield in the anion
exchange reaction of potassium (4-chloro-2-methylphenoxy)ace-
tate with trimethylvinylammonium chloride (Scheme 2).
[CC][MCPA] and [TMVA][MCPA] were soluble in water, metha-
nol, DMSO; they were insoluble in acetone, hexane, toluene, ethyl
acetate, diethyl ether, and slightly soluble in isopropanol, acetoni-
trile. [CC][MCPA] was not soluble and [TMVA][MCPA] was poorly
soluble in chloroform.
Fig. 1 shows the concentration changes in time for the reaction
of [CC][MCPA] and potassium hydroꢁx1ide in water and methanol at
30 ꢀC (303.2 K), with 0.100 mol L initial concentration of re-
actants. In addition, for comparison dehydrochlorination of CCC
was presented in Fig. 1.
Treatments
MCPA
[CC][MCPA]
[CC][MCPA]
CCCþMCPA
CCCþMCPA
CCCþMCPA
245
367
245
400
600
400
600
900a
83
88
95
97
92
85
86
87
90
98
49
67
60
69
79
367
1232a
CENCY¼Centaurea cyanus (cornflower), BRSNW¼Brassica napus (winter rape vol-
unteers).
MATIN¼Matricaria inodora (scentless chamomile).
a
Doses recommended in Poland.
Table 3
The influence of different forms of CCC and MCPA on stems length and yield of
In the performed experiments the calculated order of reaction
(n) was 2, which supports the assumed mechanism of the reaction,
i.e., E2 elimination.
The linear relationship in the Arrhenius plot demonstrated that
the assumption of the kinetic equation and reaction order was
correct. Kinetic parameters calculated for both reactions, including
winter wheat
Treatments
Dose (g haꢁ1
)
Stems length (cm)
Yield (t haꢁ1
)
CCC
245
MCPA
2010
2011
2010
2011
[CC][MCPA]
[CC][MCPA]
CCCþMCPA
CCCþMCPA
CCCþMCPA
Untreated
LSD(5%)
400
600
400
600
900a
0
98.4
94.2
98.4
95.1
87.7
100.4
75.2
72.2
67.7
63.9
59.2
79.3
4.59
8.95
8.85
8.75
8.78
8.69
7.85
0.39
6.67
6.84
7.41
7.09
7.16
6.89
0.19
367
245
367
1232a
0
rate of elimination reaction (k), reaction half-life time (
vation energy (Ea), enthalpy of activation (
s), entropy of acti-
vation (
s), Gibbs free energy of activation ( s) are summed up
in Table 1.
s1/2), acti-
DH
DS
DG
4.23
a
Doses recommended in Poland.
Scheme 1. Elimination reaction of [CC][MCPA].
Scheme 2. Synthesis of [TMVA][MCPA].

J. Pernak et al. / Tetrahedron 69 (2013) 8132e8136
8135
of [CC][MCPA] than that of CCC, especially in moderate tempera-
tures in which it would be used.
4. Biological tests
The preliminary studies conducted in greenhouse showed that
[CC][MCPA] had a similar herbicidal activity compared with com-
mercial products containing MCPA as sodiumepotassium salt,
when doses of 400 g haꢁ1 or higher were used. The results of this
experiment are presented in Fig. 3. The weak herbicidal efficacy of
[CC][MCPA] used at rates below 400 g haꢁ1 as compared to the
mixture of CCCþMCPA suggests that less of herbicide component
was uptake and transported to the sites of action in plants. MCPA
being auksin-like compound causes abnormal growth but it can
increase the mass of plants, when low rates are used.
Fig. 1. Concentration versus time for the decomposition of CCC and [CC][MCPA] in
water and methanol at 30.0 ꢀC (303.2K).
A type of solvent had a decisive influence on the rate of elimi-
nation reaction: for CCC k was more than 14 times higher, while for
[CC][MCPA] it was about 16 times higher in methanol than in water.
The effect of temperature on the reaction rate could be observed by
comparing the measured half-life times of the reactants. An in-
crease in the temperature of 40 K caused a decrease in s1/2 ap-
proximately from 1000 min to less than 20 min for CCC and [CC]
[MCPA], when the elimination reaction was conducted in water.
However, in methanol, an increase of 20 K led to an intense de-
crease in s1/2 to a few minutes only in both cases. The calculated
values of activation energy (Ea) were average, if compared with the
typical values of Ea and DH
s found in the literature of the subject:
they used to range between 20 and 150 kJ molꢁ1. The highest value
of activation energy (Ea) was manifested by the elimination re-
action of CCC in methanol, which corresponded to the high slope of
Arrhenius plot (Fig. 2).
Fig. 3. Fresh weight reduction of common lambsquarters (Chenopodium album) by
different forms of MCPA.
The herbicidal activity of [CC][MCPA] was also confirmed in the
field experiments carried out in winter wheat in 2010 and 2011. The
results shown in Table 2 indicated that the control of rape seed
volunteers and scentless chamomile treated by [CC][MCPA] man-
ifested a similar activity compared to the treatment with tank
mixture of CCC and MCPA.
Efficacy of [CC][MCPA] against cornflower was slightly lower
than the mixture of commercial products (CCCþMCPA).
The results of our experiments showed that [CC][MCPA] can be
used in cereals for weed control as well as a plant growth inhibitor.
The shorter stems were more resistant to lodging, then, this IL can
be useful not only in weed management, but also can prevent the
yield losses due to crop lodging. In our experiments the growth
inhibition of winter wheat by [CC][MCPA] varied from 2 to 6%,
compared to the untreated control (Table 3).
Tank mixture of commercial products (CCCþMCPA) gave similar
effect in 2010 but was more effective in 2011 when they were af-
fected by dramatically low amount of rainfall in the spring.
[CC][MCPA] was selective to the winter wheat and had a positive
influence on yield of winter wheat in 2010 but in 2011 we did not
find out this effect, probably due to the drought in spring when the
treatments were applied.
[CC][MCPA] may be described as a specific instance of third
generation ILs with high potential of application, which preserves
both pesticidal properties: herbicidal activity exerted by the anion
and plant growth inhibition effect resulting from the cation.
Fig. 2. Arrhenius plot of CCC and [CC][MCPA] E2 elimination reaction in water and
methanol.
Decomposition of [CC][MCPA] required an activation energy
lower by about 4 kJ molꢁ1 in water and 24 kJ molꢁ1 in methanol.
The negative values for
conditions were unfavourable. The positive value of
anol indicated a high disorder of the transition state. Also the type
of anion affected the
Ss value. MCPA, as the large size anion,
D
Ss in water indicated that the reaction
D
Ss in meth-
D
hindered a favourable arrangement of the whole molecule in the
elimination reaction, resulting in decrease of the entropy of acti-
vation by about 15 J molꢁ1 Kꢁ1 in the water and up to about
5. Conclusion
80 J molꢁ1 Kꢁ1 in methanol. The calculated values of
D
Gs dem-
onstrated that the E2 elimination reaction was faster when the
reaction environment involved methanol. The reactions carried out
in methanol had values of Gibbs free energy of activation lower by
about 7 kJ molꢁ1 Kꢁ1.The results showed a higher chemical stability
2-Chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)
acetate [CC][MCPA] may be described as specific example of third
generation ILs with a high potential of application. It was selective to
winter wheat plants and had a positive influence on yield of grains.

8136
J. Pernak et al. / Tetrahedron 69 (2013) 8132e8136
4. Pernak, J.; Niemczak, M.; Materna, K.; Marcinkowska, K.; Praczyk, T. Tetrahedron
2013, 69, 4665e4669.
5. Hough, W. L.; Rogers, R. D. Bull. Chem. Soc. Jpn. 2007, 80, 2262e2269.
6. Hough, W. L.; Smiglak, M.; Rodriguez, H.; Swatloski, R. P.; Spear, S. K.; Daly, D.
T.; Pernak, J.; Grisel, J. E.; Carliss, R. D.; Soutullo, D. M.; Davis, J. H.; Rogers, R. D.
New J. Chem. 2007, 31, 1429e1436.
The compound provides a new example of herbicidal ionic liquids
with dual-function, herbicidal activity originating from the anion
and plant growth inhibition effect reflecting action of the cation. The
compound is non-volatile and shows thermal stability. However, it is
unstable in alkaline environment, affected by dehydrochlorination.
This is an example of a reaction following the E2 mechanism.
7. Stoimenovski, J.; MacFarlane, D. R.; Bica, K.; Rogers, R. D. Pharm. Res. 2010, 27,
521e526.
8. Bica, K.; Rijksen, C.; Nieuwenhuyzen, M. Phys. Chem. Chem. Phys. 2010, 12,
2011e2017.
Acknowledgements
9. Bica, K.; Cooke, L. R.; Rijksen, C.; Rogers, R. D. Green Chem. 2011, 13, 2344e2346.
10. Rogers, R. D.; Seddon, K. R. Science 2003, 302, 792e793.
11. Stark, A.; Seddon, K. R. In KirkeOthmer Encyclopaedia of Chemical Tech-
nology; Seidel, A., Ed.; John Wiley & Sons: New Jersey, NJ, 2007; Vol. 26,
pp 836e920.
This work was supported by grant No. N N310 784040 and No. N
N209 754840.
12. Wasserscheid, P.; Welton, T. Ionic Liquids in Synthesis; Wiley-VCH: Weinheim,
Germany, 2008.
References and notes
13. Moore, J. H. A Review of 2,4-D Formulations and Vapour Drift. In Agri-
business Crop Updates; Department of Agriculture and Food and the Grains
Research & Development Corporation: Perth, Western Australia, 2008; pp
93e97.
1. Pernak, J.; Syguda, A.; Janiszewska, D.; Materna, K.; Praczyk, T. Tetrahedron 2011,
67, 4838e4844.
2. Praczyk, T.; Kardasz, P.; Jakubiak, E.; Syguda, A.; Materna, K.; Pernak, J. Weed Sci.
14. Britt, C.; Mole, A.; Kirkham, F.; Terry, A. Herbicide Handbook, Guidance on the Use
of Herbicides on Nature Conservation Sites; English Nature/FACT: Wetherby, West
Yorkshire, 2003; pp 91e92.
2012, 60, 189e192.
3. Pernak, J.; Syguda, A.; Materna, K.; Janus, E.; Kardasz, P.; Praczyk, T. Tetrahedron
2012, 68, 4267e4273.