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manner to 2. Hammett constant of each substituent,17 reac-
tion temperatures, yields, melting points, and IR (C@O, ATR)
data are summarized in Table 1. 1H and 13C NMR spectro-
scopic data are summarized in Tables 2 and 3.
Preparation of Formulations and Differential Scanning
Calorimetry Measurements
Diglycidyl ether of bisphenol A (DGEBA) (5.00 g, 14.70
mmol) and urea (0.29 mmol) were mixed (10 min) and
degassed (3 min) with a conditioning mixer (AR-100, Thinky,
Tokyo). A portion of the resulting formulation (8–12 mg)
was transferred to an aluminum pan, sealed, and set into dif-
ferential scanning calorimetry (DSC) instrument (Seiko
Instrument DSC-6200). Under a nitrogen flow, the sample
was heated from 30 to 250 8C in a heating rate of 10 8C/
min. From the resulting heat-evolution profile, the corre-
sponding onset temperatures (Tonset), peak temperatures
(Tpeak), and enthalpy changes (DH) were determined.
SCHEME 1 Synthesis of p-substituted N-aryl-N0-pyridyl ureas.
internal standard. IR spectra were recorded on a Thermo
Scientific Nicolet iS10 spectrometer equipped with a smart
ATR sampling accessory.
Synthesis of Urea Derivatives of 4AP (2–6)
A typical procedure is given for the synthesis of N-(4-methyl-
phenyl)-N0-(4-pyridyl)urea (2): To a solution of 4AP (1.5 g,
16 mmol) in toluene (120 mL), 4-methylphenyl isocyanate
(2.0 g, 15 mmol) was added slowly at room temperature.
The mixture was heated at 85 8C for 12 h, cooled to room
temperature, and concentrated under reduced pressure to
obtain 2 as a solid. The solid was recrystallized from ethanol
(25 mL) to obtain pure 2 as a white powder (2.42 g, 10.7
mmol, 71%). N-aryl-N0-pyridyl ureas 3–6 were synthesized
from the corresponding phenyl isocyanates having various
substituents on its benzene ring and 4AP in the similar
RESULTS AND DISCUSSION
Synthesis of N-Aryl-N0-Pyridyl Ureas
N-Aryl-N0-pyridyl ureas 1–6 were synthesized by the addi-
tion reaction of the corresponding aryl isocyanates and 4AP
(Scheme 1). The structures of the ureas were confirmed by
1H, 13C NMR, and IR spectroscopy.
TABLE 1 Synthesis of N-Aryl-N0-Pyridyl Ureas and Their Properties
N-Aryl-N0-Pyridyl
Hammett
Constant
Reaction
IR (C@O)
Urea
X
Temperature (8C)
Yield (%)
Melting Point (8C)
(cm21
)
1
2
3
4
5
6
H
0
85
85
85
90
90
90
78
71
65
80
73
76
156–158
1714
1716
1713
1718
1727
1745
Me
OMe
Cl
20.17
20.27
0.23
0.54
0.78
186–200 (decomposing)
164–168
226–230 (decomposing)
216–218
CF3
NO2
264–268 (decomposing)
1
TABLE 2 H NMR Spectroscopic Data of N-Aryl-N0-Pyridyl Ureas
N-Aryl-N0–Pyridyl
Ureas
X
1H-NMR Spectroscopic Data (Measured in DMSO-d6)
1
H
7.01 (t, 1H, J 5 6.8 Hz), 7.31 (t, 2H, J 5 6.8 Hz), 7.44 (dd, 2H, J 5 4.8, 1.6 Hz),
7.48 (d, 2H, J 5 6.8 Hz), 8.36 (dd, 2H, J 5 4.8, 1.6 Hz), 8.87 (s, 1H), 9.11 (s, 1H)
2
3
4
5
6
Me
2.23 (s, 3H), 7.09 (d, 2H, J 5 8.8 Hz), 7.33 (d, 2H, J 5 8.8 Hz),
7.41 (d, 2H, J 5 4.8 Hz), 8.33 (d, 2H, J 5 4.8 Hz), 8.73 (s, 1H), 9.03 (s, 1H)
OMe
Cl
3.70 (s, 3H), 6.88 (d, 2H, J 5 8.8 Hz), 7.35 (d, 2H, J 5 8.8 Hz), 7.41 (d, 2H, J 5 4.8 Hz),
8.32 (d, 2H, J 5 4.8 Hz), 8.65 (s, 1H), 9.01 (s, 1H)
7.33 (d, 2H, J 5 8.4 Hz), 7.41 (d, 2H, J 5 6.0 Hz), 7.48 (d, 2H, J 5 8.4 Hz),
8.35 (d, 2H, J 5 6.0 Hz), 8.98 (s, 1H), 9.12 (s, 1H)
CF3
NO2
7.44 (d, 2H, J 5 6.4 Hz), 7.63 (d, 2H, J 5 8.8 Hz), 7.67 (d, 2H, J 5 8.8 Hz),
8.37 (d, 2H, J 5 6.4 Hz), 9.21 (s, 1H), 9.26 (s, 1H)
7.45 (d, 2H, J 5 6.4 Hz), 7.71 (d, 2H, J 5 8.8 Hz), 8.20 (d, 2H, J 5 8.8 Hz),
8.38 (d, 2H, J 5 6.4 Hz), 9.36 (s, 1H), 9.62 (s, 1H)
2570
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 2569–2574