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TEMPO reacts with oxygen-centered radicals under acidic conditions Riccardo Amorati, Gian Franco Pedulli, Derek A. Pratt* and Luca Valgimigli*

University of Bologna, Department of Organic Chemistry “A. Mangini”, Bologna, Italy and

Queen’s University, Department of Chemistry, Kingston, ON, Canada.

[email protected]; [email protected]

Supporting Information

Cover

Pages 2-13 Experimental

Pages 13-18 Tables of Cartesian coordinates and gas-phase enthalpies.

Page 19 References

Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010

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Experimental

Materials

Solvents (chlorobenzene and acetonitrile) and organic acids (acetic acid, benzoic acid, dichloroacetic

acid, trichloroacetic acid, trifluoroacetic acid and 4-toluensulfonic acid) were of the highest grade

commercially available (Fluka-Aldrich) and were used as received. α,α’-Azobis(isobutyronitrile), AIBN

(Aldrich), was stored at –20°C and used without further purification. 2,2,6,6-Tetramethylpiperidine-N-

oxide (TEMPO) and 2,2,5,7,8-pentamethyl-chroman-6-ol (Aldrich) were stored at +5°C and used without

further purification. 1-Hydroxy-2,2,6,6-tetramethylpiperidine (TEMPO-H) was prepared from TEMPO

according to literature.1 Briefly, a dichloromethane solution was vigorously stirred under N2 with an

aqueous solution of excess Na2S2O4 at r.t. for 60 min. The organic layer was separated, dried over dry

Na2SO4, concentrated under vacuum, then completely removed under a stream of nitrogen. The crude

hydroxylamine was purified by sublimation. 1H-NMR (CD3CN): δ 1.1 (s, 12H), 1.5 (s, 6H), 4.3 (br s,

1H); IR: νOH 3595 cm-1 (CCl4). Styrene (Aldrich, 99+%) and cumene (Aldrich) were distilled under

reduced pressure and percolated twice trough silica and once through activated basic alumina. Di-tert-

butylperoxide (Aldrich) was percolated twice trough through activated basic alumina.

Autoxidation Studies

Autoxidation experiments were performed in a two-channel oxygen uptake apparatus, based on a

Validyne® DP 15 differential pressure transducer, described elsewhere.2 The entire apparatus was

immersed in a thermostated bath ensuring a constant temperature within ±0.1 °C.

Peroxyl radicals kinetics.

In a typical experiment, an air-saturated solution of styrene (4.3 M, 50% v/v) in acetonitrile (or

chlorobenzene) containing AIBN (5×10-2 M) was equilibrated with a reference solution containing an


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excess of 2,2,5,7,8-pentamethyl-chroman-6-ol (PMC; 1×10-4 M) at 30 °C. When a constant oxygen

consumption rate was reached, a small amount of a solution of the antioxidant was added to the

autoxidizing mixture and the oxygen consumption in the sample was measured from the differential

pressure between the two channels recorded as a function of time. Induction (inhibition) period lengths

(τ) were determined by the intersection between the regression lines to the inhibited and the uninhibited

traces. Initiation rates, Ri, were determined in preliminary experiments by the inhibitor method using

PMC as reference antioxidant: Ri=2[PMC]/τ. The absolute rate constant for inhibition kinh was obtained

by equation 1,3 where kp is the propagation rate constant, that in the case of styrene is 41 M-1s-1.3

)/1ln(][

][ 2 τtk

styrenekO

inh

pt −=Δ− (1)

In the case of compounds which did not give a clear induction period, the kinh value was determined by

means of a kinetic treatment consisting in the measure of the initial rates of oxidation of styrene both in

the presence (-d[O2]/dt =Rox) and in the absence ((-d[O2]/dt)0 =Rox,0) of antioxidant, AH, and calculating

kinh from these data by means of Equation (2).2

it

inh

ox

ox

ox

ox

RkAHnk

RR

RR

2][ 0

0,

0, =−

(2)

This equation allows evaluation of kinh even when the rates of inhibition and termination are comparable.

The use of equation (2) requires knowledge of the initiation rate Ri and of the termination constant 2kt for

the self-combination of styrylperoxyl radicals (2kt = 2.1x107 M–1s–1).3 Experiments were performed using

TEMPO-H or TEMPO in the concentration range (0.1-10) x 10-5 M. Experiments with TEMPO (tipically

1.25x10-5M) were performed both in the absence and in the presence of variable amounts of organic acids

0.4-43mM (acetic, dichloroacetic, trichloroacetic, trifluoroacetic, benzoic, p-toluenesulfonic). Preliminary

experiments showed that, using acetonitrile as solvent, the rate of uninhibited styrene autoxidation is not


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affected by small additions of acids or water. Hence we could establish that observed effects of acid

additions are not due to changes in the rate of propagation kp or termination 2kt.

A glance of the reactions involved in the inhibited autoxidation process is exemplified in Scheme S1 for

hydroxylamine TEMPO-H.

Initiator Ri

+ O2 ROO

kp

Non-radical products2kt

(7)

(8)

(6)

+ TEMPO + TEMPOH

(3)

(4)

kinh

RRPhCH=CH2 + ROO

PhCH-C(H)OOR + O2 PhC(OO )H-C(H)OOR

PhC(OO )H-C(H)OOR + PhCH=CH2

PhCH-C(H)OOR (5)

PhC(OO )H-C(H)OOR'

PhC(OO )H-C(H)OOR'2

PhC(OO )H-C(H)OOR' (9)PhC(OOH)H-C(H)OOR' Scheme S1. Reactions involved in the controlled autoxidation of a styrene (PhCH=CH2) inhibited by TEMPOH as antioxidant.

The raw data obtained upon addition of acetic, trifluoroacetic and p-toluensulfonic acids are collected in

table S1, while typical autoxidation traces for TEMPO and TEMPO-H, together with significant

correlations are displayed in figures S1-S5. The addition of acids per se to autoxidating styrene mixtrure,

in the absence of TEMPO did not produce any significant variation of the oxygen consumption kinetics.

Table S1. Average inhibition rate constants kinh determined at 303 K from styrene autoxidations inhibited by TEMPO in CH3CN containing varying amounts of acids.

Acetic acid Trifluoroacetic acid p-Toluensulfonic acid

[acid] / M kinh /M-1s-1 [acid] / M kinh /M-1s-1 [acid] / M kinh /M-1s-1

0 6.2 x 104 0 6.2 x 104 0 6.2 x104

4.3 x 10-4 6.3 x 104 6.5 x 10-4 2.1 x 105 4.3 x 10-3 7.0 x 106

4.3 x 10-3 1.8 x 105 3.3 x 10-3 1.1 x 106 10.0 x 10-3 1.4 x 108

2.1 x 10-2 4.0 x 105 4.3 x 10-3 1.3 x 106

4.3 x 10-2 1.5 x 106 9.7 x 10-3 4.1 x 106

3.2 x 10-2 2.2 x 107


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Figure S1. Oxygen consumption plots recorded during the autoxidation of 4.3M styrene in MeCN

initiated at 303K by 0.05M AIBN. Left: no inhibitor (gray, dash-dot-dot), inhibited by 1.25x10-5M

TEMPO (black, dotted), or inhibited by 1.25x10-5M TEMPO in the presence of the indicated

concentrations of acetic acid. Right: no inhibitor (black, dashed), or inhibited by 1.25x10-5M TEMPO in

the presence of the indicated concentrations of p-toluensulfonic acid.

Figure S2. Dependence of the measured kinh for TEMPO, in the autoxidation of styrene in MeCN at

303K, on the concentration of added acetic acid (A), or of added trifluoroacetic acid (B).

A B


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Figure S3. Typical oxygen consumption plots recorded during the autoxidation of 4.3M styrene in MeCN

initiated at 303K by 0.05M AIBN and inhibited by 1.25x10-5M TEMPO in the absence or presence of 4.3

mM organic acids (left) and dependence of the measured kinh on the acids pKa in MeCN4 (right).

Figure S4. Typical oxygen consumption plots recorded during the autoxidation of 4.3M styrene in

chlorobenzene initiated at 303K by 0.05M AIBN.

time / s

0 2000 4000 6000 8000

-Δ[O

2] / m

M

-3.0-2.5-2.0-1.5-1.0-0.50.0

time / s

0 1000 2000 3000 4000 5000 6000

a b

Figure S5. Typical oxygen consumption plots recorded during the autoxidation of 4.3M styrene at 303K

with 0.05M AIBN, not inhibited (dashed line) or inhibited by TEMPO-H 1.9x10-5M in ClBz (a) or

1.7x10-5M MeCN (b).


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Effect of acids (in the absence of TEMPO) on the autoxidation of styrene.

A set of styrene autoxidation experiments was performed to rule out the possibility that the observed acid

catalysis on the antioxidant activity of TEMPO was due to some interference of the acids themselves on

styrene autoxidations, e.g. by altering the rate of initiation, the rate of propagation, or its oxidizability (=

kp/(2kt)1/2). In other words we checked whether the acids themselves, in the absence of TEMPO or any

other antioxidant, had any antioxidant (or pro-oxidant) activity. Oxygen consumption was recorded

during a set of identical styrene autoxidation experiments at 303K initiated by 0.05M AIBN in the

absence or presence on 1-10 mM acetic, trichloroacetic, trifluoroacetic, or para-toluensulfonic acid. As

illustrated in figure S6, no significant variation of the rate of oxygen consumption was observed,

suggesting that, under our experimental conditions, acids have no influence on styrene autoxidation.

Nevertheless, by experimental design, any of the kinetic measurement in the presence of TEMPO + acids

was benchmarked versus a corresponding oxygen-consumption plot, recorded during the same

experiment, first on the uninhibited autoxidation of styrene alone and subsequently on a uninhibited

autoxidation of styrene in the presence of the desired amount of acid. The desired amount of TEMPO was

then injected in the latter autoxidating mixture after about 1000s.

Figure S6. Typical oxygen consumption plots recorded during the autoxidation of 4.3M styrene in MeCN

initiated at 303K by 0.05M AIBN, in the absence of TEMPO and in the absence/presence of some

investigated organic acids (10 mM).

time / s0 1000 2000 3000 4000

Δ[O

2] / m

M

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

Acetic 10 mMTFA 10 mM p-TSA 10 mM TCA 10 mM No acid


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Autoxidations of Cumene

To check the independence of the observed acid-catalysis of the oxidizable substrate, a parallel set of

autoxidation experiments was performed using cumene as oxidizable substrate in place of styrene, under

otherwise identical experimental settings. The reaction sequence for cumene is illustrated in scheme S2,

were the propagation rate constant is kp = 0.32 M-1s-1. Qualitatively similar results were obtained as

illustrated in figure S7.

Initiator Ri

+ O2 ROO

ROO + RH ROOH + Rkp

ROO + ROO Non-radical products2kt (13)

(14)

(12)

ROOH + TEMPOROO + TEMPO-H

(10)

(11)

kinh

R

R

Scheme S2. Reactions involved in the controlled autoxidation of a hydrocarbon (RH = cumene) inhibited by TEMPO-H as antioxidant.

time / s

0 5000 10000 15000 20000

- Δ[O

2] / m

M

-2.0

-1.5

-1.0

-0.5

0.0

1

2

Figure S7. Oxygen consumption observed during the autoxidation of cumene (3.6 M) initiated by AIBN

(0.05 M) at 303 K with the addition of TEMPO (1.2 x10-5 M) in MeCN in the absence (1) and in the

presence (2) of 44 mM acetic acid.


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Deuterium kinetic Isotope Effect.

To measure the Deuterium Kinetic Isotope Effect, in styrene inhibited autoxidation experiments, 1% D2O

or 1% H2O was added to dry acetonitrile in matched sets of 4.3M styrene autoxidation experiments, in the

presence of 4.3 mM CD3COOD (or CH3COOH) or 3.3 CF3COOD (or CF3COOH), initiated by 0.05 M

AIBN and inhibited by 1.25x10-5M TEMPO at 303K. Under the above experimental settings deuteration

of the mobile hydrogens in the antioxidant species is achieved by H → D dynamic exchange.5 Each

measurement was performed in triplicate and results in Table S2 are expressed as average ± 2SD.

Table S2. DKIE for the reaction of phenols with peroxyl radicals, measured at 303 K from inhibited

autoxidations of styrene in acetonitrile containing 1% H2O (or D2O) in the presence or absence of acetic

or trifluoroacetic acids. Errors correspond to ±2SD.

Acid kH/kD

CH3COOH (4.3mM) 2.4±0.2

CF3COOH (3.3mM) 2.2±0.3

Figure S8. Typical oxygen consumption plots during matched autoxidations of 4.3M styrene in MeCN

initiated at 303K initiated by 0.05M AIBN and inhibited by 1.25x10-5M TEMPO in the presence of 1%

D2O/H2O and 4.3 mM CD3COOD/CH3COOH (left) or 3.3 mM CF3COOD/CF3COOH (right).


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Autoxidations inhibited by TEMPO-H

In order to evaluate the possible contribution of the corresponding hydroxylamine TEMPO-H, formed by

disproportionation of TEMPO under acidic conditions (vide infra), to the observed inhibition of styrene

(or cumene) autoxidation in the presence of organic acids, we performed a parallel set of autoxidation

experiments in acetonitrile or chlorobenzene, using a pure specimen of TEMPO-H as antioxidant, both in

the absence and presence of growing amounts of acetic acid. While TEMPO-H itself possesses good

chain-breaking antioxidant activity (kinh = 2.4 x 106 M-1s-1 in MeCN and 3.0 x 106 M-1s-1in ClBz at 303K),

no significant acid-catalysis was recorded by addition of 1-10 mM acetic acid. As can be observed in

Figure S9, the slope of the inhibited period (ca. 2000s) is identical within experimental error in the

presence or absence of the acid, while the addition of acetic acid (progressively) decreases the slope of

the uninhibited period, where the hydroxylamine (TEMPO-H) has been quantitatively converted in the

corresponding nitroxide (TEMPO). Hence the reactivity of TEMPO but not that of TEMPO-H with

peroxyl radicals is catalyzed by acetic acid.

time / s

0 1000 2000 3000 4000 5000 6000

-Δ[O

2] / m

M

-4

-3

-2

-1

0

1

1

2

Figure S9. Oxygen consumption observed during the autoxidation of styrene (4.3 M) initiated by AIBN

(0.05 M) in the presence of TEMPOH with (2) and without (1) acetic acid 4.3 mM.

EPR kinetics

EPR experiments were performed with a Bruker Elexsys 500 spectrometer equipped with a Super X-Band

ER049 microwave bridge and a quartz Dewar. Temperature was maintained at the desired value by a

Bruker B-VT100 variable temperature unit and monitored before and after each experiment with a Delta


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OHM HD9218 type K thermocouple and was stable within ± 0.1°C.

Time-course of TEMPO during autoxidations

Matched sets of autoxidation experiments (50% v/v MeCN in styrene, [AIBN] = 0.05M, air saturated)

inhibited by 1.25x10-5M TEMPO in the presence of variable amounts of organic acids were run either in

the oxygen uptake apparatus (vide supra) on in the cavity of the EPR spectrometer at 303K in an open 4

mm ID quartz tube. In EPR experiments the time-evolution of the concentration of TEMPO was

monitored at regular intervals, both from the intensity of the first spectral line (aN= 15.6 G, g = 2.0062)

and from the double integral of the EPR spectrum. With dichloroacetic, trichloroacetic, trifluoroacetic and

p-toluensulfonic acids, TEMPO was completely consumed approximately within the inhibition time τ (ca.

2000 s), while with acetic or benzoic acids TEMPO showed slower or no decay during monitoring times

up to 4τ.

Figure S10. Matched styrene autoxidation experiments inhibited by TEMPO in the presence of

CF3COOH (left) or CH3COOH (right), monitoring the oxygen uptake (top) or the concentration of

TEMPO (bottom).

[TEMPO]0 = 1.25x10-5M [TEMPO]0 = 1.25x10-5M


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Disproportionation of TEMPO

The disproportionation of TEMPO in acetonitrile or chlorobenzene in the presence of variable amounts of

p-toluensulfonic, acetic, or trifluoroacetic acids was investigated by EPR spectroscopy at 298K by

monitoring the decay of 1-5x10-4M TEMPO from the intensity of its first spectral line, or from the double

integral of its full spectrum. With any investigated acid at any tested concentration the decay was very

slow, following apparent second-order kinetics in accordance to scheme S3. The apparent bimolecular

rate constant k2 grew with the concentration and pKa of the acid, in excellent agreement with the results of

a recent investigation in water.6 The maximum values of k2 recorded in our measurements (with acid

concentrations much larger than those used in our autoxidations) are collected in table S3, while some

representative kinetic traces are displayed in figure S11.

Scheme S3. Kinetic scheme for the disporportionation of TEMPO in acidic media.

Table S3. Apparent rate constants measured at 298 K for the bimolecular decay of TEMPO.

Figure S11. Kinetic-EPR decay traces of TEMPO in MeCN at 298K in the presence of 20 mM p-

TSA (A) and 1700 mM (10% v/v) acetic acid (B) and corresponding 2nd order fitting (red trace).

N O2 N OH N O+-d[TEMPO]

dt= k2 [TEMPO]2H

BA


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Theoretical Calculations

All computations were carried out with the CBS-QB3 approach of Petersson and co-workers7

as implemented in the Gaussian-03 suite of programs,8 compiled to run on Sun Microsystems

SunFire 25000 or Enterprise M9000 servers with UltraSPARC-IV+ or Sparc64 VII CPUs,

respectively.

Table S4. Calculated gas-phase enthalpies and Cartesian coordinates for relevant structures.

Me2NOH•+ (H = -209.681353 a.u.) O -0.00639700 1.34005400 0.02390600 H -0.92629200 1.66334400 -0.01396200 N 0.00640800 0.01773900 -0.08520800 C 1.33980800 -0.55522800 0.01209300 H 1.34857300 -1.49973600 -0.53001000 H 2.04947500 0.15088500 -0.41601900 H 1.57845500 -0.72964700 1.06833800 C -1.24149100 -0.72698500 0.01682600 H -1.99669400 -0.25655700 -0.61787100 H -1.06152400 -1.74583900 -0.32011500 H -1.57558100 -0.73377500 1.06133400 Me2NO+ (H = -209.086160 a.u.) N -0.00000000 0.15299100 0.00001000 C -1.27838800 -0.59336700 -0.00429500 H -1.38945400 -1.03236300 0.99371500 H -2.07748300 0.11126400 -0.21953200 H -1.20388300 -1.39593800 -0.74071100 C 1.27838900 -0.59336600 0.00429000 H 2.07748900 0.11127000 0.21949100 H 1.20390500 -1.39592000 0.74072800 H 1.38942500 -1.03238600 -0.99371200 O -0.00000100 1.33544100 -0.00000300 (t-Bu)2NOH•+ (H = -445.063981 a.u.) O -0.09084800 -1.79526700 -0.07766600 H 0.81065100 -2.16452500 -0.08742400 N -0.00060800 -0.46524300 -0.11419900 C -1.40299900 0.13392100 -0.00559000 C 1.39935000 0.15388500 -0.00928100 C -2.29369400 -0.60959100 -1.02115800 H -3.28238900 -0.14910000 -0.99583900 H -1.90288400 -0.51248300 -2.03605100 H -2.40388200 -1.66502900 -0.78042400


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C -1.41550600 1.63099600 -0.32598100 H -0.79015500 2.22689600 0.33655800 H -1.15027000 1.83227400 -1.36343100 H -2.44229600 1.97127900 -0.18264600 C -1.88101200 -0.12604600 1.44022600 H -2.91105600 0.22584400 1.52253400 H -1.86549200 -1.18948800 1.67923200 H -1.28082700 0.41722100 2.17117600 C 2.44541200 -0.97095500 -0.10765300 H 3.43201900 -0.51106000 -0.05230900 H 2.40419800 -1.67692700 0.72986700 H 2.40871000 -1.50235400 -1.06423000 C 1.60790300 1.12687500 -1.18467900 H 1.39418900 0.64824900 -2.14229800 H 1.01284800 2.03068500 -1.09602700 H 2.65806400 1.42495200 -1.18720600 C 1.52371800 0.84974900 1.35984100 H 0.83338200 1.68320500 1.47255300 H 1.37039000 0.14689800 2.18068600 H 2.53679800 1.24929400 1.44164600 (t-Bu)2NO+ (H = -444.473758 a.u.) O -0.00000100 1.75397400 -0.00001500 N -0.00000000 0.56996300 -0.00000600 C -1.41897400 -0.11522500 -0.00020500 C 1.41897000 -0.11522500 0.00020000 C -2.41596600 0.95153100 0.45808700 H -3.39904000 0.48022200 0.50008700 H -2.17928600 1.32621400 1.45589100 H -2.47430800 1.79441100 -0.22892800 C -1.45311300 -1.32743000 0.93547800 H -0.76891600 -2.12390800 0.65312700 H -1.27585300 -1.04178400 1.97291500 H -2.46332500 -1.73776700 0.87822700 C -1.67765200 -0.49758900 -1.47587900 H -2.72017900 -0.81768000 -1.53555800 H -1.55605200 0.36071600 -2.13915200 H -1.05497100 -1.31893800 -1.82187700 C 2.41596500 0.95151000 -0.45814900 H 3.39904600 0.48021100 -0.50009700 H 2.17929600 1.32612100 -1.45598200 H 2.47427900 1.79443600 0.22881100 C 1.67765900 -0.49751000 1.47589500 H 1.55610300 0.36084200 2.13911400 H 1.05494600 -1.31881200 1.82195300 H 2.72017200 -0.81764200 1.53557300 C 1.45311100 -1.32748000 -0.93541400 H 0.76891700 -2.12394800 -0.65302400 H 1.27585800 -1.04189600 -1.97286900 H 2.46332300 -1.73781300 -0.87813400


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Me2NOH (H = -209.979744 a.u.) O 0.00056800 1.33275600 0.19711800 H 0.00069500 1.91584000 -0.56919000 N -0.00001800 0.01612100 -0.41195400 C 1.20775700 -0.64775500 0.06778000 H 1.24045000 -1.65585800 -0.35319800 H 2.08015200 -0.09489700 -0.28180500 H 1.24340200 -0.71244500 1.16618600 C -1.20829300 -0.64686000 0.06779200 H -2.08035100 -0.09390800 -0.28250400 H -1.24127700 -1.65529500 -0.35240300 H -1.24426900 -0.71065100 1.16622500 Me2NO• (H = -209.364375 a.u.) O -0.00000900 1.37902100 0.04518200 N 0.00000000 0.11737800 -0.16032100 C 1.25780900 -0.60127900 0.02688400 H 1.23371500 -1.55153100 -0.51074200 H 2.05637100 0.02781000 -0.36229100 H 1.44138000 -0.79545000 1.09212700 C -1.25780100 -0.60129100 0.02688400 H -2.05636100 0.02772700 -0.36241500 H -1.23364500 -1.55160500 -0.51063000 H -1.44143400 -0.79534000 1.09213800 (t-Bu)2NOH (H = -445.333437 a.u.) O -0.02840400 -1.79818700 -0.01929000 H 0.04157800 -2.27670600 -0.85114200 N 0.00317300 -0.40838500 -0.44808000 C -1.33482700 0.14616600 -0.02812000 C 1.33739900 0.14228900 -0.01567000 C -2.36297100 -0.56626900 -0.93462000 H -3.36632100 -0.17310900 -0.75112800 H -2.11260800 -0.40587000 -1.98621300 H -2.37950000 -1.63864600 -0.73888200 C -1.44265600 1.65238600 -0.30756100 H -0.86919600 2.25321200 0.39852700 H -1.12687500 1.89885600 -1.32286700 H -2.48997800 1.94608900 -0.20090600 C -1.70555500 -0.12870600 1.44630400 H -2.75899800 0.11721900 1.60826300 H -1.56040700 -1.18139000 1.68753300 H -1.11742100 0.47277300 2.13972500 C 2.40078000 -0.82960100 -0.57589500 H 3.39670300 -0.40540900 -0.42754400 H 2.36390400 -1.79684300 -0.07739100 H 2.25116200 -0.97920300 -1.64904700 C 1.59491100 1.50191700 -0.69475000 H 1.35119600 1.45147500 -1.75823300 H 1.03764500 2.32195400 -0.24789300 H 2.65624400 1.74575600 -0.60113400


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C 1.53134600 0.25577200 1.50911300 H 0.92905600 1.05741100 1.94065200 H 1.26950300 -0.68332100 1.99991900 H 2.57876400 0.47623300 1.73584200 (t-Bu)2NO• (H = -444.725980 a.u.) O -0.03333200 -1.80304600 -0.11282900 N 0.00342100 -0.52423500 -0.19330600 C -1.36167700 0.11652100 -0.01283600 C 1.36912700 0.11535800 -0.01179100 C -2.27994400 -0.53748700 -1.06217100 H -3.29895800 -0.15845500 -0.94894300 H -1.93514000 -0.30411000 -2.07296900 H -2.28466000 -1.61904200 -0.94117900 C -1.38934400 1.63512800 -0.22449500 H -0.76345800 2.17940300 0.48320700 H -1.10383700 1.91285600 -1.23984600 H -2.41726500 1.97288800 -0.06956600 C -1.86347500 -0.22569600 1.40425400 H -2.90513600 0.08647400 1.51864600 H -1.79926700 -1.30186700 1.56671500 H -1.27294900 0.27991200 2.17154800 C 2.41360000 -0.98391600 -0.26787500 H 3.40991000 -0.54540300 -0.16840600 H 2.31142900 -1.80377200 0.43971300 H 2.31054500 -1.39595400 -1.27292000 C 1.60433500 1.24067800 -1.03766200 H 1.35064700 0.90105100 -2.04460500 H 1.04142200 2.14624600 -0.82295300 H 2.66434700 1.50746400 -1.03153600 C 1.53478600 0.63240600 1.43055100 H 0.84753600 1.44657000 1.66505100 H 1.37095800 -0.17701600 2.14525100 H 2.55214700 1.00881900 1.57071500 PrOO• (H = -268.416424 a.u.) O -1.92880300 -0.16150500 -0.11665800 O -0.77858900 -0.62579900 0.32249300 C 0.37279900 0.02200100 -0.34209500 H 0.15544400 -0.03603800 -1.41149300 C 0.45775800 1.47022500 0.11007700 H 1.27037500 1.97987400 -0.41397600 H -0.47689200 1.98636200 -0.11328400 H 0.64743200 1.52848400 1.18519800 C 1.57358600 -0.83117200 0.02513100 H 1.42861900 -1.86562300 -0.29233600 H 2.46918200 -0.44188000 -0.46467200 H 1.74011900 -0.81907000 1.10520100


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Me2NO---H---OOPr (H = -478.389458 a.u.) O 1.65305100 -1.11620000 -0.61693800 H 0.68623800 -1.47219200 -0.32809000 O -0.60782700 -1.65610800 0.04053300 O -0.89909700 -0.45032500 0.62090900 N 1.76838700 0.12208600 -0.05967500 C 2.41201500 0.07932100 1.24665000 H 2.38546600 1.07557100 1.69205900 H 1.85556800 -0.60960700 1.88067000 H 3.45460100 -0.26182300 1.16993000 C 2.30265100 1.07437100 -1.01816800 H 1.67615600 1.06062500 -1.90970300 H 2.28920400 2.07324100 -0.57807400 H 3.33343300 0.82174200 -1.30788700 C -1.77579400 0.33010800 -0.24129900 H -1.30142700 0.34397000 -1.22748200 C -3.14075900 -0.34000200 -0.32857800 H -3.78772100 0.20787300 -1.01917300 H -3.02729600 -1.36241300 -0.68967800 H -3.62010000 -0.36364600 0.65382600 C -1.80526500 1.72254200 0.36858400 H -0.79911900 2.14259100 0.41764400 H -2.43172900 2.38309700 -0.23564100 H -2.21808700 1.68939200 1.38015400 Me2NOH---OOPr (H = -478.389458 a.u.) O 1.99964300 -0.73243700 0.76178400 H 1.10746600 -0.88083400 0.41132900 O -0.72360900 -1.09109600 -0.25144400 O -1.32262200 0.03265600 0.07343400 N 2.58700100 0.15014000 -0.21786300 C 2.91576100 1.38229800 0.48959500 H 3.38659400 2.07678000 -0.21177300 H 1.99454500 1.83153200 0.86245700 H 3.59523400 1.21022700 1.33976500 C 3.78318900 -0.52576700 -0.70604000 H 3.48941800 -1.45442900 -1.19637800 H 4.27722600 0.11785700 -1.43912900 H 4.49226500 -0.76233400 0.10358700 C -2.72791300 0.06727000 -0.39719200 H -2.68274900 -0.24636100 -1.44247500 C -3.54777000 -0.91112900 0.42692300 H -4.57713400 -0.93204700 0.06040800 H -3.13099900 -1.91577300 0.34497500 H -3.55994800 -0.61544600 1.47901800 C -3.14789900 1.52002600 -0.26990200 H -2.49172600 2.16876600 -0.85285900 H -4.16913100 1.64058600 -0.63843100 H -3.11957200 1.84131800 0.77405800


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Me2NO+---H---OOPr (H = -478.1348847 a.u.) O 1.67264400 -0.68900100 -0.00284700 H 0.39568600 -0.13163200 -0.00090800 O -0.59539400 0.26481500 0.00056300 O -1.38961200 -0.81176700 -0.00420500 N 2.73757100 0.00454100 0.00173400 C 2.65111200 1.46183200 0.00585200 H 2.10465900 1.78525700 0.89666600 H 3.65314100 1.88459800 0.01256200 H 2.11423300 1.79107100 -0.88872900 C 4.01615700 -0.70168700 -0.00315300 H 4.59027700 -0.41766100 0.88315700 H 3.80586400 -1.76746300 0.00160500 H 4.58000900 -0.42417400 -0.89828400 C -2.84071800 -0.43316500 -0.00222600 H -3.26544700 -1.43850200 -0.00760300 C -3.16631800 0.29970800 1.28914300 H -2.69710300 1.28417400 1.31358500 H -4.24908900 0.43338300 1.33945100 H -2.85578800 -0.27723200 2.16145500 C -3.16652200 0.31361200 -1.28552600 H -2.85613000 -0.25386600 -2.16407600 H -4.24930700 0.44777000 -1.33420500 H -2.69738100 1.29830900 -1.29943900 Me2NOH+---OOPr (H = -478.1422944 a.u.) O -1.74812900 -0.81449700 -0.23871400 H -0.80340500 -0.39817900 -0.05611600 O 0.56351100 0.12111700 0.18385000 O 1.37625900 -0.70200100 -0.43439900 N -2.70931600 0.05837400 -0.06317600 C -2.42646500 1.33036400 0.59293400 H -1.52128100 1.76310300 0.16528400 H -3.27092500 1.99671900 0.43082700 H -2.28487200 1.16481800 1.66670500 C -4.05097500 -0.47834500 -0.23752100 H -4.71075000 0.32595900 -0.56025800 H -4.00670200 -1.26751200 -0.98520800 H -4.40632600 -0.88830000 0.71450900 C 2.83082300 -0.33398300 -0.26557600 H 3.27686300 -1.13836300 -0.85247000 C 3.07592900 1.02045900 -0.90440500 H 2.57424700 1.81350700 -0.34771200 H 4.14955100 1.22035100 -0.89248100 H 2.74210000 1.03538100 -1.94332700 C 3.19902100 -0.44747700 1.20208000 H 2.95185600 -1.43406900 1.59744300 H 4.27708100 -0.30382500 1.30125900 H 2.69465200 0.31873800 1.79282100


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References 1 a) Ozinskas, A. J.; Bobst, A. M. Helv. Chim. Acta 1980, 63, 1407-1411. b) Mader, E. A.;

Davidson, E. R.; Mayer, J. M. J. Am. Chem. Soc. 2007, 129, 5153.

2 Amorati, R.; Pedulli, G. F.; Valgimigli, L.; Attanasi, O. A.; Filippone, P.; Fiorucci, C.; Saladino,

R., J. Chem. Soc., Perkin Trans. 2 2001, 2142-2146.

3 Burton, G. W.; Doba, T.; Gabe, E.; Hughes, L.; Lee, F. L.; Prasad, L.; Ingold, K. U., J. Am. Chem.

Soc. 1985, 107, 7053-65.

4 Kütt, A.; Leito, I..; Kaljurand, I.; Sooväli, L.; Vlasov, V.M.; Yagupolskii, L.M.; Koppel, I.A. J.

Org. Chem. 2006, 71, 2829-2838.

5 Howard, J. A.; Ingold, K. U., Can. J. Chem. 1962, 40, 1851-64.

6 Sen , V. D.; Golubev, V. A. J. Phys. Org. Chem. 2009, 22, 138-143. 7 J. A. Montgomery, Jr., J.W. Ochterski,G. A. Petersson, J. Chem. Phys. 1994, 101, 5900-5909. 8 Gaussian 03, Gaussian, Inc., Carnegie, PA, 2003.


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