Ionic liquid forms of the herbicide dicamba with increased efficacy and reduced volatility

Article abstract of DOI:10.1039/c3gc37143c

Twenty eight new dicamba (3,6-dichloro-2-methoxybenzoic acid)-based herbicidal salts, have been synthesized and characterized in order to attempt to improve the efficacy of this widely known herbicide used to protect maize, grassland, and other cultures. The new compounds, most of which are ionic liquids by definition and three of which are solids melting above 100 °C, were prepared by pairing quaternary tetraalkyl- or alkoxyammonium, piperidinium, imidazolium, pyridinium, morpholinium, quinolinium, and phosphonium cations with the dicamba anion. Growth chamber and field test data suggested that ionic liquid forms of dicamba offer substantially increased efficacy which would allow less to be applied in the field. Compared to the commercial dicamba free acid product, improved physical properties were observed including higher decomposition temperatures and reduced volatilities, suggesting a potential reduction of overall environmental impact of this herbicide.

Full text of DOI:10.1039/c3gc37143c

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Ionic liquid forms of the herbicide dicamba with
increased efficacy and reduced volatility
Cite this: DOI: 10.1039/c3gc37143c
O. Andreea Cojocaru,a Julia L. Shamshina,a Gabriela Gurau,a Anna Syguda,b
Tadeusz Praczyk,c Juliusz Pernak*b and Robin D. Rogers*a
Twenty eight new dicamba (3,6-dichloro-2-methoxybenzoic acid)-based herbicidal salts, have been syn-
thesized and characterized in order to attempt to improve the efficacy of this widely known herbicide
used to protect maize, grassland, and other cultures. The new compounds, most of which are ionic
liquids by definition and three of which are solids melting above 100 °C, were prepared by pairing qua-
ternary tetraalkyl- or alkoxyammonium, piperidinium, imidazolium, pyridinium, morpholinium, quinoli-
nium, and phosphonium cations with the dicamba anion. Growth chamber and field test data suggested
that ionic liquid forms of dicamba offer substantially increased efficacy which would allow less to be
applied in the field. Compared to the commercial dicamba free acid product, improved physical pro-
perties were observed including higher decomposition temperatures and reduced volatilities, suggesting
a potential reduction of overall environmental impact of this herbicide.
Received 31st December 2012,
Accepted 3rd June 2013
DOI: 10.1039/c3gc37143c
www.rsc.org/greenchem
The vapor pressure of dicamba acid is 2.6 × 10−8 atm at
25 °C, indicating substantial volatilization after application.10
Introduction
Many herbicides, widely used in agriculture to eliminate Burnside et al.11 studied dicamba volatility under laboratory
unwanted species of plants, have secondary environmental conditions, finding that as high as 29% of dicamba acid volati-
impacts due to their high volatility,1–3 water solubility,4 and lized from planchets at 35 °C, after 7 days. Similar studies by
droplet drift5 during application. DuPont’s Imprelis herbicide, Baur et al.12 reported 58% volatilization loss from glass
for example, was removed from commercial use6 based on con- beakers in 4 days at 30 °C.
cerns suggesting a link between the herbicide’s use and a
negative impact on neighboring conifers, deciduous trees, and plant surfaces. Burnside and Lavy11 established that evapora-
shrubs.7
tive losses of dicamba from soil were very small compared to
Volatility, of course, differs from glass beakers, soil, and
Dicamba free acid (3,6-dichloro-2-methoxybenzoic acid) is a losses from planchets due to herbicide binding to soil par-
selective systemic herbicide, absorbed by the plants’ leaves ticles. However, dicamba is often applied as an aerial spray
and roots, with ready translocation throughout the plant via and losses can occur from a variety of surfaces such as plant
both the symplastic and apoplastic systems. Dicamba acts as leaf or foliage. In one study, volatilization injury to soybean
an auxin-like growth regulator. Dicamba is the active ingredi- has been reported to be 37% and 48% after the 1st and 2nd
ent in the commercial herbicide Banvel®, and one of the most application, respectively,13 due to dicamba evaporation from
widely used agrochemicals.8 This herbicide exhibits all the dis- the leaf surface.
advantages previously mentioned. Dicamba has been reported
Any modification or new formulations of such a widely uti-
to have a high water solubility (and therefore persists in lized herbicide will need to reduce the potential for environ-
groundwater),9 and does not bind to soil particles (soil sorp- mental exposure, while increasing efficacy in order to reduce
tion coefficient normalized to organic carbon, Koc = 2 g mL−1
)
the application rates. Current approaches include the use of
which leads to a high leaching rate. Its leaching potential emulsified esters, ammonium salts, metal salts, or additives.14
increases with the volume of the herbicide applied.
However these methods have only minimally improved the
reported environmental impact.15
Dicamba, a benzoic acid derivative with a pKa of 1.9, fits the
normal design rules for choosing ions to generate ionic liquids
(ILs), generally defined as salts that melt below 100 °C and
composed of at least two ions.16 Both ions comprising an IL
can independently and/or simultaneously introduce a specific
functionality or property beyond low melting character.
aCenter for Green Manufacturing and Department of Chemistry, The University of
Alabama, Box 870336, Tuscaloosa, AL 35487, USA. E-mail: RDRogers@as.ua.edu;
Tel: +1 205 348 4323
bDepartment of Chemical Technology, Poznan University of Technology,
Poznan 60-965, Poland. E-mail: Juliusz.Pernak@put.poznan.pl
cInstitute of Plant Protection – National Research Institute, Poznan 60-318, Poland
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Applying the IL concept to herbicides should allow controlled from the GRAS, ‘generally regarded as safe’ list24–26). Quatern-
modification of important properties such as thermal stability, ary tetraalkylammonium,27 imidazolium,28 and pyridinium
volatility, and water solubility.17
cations,28 especially those with longer alkyl chain lengths,
Herbicidal ionic liquids (HILs) have been previously were selected for their antimicrobial effects. These cations are
synthesized from 2,4-dichlorophenoxyacetic acid (2,4-D),18 active against both gram-positive and gram-negative bacteria,
N-(phosphonomethyl)glycine (glyphosate),19 3,5,6-trichloro- yeast, mold, viruses, protozoans, and fungi. The same activity
2-pyridinyloxyacetic acid (triclopyr),18a (R)-2-[4-(4-cyano-2-fluoro- is observed for piperidinium and morpholinium cations,
phenoxy)phenoxy]propionic acid (cyhalofop),18a and 2-methyl- where in general, most active compounds are compounds with
4-chlorophenoxyacetic acid (MCPA).18d Dicamba ILs have been longer N-alkyl group substituents (n = 8–16).29 N,N-Dialkyl-
reported in a recent patent application from Dow Agroscien- morpholinium and -piperidinium cations additionally display
ces18a that described pairing acidic herbicides with inert amines herbicidal activity which is the greatest in the compounds with
to create quaternary ammonium salts for overcoming volatility alkyl chains from 12 to 16 atoms.29 8-Hydroxyquinolines
problems of the parent herbicides. The patent examples (8HQs) cations possess diverse biological properties such
suggested that ILs formed by combining dicamba with certain as being antibacterial and antifungal.30 In addition, many of
amines possessed herbicidal activity on an acid equivalent the cations that have been used possess surfactant/membrane-
basis, but substantially less volatile.18a However, Dow Agro- disruptive properties due to the presence of the long alkyl
sciences did not take into the account that there are a number chains.
of key differences between the usually higher volatility of protic
ILs vs. aprotic ILs. For example, Baur et al.12 compared dimethyl-
ammonium dicamba herbicides (a protic cation) with tetra- Results and discussion
methylammonium dicamba (an aprotic cation) and found 70%
Synthesis of dicamba ILs
injury to grapes from vapor exposure of [N(CH3)2H2]+ salt vs.
only 12% injury to grapes, with the [N(CH3)4]+ salt.12 With judi-
cious selection of appropriate aprotic (so-called “permanent”)
Twenty eight dicamba-based salts utilizing eight different
classes of cations were synthesized (Scheme 1). To test
different strategies for pairing the dicamba with different
cations, two different approaches were attempted: (a) meta-
biologically active cations, liquid salt forms might not only
allow for modified physical properties, but also for dual func-
tional performance20,21 or even synergistic effects by the incor-
thesis reactions between the sodium/potassium salt of
dicamba and quaternary tetraalkylammonium, pyridinium,
poration of two biologically active ions into a single IL. Such
imidazolium, quinolinium, isoquinolinium, piperidinium,
herbicidal ILs should not only retain their biological activity,
morpholinium, and phosphonium halides, and (b) acid–base
reactions between dicamba free acid and the ammonium,
piperidinium, morpholinium, and pyrrolidinium hydroxides.
but also introduce new herbicidal/fungicidal/antimicrobial pro-
perties not inherent in the pure neutral forms,22 and even
potentially increase efficacy through, for example, better leaf
transport or reduced rain wash-off.19
In the study we report here, we have combined the hydro-
philic dicamba anion with hydrophobic, antimicrobial/anti-
fungal ammonium cations to produce hydrophobic ILs
(Fig. 1). Several criteria were taken into consideration for the
choice of the cations to be paired with dicamba.
It is known that when surfactants are added to dicamba,
total absorption (the amount of herbicide in the plant)
increases compared to dicamba without surfactant.23 There-
fore, we chose cations with surfactant character (hydrophobic
agents which also decrease water solubility).
We also focused on cations with additional biological
activity (e.g., fungicidal or antibacterial activity to complement
the herbicidal activity) and cations of low toxicity (e.g., cations
Scheme 1 General synthesis of HILs derived from dicamba (for substituents on
Fig. 1 Hydrophilic dicamba vs. hydrophobic dicamba HILs.
the cation see Table 1).
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Both approaches resulted in successfully obtaining the
Representative examples of salts with the different cation
salts (Table 1) that were isolated in excellent yields (>90%). classes are presented below, while the synthetic and character-
All isolated compounds were of high purities (98–99.5%), ization data for all compounds are provided in the Experi-
with water content below 0.5% (measured via Karl-Fischer mental section.
titration).
Thermal analysis
The formation of the desired compounds was proven via
spectroscopy (NMR and FT-IR). Particularly, in the 1H NMR
Thermal transitions for selected compounds were determined
spectra, the disappearance of the acidic –COOH peak, corres-
ponding to the dicamba free acid, and an upfield chemical
shift for the aromatic protons from dicamba (due to an
increase of electron density on the ring from the formation of
the dicamba anion) support the fully ionized nature of the
compounds. In the FT-IR spectra, a blue shift of the carboxylic
acid CvO stretch from ca. 1700 cm−1 to the carboxylate at
∼1600 cm−1 is also characteristic of the formation of the carb-
oxylate anion.
using differential scanning calorimetry (DSC), while the
melting points for the solid compounds were determined
using a Fisher-Johns melting point apparatus. Decomposition
temperatures (T5% onset, onset for 5% decomposition, and Tdec
,
decomposition temperature) were determined using thermal
gravimetric analysis (TGA). All data are presented in Table 2.
Most of the synthesized compounds are liquids or waxes
with melting points or glass transitions below 100 °C, being
classified as ILs (dicamba-HILs); only three compounds have
Table 1 New dicamba herbicidal compounds
Cation
R1
R2
R3
R4
Statea
1
2
3
4
5
6
7
8
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C4H9
C12H25
CH3
CH3
CH3
CH3
Tallow
CH2CH2OH
CH3
CH3
CH3
C12H25/C14H29
C10H21
C12H25
CH2C6H5
C10H21
Liquid
Solid
Liquid
Wax
Liquid
Wax
Liquid
Wax
Wax
Wax
Wax
Wax
Wax
CH2CH2OC6H5
CH3
Coco-b
d
d
—
—
Coco-b
CH2CH2OH
CH2O–C11H21
CH2O–C12H23
C10H21
(CH2)2OH
(CH2)2OH
(CH2)2OH
H-Tallowe
(CH2)2OH
CH3
(CH2)2OCOR
CH2CHvCH2
CH3
9
10
11
12
13
14
15
16
17
18
CH3
H-Tallowe
(CH2)2OH
Soya-c
Oleylf
CH3
CH3
CH3
CH3
CH3
C4H9
—
CH2CH2OCOR
CH2CHvCH2
(CH2)2OH
C14H29
C4H9
—
Wax
Solid
Solid
Solid
Liquid
CH3
C4H9
—
19
20
CH3
C10H21
CH2OC18H17
C10H21
—
—
—
—
Liquid
Liquid
21
C4H9
—
—
—
Solid
22
23
24
CH3
CH3
C10H21
CH3
C10H21
C10H21
—
—
—
—
—
—
Liquid
Liquid
Wax
25
26
CH3
CH3
C4H9
C4H9
—
—
—
—
Wax
Wax
27
28
CH3
H
C4H9
OH
—
—
—
—
Liquid
Glass
a State is shown at 25 °C. b Cocoalkyl chain distribution C8H16 – 5, C10H21 – 6, C12H25 – 50, C14H29 – 19, C16H33 – 10, C18H37 – 10%. c Soyaalkyl
chain distribution, C14H29 – 6, C16H33 – 14, C18H37 – 80%. d (CH2CH2O)(x or y)H with x + y = 15. e Alkyl hydrogenated tallow chain distribution
C12H25 – 1, C14H29 – 4, C16H33 – 31, C18H H25 – 1, C14H29 – 4, C16H33 – 12, C18H37 – 82%.
37 – 64%. f Oleyl chain distribution C12
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Table 2 Thermal analysis (DSC and TGA) for selected dicamba-HILs and
dicamba salts
a
b
c
d
Tg
[°C]
Tm
[°C]
T5% onset
[°C]
Tdec
[°C]
Compound
#
Dicamba free acid
Dicamba HILs 2–28
—
2
4
−78.8 114–116 132.5
150
232
−47
−47
−40
86
178
187
200
187
180
188
185
185
190
177
—
37
—
64–65
—
213, 312e
260
6
18 −25
21
23 −31
26 −20
27 −41
28
210, 355e
232, 355e
240
240
215
215
181
206
156
6
—
—
Dicamba salts 15–17 15
—
—
—
105
16
17
179–180 191
126–127 154
a Tg – glass transition. b
T
m – melting point. c
T5% onset – decomposition
■
Fig. 2 Decomposition temperatures for dicamba free acid ( ), several dicamba
of 5% of the sample. d
observed.
T
dec – decomposition. e Two step decomposition
○
◊
HILs ( ), and the three higher melting crystalline dicamba salts ( ).
more stable than higher melting dicamba salts 15, 16, and 17
(Tdec ≤ 200 °C; Fig. 2).
melting points above 100 °C, being classified here as “higher
melting crystalline salts” (dicamba salts). Out of 28 com-
pounds, 17 belong to the tetraalkylammonium class, with
three salts 15, 16, and 17 being solids. Yet, most of tetraalkyl-
ammonium compounds are liquids or waxes with a melting
point that decreases with an increase in the substituent alkyl
chain length. The presence of as many as three N-methyl
groups in the 16 and 17 results in melting point enhancement
(the effect is not observed in the presence of long coco- or
soya-substituted 4 and 12 as they are in fact mixtures of
different alkyl chain lengths).
In general, differences in Tdec were observed by changing
the alkyl substituents in tetraalkylammonium dicamba. Pre-
viously, Prasad et al. studied the thermal decomposition temp-
eratures for ammonium salts and showed that, as the size of
the substituted alkyl group increases, the thermal stability of
these compounds decreases.32 However, in our case, tetrabutyl-
ammonium 17 bearing four relatively short butyl groups had
the lowest decomposition temperature, only 10 °C above that
of the dicamba free acid.
Decomposition temperatures Tdec for all other tested com-
pounds were higher by at least 30 °C when compared to
the free acid starting material. Tetraalkylammonium 6 bearing
two hydroxyethyl-substituents and a long coco-alkyl has a
decomposition temperature as high as 260 °C; while pyrrolidi-
nium dicamba 27 and morpholinium dicamba 25 bearing the
same substituents have exactly the same decomposition temp-
eratures. However, a complete analysis of these trends is
difficult, since the choice of cation targets was based on their
biological properties rather than structural similarities.
Tetraalkylammonium with coco-, soya-, and tallow-substitu-
ents 4, 12, and 5 underwent two-step and three-step decompo-
sition, due to the presence of a mixture of different alkyl
chains. A similar observation was made for the phosphonium
salt that underwent a two-step decomposition, potentially due
to release of the volatile tributyl phosphine and/or tributyl
phosphine oxide above 250 °C.33 1-Dodecylpyridinium
dicamba also had a two-step decomposition event. The highest
overall decomposition point was observed for N-methyl-N,N-
dihydroxyethyl-N-cocoammonium dicamba.
Similarly, tetrabutylphosphonium dicamba 21 was a solid
with mp of 65 °C, probably due to all four alkyl chains being
relatively short identical 4 carbon ones resulting in a sym-
metric cation. All of the pyridinium, piperidinium, morpholi-
nium, and imidazolium compounds were liquids or waxes,
though more compounds of the same class have to be pre-
pared to statistically verify the trend.
As predicted,31 the general trends in the melting points of
the solid salts show that the presence of a hydroxyethyl-group
decreases the temperature of melting transitions when com-
pared to the alkyl substituents.
All the liquids or waxes show a glass transition below 0 °C.
The lowest glass transition temperature, as well as the
lowest melting point was observed for tetraalkylammonium
dicamba 5, with two polyethylene glycol (PEG)-like substitu-
ents and a “tallow” tail, a mixture of different alkyl chain
lengths. Unfortunately, there were not enough compounds syn-
thesized to determine a trend in Tg data for other compound
classes.
All the new dicamba derived compounds exhibited
improved thermal stabilities when compared to the neutral
dicamba acid. Many ILs showed improved thermal stability
when compared to parent neutral compounds, and similarly,
Volatility
It is generally believed that reducing a herbicide’s volatility
should reduce the impact of the herbicide on environment by
minimizing its vapor drift. Dicamba in its acid form has a
vapor pressure of 2.0 × 10−5 mm Hg at 25 °C and volatilization
dicamba HILs showed an improved thermal stability (Tdec
>
200 °C) when compared to dicamba free acid. They were also
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is substantial.34,35 Relative volatility rates of the acid form of
HIL 2, [DDA][Dicamba], was selected for efficacy compari-
dicamba and its ammonium salts, namely the dimethyl- son against dicamba free acid. The plants were separated into
ammonium, tallowammonium, and diethanolammonium three main groups, where Group I was treated with HIL of
salts were reported previously36 and it was shown that after three different concentrations, Group II was treated with
plant exposure to 40 °C for 12 h, volatility depended on alkyl- dicamba free acid of three different concentrations, and Group
ammonium substituent length, and decreased in the order: III was a control. Specifically, Group I was treated with
dicamba
dicamba diethanolammonium salt (DEOA) ≫ dicamba tallo- trations of active compound were (i) 0.001 mol L−1 (1 equiv.,
wammonium salt (DT) (92%, 43%, 4%, and 2%, respectively).
0.546 g L−1), (ii) 0.002 mol L−1 (2 equiv., 1.092 g L−1), and (iii)
>
dicamba dimethylammonium salt (DMA)
≫
dicamba HIL 2 solution in water–DMSO (2 : 1 v/v); concen-
We have measured the relative volatility rates of both 0.004 mol L−1 (4 equiv., 2.184 g L−1), respectively. In turn,
dicamba-ILs and dicamba salts after 12 h, and compared these Group II was treated with Banvel® (dicamba free acid) solution
with reported values for the acid form of dicamba and its di- in water–DMSO (2 : 1 v/v). Concentrations of active applied
methylammonium salts. The dicamba ammonium and phos- were (i) 0.001 mol L−1 (1 equiv., 0.221 g L−1), (ii) 0.002 mol L−1
phonium HILs 2 and 21, and dicamba tetraalkylammonium (2 equiv., 0.442 g L−1), and (iii) 0.004 mol L−1 (4 equiv., 0.884 g
salts 15, 16, and 17 were subjected to thermogravimetric analy- L−1) of active component, respectively. Group III was sprayed
sis (TGA) with isothermal heating at 75 °C for 12 h. All the with a control solution of water–DMSO (2 : 1 v/v). The study
compounds were thoroughly characterized to ensure the was carried out in 4 replications in a completely randomized
absence of any residual water or solvent that would interfere setup.
with the study. Volatility was defined as the weight loss of the
The application was performed using a sprayer equipped
herbicide when it was held under isothermal conditions with a flat fan Tee Jet 1103 XR nozzle, using a steady pressure
at 75 °C for a period of 12 h under a constant flow of nitrogen. of 0.2 MPa at 200 L ha−1 application rate. After spraying the
(It should be noted that this test does expose the herbicidal IL plants, the pots were placed back into a growth chamber at the
to relatively high temperatures, much higher than operational same controlled environmental conditions as before spraying
conditions, and exceeds the temperature conditions in the (20 °C, 60% humidity, 16/8 h day/night photoperiod). After a
area around a plant.)
period of 2 weeks, the plants were cut right to the soil level
The HILs 2 and 21 showed less than 2.5% mass loss (2.4% and weighed (0.1 g accuracy). The reduction of plant fresh
for 2 and 1.6% for 21; Table 3). The higher melting salts 15, weight as compared to control (no sprayed plants) was
16, and 17, exhibited less than 0.7% mass loss. Dicamba free measured.
acid, however, lost more than 10% of its mass during the 12 h
of this test.
In growth chamber experiments, dicamba HIL 2 showed
an improved efficacy over dicamba free acid (Banvel®). Results
for the tests on Sinapis alba species showed a better activity
of [DDA][Dicamba] 2 than of Banvel® on the fresh weight
reduction, while no reduction was observed when dicamba
free acid was used. The activity of 2 was dependent on the con-
centration used, increasing from 6.8% (for a concentration of
0.001 M) to 18.5% (for 0.002 M) and to 27.1% (for 0.004 M).
However, the activity of 2 was comparable to the activity of
dicamba free acid when lambsquarters (Chenopodium album)
species were used (the results are presented in Table 4 and
Fig. 3).
Initial field experiments (visual evaluation). The research was
conducted in the Field Experimental Station of the Institute of
Plant Protection in Winna Gora in 1.5 m × 5 m areas. The test
plants were common lambsquarters (Chenopodium album) and
cornflower (Centaurea cyanus). At the time of herbicide appli-
cation, common lambsquarters were at 4–10 leaves develop-
mental phase and cornflower was a fully-formed rosette.
Didecyldimethylammonium 3,6-dichloro-2-methoxybenzo-
ate ([DDA][Dicamba]) 2 was chosen for the initial testing. For
application, 2 was dissolved in a mixture of water and ethanol
(1 : 1 v/v) in an amount corresponding to a concentration of
0.01 and 0.02 mol L−1. Dicamba solution was prepared in pure
water with no ethanol added, also at 0.01 and 0.02 mol L−1
concentration.
Efficacy
Growth chamber experiments. Initial efficacy tests were con-
ducted in a growth chamber as typically approval for field
testing is granted only after growth chamber test results are
available. These experiments were performed under controlled
environmental conditions (20 °C, 60% humidity, 16/8 h
day/night photoperiod). Common lambsquarters (Chenopodium
album) and white mustard (Sinapis alba) were used as test
plants, because both plants are typically controlled via
dicamba applications. Plants seeds were placed into soil-filled
containers, at planting depths of 1 cm. After producing leaves,
only 5 plants were left in each pot; other plants were removed.
At the time of herbicide application, both types of plants were
at the 3 leaves developmental phase.
Table 3 Mass loss after 12 h isotherms at 75 °C
Compound
Mass loss (12 h; 75 °C; %)
Dicamba free acid
Dicamba HILs
—
2
21
15
16
17
10.6
2.4
1.6
0.7
0.7
0.5
Higher melting dicamba salts
Plants were separated into three groups. Group I was
sprayed using HIL 2 and Group II was sprayed using dicamba
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Table 4 Growth chamber experiments for dicamba HIL 2 and commercial
Banvel® (dicamba free acid active ingredient)
Table 5 Efficacy tests for dicamba HIL 2 and commercial Banvel® (dicamba free
acid active ingredient) conducted on lambsquarters (Chenopodium album) and
cornflower (Centaurea cyanus) species in the field experiments
White mustard
Lambsquarters
(Sinapis alba)b
(Chenopodium album)b
Lambsquarters
Cornflower
Conc.a
(Chenopodium album)b
(Centaurea cyanus)b
Herbicide
(mol L−1
)
Fresh weight reduction (%)
Effectiveness of weed eradication (%) (visually
determined)
Herbicidea
[DDA]
[Dicamba], 2
0.001
0.002
0.004
0.001
0.002
0.004
6.8
18.5
27.1
No reduction
No reduction
No reduction
16.7
41.7
45.7
20.9
49.2
60.2
[DDA][Dicamba], 2
92
83
95
90
Banvel® c
Banvel® c
a Conditions included 4 weeks after treatment (4 WAT). b Plants were
grown at all otherwise identical conditions and differed in herbicidal
treatment. c Banvel® commercial herbicide containing active
ingredient as a pure acid.
a Other conditions included
2 weeks after treatment (2 WAT);
temperature of 20 °C ( 2 °C), humidity 60%, illumination time 16/24.
b Plants were grown under identical conditions and differed only in
herbicidal treatment. c Banvel® commercial herbicide containing active
ingredient as a pure acid.
reduction method was employed (see below) to quantify the
visual comparisons above.
Field experiments (fresh weight reduction). The specific objec-
tive of these field experiments was to determine the exact
efficacy of dicamba HILs. Five HILs were randomly chosen out
of the prepared compounds for the field testing on weed
species, and the results were compared with dicamba free
acid. Liquid or waxy HILs of different cation classes were
chosen for this test: ammonium (6), piperidinium (23), and
morpholinium (26).
Determination of efficacy was conducted using the fresh
weight reduction method. The field experiments were
conducted in the Field Experimental Station on a corn field
(Winna Gora, Poland, E: 17°26′, N: 52°12′), in 2011. Common
lambsquarters (Chenopodium album) were used as test plants
while corn was cultivated according to the local agricultural
practice. All herbicides were applied at the 3 leaves growth
stage at the application rate 200 g dicamba active per ha. Field
studies were conducted as randomized complete blocks, on
Fig. 3 Comparison (5 days after treatment) between treatment of
lambsquarters with different forms of dicamba (0.001 M active): A – no treat-
ment, B – treatment with dicamba HIL 2, C – treatment with dicamba free acid
as commercial Banvel®.
free acid. Group III, a control group, was not treated with her-
bicide, but only with a solution of water and ethanol (1 : 1 v/v).
The application was performed using a knapsack sprayer areas of 16.5 m2 with at least four replications.
equipped with flat fan Tee Jet 1103 nozzles, using a steady
Similarly to the previous field studies described earlier,
pressure of 0.2 MPa at 200 L ha−1 application rate. The effec- dicamba HILs were dissolved in water–ethanol solution (1 : 1
tiveness of weed eradication was evaluated visually by compar- v/v) in an amount corresponding to 0.01 mol L−1 concen-
ing the state of weeds of Groups I, II, and III twenty eight days
tration. Dicamba free acid was dissolved in water (no ethanol
after treatment (DAT). For that, surviving plants were counted was added) to prepare solutions of the same concentrations.
in quadrats and percent stand reduction was calculated based Control group plants were not treated with any type of
on the nontreated control. The evaluation took into account
the degree of soil coverage, the vigor of the weeds, and the
plants’ height and mass.
dicamba but sprayed with a water–ethanol solution (1 : 1 v/v).
The plants were sprayed using a knapsack sprayer with Tee
Jet 1103 XR flat fan nozzles at 0.3 MPa with an application rate
of 200 L ha−1. Weed control was evaluated via fresh weight
The effectiveness of the eradication of weeds was presented
in percentage scale where 100% means the complete destruc- reduction measurements, after herbicide applications using a
tion and 0% means no action of the herbicide. Results of the scale of 0 (no control) to 100% (complete weed destruction).
efficiency of [DDA][Dicamba] and the neutral dicamba are pre-
The results indicated that the species Chenopodium album in
sented as the mean estimate of weed destruction as shown in field conditions, were substantially more susceptible to treat-
Table 5. The results indicate that the species Chenopodium ment with HILs than to dicamba free acid. Differences were
album and Centaurea cyanus in field conditions, were more sus-
found among the HILs (Table 6) however all HILs were at least
ceptible to treatment with HIL 2 than to dicamba free acid. 15% more effective than dicamba free acid. Similarly to the
These results are slightly different than the ones obtained in visual evaluation, these results are slightly different than
growth chamber experiments, probably because of a more
the ones obtained in growth chamber experiments, probably
competitive stress in the field. Nevertheless, the fresh weight because of a more competitive stress in field.
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Thermal transitions (melting point and glass transitions)
were determined on a Mettler Toledo Stare DSC1 (Columbus,
OH) unit, under nitrogen. Samples between 5–15 mg were
placed on an aluminium pan and were heated from 25 °C to
120 °C with a heating rate of 10 °C min−1 and cooled to
−100 °C min−1 with an intracooler with a cooling rate of 10 °C
min−1. Melting points were determined using a Fisher-Johns
Melting Point Apparatus.
Table 6 Control of common lambsquarters (Chenopodium album) by different
forms of dicamba
Herbicide
Lambsquarters (Chenopodium album)
Fresh weight reduction (%)
6a
62.5
57.5
62.5
62.5
56.3
42.5
26a
23a
4a
11a
Banvel® b
Syntheses
a Spraying with a knapsack sprayer with Tee Jet 1103 XR flat fan
nozzles at 0.3 MPa. b Commercial product containing 480 g of dicamba
per 1 L.
Synthesis by metathesis reactions (method A)
Method A1 (1–13, 15, 17–21, 23, 24, 26). 0.01 mol of dicamba
acid, 20 mL distilled water, and 0.011 mol of 10% aqueous
solution of NaOH were mixed in a round-bottom flask,
equipped with a magnetic stir bar, a reflux condenser, and an
addition funnel. The mixture was heated at 50 °C until a clear
solution was obtained. After that 0.01 mol of ammonium
chloride or bromide dissolved in 30 mL water was added and
stirred for 30 min at room temperature. The resulting product
was extracted from the aqueous phase with 50 mL of chloro-
form and washed with distilled water until chloride or
bromide ions were no longer detected using AgNO3 test. After
removal of chloroform the product was dried under reduced
pressure at 60 °C for 24 h.
Method A2 (28). Stoichiometric amounts of sodium/
potassium salt of dicamba and quinolinium hydrochloride
were mixed in water and stirred at room temperature for 24 h.
After evaporation of water, the reaction product was extracted
with anhydrous acetone. The precipitate (NaCl) was filtered by
gravity and the filtrate was evaporated under reduced pressure.
Finally, the product was dried at 60 °C under reduced
pressure.
Conclusions
New dicamba-based HILs were synthesized and analyzed for
volatility, thermal stability, and efficacy in both growth
chamber and field trials. These new compounds demonstrate
increased thermal stability, reduced volatility, and substan-
tially improved efficacy over dicamba free acid, indicating that
HILs may offer significant advantages over and be viable
alternatives to other currently used forms of dicamba. In
addition, the HIL strategy offers a way to access dual func-
tional herbicidal ILs by combining the herbicidal activity of
the dicamba anion with fungicidal, antibacterial, and/or herbi-
cidal activity of the cation; an area that is currently under
research in our groups. Moreover, by using the IL strategy, the
negative impacts of dicamba free acid on the environment
caused by runoff, vapor drift, and the need to use higher con-
centrations, might be reduced or eliminated.
Synthesis by acid–base reactions (method B) (14, 16, 22, 25,
27). 0.011 mol of a 40% aqueous solution of ammonium
hydroxide was mixed with 0.011 mol dicamba free acid. The
excess of dicamba acid was filtered out, and the water was
evaporated. The product was dried under reduced pressure at
60 °C for 24 h. The ammonium hydroxide was used as received
or prepared via ion exchange (an amount of 0.01 mol of piperi-
dinium, morpholinium, or pyrrolidinium halide (chloride,
bromide or iodide) was passed through an OH anion exchange
resin Dowex-Monosphere 550A (OH)).
Experimental
General methods
All chemicals, unless otherwise stated, were purchased from
Aldrich Chemical Company (Saint Louis, MO) in reagent grade
≥98% and used without further purification. Dicamba free
acid and dicamba sodium salt were provided by Monsanto Co.
Quaternary ammonium chlorides with soya, oleyl, hydro-
genated tallow, and coco alkyl groups were purchased from
AkzoNobel, The Netherlands.
Characterization
The 1H and 13C NMR spectra were collected utilizing a
Bruker spectrometer 500 MHz Bruker Avance Spectrometer
Benzalkonium 3,6-dichloro-2-methoxybenzoate (1). Liquid,
1
Bruker/Magnex UltraShield 500 MHz magnet (Madison, WI) 92% yield, 99.5% purity, H NMR (CDCl3) δ ppm = 0.88 (t, J =
operating at 500 MHz for 1H spectra and 125 MHz for 13C 6.7 Hz, 3H), 1.26 (m, 20H), 1.71 (q, J = 6.8 Hz, 2H), 3.22 (s, 6H),
spectra, respectively.
3.34 (t, J = 4.3 Hz, 2H), 3.92 (s, 3H), 4.86 (s, 2H), 6.99 (d, J =
Thermogravimetric analyses were performed on a TA Instru- 8.5 Hz, 1H), 7.09 (d, J = 8.8 Hz, 1H), 7.38 (d, J = 6.3 Hz, 2H),
ments (New Castle, DE) model 2950 thermogravimetric 7.41 (t, J = 2.8 Hz, 1H), 7.55 (t, J = 3.9 Hz, 2H); 13C NMR
analyzer. The experiments were performed under nitrogen (CDCl3) δ ppm = 14.0, 22.6, 22.7 26.1, 29.1, 29.21, 29.24, 29.29,
atmosphere. Samples between 5–10 mg were placed on a plati- 29.34, 29.47, 29.52, 29.56, 31.8, 49.6, 61.6, 63.2, 67.4, 125.4,
num pan and were heated from 25 °C to 800 °C with a heating 126.0, 127.4, 127.6, 127.9, 129.0, 130.4, 133.1, 139.8, 151.8,
rate of 5 °C min−1. Decomposition temperatures are reported 168.3; Tg = −26 °C; T5% onset = 175 °C; Tdec = 212 °C.
as T5% onset (onset for 5% decomposition) and Tdec (decompo-
sition temperature).
Didecyldimethylammonium 3,6-dichloro-2-methoxybenzoate
(2). Liquid, 99% yield, 99.0% purity, 1H NMR (CDCl3) δ ppm =
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0.88 (t, J = 6.7 Hz, 6H), 1.25 (m, 28H), 1.61 (q, J = 6.8 Hz, 4H), 125.4, 126.0, 127.6, 127.8, 138.6, 151.6, 168.9; Anal. Calcd for
3.34 (s, 6H), 3.39 (t, J = 6.3 Hz, 4H), 3.95 (s, 3H), 6.99 (d, J = C24H41O5NCl2: C 58.28, H 8.37, N 2.83; Found: C 58.57, H 8.16,
8.5 Hz, 1H), 7.08 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3) δ ppm = N 2.59.
14.0, 22.5, 26.1, 29.1, 29.25, 29.27, 31.7, 50.9, 61.5, 63.1,
Cyclododecyloxymethyl(2-hydroxyethyl)dimethylammonium
125.3, 125.9, 127.0, 127.8, 140.2, 151.7, 167.9; Anal. Calcd for: 3,6-dichloro-2-methoxybenzoate (8). Wax, 95% yield, 99.0%
1
C30H53O3NCl2: C 65.90, H 9.79, N 2.56; Found: C 65.62, H 9.65, purity, H NMR (CDCl3) δ ppm = 1.31 (m, 18H), 1.47 (m, 2H),
N 2.33; Tg = −47 °C, Tm = 86 °C, T5%
232 °C.
= 178 °C; Tdec
=
1.61 (m, 2H), 3.20 (s, 6H), 3.60 (t, J = 4.7 Hz, 2H), 3.78 (q, J =
3.7 Hz, 1H), 3.93 (s, 3H), 4.06 (t, J = 4.5 Hz, 2H), 4.74 (s, 2H),
onset
Dodecyldimethylphenoxyethylammonium 3,6-dichloro-2- 5.58 (s, 1H), 7.01 (d, J = 8.5 Hz, 1H), 7.13 (d, J = 8.8 Hz, 1H);
methoxybenzoate (3). Liquid, 99% yield, 99.5% purity. 1H 13C NMR (CDCl3) δ ppm = 19.8, 22.5, 22.6, 24.7, 24.9, 28.4,
NMR (CDCl3) δ ppm = 0.88 (t, J = 6.7 Hz, 3H), 1.25 (m, 18H), 48.2, 55.7, 61.7, 63.0, 81.5, 89.9, 125.5, 126.1, 127.8, 128.0,
1.75 (q, J = 6.8 Hz, 2H), 3.44 (s, 6H), 3.55 (t, J = 8.4 Hz, 2H), 138.5, 151.8, 169.0; Anal. Calcd for C25H41O5NCl2: C 59.27,
3.94 (s, 3H), 4.18 (t, J = 6.5 Hz, 2H), 4.43 (t, J = 6.6 Hz, 2H), H 8.17, N 2.77; Found: C 59.11, H 8.23, N 2.83.
6.88 (d, J = 7.7 Hz, 2H), 7.00 (d, J = 8.5 Hz, 1H), 7.07 (d, J =
Decyl(2-hydroxyethyl)dimethylammonium 3,6-dichloro-2-
1
5.2 Hz, 1H), 7.26 (t, J = 2.2 Hz, 2H), 7.29 (t, J = 3.4 Hz, 1H); methoxybenzoate (9). Wax, 79% yield, 98.5% purity, H NMR
13C NMR (CDCl3) δ ppm = 14.1, 22.6, 22.9, 26.16, 26.19, 29.2, (CDCl3) δ ppm = 0.88 (t, J = 6.9 Hz, 3H), 1.20 (m, 16H), 1.24 (q,
29.33, 29.38, 29.49, 29.50, 31.8, 51.7, 61.6, 62.0, 62.1, 65.6, J = 6.2 Hz, 2H), 3.19 (s, 6H), 3.29 (t, J = 5.9 Hz, 2H), 3.55 (t, J =
114.1, 121.8, 125.3, 125.9, 127.1, 127.7, 129.6, 140.0, 151.5, 4.6 Hz, 2H), 3.89 (s, 3H), 4.04 (t, J = 4.5 Hz, 2H), 4.69 (s, 1H),
156.7, 167.8; Anal. Calcd for: C30H45O4NCl2: C 64.96, H 8.19, 7.01 (d, J = 8.6 Hz, 1H), 7.12 (d, J = 8.6 Hz, 1H); 13C NMR
N 2.53; Found: C 65.12, H 8.38, N 2.41; Tg = −18 °C; T5% onset
177 °C; Tdec = 236 °C.
=
(CDCl3) δ ppm = 14.0, 22.56, 22.62, 26.2, 29.1, 29.2, 29.4, 31.8,
51.6, 55.7, 61.7, 65.5, 65.6, 125.5, 126.1, 127.7, 128.6, 138.7,
Cocotrimethylammonium 3,6-dichloro-2-methoxybenzoate (4). 151.8, 168.9; Anal. Calcd for C22H37O4NCl2: C 58.65, H 8.30,
1
Wax, 75% yield, 99.0% purity, H NMR (CDCl3) δ ppm = 0.88 N 3.11; Found: C 58.17, H 8.42, N 2.99.
(t, J = 6.7 Hz, 3H), 1.26 (m, 20H), 1.60 (q, J = 7.3 Hz, 2H), 3.27
Di(hydrogenatedtallowalkyl)dimethylammonium 3,6-dichloro-
(s, 9H), 3.30 (t, J = 8.5 Hz, 2H), 3.91 (s, 3H), 6.97 (d, J = 8.5 Hz, 2-methoxybenzoate (10). Wax, 98% yield, 99.5% purity, 1H
1H), 7.08 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3) δ ppm = 14.1, NMR (CDCl3) δ ppm = 0.88 (t, J = 6.7 Hz, 6H), 1.26 (m, 49H),
22.7, 23.1, 26.2, 29.25, 29.32, 29.4, 29.5, 29.6, 31.9, 53.1, 61.7, 1.61 (q, J = 6.8 Hz, 4H), 3.31 (s, 6H), 3.35 (t, J = 6.3 Hz, 4H),
66.5, 125.3, 126.0, 127.4, 127.6, 139.6, 151.6, 168.1; Tg
−12 °C; T5% onset = 187 °C; Tdec = 213 °C, 312 °C.
=
3.93 (s, 3H), 6.98 (d, J = 8.5 Hz, 1H), 7.10 (d, J = 8.5 Hz, 1H);
13C NMR (CDCl3) δ ppm = 14.0, 22.5, 26.1, 29.1, 29.25, 29.29,
Polyoxyethylene(15)(hydrogenatedtallow)methylammonium 29.37, 29.50, 29.55, 29.59, 31.8, 51.03, 61.6, 63.2, 125.3, 126.0,
3,6-dichloro-2-methoxybenzoate (5). Liquid, 89% yield, 99.0% 127.6, 128.0, 139.1, 51.99, 168.0.
1
purity, H NMR (CDCl3) δ ppm = 0.88 (t, J = 6.7 Hz, 3H), 1.26
Oleyldi(2-hydroxyethyl)methylammonium 3,6-dichloro-
(m, 28H), 1.71 (m, 2H), 3.29 (s, 3H), 3.38 (s, 3H), 3.62 (t, J = 2-methoxybenzoate (11). Wax, 92% yield, 99.0% purity, 1H
6.6 Hz, 2H), 3.64 (m, 44H), 3.65 (m, 8H), 3.95 (m, 8H), 6.97 (d, NMR (CDCl3) δ ppm = 0.88 (t, J = 5.3 Hz, 3H), 1.26 (m, 26H),
J = 8.5 Hz, 1H), 7.07 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3) 1.59 (q, J = 7.3 Hz, 2H), 2.01 (m, 3H), 3.19 (s, 3H), 3.34 (t, J =
δ ppm = 14.1, 22.6, 26.3, 29.2, 29.3, 29.50, 29.59, 29.64, 31.8, 8.4 Hz, 2H), 3.55 (t, J = 4.0 Hz, 4H), 3.89 (s, 3H), 4.01 (t, J =
49.2, 61.4, 61.6, 63.8, 64.8, 70.1, 70.4, 72.5, 125.1, 125.8, 127.1, 4.0 Hz, 4H), 5.35 (m, 2H), 7.01 (d, J = 8.7 Hz, 1H), 7.12 (d, J =
127.8, 139.6, 151.6, 168.2; Tg = −57 °C, Tm = −36 °C; T5% onset
170 °C; Tdec = 200 °C, 322 °C, 387 °C.
=
8.7 Hz, 1H); 13C NMR (CDCl3) δ ppm = 14.1, 22.4, 22.6, 26.3,
27.17, 27.19, 29.17, 29.27, 29.29, 29.41, 29.44, 29.49, 29.63,
Cocodi(2-hydroxyethyl)methylammonium 3,6-dichloro-2- 29.72, 31.85, 31.89, 50.0, 55.6, 61.8, 63.6, 64.1, 125.6, 126.2,
1
methoxybenzoate (6). Wax, 99% yield, 98.0% purity, H NMR 127.7, 128.2, 129.6, 130.0, 138.5, 151.8, 169.5.
(CDCl3) δ ppm = 0.88 (t, J = 6.6 Hz, 3H), 1.26 (m, 20H), 1.61
Soyatrimethylammonium 3,6-dichloro-2-methoxybenzoate
1
(q, J = 7.3 Hz, 2H), 3.19 (s, 3H), 3.37 (t, J = 8.0 Hz, 2H), 3.58 (t, (12). Wax, 97% yield, 99.0% purity, H NMR (CDCl3) δ ppm =
J = 4.0 Hz, 4H), 3.91 (s, 3H), 3.99 (t, J = 4.0 Hz, 4H), 7.01 (d, J = 0.88 (t, J = 6.6 Hz, 3H), 1.26 (m, 24H), 1.59 (q, J = 7.3 Hz, 2H),
8.5 Hz, 1H), 7.13 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3) δ ppm = 2.02 (m, 3H), 3.22 (s, 9H), 3.28 (t, J = 8.5 Hz, 2H), 3.88 (s, 3H),
14.1, 22.4, 22.5, 22.6, 26.3, 29.2, 29.3, 29.5, 29.6, 31.8, 50.0, 5.39 (m 2H), 6.98 (d, J = 8.6 Hz, 1H), 7.11 (d, J = 8.6 Hz, 1H);
55.6, 61.7, 63.6, 64.1, 125.4, 126.0, 127.5, 127.9, 138.5, 151.6, 13C NMR (CDCl3) δ ppm = 14.0, 18.9, 22.5, 22.6, 23.0, 26.1,
168.9; Tg = −12 °C; T5% onset = 208 °C; Tdec = 274 °C.
27.1, 28.97, 29.12, 29.16, 29.23, 29.28, 29.38, 29.40, 29.45,
(2-Hydroxyethyl)dimethyl(undecyloxymethyl)ammonium 3,6- 29.53, 29.58, 29.63, 31.81, 31.83, 32.50, 32.53, 35.58, 53.1, 61.8,
dichloro-2-methoxybenzoate (7). Liquid, 92% yield, 98.0% 66.6, 125.5, 126.1, 127.8, 128.1, 129.9, 130.0, 130.2, 130.3,
1
purity, H NMR (CDCl3) δ ppm = 0.88 (t, J = 6.7 Hz, 3H), 1.26 130.4, 138.3, 151.9, 168.8.
(m, 16H), 1.55 (q, J = 6.2 Hz, 2H), 3.19 (s, 6H), 3.57 (t, J =
Dialkanoyloxyethyldimethylammonium 3,6-dichloro-2-methoxy-
1
4.4 Hz, 2H), 3.69 (t, J = 6.6 Hz, 2H), 3.92 (s, 3H), 4.04 (t, J = benzoate (13). Wax, 96% yield, 99.5% purity, H NMR (CDCl3)
4.5 Hz, 2H), 4.76 (s, 2H), 5.14 (s, 1H), 7.01 (d, J = 8.5 Hz, 1H), δ ppm = 0.88 (t, J = 6.6 Hz, 6H), 1.26 (m, 42H), 1.57 (q, J =
7.12 (d, J = 8.8 Hz, 1H); 13C NMR (CDCl3) δ ppm = 14.1, 22.6, 6.9 Hz, 4H), 2.29 (m, 4H), 2.32 (t, J = 9.3 Hz, 4H), 3.41 (s, 6H),
25.7, 29.3, 29.47, 29.54, 31.8, 48.1, 55.5, 61.7, 62.9, 73.3, 91.2, 3.90 (s, 3H), 3.97 (t, J = 4.6 Hz, 4H), 4.52 (t, J = 4.6 Hz, 4H),
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5.34 (m 2H), 7.00 (d, J = 8.6 Hz, 1H), 7.12 (d, J = 8.6 Hz, 1H); C21H30O4N2Cl2: C 56.62, H 6.80, N 6.29; Found: C 56.18, H
13C NMR (CDCl3) δ ppm = 14.1, 22.6, 24.6, 27.1, 27.2, 28.9, 6.15, N 6.23.
29.03, 29.08, 29.15, 29.25, 29.30, 29.45, 29.60, 29.65, 29.69,
31.83, 31.86, 33.9, 52.2, 57.6, 61.8, 63.5, 125.6, 126.2, 127.9, Liquid, 77% yield, 99.5% purity, 1H NMR (CDCl3) δ ppm = 0.88
128.2, 129.6, 130.0, 138.2, 151.9, 168.8, 172.7. (t, J = 6.7 Hz, 6H), 1.24 (m, 24H), 1.84 (q, J = 6.3 Hz, 4H), 3.95
1,3-Didecylimidazolium 3,6-dichloro-2-methoxybenzoate (20).
Diallyldimethylammonium 3,6-dichloro-2-methoxybenzoate (s, 3H), 4.27 (t, J = 7.4 Hz, 4H), 6.98 (d, J = 8.5 Hz, 1H), 7.08 (d,
(14). Wax, 95% yield, 1H NMR (D2O) δ ppm = 3.00 (s, 6H), 3.88 J = 8.6 Hz, 1H), 7.40 (t, J = 1.8 Hz, 1H), 7.41 (t, J = 1.7 Hz, 1H),
(d, J = 7.4 Hz, 4H), 4.85 (s, 3H), 5.65 (m, 2H), 5.73 (m, 2H), 10.57 (t, J = 1.0 Hz, 1H); 13C NMR (CDCl3) δ ppm = 13.9, 22.5,
6.02 (m, 2H), 7.22 (d, J = 8.7 Hz, 1H), 7.38 (d, J = 8.7 Hz, 1H); 26.1, 26.3, 28.9, 29.1, 29.2, 29.3, 30.1, 31.7, 46.9, 49.7, 61.5,
13C NMR (D2O) δ ppm = 52.2 (t, J = 4.2 Hz), 64.7, 68.8 (t, J = 121.6, 125.2, 125.9, 127.4, 128.0, 138.2, 139.3, 151.7, 168.5;
3.2 Hz), 127.0, 128.7, 128.9, 130.1, 131.9, 132.3, 138.9, 153.7, Anal. Calcd for C31H50O3N2Cl2: C 65.38, H 8.86, N 4.92; Found:
174.4; Anal. Calcd for C16H21O3NCl2: C 55.49, H 6.13, N 4.05; C 65.69, H 8.99, N 4.78.
Found: C 55.55, H 6.24, N 3.98.
Tetrabutylphosphonium 3,6-dichloro-2-methoxybenzoate (21).
1
Choline-3,6-dichloro-2-methoxybenzoate (15). Solid, 90% Wax, 84% yield, H NMR (CDCl3) δ ppm = 0.94 (t, J = 6.9 Hz,
1
yield, 99.0% purity, H NMR (DMSO-d6) δ ppm = 3.12 (s, 9H), 12H), 1.47 (m, 16H), 2.34 (m, 8H), 3.98 (s, 3H), 6.95 (d, J =
3.42 (m, 2H), 3.80 (s, 3H), 3.85 (m, 2H), 7.05 (d, J = 8.8 Hz, 2H), 8.5 Hz, 1H), 7.04 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3) δ ppm =
7.17 (d, J = 8.8 Hz, 2H); 13C NMR (DMSO-d6) δ ppm = 53.53, 13.3, 18.4 (d, JCP = 47.4 Hz), 23.6 (d, JCP = 4.9 Hz), 23.9,
55.54, 61.45, 67.53, 125.58, 125.76, 127.13, 127.90, 141.31, 61.3, 124.8, 125.5, 126.4, 127.8, 140.2, 151.4, 167.3; Anal.
151.60, 166.09; Tm = 105 °C; T5% onset = 177 °C; Tdec = 181 °C.
Calcd for C24H41O3PCl2: C 60.11, H 8.64; Found: C 60.25,
Trimethyltetradecylammonium-3,6-dichloro-2-methoxy- H 8.52; Tg = 6 °C; Tm = 64–65 °C; T5% onset = 180 °C; Tdec
benzoate (16). Solid, 1H NMR (CDCl3) δ ppm = 0.88 (t, J = 232 °C, 355 °C.
=
6.6 Hz, 6H), 1.26 (m, 42H), 1.57 (q, J = 6.9 Hz, 4H), 2.29 (m,
1,1-Dimethylpiperidinium 3,6-dichloro-2-methoxybenzoate (22).
4H), 2.32 (t, J = 9.3 Hz, 4H), 3.41 (s, 6H), 3.90 (s, 3H), 3.97 (t, Liquid, 99% yield, 1H NMR (DMSO-d6) δ ppm = 1.50 (q, J =
J = 4.6 Hz, 4H), 4.52 (t, J = 4.6 Hz, 4H), 5.34 (m 2H), 7.00 (d, J = 5.9 Hz, 2H), 1.75 (q, J = 5.2 Hz, 4H), 3.08 (s, 6H), 3.33 (t, J =
8.6 Hz, 1H), 7.12 (d, J = 8.6 Hz, 1H); 13C NMR (CDCl3) δ ppm = 5.9 Hz, 4H), 3.80 (s, 3H), 7.28 (d, J = 8.6 Hz, 1H), 7.80 (d, J =
14.1, 22.6, 24.6, 27.1, 27.2, 28.9, 29.03, 29.08, 29.15, 29.25, 8.6 Hz, 1H); 13C NMR (DMSO-d6) δ ppm = 19.7, 20.6, 50.9,
29.30, 29.45, 29.60, 29.65, 29.69, 31.83, 31.86, 33.9, 52.2, 57.6, 61.0, 61.5, 125.0, 125.2, 126.5, 127.4, 140.9, 151.0, 165.2; Anal.
61.8, 63.5, 125.6, 126.2, 127.9, 128.2, 129.6, 130.0, 138.2, 151.9, Calcd for C15H21O3NCl2: C 53.89, H 6.35, N 4.19; Found:
168.8, 172.7; Tm = 179–180 °C; T5%
= 191 °C; Tdec
=
C 53.59, H 6.16, N 4.27; Tg = −54 °C; T5% onset = 195 °C; Tdec =
onset
206 °C.
240 °C.
Tetrabutylammoniun-3,6-dichloro-2-methoxybenzoate (17).
1-Decyl-1-methylpiperidinium 3,6-dichloro-2-methoxybenzo-
Solid, H NMR (DMSO-d6) δ ppm = 0.93 (t, 12H); 1.30 (m, 8H); ate (23). Wax, 92% yield, 98.5% purity, 1H NMR (CDCl3)
1.55 (m, 8H); 3.17 (m, 8H); 3.79 (s, 3H); 7.00 (d, 1H); 7.12 (d, δ ppm = 0.88 (t, J = 6.8 Hz, 3H), 1.25 (m, 14H), 1.63 (q, J =
1H); 13C NMR (DMSO-d6) δ ppm = 13.93, 19.67, 23.55, 58.01, 7.4 Hz, 2H), 1.72 (q, J = 5.9 Hz, 4H), 1.82 (q, J = 5.9 Hz, 4H),
61.20, 125.34, 125.48, 126.41, 128.03, 142.11, 151.53, 164.96; 3.25 (s, 3H), 3.51 (t, J = 8.6 Hz, 4H), 3.62 (t, J = 8.7 Hz, 2H),
1
Tm = 126–127 °C; T5% onset = 154 °C; Tdec = 156 °C.
3.95 (s, 3H), 6.98 (d, J = 8.6 Hz, 1H), 7.07 (d, J = 8.5 Hz, 1H);
1-Dodecylpyridinium 3,6-dichloro-2-methoxybenzoate (18). 13C NMR (CDCl3) δ ppm = 13.9, 20.0, 20.5, 21.8, 22.4,
Liquid, 91% yield, 99.0% purity, 1H NMR (CDCl3) δ ppm = 0.87 26.2, 29.0, 29.1, 29.2, 31.6, 48.0, 60.5, 61.5, 62.5, 125.2,
(t, J = 6.7 Hz, 3H), 1.24 (m, 18H), 1.94 (q, J = 6.6 Hz, 2H), 3.91 125.9, 127.0, 127.8, 140.1, 151.6, 167.7; Anal. Calcd for
(s, 3H), 4.82 (t, J = 7.4 Hz, 2H), 6.98 (d, J = 8.8 Hz, 1H), 7.21 (d, C24H39O3NCl2: C 62.59, H 8.55, N 3.04; Found: C 62.21, H 8.39,
J = 8.5 Hz, 1H), 8.10 (t, J = 7.0 Hz, 2H), 8.41 (t, J = 7.7 Hz, 1H), N 2.93.
9.46 (d, J = 6.0 Hz, 2H); 13C NMR (CDCl3) δ ppm = 14.1, 22.6,
26.0, 29.0, 29.2, 29.3, 29.4, 29.5, 31.8, 31.9, 61.7, 61.9, 125.3, Wax, 78% yield, 99.5% purity, H NMR (CDCl3) δ ppm = 0.88
125.9, 127.9, 128.2, 138.3, 144.4, 145.2, 151.7, 168.1; Anal. (t, J = 6.7 Hz, 6H), 1.26 (m, 28H), 1.32 (q, J = 7.4 Hz, 2H), 1.59
Calcd for C25H35O3NCl2: C 64.09, H 7.54, N 2.99; Found: C (q, J = 5.9 Hz, 4H), 1.82 (q, J = 5.9 Hz, 4H), 3.37 (t, J = 8.4 Hz,
1,1-Didecylpiperidinium 3,6-dichloro-2-methoxybenzoate (24).
1
64.28, H 7.42, N 2.89; Tg = −25 °C; T5% onset = 187 °C; Tdec
210 °C, 355 °C.
=
4H), 3.65 (t, J = 8.7 Hz, 4H), 3.97 (s, 3H), 6.96 (d, J = 8.5 Hz,
1H), 7.05 (d, J = 8.6 Hz, 1H); 13C NMR (CDCl3) δ ppm = 13.9,
1-Methyl-3-octyloxymethylimidazolium 3,6-dichloro-2-methoxy- 19.7, 20.4, 21.4, 22.4, 26.1, 28.95, 29.00, 29.14, 29.16, 31.6,
benzoate (19). Liquid, 74% yield, 98.0% purity, 1H NMR 57.8, 58.6, 61.4, 125.0, 125.7, 126.7, 127.9, 140.1, 151.6, 167.6;
(CDCl3) δ ppm = 0.87 (t, J = 6.7 Hz, 3H), 1.23 (m, 10H), 1.51 (q, Anal. Calcd for C33H57O3NCl2: C 67.54, H 9.81, N 2.39; Found:
J = 6.3 Hz, 2H), 3.48 (t, J = 6.5 Hz, 2H), 3.91 (s, 3H), 4.03 (s, C 67.99, H 9.43, N 2.45.
3H), 5.64 (s, 2H), 6.99 (d, J = 8.5 Hz, 1H), 7.07 (d, J = 8.5 Hz,
4-Butyl-4-methylmorpholinium 3,6-dichloro-2-methoxy-
1H), 7.40 (t, J = 1.8 Hz, 1H), 7.46 (t, J = 1.8 Hz, 1H), 10.37 ((t, benzoate (25). Wax, 99% yield, 1H NMR (DMSO-d6) δ ppm =
J = 1.0 Hz, 1H); 13C NMR (CDCl3) δ ppm = 14.1, 22.6, 25.8, 0.92 (t, J = 7.3 Hz, 3H), 1.29 (sex, J = 7.4 Hz, 2H), 1.65 (q, J =
29.2, 29.3, 29.4, 31.8, 36.4, 61.7, 70.3, 79.0, 120.5, 123.7, 125.3, 4.0 Hz, 2H), 3.15 (s, 3H), 3.43 (t, J = 7.1 Hz, 4H), 3.71 (t, J =
125.9, 127.8, 127.9, 138.1, 138.6, 151.7, 168.6; Anal. Calcd for 4.4 Hz, 2H), 3.80 (s, 3H), 3.91 (t, J = 4.9 Hz, 4H), 7.06 (d, J =
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8.4 Hz, 1H), 7.20 (d, J = 8.4 Hz, 1H); 13C NMR (DMSO-d6) δ
ppm = 13.6, 19.2, 22.8, 45.8, 58.9, 59.9, 61.0, 63.6, 125.0, 125.2,
126.7, 127.4, 140.2, 151.0, 165.1; Anal. Calcd for
C17H25O4NCl2: C 53.97, H 6.67, N 3.70; Found: C 53.62, H 6.44,
N 3.85; Tg = −16 °C; T5% onset = 187 °C; Tdec = 215 °C.
4-Decyl-4-ethylmorpholinium 3,6-dichloro-2-methoxybenzo-
ate (26). Liquid, 88% yield, 99.0% purity, 1H NMR (D2O)
δ ppm = 0.98 (t, J = 6.0 Hz, 3H), 1.13 (m, 14H), 1.21 (t, J =
6.0 Hz, 3H), 1.49 (q, J = 4.0 Hz, 2H) 3.22 (t, J = 4.4 Hz, 2H), 3.44
(t, J = 4.4 Hz, 2H), 3.49 (t, J = 4.4 Hz, 4H), 3.86 (s, 3H), 3.99 (t,
J = 4.9 Hz, 4H), 7.07 (d, J = 8.6 Hz, 1H), 7.12 (d, J = 8.6 Hz, 1H);
13C NMR (D2O) δ ppm = 8.7, 16.1, 23.1, 24.9, 28.3, 31.3, 31.7,
31.8, 34.2, 55.9, 59.7, 60.5, 62.3, 64.0, 127.7, 128.0, 130.1,
130.3, 140.3, 153.9, 171.9; Anal. Calcd for C24H39O4NCl2:
C 60.49, H 8.27, N 2.94; Found: C 60.01, H 8.00, N 2.79.
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1–3.
1-Butyl-1-methylpyrrolidinium 3,6-dichloro-2-methoxybenzo-
1
ate (27). Liquid, 99% yield, H NMR (DMSO-d6) δ ppm = 0.91
(t, J = 7.3 Hz, 3H), 1.28 (sex, J = 7.4 Hz, 2H), 1.65 (q, J = 4.1 Hz,
2H), 2.05 (m, 4H), 2.99 (s, 3H), 3.33 (t, J = 8.5 Hz, 2H), 3.51 (m, 11 O. C. Burnside and R. L. Lavy, Weeds, 1966, 14, 211–214.
4H), 3.80 (s, 3H), 7.04 (d, J = 9.3 Hz, 1H), 7.16 (d, J = 9.3 Hz, 12 J. R. Baur, R. W. Bovey and H. G. McCal, Arch. Environ.
1H); 13C NMR (DMSO-d6) δ ppm = 13.6, 19.3, 21.0, 25.0, 47.2,
Contam. Toxicol., 1973, 1, 289–302.
60.8, 62.7, 63.2, 124.9, 125.0, 126.1, 127.3, 141.3, 150.8, 164.7; 13 http://www.weeds.iastate.edu/mgmt/2001/dicambavolatility.
Anal. Calcd for C17H25O3NCl2: C 56.35, H 6.97, N 3.87; Found:
htm, last accessed 04/10/13.
C 55.01, H 6.79, N 3.99; Tg = −41 °C; T5% onset = 185 °C; Tdec
215 °C.
=
14 http://www.agriculture.purdue.edu/fnr/html/faculty/holt/
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8-Hydroxyquinolinium 3,6-dichloro-2-methoxybenzoate (28). 15 (a) H. A. Powell, N. W. Kirby and P. Rowell, New Phytol.,
Glass, 94% yield, 1H NMR (DMSO-d6) δ ppm = 3.84 (s, 3H),
4.85 (s, 1H), 7.12 (dd, J = 1.6 Hz, J = 5.6 Hz, 1H), 7.32 (d, J =
8.7 Hz, 1H), 7.40 (d, J = 1.5 Hz, 1H), 7.43 (d, J = 7.3 Hz, 1H),
7.53 (d, J = 3.8 Hz, 1H), 7.56 (d, J = 4.3 Hz, 1H), 8.33 (dd, J =
1.6 Hz, J = 6.7 Hz, 1H), 8.85 (dd, J = 1.6 Hz, J = 2.6 Hz, 1H);
13C NMR (DMSO-d6) δ = 62.1 ppm, 111.5, 117.8, 121.8, 126.0,
126.1, 127.6, 128.0; 128.8, 131.5, 131.7, 136.5, 137.9, 147.9,
1991, 119, 421–426; (b) G. L. Diamond and P. R. Durkin,
“Effects of surfactants on the toxicity of glyphosate,
with specific reference to Rodeo”, prepared under USDA FS
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1197.
152.4, 153.0, 165.1; Anal. Calcd for C17H13O4NCl2: C 55.75, 16 Ionic Liquids: Industrial Applications for Green Chemistry,
H 3.59, N 3.83; Found: C 55.98, H 3.63, N 3.73; T5%
190 °C; Tdec = 215 °C.
=
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JP acknowledges the support provided by National Science
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