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Trihexylamine: Dropwise addition of 1 mL N(C6H13 3
)
diluted in
Triethylamine: Dry triethylamine, storing over CaCl2, followed by
distillation and storage over molecular sieves, is added dropwise to
≈ 10 mL of N2O3 solution in toluene, in a 1:2 triethylamine/N2O3
ratio. This results in rapid formation of a red color followed by dark-
ening to brown, with a steady evolution of nitric oxide gas (1 mL
yields 130 mL NO gas); a precipitate forms after a few seconds
of stirring. The supernatant is decanted off within 5 min, and the
precipitate is washed with cold ether under inert gas, then dried
3 mL of dichloromethane to an equimolar dichloromethane/N2O3
solution at 0 °C consumes the blue color before half of the amine
is added, with a small amount of nitric oxide gas evolution
(<20 mL), forming a yellow solution which becomes pale red-violet
within minutes. The solvent is removed under vacuum at 0 °C and
the crude product is a deep violet color. UV/Vis (CH2Cl2): 330 nm
(intense), 552 nm (weak). IR (thin film): ν = 2960, 2931, 2859, 1671
˜
(w), 1467, 1402, 1378, 1297, 1092, 951, 891, 730 cm–1. Raman: 2879, under vacuum. The composition of this precipitate has mixed an-
1661, 1444, 1341, 1321 (w), 1039, 890, 702.
ions, but corresponds to a ≈ 50 % conversion to an 2:1 mixture of
triethylammonium nitrite/nitrate[21] as a light yellow to red semi-
crystalline material. 1H NMR: δ = 10.79 (broad s, not always seen),
Exposure of this adduct to the atmosphere for a few minutes produ-
ces trihexylamine N-oxide[18] (C6H13)3NO as a yellow oil. Yield
3.148 (q), 1.329 (t) ppm. IR: ν = 2960 (w) 2944 (m), 2738 (m), 2678
˜
(from initial trihexylamine): 94 %. UV/Vis: 330 nm, 370 nm. IR: ν =
˜
(st), 2493 (w), 1475 (w), 1386 (vs), 1265 (w) 1169 (w), 1036 (w), 847
(w), 823 (w), 802 (w) cm–1. EA %: Calculated for triethylammonium
nitrate (C6H16N2O3): C 43.87, N 17.06, H 9.83 %. Calculated for trieth-
ylammonium nitrite. C6H16N2O2 (148.20): calcd. C 48.61, N 18.90, H
10.90; found C 45.32, N 17.56, H 10.22, (thus ca. 67 % nitrate salt
and 33 % nitrite).
3447, 2960, 2931, 2859, 1700, 1640, 1467, 1390, 1088, 1020, 730. 1H
NMR: δ = 2.905 (t, 6 H), 1.632 (br., 6 H), 1.328 (br., 18 H), 0.902 (t, 9
H) cm–1
.
The use of a four fold excess of trihexylamine with N2O3 gives a
deep orange colored solution which on concentration results in an
orange oil. UV/Vis: 376 nm. The addition of more trihexylamine to
this product will reproduce the violet color. Exposure to air will
produce a single peak at 348 nm in the UV spectrum. This product
is otherwise identical to the product of the 1:1 mixture by IR, Ra-
man, and reactivity.
With a 1:1 ratio of triethylamine to N2O3, and under these condi-
tions a white or off-white product of triethylammonium nitrite is
isolated by filtration in 48 % yield. 1H NMR (CD2Cl2): δ = 10.79
(broad s, not always seen), 3.148 (q), 1.329 (t) ppm. IR: ν = 2980 (w),
˜
2674 (w), 2493 (w), 1478 (m), 1349 (m), 1192 (vs), 1168 (vs), 1072
(m) 1040 (s), 850 (m), 802 (m), 556 (w), 456 (w) cm–1. UV/Vis: 370 nm.
NOTE: Pure triethylammonium nitrite is aggressively deliquescent,
and will dissolve in normal atmospheric conditions in minutes; in
warm, humid summer air,[21] it will dissolve in a few seconds. It
must be handled under inert atmosphere and carefully dried. It can
be purified by sublimation. Greater quantities of water in the start-
ing materials cause corresponding losses in yield due to dissolution.
Analysis of the crude soluble reaction mixture shows minor yields
Tribenzylamine: Tribenzylamine, 1 g, is dissolved in 3 mL toluene
and added to an equimolar toluene/N2O3 solution. After three min-
utes a white precipitate forms and within 10 min precipitation
ceases with a trace of blue remaining in solution. The precipitate is
filtered and dried to a snow white powder. Recrystallizing from eth-
anol gives tribenzylammonium nitrate, [(C6H5CH2)3NH]+[NO3]–,
86 %,[19] confirmed spectroscopically and by X-ray crystallography.
1H NMR (CD2Cl2): δ = 7.473 (m, 15 H), 4.260 (s, 6 H) ppm. 13C NMR:
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of diethylnitrosamine with H NMR methylene peaks[22] at 4.15 (q),
δ = 131.07, 129.97, 129.36, 30.56 ppm. IR: ν = 3439 (br., w), 3040
˜
and 3.6 (q) as well as three other trace products of similar nature
with α-methylene resonances in the 3.5–4.2 ppm range in the 1H
NMR spectrum.
(w), 3000 (w), 2734 (w), 2605 (br., w), 1454, 1390 (vs), 1297 (vs) 1277,
1040, 1016, 911, 758, 698, 501 cm–1
.
When the reaction of N2O3 and tribenzylamine is performed in dry
dichloromethane under nitrogen, a yellow liquid forms without any
precipitate. Removing the solvent under vacuum produces a white
Reversing the order of addition, that is adding the N2O3 solution to
the triethylamine solution, such that triethylamine is in excess at all
times, produces the same product in similar yields, but with no gas
evolution. Triturating the product with alcoholic KOH after isolation
produces 1 equiv. of KNO2 per amine (the white precipitate is dried,
then dissolved and triturated with HCl to determine the mass of
residual KOH). As detailed in the discussion a second solution is
isolated from air and purged for 5 min with argon, then triturated
in situ; this allows 1.4 KNO2 to be recovered per reacted amine.
solid. IR (Nujol mull): ν = 2972, 2883, 2847, 1744 (w), 1712 (w), 1656,
˜
1595 (w), 1454 (s), 1378 (s), 1346, 1297 (s), 1040, 1012, 907, 823,
754 (s), 698 (s), 501 cm–1. Exposure of this solution to air leads to
tribenzylammonium nitrate. When tribenzylamine is treated with
excess N2O3 the products include increasing quantities of benz-
aldehyde.
Triphenylphosphine: One gram of triphenylphosphine is dissolved
in 5 mL toluene and added to an equimolar N2O3/toluene solution
at 0 °C, causing the evolution of nitric oxide gas and the formation
of a clear solution. Evaporation yields triphenylphosphine oxide
Triphenylamine: Triphenylamine, 1 g, is dissolved in 3 mL dichloro-
methane and added to an equimolar N2O3/dichloromethane solu-
tion at 0 °C, which consumes the blue color immediately and produ-
ces an intense amber yellow solution. The solvent is removed by
evaporation, and the resulting solid is redissolved in a minimum of
dichloromethane, diluted in 10-fold hexane, and then chilled to give
(4-nitrophenyl)diphenylamine [(O2NC6H4)(Ph)2N] as orange crys-
tals in 42 % yield.[20] 1H NMR (CDCl3): δ = 8.038 (d, 2 H), 7.368 (t, 4
H), 7.193–7.172 (d overlapping t, 6 H), 6.922 (d, 2 H) ppm. 13C NMR
(O=PPh3) in 95 % yield, as a snow white powder. IR: ν = 3057,
˜
1589, 1482, 1436 (s), 1311, 1188 (s), 1121 (s), 720 (s), 696 (s), 538 (s)
cm–1
.
When this reaction is repeated with N2O3 in excess, and in rigor-
ously dry conditions, the result is precipitate of a triphenylphos-
phine adduct. However, the presence of small amounts of moisture
will cause the formation of a second product as a waxy yellow,
slowly crystallizing solid, an adduct of nitric acid and triphenylphos-
(CDCl3): δ = 129.93, 126.52, 125.73, 125.47, 118.15 ppm. IR: ν = 3435,
˜
1583, 1491, 1297, 1314, 1285, 1108, 843, 750, 604 cm–1
.
Repeating with a large excess of N2O3 (>2 equiv.) followed by col-
umn chromatography on a silica with hexane/ethyl acetate as elu-
ent, (4,4′-dinitrophenyl)phenylamine[20] [(O2NC6H4)2(Ph)N] is isola-
phine oxide, Tranter's salt,[14,23,24] [Ph3P=O][HONO2]. IR: ν = 3084,
˜
3060, 1635 (br), 1438, 1422, 1285, 1249, 1120 (s), 1051, 947, 725,
693, 536 cm–1 31P NMR: δ = 34.18 ppm. Mp. 79–80 °C.
.
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ble as yellow crystals in 90 % yield. H NMR: δ = 8.15 (d, 4 H), 7.15
(d, 2 H), 7.44 (t, 1 H), 7.32 (t), 7.18 (d) ppm. IR: ν = 1579, 1491, 1342,
X-ray Crystallography for [Bz3NH][NO3]: A crystal mounted on a
glass fiber with epoxy was subjected to single-crystal X-ray diffrac-
˜
1314, 1281, 1181 (w), 1108, 847, 750, 698 cm–1
.
Eur. J. Inorg. Chem. 0000, 0–0
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