SUPPORTING INFORMATION TO
Kinetics and thermodynamics of reversible disproportionation–
comproportionation in redox triad oxoammonium cations – nitroxyl
radicals – hydroxylamines
V.D. Sen’1, I.V. Tikhonov2, L.I. Borodin2, E.M. Pliss2, V.A. Golubev1, M.A. Syroeshkin3, A.I.
Rusakov2
1
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka,
142432, Russian Federation, senvd@icp.ac.ru
2
3
P.G. Demidov Yaroslavl State University, Yaroslavl, 150000, Russian Federation
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991,
Russian Federation.
CONTENT
1. Synthesis
1.1. Nitroxyl radicals 1
1.2. Oxoammonium salts 2
1.3. Hydroxyammonium salts 3H+
2. Equilibrium and kinetics
3. Reduction potentials
4. Correlations
1
1. Synthesis
1.1. Nitroxyl radicals 1
Nitroxyl radicals 1a,d,e,g–i,k,q,w were synthesized according to [1], methods for the synthesis of
other radicals are described in the following references: 1b [2], 1c [3], 1f,j [4], 1m [5], 1o [6], 1p [7],
1r [8], 1s [9].
The purity of nitroxyl radicals 1 was checked by TLC and HPLC [Milikhrom chromatograph
equipped with a 264-mm column (Separon C18, 5 μm) and a UV detector (λ 220 nm), eluent
40% aqueous MeCN]. The purity of oxoammonium salts 2 was checked by 1H MNR spectra
and/or by iodometric titration. The purity of hydroxyammonium salts 3H+ was checked by 1H
MNR spectra. All compounds had a purity of at least 97%. IR reflection spectra were taken with
a Perkin Elmer Spectrum 100 spectrometer, NMR spectra were registered on a spectrometer
Bruker AIII (500 MHz).
2,2,6,6-Tetramethyl-4-trifluoroacetylaminopiperidine-1-oxyl 1n. Ethyl trifluoroacetate (3.4
ml, 28 mmol) was added to a stirred solution of 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl
2
(3.42 g, 20 mmol) in 10 ml of absolute EtOH at ~20°C. After stirring for 2 hr the volatile
components of the mixture were removed in vacuo and the residue was treated with 20 g of
crushed ice. The resulting suspension of 1n was filtered, washed on the filter with a cold water
and then air-dried; yield of 1n: 4.50 g (84%), orange crystals with mp 152–153°C (MTBE–
hexane, 1:2) (149–152°C [10]).
3-Acetylaminomethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl 1t. Acetic anhydride (1.1 ml, 11
mmol) was added to a stirred mixture of 3-aminomethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl
[11]
(1.71 g, 10 mmol) and Et3N (1.5 ml, 11 mmol) in 10 ml of MeCN at ~20°C and left for 6 hr.
Volatile components of the mixture were removed in vacuo, the residue was dissolved in 20 ml
of water and extracted with ethyl acetate (15 mL  3). The combined extract was washed
sequentially with 0.1 N HCl, 1 M NaHCO3 and dried with Na2SO4. After removal of the solvent
yield of 1t: 1.79 g (84%), mp 54–56 ° C (EtOAc – hexane). IR-spectrum, ν, cm1: 3346, 3070,
1666, 1543 (CONH), 2974, 2936, 2907, 1455, 1420, 1366, 1320, 1278, 1255, 1192, 1179, 1158,
1113, 959, 927, 907, 857. Found, %: C, 61.7; H, 9.98; N, 12.9. C11H21N2O2. Calculated, %: C,
61.94; H, 9.92; N, 13.13. M 213.30.
3-Cyano-2,2,5,5-tetramethylpyrrolidine-1-oxyl 1v. Cyanurchloride (0.93 g, 5 mmol) was
added in one batch to a stirred solution of 3-aminocarbonyl-2,2,5,5-tetramethylpyrrolidine-1oxyl (1.85 g, 10 mmol) in 10 ml of DMF at 0С. Stirring was continued while cooling until a
total reaction time of 40 min. The reaction mixture was poured onto 50 g of ice and then
extracted with MTBE (20 mL  6). The combined extract was dried (Na2SO4) and evaporated in
vacuo to give 0.7 g (42%) 1v as a red oil. This was purified by flash chromatography on silica
gel (MTBE – hexane, 3:1) and sublimed in vacuo. Orange crystals, mp 31–33°C, lit. mp 31.5–
32.5°C. [1]
1.2. Oxoammonium salts 2
Spectra of oxoammonium salts
Proton signals in the 1H NMR spectra of solutions of oxoammonium salts 2 broadened due to
rapid electron exchange with minor impurities of radicals 1. To prevent this phenomenon in the
solution was added ~10 mol% of the oxidant, namely, SbCl5. Large coupling constants (J 12–14
Hz) of protons Ha3 and Ha5 with vicinal protons Ha4 show that cycles oxopiperidinium salts
2a,b,d–f have a chair conformation and that their R-substituents are in the equatorial position.
Similar conclusions about the structure of 2d tetrafluoroborate were made from X-ray data.[12]
For 2c, close coupling constants (J 6–7 Hz) of axial and equatorial protons H3 and H5 with
3
vicinal proton H4 indicate the axial position of the methoxy group. As compared with the
hydroxyammonium salts 3H+, the signals of the methylene and methine protons of salts 2 are
shifted downfield by ~0.5 ppm. Consequently, >N+=O group exerts a larger deshilding than the
>N+HOH group (see spectra of salts 2 and 3H+).
Oxoammonium group is isoelectronic to carbonyl group. Similarly to cyclic ketones, in the IR
spectra of salts 2 the absorption frequency of >N+=O increases with decreasing ring size from
~1630 cm–1 for piperidine derivatives to 1660–1670 cm–1 for the derivatives of pyrrolidine and
pyrroline. By analogy with ketones,[13] this indicates an increase in -character of intracyclic N–
C bonds and -character of the N+=O bond. These changes have a strong influence on the
quantitative characteristics of the disproportionation reaction, in particular, the reduction
potentials E2/1 increase, and the equilibrium constants K4 decrease sharply (Table 1).
Perchlorates 2a,b,g were prepared according to
[14-16]
. The remaining salt 2 were prepared
according to the general methods A, B, which are suitable for the synthesis of oxoammonium
salts with low and high solubility in water, respectively.
Method A. 4-Methoxy-2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate 2с. Solution of Cl2
(0.86 eq·l–1) in 1.19 ml of CCl4 was added drop-wise during 5 min to a stirred suspension of
nitroxyl radical 1c (186 mg, 1.0 mmol) in solution of NaClO4 (146 mg, 1.2 mmol) in 1.5 ml of
water at ace cooling. After stirring for 30 min the resulting yellow suspension of salt 2c was
filtered, crystals were washed with 1 ml of cold water, dry ether (2 ml  3) and dried in vacuo
yielding 228 mg (80%) of 1t. Yellow needle with mp 161–162°C (dec.) (MeCN – ether). IRspectrum, ν, cm1: 1628 (NO+), 1089 (ClO4–), 3010, 2979, 2945, 2904 и 2824 (CH3), 1470,
1445, 1393, 1382, 1371, 1288, 1247, 1217, 1184, 1159, 1017, 973, 952, 896, 863, 817. NMR 1H,
(CD3CN), δ, ppm: 1.69 (s, 6 H, 2 CH3a), 1.74 (s, 6 H, 2 CH3e), 2.67 (dd, 2 H, Ha3 and Ha5, J 14.8,
6.5 Hz), 2,83 (dd, 2H, He3 and He5, J 14.8, 4.5 Hz), 3.48 (s, 3 H, OCH3), 4.30 (tt, 1 H, He4, J 6.5,
4.5 Hz). Found, %: C, 42.0, H, 7.04, Cl, 12.0, N, 4.78. C10H20ClNO6. Calculated, %: C, 42.04, H,
7.06, Cl, 12.41, N, 4.90. M 285.72.
Method B. 3-Carbamoyl-2,2,5,5-tetramethyl-1-oxopyrrolidinium perchlorate 2h. Solution of
Cl2 (0.98 eq·l–1) in 6.3 ml of CCl4 was added drop-wise during 5 min to a stirred suspension of
nitroxyl radical 1h (1.12 g, 6.0 mmol) in solution of NaClO4 (1.02 g, 7.3 mmol) in 10 ml of
water at ace cooling. After stirring for 30 min the colored aqueous phase was separated and
freeze-dried in vacuo. The remaining yellow solid was further dried in a vacuum desiccator over
P2O5. After a single reprecipitation from MeCN-ether and then double reprecipitation from
MeCN-EtOAc 0.71 g (67%) of 2h was obtained as small yellow prisms, mp 130-132C (dec.).
4
IR-spectrum, ν, cm1: 3450, 3350, 1698, 1618 (CONH2), 1659 (NO+), 1101, 1073 (ClO4–), 3009,
2952, 2882, 2789, 1466, 1411, 1376, 1323, 1274, 1248, 1213, 1021, 975, 893, 789. NMR 1H,
(CD3CN), δ, ppm: 1.58, 1.70, 1.75, 1.81 (s, 12 H, 4 CH3), 3.02 (dd, 1 H, H4, J 14.1, 7.7 Hz), 3.16
(dd, 1 H, H4, J 14.1, 7.4 Hz), 3,87 (t, 1 H, H3, J 7.5 Hz), 6.30, 6.77 (s, 2 H, NH2). Found, %: C,
37.6, H, 6.34, N, 9.69. C9H17ClN2O6. Calculated, %: C, 37.97, H, 6.02, N, 9.84. M 284.69.
4-Acylamino-2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate 2d. Prepared by the method
A, yield 90%, mp 173–176°C (dec.) (MeCN), lit. mp 177–178°C. [17] IR-spectrum, ν, cm1:
3270, 3098, 1658, 1569 (CONH), 1626 (N+=O), 1082 (ClO4–), 3006, 2974, 2952, 2884, 2841,
1466, 1445, 1370, 1322, 1283, 1245, 1218, 1205, 1165, 969, 886, 865, 820. NMR 1H, (CD3CN +
SbCl5), δ, ppm: 1.56 (s, 6 H, 2 CH3a), 1.90 (s, 6 H, 2 CH3e), 2.48 (s, 3 H, CH3CO), 2.68 (t, 2 H,
Ha3 and Ha5, J 13.6 Hz), 2.82 (ddm, 2 H, He3 and He5, J 14.2, 4.4, ~2 Hz), 5.22 (dtt, 1 H, Ha4, J
13.6, 4.4, ~8 Hz), 9.36 (br s, 1 H, NH). Found, %: C, 42.0, H, 6.69, N, 8.96. C11H21ClN2O6.
Calculated, %: C, 42.24, H, 6.77, N, 8.96. M 312.75.
4-Chloro-2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate 2e. Prepared by the method A,
yield 89%, mp 155–159°C (dec.) (MeCN–ether). IR-spectrum, ν, cm1: 1629 (N+=O), 1096
(ClO4–), 3014, 2987, 2958, 2887, 1465, 1447, 1399, 1382, 1372, 1358, 1303, 1240, 1227, 1186,
979, 958, 900, 853, 776, 710. NMR 1H, (CD3CN + SbCl5), δ, ppm: 1.55 (s, 6 H, 2 CH3a), 1.89 (s,
6 H, 2 CH3e), 2.85 (dd, 2 H, Ha3 and Ha5, J 14.3, 11.7 Hz), 3.02 (ddt, 2 H, He3 and He5, J 14.3,
4.5, 1.6 Hz), 5.34 (tt, 1 H, Ha4, J 11.7, 4.5 Hz). Found, %: C, 37.5, H, 5.84, Cl, 24.8, N, 4.73.
C9H17Cl2NO5. Calculated, %: C, 37.26, H, 5.91, Cl, 24.44, N, 4.83. M 290.14.
4-Cyano-2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate 2f. Prepared by the method A,
yield 92%, mp 150–155°C (dec.) (MeCN). IR-spectrum, ν, cm1: 2249 (CN), 1629 (N+=O),
1083, 1074 (ClO4–), 3007, 2949, 2878, 1461, 1382, 1292, 1245, 1222, 1196, 1165, 946, 933,
912, 888, 869, 817, 758. NMR 1H, (CD3CN + SbCl5), δ, ppm: 1.58 (s, 6 H, 2 CH3a), 1.84 (s, 6 H,
2 CH3e), 2.84 (dd, 2 H, Ha3 and Ha5, J 14.5, 11.8 Hz), 2.93 (dd, 2 H, He3 and He5, J 14.5, 4.3 Hz),
4.17 (tt, 1 H, Ha4, J 11.8, 4.3 Hz). Found, %: C, 42.8, H, 6.07, Cl, 12.5, N, 9.87. C10H17ClN2O5.
Calculated, %: C, 42.79, H, 6.10, Cl, 12.63, N, 9.98. M 280.71.
3-Ethoxycarbonyl-2,2,5,5-tetramethyl-1-oxopyrrolinium perchlorate 2h. Prepared by the
method A, yield 43%, mp 149–152°C (dec.) (H2O). IR-spectrum, ν, cm1: 3103 (HC=C), 1722
(C=O), 1672 (N+=O), 1632 (C=C), 1088 (ClO4–), 2956, 2909, 1467, 1443, 1401, 1374, 1348,
1284, 1260, 1158, 1067, 1030, 990, 962, 933, 894, 867, 763. NMR 1H, (CD3CN + SbCl5), δ,
ppm: 1.37 (t, 3 H, CH3CH2, J 7.2 Hz), 1.80 (s, 6 H, 2 CH3), 1.87 (s, 6 H, 2 CH3), 4.38 (q, 2 H,
CH3CH2, J 7.2 Hz), 7.65 (s, 1 H, HC=C). Found, %: C, 42.6, H, 5.93, N, 4.38. C11H18ClNO7.
Calculated, %: C, 42.38, H, 5.82, N, 4.49. M 311.72.
5
1.3. Hydroxyammonium salts 3H+
NMR 1H spectra
Substituted in the 4th position 1-hydroxypiperidinium salts may exist as e,a- and a,e-cis– or aaand ee-trans–isomers.
There are two sets of signals corresponding to the dominant isomer in the NMR 1H spectra of the
majority of 1-hydroxypiperidinium salts. For the most abundant of the two isomers, signals of
axial methylene protons Ha3 and Ha5 have pseudo-triplet structure due to their interaction with
the geminal e-protons (J ~ 14 Hz) and vicinal proton Ha4 (J ~ 12 Hz). These data match two
isomers with 4e-R-substituents having the ee-trans- and ae-cis-structure. Signals of methylene
protons He3 and He5 in both types of isomers have a doublet-doublet structure due to their
interaction with the geminal a-protons (J ~ 14 Hz) and the vicinal proton Ha4 (J ~ 4 Hz).
Methine proton Ha4 in these isomers gives triplet-triplet signal due to the interaction with protons
Ha3 / Ha5 (J ~12 Hz) and He3 / He5 (J ~4 Hz). ee-Isomers of hydroxyammonium salts are more
stable and predominates in the mixture due to spatial repulsion of OH-groups and Ha3 / Ha5
protons in ae-isomers.[17] Axial and equatorial H3 / H5 protons in ea-isomers interact equally with
Ha4 proton (J ~ 4 Hz), and their signals have a doublet-doublet structure with J ~14 and ~4 Hz.
At the same time ea-isomers energetically are less favorable than ee-isomers due to the mutual
repulsion of R-substituents and two axial methyls. Therefore, we believe that salt 3H+ with one
set of signals are pure ee-isomers.
Protons of >N+HOH group are deshilded by positive charge ( 11-12.5 ppm) and the position of
their signals strongly depends on the solvent. Signals of OH groups in trans-and cis-isomers
have similar chemical shifts or overlap. In dry organic solvents interaction of protons of OH and
N+H groups split their signals into doublets (J ~ 5 Hz). In the spectrum of each isomer of salts
3H+ four methyl groups show two signals with  1.4-1.5 and 1.6-1.7 ppm. According to two‐
dimensional NOE 1H‐NMR in CDCl3, in ee-isomers signals in higher field belong to axial
methyls as they interact spatially with proton Ha4.
Spectra of salts 3H+ in dry organic solvents reflect the content of cis,trans-isomers in the
obtained crystalline samples. Traces of water cause the inversion of nitrogen in 3H+ and the
6
ratios of isomers change to equilibrium ones depending on the substituent R and the solvent.
Because of the asymmetry of the molecules 1H NMR spectra of 1-hydroxypyrrolidinium
3H+h,s–v and 1-hydroxypirrolinium 3H+i,w salts are more complex. All methyl groups at
positions 3 and 5 give separate signals. In the spectra of 1-hydroxypyrrolidinium salts there are
two sets of signals corresponding to the isomers with trans- and cis- orientation of 1-OH and 3-R
substituents.
Hydrochlorides 3H+a,b,h,k,q were prepared according to
[15, 18-21]
. The remaining salt 3H+ were
obtained by the general methods C–F.
Method C. 1-Hydroxy-4-methoxy-2,2,6,6-tetramethylpiperidinium chloride 3H+с. Aqueous
9.7 N HCl (1.65 ml, 16 mmol) was added drop-wise during 5 min to a stirred suspension of
nitroxyl radical 1c (2.79 g, 15 mmol) in 12 ml of EtOH at ace cooling. The reaction mixture was
left at ~20C for 16 hours. The resulting colorless solution was evaporated, the residue was
triturated with acetone and filtered to give 2.72 g (12.2 mmol, 81%) of chloride, 3H+с. Colorless
prismatic crystals decomposing at 200–205С (MeOH-ether). IR-spectrum, ν, cm1: 3070, 2541,
1500 (N+HOH), 2992, 2947, 2856, 1469, 1411, 1392, 1382, 1328, 1283, 1248, 1214, 1193, 1177,
1155, 1103, 1065, 1032, 988, 967, 922, 896, 731. NMR 1H, (CDCl3), δ, ppm: mixture of ee- и
ea-isomers (~2:1), ee-3H+с: 1.42 (s, 6 H, 2 CH3a), 1.71 (s, 6 H, 2 CH3e), 2.10 (dd, 2 H, He3 and
He5, J 14.0 and 4.1 Hz), 2.29 (dd, 2 H, Ha3 and Ha5, J 14.0 and 11.5 Hz), 3.33 (s, 3 H, OCH3e),
3.65 (tt, 1 Ha4, J 11.5 and 4.1 Hz), 10.83 (d, 1 H, OHe, J 5.4 Hz), 11.65 (d, 1 H, NHa, J 5.4 Hz).
ea-3H+с: 1.57 (s, 6 H, 2 CH3a), 1.65 (s, 6 H, 2 CH3e), 2.15 (dd, 2 H, He3 and He5, J 14.7 and 3.0
Hz), 2.47 (dd, 2 H, Ha3 and Ha5, J 14.7 and 3.2 Hz), 3.31 (s, 3 H, OCH3a), 3.61 (quintet, 1 H, He4,
J 3.2 Hz), 10.79 (d, 1 H, OHe, J 5.5 Hz), 11.36 (d, 1 H, NHa, J 5.5 Hz). Found, %: C 54.0, H
9.97, N 6.15. C10H22ClNO2. Calculated, %: C 53.68, H 9.91, N 6.26. M 223.74.
Method
D.
1-Hydroxy-4-oxo-2,2,6,6-tetramethylpiperidinium
chloride
3H+g.
In
a
hydrogenation apparatus catalyst Pd/C (0.15 g, 5% Pd) was added to a solution of nitroxyl
radical 1g (8.50 g, 50 mmol) in 12 ml of methanol. The system was purged with hydrogen,
closed, mixing was turned on and hydrogen uptake was monitored by a gas meter. After uptake
of the theoretical amount of hydrogen the apparatus was purged with nitrogen, the catalyst was
filtered and washed with methanol. The methanolic solution of hydroxylamine 3g was acidified
with concentrated HCl to pH 2 under stirring and cooling with cold water. The solution was
evaporated to dryness, the residue was triturated with acetone and filtered to give 9.55 g (92%)
of chloride 3H+g. Colorless prismatic crystals with mp 185–186С (dec.) (MeCN); lit.
[22]
mp
163–166°C. IR-spectrum, ν, cm1: 2522, 1504 (N+HOH), 1728 (C=O), 3045, 2628, 2569, 2540,
1464, 1417, 1382, 1343, 1303, 1274, 1208, 1132, 1049, 1027, 985, 946, 918, 850, 736. NMR 1H,
7
(CDCl3), δ, ppm: 1.43 (s, 6 H, 2 CH3a), 1.81 (s, 6 H, 2 CH3e), 2.48 (dd, 2 H, He3 and He5, J 13.7
Hz), 3.69 (d, 2 H, Ha3 and Ha5, J 13.7 Hz), 11.33 (d, 1 H, OHe, J 5.7 Hz), 12.24 (d, 1 H, NHa, J
5.7 Hz). NMR 13C (CDCl3), δ, M.д.: 22.04, 27.79 (4 CH3), 51.17 (C3, C5), 71.0 (C2, C6), 201.9
(C4).
Method E. 1-Hydroxy-3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidinium chloride 3H+s.
Na2S2O4
[23]
(1.18 g, 6.7 mmol) was added under Ar to a stirred solution of nitroxyl radical 1s
(0.69 g, 4 mmol) in 15 ml of acetone–water (1:1). Within 5 min the yellow solution was
decolorized. After 15 minutes acetone was removed in vacuo and the aqueous phase was
extracted under Ar with EtOAc (5 mL  3). Combined extracts were acidified with a solution of
alcoholic HCl to pH ~1–2 while cooling with ice, evaporated to dryness and further dried in a
vacuum desiccator over CaCl2. Yield of 3H+s 0.63 g (75%); colorless prisms, mp 150–155°C
(dec.) (MeCN). IR-spectrum, ν, cm1: 3408 (CH2O–H), 2729, 1500 (N+HOH), 2989, 2935, 2905,
2883, 2817, 1476, 1459, 1437, 1389, 1381, 1310, 1290, 1246, 1170, 1153, 1121, 1101, 1052,
1032, 980, 954, 909, 860, 734. NMR 1H, (CDCl3), δ, ppm: mixture of two isomers (~4:1), isomer
1 (~80%): 1.42, 1.45, 1.60, 1.67 (s, 12 H, 4 CH3), 2.07 (m, 1 H, H4), 2.20 (m, 1 H, H4), 2.42 (m,
1 H, H3), 3.71, 3.90 (m, 2 H, CH2), 4.96 (s, 1 H, COH), 9.74 (s, 1 H, NOH), 10.34 (s, 1 H, NH).
Isomer 2 (~20%): 1.28, 1.45, 1.70, 1.70 (s, 12 H, 4 CH3), 2.07 (m, 1 H, H4), 2.20 (m, 1 H, H4),
2.59 (m, 1 H, H3), 3.68, 3.92 (m, 2 H, CH2), 4.96 (s, 1 H, COH), 10.00 (s, 1 H, NOH), 10.88 (s, 1
H, NH). Found, %: C, 51.3; H, 9.69; Cl, 16.8; N, 6.44. C9H20ClNO2. Calculated, %: C, 51.54; H,
9.61; Cl, 16.91; N, 6.68. M 209.71.
Method F. 1-Hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidinium chloride 3H+u.
Solution of 3-carboxy-2,2,5,5-tetrametilpipirrolidin-1-oxyl (1.1 g, 5.9 mMol) in 6 ml of absolute
MeOH was saturated with dry HCl at 35–40°C and kept at this temperature for 24 hrs. The
resulting colorless solution was evaporated and the residual gum was dissolved twice in 5 ml
portions of dry MeCN and evaporated in vacuo. The residue was treated with dry ether to give
1.28 g (91%) of crystalline 3H+u, m.p. 122–125°C (dec) (EtOAc). IR-spectrum, ν, cm1: 2736,
2576, 1506 (N+HOH), 1742 (C=O), 2998, 2905, 1462, 1437, 1387, 1371, 1306, 1297, 1204,
1163, 1143, 1117, 1052, 1012, 984, 936, 854, 792, 776. NMR 1H, (CDCl3), δ, ppm: mixture of
two isomers (~7:3), isomer 1 (~70%): 1.30, 1.50, 1.77, 1.84 (s, 12 H, 4 CH3), 2.20 (dd, 1 H, H4, J
13.7, 7.8 Hz), 2.50 (m, 1 H, H4), 3.40 (t, 1 H, H3, J 7.7 Hz), 3.76 (s, 3 H, OCH3), 10.60 (s, 1 H,
OH), 11.61 (s, 1 H, NH). Isomer 2 (~30%): 1.41, 1.60, 1.60, 1.73 (s, 12 H, 4 CH3), 2.20 (dd, 1 H,
H4, J 13.7, 7.8 Hz), 2.50 (m, 1 H, H4), 3.18 (m, 1 H, H3), 3.76 (s, 3 H, OCH3), 10.35 (s, 1 H,
OH), 11.49 (s, 1 H, NH). Found, %: C, 50.2; H, 8.69; Cl, 14.8; N, 5.64. C10H20ClNO3.
Calculated, %: C, 50.52; H, 8.48; Cl, 14.91; N, 5.89. M 237.72.
8
4-Acethylamino-1-hydroxy-2,2,6,6-tetramethylpiperidinium chloride 3H+d was obtained by
the method C, yield 92%, mp 236–239 (dec.) (EtOH–ether). IR-spectrum, ν, cm1: 3398 (H2O),
3234, 1639, 1553 (CONH2), 3072, 2624 (N+HOH), 2997, 2943, 2879, 1437, 1390, 1373, 1326,
1298, 1247, 1214, 1183, 1163, 1109, 1089, 1063, 1046, 1027, 1009, 959, 921, 890, 748. NMR
1
H, (CDCl3), δ, ppm: ee-isomer, 1.47 (s, 6 H, 2 CH3a), 1.65 (s, 6 H, 2 CH3e), 1.98 (s, 3 H, OCH3),
2.02 (dd, 2 H, He3 and He5, J 13.6, 3.1 Hz), 2.35 (t, 2 H, Ha3 and Ha5, J 13.0 Hz), 4.39 (m, 1 H,
Ha4), 6.14 (d, 1 H, CONH, J 7.5 Hz), 10.75 (s, 1 H, OHe), 11.36 (s, 1 H, NHa). Found, %: C,
49.3; H, 9.19; Cl, 13.4; N, 10.7. C11H23ClN2O2·H2O. Calculated, %: 49.15; H, 9.38; Cl, 13.19; N,
10.42. M 268.78. The IR spectrum, elemental analysis and potentiometric titration are consistent
with structure of monohydrate.
1-Hydroxy-4-chloro-2,2,6,6-tetramethylpiperidinium chloride 3H+e was obtained by the
method C, yield 80%, mp 200–203 (dec.) (MeOH–ether). IR-spectrum, ν, cm1: 3061, 2540,
1500 (N+HOH), 3003, 2973, 2863, 2748, 1471, 1415, 1386, 1353, 1328, 1285, 1246, 1204, 1174,
1154, 1108, 1087, 1063, 1026, 975, 917, 874, 793, 733. NMR 1H, (DMSO-d6), δ, ppm: mixture
of ee- и ea-isomers (~93:7), ee-3H+e: 1.34 (s, 6 H, 2 CH3a), 1.49 (s, 6 H, 2 CH3e), 2.29 (dd, 2 H,
He3 and He5, J 13.9, 4.0 Hz), 2.42 (dd, 2 H, Ha3 and Ha5, J 13.3, 12.2 Hz), 4.73 (tt, 1 H, Ha4, J
12.2, 4.0 Hz), 11.52 (s, 1 H, OHe), 12.48 (s, 1 H, NHa). ae-3H+e: 1.34 (s, 6 H, 2 CH3a), 1.49 (s, 6
H, 2 CH3e), 2.29 (dd, 2 H, He3 and He5, J 13.9, 4.0 Hz), 2.42 (dd, 2 H, Ha3 and Ha5, J 13.3, 12.2
Hz), 4.73 (tt, 1 H, Ha4, J 12.2, 4.0 Hz), 11.61 (s, 1 H, OHa), 12.55 (s, 1 H, NHe). Found, C, 47.5,
H, 8.41, N, 6.02. C9H19Cl2NO. Calculated, %: C, 47.38, H, 8.39, N, 6.14. M 228.16.
1-Hydroxy-4-cyano-2,2,6,6-tetramethylpiperidinium chloride 3H+f was obtained by the
method C, yield 86%, mp 226–230 (dec.) (EtOH). IR-spectrum, ν, cm1: 2656, 1533 (N+HOH),
2239 (CN), 2997, 2947, 2879, 1480, 1462, 1442, 1407, 1388, 1319, 1302, 1250, 1217, 1181,
1155, 1105, 1060, 1031, 999, 973, 955, 928, 881, 860, 740, 703. NMR 1H, (DMSO-d6), δ, ppm:
ee-isomer, 1.28 (s, 6 H, 2 CH3a), 1.47 (s, 6 H, 2 CH3e), 2.19 (dd, 2 H, He3 and He5, J 13.2, 3.0
Hz), 2.33 (t, 2 H, Ha3 and Ha5, J 13.1 Hz), 3.54 (m, 1 H, Ha4), 11.59 (s, 1 H, OHe), 12.40 (s, 1 H,
NHa). Found, %: C, 54.6, H, 8.83, N, 12.63. C10H19ClN2O. Calculated, %: C, 54.91, H, 8.76, N,
12.81. M 218.72.
1-Hydroxy-3-ethoxycarbonyl-2,2,5,5-tetramethylpyrrolinium chloride 3H+i was obtained by
the method C, yield 87%, mp . 170–173 (dec.) (MeCN). IR-spectrum, ν, cm1: 3051 (C=C–H),
2701, 2528 (N+HOH), 1715 (C=O), 1636 (C=C), 2989, 2905, 2839, 1495, 1458, 1389, 1374,
1343, 1286, 1260, 1167, 1079, 1055, 1015, 963, 918, 868, 772, 753. NMR 1H, (CDCl3), δ, ppm:
1.33 (t, 3 H, H3CCH2, J 7.1 Hz), 1.55, 1.64, 1.86, 1.95 (s, 12 H, 4 CH3), 4.26 (q, 2 H, H3CCH2, J
7.1 Hz), 6.67 (s, 1 H, =CH), 10.59 (s, 1 H, OH), 12.20 (s, 1 H, NH). ). Found, %: C, 52.8; H,
9
8.33; Cl, 14.1; N, 5.55. C11H20ClNO3. Calculated, %: C, 52.90; H, 8.07; Cl, 14.20; N, 5.61. M
249.73.
1-Hydroxy-4-carboxy-2,2,6,6-tetramethylpiperidinium chloride 3H+j was obtained by the
method C, yield 86%, mp 280–285°C (EtOH–MeCN). IR-spectrum, ν, cm1: 3156, 2472, 1511
(N+HOH), 2800 (COOH), 1690 (C=O), 2991, 2942, 2901, 1461, 1436, 1415, 1401, 1391, 1305,
1288, 1235, 1206, 1178, 1110, 1091, 1063, 1033, 997, 929, 881, 750. NMR 1H, (DMSO-d6), δ,
ppm: mixture of ee- и ea-isomers (~92:8), ee-3H+j: 1.31 (s, 6 H, 2 CH3a), 1.47 (s, 6 H, 2 CH3e),
2.01 (dd, 2 H, He3 and He5, J 14.0, 3.1 Hz), 2.09 (dd, 2 H, Ha3 and Ha5, J 14.0, 12.6 Hz), 2.94 (tt,
1 H, Ha4, J 12.6, 3.3 Hz), 11.40 (s, 1 H, OHe), 12.08 (s, 1 H, NHa), 12.61 (s, 1 H, COOH). ae3H+j: 1.33 (s, 6 H, 2 CH3a), 1.56 (s, 6 H, 2 CH3e), 2.01 (dd, 2 H, He3 and He5, J 14.0, 3.1 Hz),
2.09 (dd, 2 H, Ha3 and Ha5, J 14.0, 12.6 Hz), 2.94 (tt, 1 H, Ha4, J 12.6, 3.3 Hz), 11.48 (s, 1 H,
OHa), 12.15 (s, 1 H, NHe), 12.61 (s, 1 H, COOH). Found, %: C, 50.7, H, 8.52, N, 5.78.
C10H20ClNO3. Calculated, %: C, 50.52; H, 8.48; N, 5.89. M 237.72.
4-Ethoxycarbonyl-1-hydroxy-2,2,6,6-tetramethylpiperidinium chloride 3H+l was obtained in
absolute EtOH by the method F, yield 35%, mp 175–180°C (dec.) (DME). IR-spectrum, ν, cm1:
2565, 1504 (N+HOH), 1720 (C=O), 2990, 2946, 2881, 2700, 2618, 1473, 1453, 1420, 1391,
1358, 1310, 1291, 1231, 1214, 1174, 1159, 1118, 1094, 1059, 1031, 993, 953, 925, 896, 867,
772. NMR 1H, (CDCl3), δ, ppm: ee-isomers, 1.27 (t, 3 H, H3CCH2, J 7.2 Hz), 1.41 (s, 6 H, 2
CH3a), 1.70 (s, 6 H, 2 CH3e), 2.09 (dd, 2 H, He3 and He5, J 14.5, 3.2 Hz), 2.48 (dd, 2 H, Ha3 and
Ha5, J 14.5, 13.0 Hz), 2.81 (tt, 1 H, Ha4, J 13.0, 3.2 Hz), 4.15 (q, 2 H, H3CCH2, J 7.2 Hz), 10.87
(s, 1 H, OHe), 11.60 (s, 1 H, NHa). Found, %: C, 54.45; H, 8.80; Cl, 13.5; N, 5.25. C12H24ClNO3.
Calculated, %: C, 54.23; H, 9.10; Cl, 13.34; N, 5.27. M 265.78.
1-Hydroxy-4-mesylamino-2,2,6,6-tetramethylpiperidinium chloride 3H+m was obtained by
the method C, yield 94%, mp 205–210°C (dec.) (EtOH–ether). IR-spectrum, ν, cm1: 3586,
3462, 1639 (H2O), 3239 (NH), 2778, 2656, 2627 (N+HOH), 1286, 1140 (SO2), 2993, 2937,
2860, 1482, 1445, 1416, 1389, 1377, 1314, 1304, 1247, 1216, 1181, 1076, 1030, 988, 951, 924,
887, 854, 756. NMR 1H, (DMSO-d6), δ, ppm: mixture of ee- и ae-isomers (~7:3), ee-3H+m:
1.35 (s, 6 H, 2 CH3a), 1.44 (s, 6 H, 2 CH3e), 1.99 (br t, 2 H, Ha3 and Ha5, J 12.6 Hz), 2.06 (dd, 2
H, He3 and He5, J 13.6 and 4.0 Hz), 2.98 (s, 3 H, H3CS), 3.68 (m, 1 H, Ha4), 7.36 (d, SNH, J 6.6
Hz), 11.42 (s, 1 H, OHe), 12.00 (s, 1 H, NHa). ae-3H+m: 1.35 (s, 6 H, 2 CH3a), 1.44 (s, 6 H, 2
CH3e), 1.99 (br t, 2 H, Ha3 and Ha5, J 12.6 Hz), 2.06 (dd, 2 H, He3 and He5, J 13.6 and 4.0 Hz),
2.98 (s, 3 H, H3CS), 3.68 (m, 1 H, Ha4), 7.36 (d, SNH, J 6.6 Hz), 11.49 (s, 1 H, OHa), 12.00 (s, 1
H, NH). Found, %: C, 39.2; H, 8.09; Cl, 11.6; N, 9.31; S, 10.1. C10H23ClN2O3S·H2O. Calculated,
10
%: C, 39.40; H, 8.27; Cl, 11.63; N, 9.19; S, 10.52. M 304.83. The IR spectrum, elemental
analysis and potentiometric titration are consistent with structure of monohydrate.
1-Hydroxy-4-trifluoroacetylamino-2,2,6,6-tetramethylpiperidinium
oxalate
3H+n
was
obtained by hydrogenation of mixture 1n – oxalic acid (2:1) (method D), yield 71%, mp 209–
213°C (dec.) (MeCN). IR-spectrum, ν, cm1: 3220, 1703, 1569 (CONH2), 3063 (N+HOH), 1610
(–OOCCOO–), 2997, 2927, 1440, 1386, 1312, 1294, 1208, 1186, 1169, 1113, 1089, 1057, 1019,
964, 906, 874, 768. NMR 1H, ((D2O + DCl), δ, ppm: ee-isomers, 1.48 (s, 6 H, 2 CH3e), 1.53 (s, 6
H, 2 CH3a), 1.96 (dd, 2 H, Ha3 and Ha5, J 14.4, 12.5 Hz), 2.28 (ddm, 2 H, He3 and He5, J 14.4,
3.7, 1.6 Hz), 4.42 (tt, 1 H, Ha4, J 12.5, 3.7 Hz). NMR
19
F, (D2O + DCl), –75.8 (s, 3 F, CF3).
Found, %: C, 46.4; H, 6.07; F, 17. 9; N, 9.22. C12H20F3N2O4. Calculated, %: C, 46.00; H, 6.43;
F, 18.19; N, 8.94. M 313.29
4-Acetoxy-1-hydroxy-2,2,6,6-tetramethylpiperidinium chloride 3H+o was obtained by the
method D, yield 78%, mp 203–205°C (dec.) (MeCN). IR-spectrum, ν, cm1: 2691, 2584, 2558,
2514 (N+HOH), 1737 (C=O), 2987, 2945, 2857, 1528, 1478, 1455, 1432, 1404, 1388, 1373,
1239, 1175, 1116, 1089, 1065, 1040, 988, 971, 936, 891, 852, 745. NMR 1H, (CDCl3), δ, ppm:
mixture of ee- и ea-isomers (~2:1), ee-3H+o: 1.47 (s, 6 H, 2 CH3a), 1.71 (s, 6 H, 2 CH3e), 2.04 (s,
3 H, H3CCO), 2.10 (dd, 2 H, He3 and He5, J 13.9 and 4.2 Hz), 2.52 (dd, 2 H, Ha3 and Ha5, J 13.9
and 11.8 Hz), 5.15 (tt, 1 H, Ha4, J 11.8, 4.2 Hz), 10.93 (s, 1 H, OHe), 11.62 (s, 1 H, NHa). ea3H+o: 1.58 (s, 6 H, 2 CH3a), 1.69 (s, 6 H, 2 CH3e), 2.08 (s, 3 H, H3CCO), 2.00 (m, 2 H, He3 and
He5), 2.61 (dd, 2 H, Ha3 and Ha5, J 15.1 and 3.0 Hz), 5.15 (tt, 1 H, Ha4, J 11.8, 4.2 Hz), 10.94 (s,
1 H, OHe), 11.61 (s, 1 H, NHa). Found, %: C, 52.6; H, 8.59; Cl, 14.3; N, 5.66. C11H22ClNO3.
Calculated, %: C, 52.48; H, 8.81; Cl, 14.08; N, 5.56. M 251.75.
1-Hydroxy-4-mesyloxy-2,2,6,6-tetramethylpiperidinium chloride 3H+p was obtained by the
method C, yield 95%, mp 183–186°C (dec.) (EtOH–ether). IR-spectrum, ν, cm1: 2758, 2561,
(N+HOH), 1348, 1185 (SO2), 2993, 2953, 2919, 2868, 1486, 1460, 1422, 1393, 1326, 1305,
1251, 1223, 1173, 1120, 1095, 1062, 1028, 996, 988, 967, 913, 886, 834, 757, 736. NMR 1H,
(CDCl3), δ, ppm: mixture of ee- и ea-isomers (~5:1), ee-3H+p: 1.47 (s, 6 H, 2 CH3a), 1.72 (s, 6
H, 2 CH3e), 2.27 (dd, 2 H, He3 and He5, J 13.8 and 4.2 Hz), 2.73 (dd, 2 H, Ha3 and Ha5, J 13.8 and
11.9 Hz), 3.06 (s, 3 H, H3CS), 5.10 (tt, 1 H, Ha4, J 11.9, 4.2 Hz), 11.03 (s, 1 H, OHe), 11.72 (s, 1
H, NHa). ea-3H+p: 1.62 (s, 6 H, 2 CH3a), 1.69 (s, 6 H, 2 CH3e), 2.31 (m, 2 H, He3 and He5), 2.78
(m, 2 H, Ha3 and Ha5), 3.06 (s, 3 H, H3CS), 5.10 (tt, 1 H, Ha4, J 11.9, 4.2 Hz), 11.03 (s, 1 H,
OHe), 11.61 (s, 1 H, NHa). Found, %: C, 41.5, H, 7.48, Cl, 12.4, N, 4.62, S, 11.0.
C10H22ClNO4S.. Calculated, %: C, 41.73, H, 7.70, Cl, 12.32, N, 4.87, S, 11.14. M 287.80.
11
1-Hydroxy-4-trimethylammonio-2,2,6,6-tetramethylpiperidinium methylsulfate chloride
and 1-hydroxy-4-trimethylammonio-2,2,6,6-tetramethylpiperidinium hydrosulfate chloride
(mixture ~1:1) 3H+r was obtained by the method C, yield 65%, mp 224–229°C (dec.) (MeOH–
acetone–ether).
Lit.
mp
for
1--Hydroxy-4-trimethylammonio-2,2,6,6-
tetramethylpiperidinium hydrosulfate chloride 220-228°C.[8] Formation of a 1:1 mixture due to
a partial hydrolysis of MeOSO3– anion in the HCl–MeOH solution agrees with the
potentiometric titration of 3H+r (1/3 of the alkali is consumed for the titration of a strong acid)
and its elemental analyzes. IR-spectrum, ν, cm1: 2703, 1483 (N+HOH), 1227, 1035, 1012, 873
(MeOSO3–, HOSO3–), 2982, 2948, 1428, 1391, 1357, 1328, 1178, 1144, 1059, 959, 908, 745.
NMR 1H, (D2O + DCl), δ, ppm: ee-isomers, 1.53 (s, 6 H, 2 CH3e), 1.56 (s, 6 H, 2 CH3a), 2.21
(dd, 2 H, Ha3 and Ha5, J 13.4, 12.7 Hz), 2.64 (ddm, 2 H, He3 and He5, J 13.4, 3.2, 1.5 Hz), 3.21 (s,
9 H, N(CH3)3), 3.75 (s, 3 H, CH3OSO3–), 4.06 (tt, 1 H, Ha4, J 12.7, 3.2 Hz). C, 42.3, H, 8.36, Cl,
10.2, N, 7.80, S, 8.8. C13H31ClN2O5S · C12H29ClN2O5S. Calculated for 1:1 mixture, %: C, 42.18,
H, 8.50, Cl, 9.96, N, 7.87, S, 9.01.
1-Hydroxy-3-acetylaminomethyl-2,2,5,5-tetramethylpyrrolidine 3t was obtained by the
method D without conversion to the hydrochloride salt, yield 85%, mp 136–138°C (dec.)
(MeCN). IR-spectrum, ν, cm1: 3321, 3203 (NH, OH), 1648, 1560 (CONH2), 2971, 2943, 2943,
2870, 1461, 1449, 1362, 1303, 1289, 1250, 1227, 1195, 1178, 1109, 1089, 1059, 1033, 1005,
990, 920, 863, 855, 757. NMR 1H of 3t·HCl (D2O + DCl), δ, ppm: mixture of two isomers
(~7:3), isomer 1 (~70%): 1.30, 1.44, 1.49, 1.50 (s, 12 H, 4 CH3), 1.99 (m, 1 H, H4), 2.02 (s, 3 H,
H3CCO), 2.18 (dd, 1 H, H4, J 13.2, 7.0 Hz), 2.36 (m, 1 H, H3), 3.25 (dd, 1 H, HCHNH, J 13.9,
8.0 Hz), 3.42 (dd, 1 H, HCHNH, J 13.9, 6.1 Hz). Isomer 2 (~30%): 1.39, 1.42, 1.47, 1.51 (s, 12
H, 4 CH3), 1.75 (m, 1 H, H4), 2.03 (s, 3 H, H3CCO), 2.30 (m, 1 H, H3), 2.65 (m, 1 H, H4), 3.25
(dd, 1 H, HCHNH, J 13.9, 8.0 Hz), 3.39 (dd, 1 H, HCHNH, J 13.9, 6.2 Hz). Found, %: C, 61.8,
H, 10.3, N, 12.9. C11H22N2O2. Calculated, %: C, 61.65, H, 10.35, N, 13.07. M 214.30.
1-Hydroxy-3-cyano-2,2,5,5-tetramethylpyrrolidinium chloride 3H+v was obtained by the
method C, yield 91%, mp 145-148°C (dec.) (acetone–ether). IR-spectrum, ν, cm1: 2769, 2531,
1504 (N+HOH), 2250 (CN), 2983, 2936, 2890, 1467, 1422, 1395, 1386, 1294, 1251, 1230, 1177,
1152, 1117, 1070, 1011, 984, 960, 932, 901, 859, 767, 750. NMR 1H (CDCl3), δ, ppm: mixture
of two isomers (~4:1), isomer 1 (~80%): 1.56, 1.81, 1.86 (br s, 12 H, 4 CH3), 2.45 (m, 2 H,
CH24), 3.63 (m, 1 H, H3), 11.01 (s, 1 H, OH), 11.85 (s, 1 H, NH). Isomer 2 (~20%): 1.56, 1.81,
1.86 (s, 12 H, 4 CH3), 2.45 (m, 2 H, CH24), 3.36 (m, 1 H, H3), 11.01 (s, 1 H, OH), 12.34 (s, 1 H,
NH). Found, %: C, 52.5, H, 8.36, N, 13.4. C9H17ClN2O. Calculated, %: C, 52.81, H, 8.37, N,
13.69. M 204.70.
12
1-Hydroxy-3-carbamoyl-2,2,5,5-tetramethylpyrrolinium chloride 3H+w was obtained by the
method D, yield 80%, mp >195°C (dec.) (H2O). IR-spectrum, ν, cm1: 3285, 3112, 1660, 1595
(CONH2), 2695, 2500, 1509 (N+HOH), 1642 (C=C), 3003, 2980, 1453, 1438, 1425, 1379, 1373,
1315, 1276, 1203, 1177, 1133, 1075, 1047, 1014, 961, 900, 822, 775. NMR 1H (D2O + DCl), δ,
ppm: mixture of two isomers (~6:4), isomer 1 (~60%): 1.44, 1.45, 1.54, 1.56 (s, 12 H, 4 CH3),
2.20 (dd, 1 H, H4, J 14.1, 7.9 Hz), 2.43 (dd, 1 H, H4, J 14.1, 7.9 Hz), 3.25 (t, 1 H, H3, J 7.9 Hz).
Isomer 2 (~40%): 1.31, 1.49, 1.52, 1.60 (s, 12 H, 4 CH3), 2.21 (dd, 1 H, H4, J 13.3, 7.2 Hz), 2.49
(dd, 1 H, H4, J 13.3, 12.4 Hz), 3.09 (dd, 1 H, H3, J 12.4, 7.2 Hz). Found, %: C, 48.8, H, 7.53, Cl,
16.1, N, 12.5. C9H17ClN2O2 Calculated, %: C, 48.98; H, 7.76; Cl, 16.06; N, 12.69. M 220.70.
13
2. Equilibrium and kinetics
Equilibrium. The equilibrium constant for the disproportionation reaction K4 (Scheme 2, eq.4)
is defined as
K4 = [2][3]/[1]2aH+2,
where [3] = [3H+] + [3] + [3–] (see Eqns 4 and 7); at pH << pK3H+, [3] ≈ [3H+]. For each
nitroxyl radical there is the equilibrium value pHeq wherein concentrations of the reagents are
equal [2]=[3]=[1] and K4aH+2 = [2][3] / [1]2 = 1. At pHeq reduction potentials of direct and
reverse half reactions of equilibrium (4) are equal: E1/3Σ = E2/1. In Fig. 3, the points of
intersection of pH-independent potentials E2/1 (horizontal lines), and pH-dependent potentials
E1/3Σ (inclined lines) correspond to values of pHeq for which [2][3]/[1]2 = 1.
Kinetics. Kinetic data show that the rate limiting step of comproportionation is the oxidation of
the base 3 by cation 2. The consumption of one mole of 2 and one mole of 3H+ is accompanied
by the formation of two moles of 1. Then, according to the mechanism (1-3), the rate of reaction
is determined by Eqn S1.
–d[2]/dt = 0.5 d[1]/dt = k–2[2] [3]
(S1)
Hydroxyammonium salts 3H+ in solution are in three equilibrium forms (see Eqns 3, 7):
[3H+]0 = [3H+] + [3] + [3–]
It is reasonable to suggest that K3 values (Eqn 7) for hydroxylamines 3 are close enough to
known value of K3 = 2×10–14 M for H2NOH,[24] so that at studied pH < 4 concentration of [3–] is
to low to contribute to the rate of comproportionation. Using stopped-flow technique, the rate
constant of cation 2a with anion 3a– was found to be 3.3×104 M–1s–1 and 2a + 3a–
comproportionation contributed to the rate of reaction only at pH > 9.[25]
Acidity constant for 3H+ (see Eqn 3)
K3H+ = [3] aH+/[3H+],
therefore, [3H+]0 = [3] + [3] aH+/ K3H+ = [3][(K3H+ + aH+)/ K3H+]
(S2)
Substituting [3] in Eqn S1 by its expression from Eqn S2 we obtain Eqn 5.
–d[2]/dt = 0.5 d[1]/dt = k–2[2] [3] = k–2 K3H+[2] [3H+]0/(K3H+ + aH+)
(5)
14
Table S1. Kinetic data on comproportionation of oxoammonium 2 (3·10–4 M) and
hydroxyammonium salts 3H+ (3·10–3 M) in aqueous buffer solutions at 20 ± 1°C
Reaction
pK3H+
pH
kef103, s–1
k–2, M–1s–1
Buffer: 0.1 M glycine + HCl
2b+3H+b
6.31
2.97
0.175
128
3.49
0.675
149
3.51
0.608
128
135±10 1
Buffer: 0.1 M glycine + HCl
+
2c+3H c
5.82
2.56
0.277
168
2.58
0.317
183
2.97
0.655
155
2.97
0.672
159
3.50
1.98
138
3.53
2.08
135
156±18
Buffer: 0.1 M glycine + HCl
+
2d+3H d
5.83
2.55
0.312
198
2.76
0.580
227
2.97
1.51 2
183
2.97
3.39 3
205
2.97
1.66 4
201
3.17
1.44
220
3.41
2.60
229
Buffer: 0.1 M glycine + HClO4
2.97
0.913
221
2.97
0.817
198
2.97
0.808
195
3.41
2.28
201
207±15
2e+3H+e
5.48
Buffer: 0.1 M glycine + HCl
15
1.93
0.178
211
1.93
0.190
225
2.56
0.785
218
2.56
0.937
260
2.56
0.790
219
2.97
2.39
258
2.97
2.33
251
234±21
Buffer: 0.1 M glycine + HCl
2f+3H+f
5.17
1.48
0.185
302
1.48
0.180
294
1.88
0.465
302
1.90
0.493
306
2.52
2.34
349
310±22
Buffer: 0.1 M HClO4
1.11
1.04
407
1.11
1.00
391
Buffer: 0.1 M KCl + 0.1 M HCl
2g+3H+g
4.18
1.15
0.981
350
1.16
1.16
404
1.15
0.950
339
Buffer: 0.1 M glycine + HCl
1.15
1.14
408
1.16
1.01
353
1.73
5.22
467
1.76
5.32
444
396±43
Buffer: 0.1 M glycine + HCl
2h+3H+h
5.27
1.03
0.635
3680
1.03
0.578
3350
1.04
0.608
3440
1.13
0.857
3940
1.13
0.818
3760
16
1.38
1.48
3820
1.38
1.43
3700
1.54
1.98
3540
1.54
1.96
3500
3640±190
Buffer: HCl
2i+3H+i
[HCl],
aH+,
M
M5
0.5
0.38
4.83
19400
0.5
0.38
4.84
19300
1.0
0.81
2.19
18400
1.0
0.81
2.28
19100
4.50
19100±500
1
Mean ± standard deviation
2
[3H+]0=610–3 M
3
[3H+]0=1.210–2 M
4
[2]0 = 610–4, [3H+]0=610–3 M
5
Calculated taking into account the activity coefficients for HCl.
17
3. Reduction potentials
Table S2. Reduction potentials E1/3 (see Eqn 22) and E1/3 vs pH dependence (see Eqn 9 and Fig. 3)
Com-
E1/3 at pH, V (±0.010)
E1/3,
ponent V±0.010
-1.0
0.0
1.0
2.0
3.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
8.0
9.0
10.0
1a
0.601
1.127
1.009
0.891
0.773
0.655
0.537
0.478
0.419
0.361
0.304
0.250
0.203
0.131
0.071
0.012
1b
0.597
1.088
0.970
0.852
0.734
0.616
0.498
0.439
0.381
0.324
0.272
0.227
0.189
0.126
0.066
0.007
1c
0.627
1.088
0.970
0.852
0.734
0.616
0.499
0.440
0.384
0.331
0.286
0.248
0.215
0.155
0.096
0.037
1d
0.608
1.078
0.960
0.842
0.724
0.607
0.489
0.431
0.374
0.321
0.276
0.238
0.205
0.145
0.086
0.027
1e
0.642
1.083
0.965
0.847
0.729
0.611
0.494
0.437
0.383
0.335
0.295
0.261
0.230
0.170
0.111
0.052
1f
0.632
1.053
0.935
0.817
0.699
0.582
0.465
0.409
0.359
0.316
0.280
0.248
0.218
0.158
0.099
0.040
1g
0.646
1.011
0.893
0.775
0.657
0.541
0.434
0.391
0.355
0.323
0.293
0.263
0.234
0.174
0.115
0.056
1h
0.515
0.945
0.827
0.709
0.591
0.473
0.356
0.300
0.248
0.203
0.166
0.134
0.103
0.044
-0.015
-0.074
1i
0.542
0.914
0.796
0.678
0.560
0.443
0.331
0.283
0.242
0.208
0.177
0.147
0.117
0.058
-0.001
-0.060
1k
0.613
1.085
0.967
0.849
0.731
0.613
0.496
0.437
0.380
0.325
0.277
0.237
0.203
0.142
0.082
0.023
1n
0.629
1.074
0.956
0.838
0.720
0.602
0.485
0.427
0.373
0.323
0.282
0.248
0.217
0.157
0.098
0.039
1p
0.650
1.065
0.947
0.829
0.711
0.593
0.477
0.422
0.374
0.333
0.299
0.268
0.238
0.178
0.119
0.060
1q
0.649
1.054
0.936
0.818
0.700
0.583
0.467
0.414
0.368
0.330
0.297
0.266
0.237
0.177
0.118
0.059
1r
0.691
1.035
0.917
0.799
0.681
0.566
0.468
0.430
0.397
0.367
0.337
0.307
0.278
0.219
0.160
0.101
18
Figure S1. Determination of potential E2/1 from voltammetric curves of
oxidation of 5·10–3 M 1a in 0.1 M LiClO4 aqueous solution at sweep rate
0.05, 0.1, 0.2, 0.3 и 0.4 V·s–1. Scale 100 mV × 10 μA.
19
Figure S2. Voltammetric curves of reduction of 5·10–3 M 1a in 0.1 M
LiClO4 aqueous solution at sweep rate 0.05, 0.1, 0.2, 0.3 и 0.4 V·s–1. Scale
100 mV × 10 μA.
20
4. Correlations
Table S3. Literature data on the inductive substituent constants I and reduction potentials E2/1
Substance
I for subst. R 1
E2/1, mV vs NHE
0
750 2,[26] 740,[27] 732,[28]
a
729 [29]
1
b
0.12
–
c
0.30
824 [30]
d
0.28
–
e
0.47.
–
f
0.57
–
g
–
918,[27] 914,[31] 911 [30]
h
0.28
874,[31] 864 [28]
i
0.32
–
j
–
805 [27]
k
0.24
825,[27] 818,[29] 806 [30]
l
0.32
–
m
–
–
n
–
–
o
0.40
–
p
–
–
q
0.60
892 [27]
r
0.90
940 [27]
s
0.12
809 [32]
t
0.11
–
u
0.32
889[32]
v
0.57
999[32]
w
0.28
974,[31] 955 [27]
Values of I for substituents R in a-f,h-l,o,s,u-w were taken from,[33, 34] for q,r from [35], for t
calculated as 0.28 (NHAc [33])  0.4.
2
Value approximated to the ionic strength  = 0. At  = 0.001, 0.01 and 0.1 M (KCl) E2/1 = 749,
746 and 740 mV.[26]
21
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22