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Supporting InformationOxidative Ionization Under Certain Negative-Ion Mass Spectrometric Conditions

Isra Hassan, Julius Pavlov, Ramu Errabelli and Athula B. Attygalle*

Table of Contents

Page no.List of Chemical Sources 5Supplementary Figure S1. a) Sample placement in an open HePI source on a Quattro

Ultima mass spectrometer; b) Sample placement and introduction of SF6 to a

closed HePI source on the same instrument. The original ESI source has the

same configuration, excepting that a methanolic solution of the sample is

sprayed through the capillary held at high voltage (instead of passing helium to

generate HePI plasma).

6

Supplementary Figure S2. Negative-ion HePI mass spectra acquired on a Waters

Micromass ZQ single-quadrupole mass spectrometer from background ambient

air at capillary voltage settings of (a) 4.0 kV , (b) 3.0 kV, (c) 2.5 kV, and (d)

1.8 kV. The peak intensities are normalized to the absolute intensity (in

arbitrary units) of the m/z 32 peak recorded at capillary voltage 4.0 kV.

7

Supplementary Figure S3. CID mass spectra acquired under ESI-MS conditions from

mass-isolated m/z 108 (a, b, c, and d), and m/z 109 (e, f, g, and h) ions,

generated from a methanolic solution of 1,4-hydroquinone, on a Waters

Micromass Quattro ultima triple quadrupole mass spectrometer. The CID

spectra of the m/z 108 ion were acquired at a capillary voltage 4.0 kV and at

laboratory-frame collision energies of (a) 10 eV, (b) 20 eV, (c) 30 eV, and (d)

8

1

40 eV, and those of the m/z 109 ion were acquired at a capillary voltage of 1.5

kV and at laboratory-frame collision energies of (e) 10 eV, (f) 20 eV, (g) 30

eV, and (h) 40 eV.

Supplementary Figure S4. Absolute intensity of m/z 108 (blue trace) and 109 (red

trace) ions, generated from a methanolic solution of 1,4-hydroquinone by ESI

at a capillary voltage of 3.20 kV, monitored against time by a selective ion

recording (SIR) experiment on a Waters Micromass Quattro Ultima triple

quadrupole mass spectrometer. After two minutes of signal acquisition, the

source was engulfed with sulfur hexafluoride, and at 7.5 min, the flow of SF6

was switched off. Insets show mass spectra corresponding to each region.

9

Supplementary Figure S5. Negative-ion nanospray ESI mass spectra recorded on a

Waters SYNAPT G2 Q-TOF mass spectrometer at different cone voltage

settings (10-80 V) from methanolic solutions of (a) catechol, (b) resorcinol,

and (c) hydroquinone. Other experimental conditions: flow rate 1 mL/min,

capillary voltage 4.0 kV, extraction cone voltage 3 V. Row 9 depicts typical

spectra recorded at a cone voltage setting of 20 V, from the same solutions and

under the same conditions after positioning the capillary tip closer to the

entrance cone to effect a plasma discharge.

10

Supplementary Figure S6. Negative-ion ESI mass spectra recorded on a Waters

SYNAPT G2 Q-TOF mass spectrometer of a) catechol , b) resorcinol and c)

hydroquinone (nanospray) under the following instrumental conditions:

extraction-cone voltage 1.5 V, sampling-cone voltage 20 V, Vernier probe

adjustment screw 5.92 mm, source temperature 100 oC, desolvation gas flow

rate 450 L/hr. The capillary voltage was varied between 1.4 and 4.0 kV.

11

Supplementary Figure S7. Negative-ion HePI mass spectra recorded on a Waters

Micromass Quattro Ultima triple quadrupole mass spectrometer from samples

12

2

of a) 2,3-dimethylbenzene-1,4-diol, b) 2,3,5-trimethylbenzene-1,4-diol, c) 2,5-

dihydroxybenzonitrile, d) 2,5-dihydroxybenzaldehyde, and e) 2,5-

dihydroxycyclohexa-2,5-diene-1,4-dione.



of a) 2,3-dihydroxybenzaldehyde, b) 3,4-dihydroxybenzaldehyde and c) 2,3-

dihydroxybenzonitrile.

13



of a) 2-methylbenzene-1,3-diol; b) 2,5-dimethylbenzene-1,3-diol; c) 2,6-

dihydroxybenzonitrile; d) 1-(2,6-dihydroxyphenyl)ethanone at a cone voltage

of 10 V, hexapole transfer 1 lens voltage of 20 V, source temperature of 150

oC, desolvation temperature of 300 oC and a capillary voltage of 3.2 kV.

14



of a) 5-methylbenzene-1,3-diol; b) 1-(2,4-dihydroxyphenyl)ethanone; c) (2,4-

dihydroxyphenyl)(phenyl)methanone; d) 1-(2,4,6-trihydroxyphenyl)ethanone;

e) 2,3,4-trihydroxybenzonitrile at a cone voltage of 10 V, hexapole transfer 1

lens voltage of 20 V, source temperature of 150 oC, desolvation temperature of

300 oC and a capillary voltage of 3.2 kV.

15

Supplementary Figure S11. Full-scan HePI mass spectra (left) and product-ion mass

spectrum of the O2-• adduct (right) from samples of a) 2-methoxyphenol; b) 3-

methoxyphenol; c) 4-methoxyphenol at a cone voltage of 10 V, hexapole

transfer 1 lens voltage of 20 V, source temperature of 150 oC, desolvation

temperature of 300 oC and a capillary voltage of 3.2 kV recorded on a Waters

16

3

Micromass Quattro Ultima triple quadrupole mass spectrometer.

Table T1. Calculation of the energy released or absorbed as hydroquinone, catechol,

and resorcinol lose hydrogen gas to produce their respective quinones. The

Gaussian 09 program, using the unrestricted HF method and 6-31G + (d,p)

basis set for all atoms, was used to calculate the sum of electronic and zero-

point energies for each molecule.

17

Table T2. Atom coordinates, select bond lengths, and absolute energies of energy-

optimized product ions and transition states of the superoxide radical-anion

adduct of hydroquinone

18 - 27

Table T3. Bond dissociation energies of H-O-O-H at 298 K 28

4

Chemical Sources:

The following chemicals were purchased from Paragos e. K. (Herdecke, Germany) and used as

obtained: 2,3,4-trihydroxybenzonitrile, 2,6-dihydroxybenzonitrile, 2,3-dihydroxybenzonitrile,

2,4-dihydroxybenzonitrile, 2,5-dihydroxybenzonitrile, 2,5-dihydroxybenzoquinone. 2,4,6-

Trihydroxyacetophenone was purchased from Indofine Chemical Company (Hillsborough, NJ)

and used as obtained.

1,4-Benzoquinone-d4 was purchased from Cambridge Isotope Laboratories (Cambridge, MA).

The following chemicals were purchased from Aldrich (St. Louis, MO): 1,4-benzoquinone, 1,2-

dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), 1,4-dihydroxybenzene (1,4-

hydroquinone), 2-aminophenol, 3-aminophenol, 4-aminophenol, 2-methoxyphenol (guaiacol), 3-

methoxyphenol, 4-methoxyphenol (mequinol), 2-hydroxybenzaldehyde, 3-

hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2,3-dimethyl-1,4-hydroquinone, trimethyl-1,4-

hydroquinone, 5-methylresorcinol, 2,5-dimethylresorcinol, 2,3-dihydroxybenzaldehyde, 3,4-

dihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 2,4-dihydroxyacetophenone, 2,6-

dihydroxyacetophenone, 2’,4’-dihydroxybenzophenone.

Sulfur hexafluoride was provided by Concorde Specialty Gases (Eatontown, NJ).

5

a)

b)

Supplementary Figure S1. a) Sample placement in an open HePI source on a Quattro Ultima

mass spectrometer; b) sample placement and introduction of SF6 to a closed HePI source on the

same instrument. The original ESI source has the same configuration, excepting that a

methanolic solution of the sample is sprayed through the capillary held at high voltage (instead

of passing helium to generate HePI plasma).

6

Supplementary Figure S2. Negative-ion HePI mass spectra acquired on a Waters Micromass ZQ single-

quadrupole mass spectrometer from background ambient air at capillary voltage settings of (a) 4.0 kV,

(b) 3.0 kV, (c) 2.5 kV, and (d) 1.8 kV. The peak intensities are normalized to the absolute intensity (in

arbitrary units) of the m/z 32 peak recorded at capillary voltage 4.0 kV.

7

Supplementary Figure S3. CID mass spectra acquired under ESI-MS conditions from mass-isolated m/z

108 (a, b, c, and d), and m/z 109 (e, f, g, and h) ions, generated from a methanolic solution of 1,4-

hydroquinone, on a Waters Micromass Quattro ultima triple quadrupole mass spectrometer. The CID

spectra of the m/z 108 ion were acquired at a capillary voltage 4.0 kV and at laboratory-frame collision

energies of (a) 10 eV, (b) 20 eV, (c) 30 eV, and (d) 40 eV, and those of the m/z 109 ion were acquired at a

capillary voltage of 1.5 kV and at laboratory-frame collision energies of (e) 10 eV, (f) 20 eV, (g) 30 eV,

and (h) 40 eV.

8

Supplementary Figure S4. Absolute intensity of m/z 108 (blue trace) and 109 (red trace) ions, generated

from a methanolic solution of 1,4-hydroquinone by ESI at a capillary voltage of 3.20 kV, monitored

against time by a selective ion recording (SIR) experiment on a Waters Micromass Quattro Ultima triple

quadrupole mass spectrometer. After two minutes of signal acquisition, the source was engulfed with

sulfur hexafluoride, and at 7.5 min, the flow of SF6 was switched off. Insets show mass spectra

corresponding to each region.

9

Supplementary Figure S5. Negative-ion nanospray ESI mass spectra recorded on a Waters SYNAPT G2

Q-TOF mass spectrometer at different cone voltage settings (10-80 V) from methanolic solutions of (a)

catechol, (b) resorcinol, and (c) hydroquinone. Other experimental conditions: flow rate 1 L/min,

capillary voltage 4.0 kV, extraction cone voltage 3 V. Row 9 depicts typical spectra recorded at a cone

voltage setting of 20 V, from the same solutions and under the same conditions after positioning the

capillary tip closer to the entrance cone to effect a plasma discharge.

10

Supplementary Figure S6. Negative-ion ESI mass spectra recorded on a Waters SYNAPT G2 Q-TOF

mass spectrometer of a) catechol , b) resorcinol, and c) hydroquinone (nanospray) under the following

instrumental conditions: extraction-cone voltage 1.5 V, sampling-cone voltage 20 V, Vernier probe

adjustment screw 5.92 mm, source temperature 100 oC, desolvation gas flow rate 450 L/hr. The capillary

voltage was varied between 1.4 and 4.0 kV.

11

Supplementary Figure S7. Negative-ion HePI mass spectra recorded on a Waters Micromass Quattro

Ultima triple quadrupole mass spectrometer from samples of a) 2,3-dimethylbenzene-1,4-diol, b) 2,3,5-

trimethylbenzene-1,4-diol, c) 2,5-dihydroxybenzonitrile, d) 2,5-dihydroxybenzaldehyde, and e) 2,5-

dihydroxycyclohexa-2,5-diene-1,4-dione, at a cone voltage of 10 V, hexapole transfer 1 lens voltage of 20

V, source temperature of 150 oC, desolvation temperature of 300 oC and a capillary voltage of 3.2 kV.

12

.


Ultima triple quadrupole mass spectrometer from samples of a) 2,3-dihydroxybenzaldehyde, b) 3,4-

dihydroxybenzaldehyde and c) 2,3-dihydroxybenzonitrile, at a cone voltage of 10 V, hexapole transfer 1

lens voltage of 20 V, source temperature of 150 oC, desolvation temperature of 300 oC and a capillary

voltage of 3.2 kV.

13


Ultima triple quadrupole mass spectrometer from samples of a) 2-methylbenzene-1,3-diol; b) 2,5-

dimethylbenzene-1,3-diol; c) 2,6-dihydroxybenzonitrile; d) 1-(2,6-dihydroxyphenyl)ethanone at a cone

voltage of 10 V, hexapole transfer 1 lens voltage of 20 V, source temperature of 150 oC, desolvation

temperature of 300 oC and a capillary voltage of 3.2 kV.

14


Ultima triple quadrupole mass spectrometer from samples of a) 5-methylbenzene-1,3-diol; b) 1-(2,4-

dihydroxyphenyl)ethanone; c) (2,4-dihydroxyphenyl)(phenyl)methanone; d) 1-(2,4,6-

trihydroxyphenyl)ethanone; e) 2,3,4-trihydroxybenzonitrile at a cone voltage of 10 V, hexapole transfer 1

lens voltage of 20 V, source temperature of 150 oC, desolvation temperature of 300 oC and a capillary

voltage of 3.2 kV.

15

Supplementary Figure S11. Full-scan HePI mass spectra (left) and product-ion mass spectrum of the

O2-• adduct (right) from samples of a) 2-methoxyphenol; b) 3-methoxyphenol; c) 4-methoxyphenol at a

cone voltage of 10 V, hexapole transfer 1 lens voltage of 20 V, source temperature of 150 oC, desolvation

temperature of 300 oC and a capillary voltage of 3.2 kV recorded on a Waters Micromass Quattro Ultima

triple quadrupole mass spectrometer.

16

Table T1. Calculation of the energy released or absorbed as hydroquinone, catechol, and resorcinol lose

hydrogen gas to produce their respective quinones. The Gaussian 09 program, using the unrestricted HF

method and 6-31G + (d,p) basis set for all atoms, was used to calculate the sum of electronic and zero-

point energies for each molecule.

Sum of electronic and zero-point energies(Hartree/Particle)

M(Dihydroxybenzene)

M - H2

(Quinone)H2 Energy of

reaction (Hartree/Particle)

Energy of reaction (kcal/mol)

Hydroquinone -380.323052 -379.206402 -1.120774 -0.004124 -2.60Catechol -380.330234 -379.195371 -1.120774 0.014089 8.88Resorcinol -380.331414 -379.19964 -1.120774 0.011 6.93

17

Table T2. Atom coordinates, bond lengths, absolute energies and charge distributions of energy-

optimized product ions and transition states of the superoxide radical-anion adduct of hydroquinone

Number Structure Page Number

1 20

2 Front view: 21 - 25

18

Side view:

3 Front view:

Side view:

26 - 24

19

#1

14 to 15 bond length: 1.60793 ÅAnnihilation of the first spin contaminant: S**2 before annihilation 0.7782, after 0.7505Zero-point vibrational energy 317056.2 (Joules/mol) 75.77825 (Kcal/mol)Standard orientation:

--------------------------------------------------------------------- Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z --------------------------------------------------------------------- 1 6 0 2.194214 -0.368082 -0.019290 2 6 0 2.083611 1.002731 -0.083693 3 6 0 0.834434 1.593733 -0.048174 4 6 0 -0.313879 0.822209 0.059173 5 6 0 -0.190896 -0.560030 0.125853 6 6 0 1.060471 -1.147086 0.088864 7 1 0 2.970226 1.595879 -0.164257 8 1 0 0.732411 2.656890 -0.098022 9 1 0 -1.084179 -1.148186 0.223218 10 1 0 1.141128 -2.216497 0.133854 11 8 0 3.492825 -0.927827 -0.075127 12 1 0 3.531153 -1.848833 0.206371 13 8 0 -1.529138 1.427336 0.115596 14 1 0 -2.335495 0.772654 0.046730 15 8 0 -3.572383 -0.057317 -0.073112 16 8 0 -3.261676 -1.426286 -0.102893 ---------------------------------------------------------------------Zero-point correction= 0.120760 (Hartree/Particle) Thermal correction to Energy= 0.130502 Thermal correction to Enthalpy= 0.131446 Thermal correction to Gibbs Free Energy= 0.083133 Sum of electronic and zero-point Energies= -529.940889 Sum of electronic and thermal Energies= -529.930458 Sum of electronic and thermal Enthalpies= -529.929514 Sum of electronic and thermal Free Energies= -529.980692

20

#2 Front view:

#2 Side view:

#2

Distance between atoms 13 and 14: 3.30723 Å

Annihilation of the first spin contaminant: S**2 before annihilation 0.7776, after 0.7507Standard orientation: ---------------------------------------------------------------------

21

Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z --------------------------------------------------------------------- 1 6 0 -0.127007 1.154785 -0.008966 2 6 0 1.188076 1.585005 0.054027 3 6 0 2.242653 0.693111 0.053583 4 6 0 2.065215 -0.725753 -0.024027 5 6 0 0.693122 -1.116536 -0.072490 6 6 0 -0.364606 -0.210754 -0.069068 7 1 0 1.383885 2.643499 0.106516 8 1 0 3.251389 1.065082 0.107479 9 1 0 0.475789 -2.172135 -0.129328 10 1 0 -1.380427 -0.615979 -0.103206 11 8 0 -1.125515 2.123263 0.001716 12 1 0 -1.964038 1.710208 -0.060191 13 8 0 3.019375 -1.542936 -0.003902 14 1 0 -2.198688 -1.775494 0.368288 15 8 0 -3.078666 -1.497951 0.135823 16 8 0 -3.034273 -0.224167 -0.119626 ---------------------------------------------------------------------Zero-point correction= 0.119366 (Hartree/Particle) Thermal correction to Energy= 0.129598 Thermal correction to Enthalpy= 0.130543 Thermal correction to Gibbs Free Energy= 0.080658 Sum of electronic and zero-point Energies= -530.080701 Sum of electronic and thermal Energies= -530.070469 Sum of electronic and thermal Enthalpies= -530.069525 Sum of electronic and thermal Free Energies= -530.119410

22

Charge Distribution (Mulliken) #2

23

Mulliken atomic spin densities #2:

1 C 0.170003 2 C -0.136490

24

3 C 0.141609 4 C -0.089712 5 C 0.118288 6 C -0.182213 7 H 0.008019 8 H -0.008572 9 H -0.006196 10 H 0.008970 11 O -0.002795 12 H -0.002892 13 O -0.020092 14 H -0.011087 15 O 0.106716 16 O 0.906445 Sum of Mulliken atomic spin densities = 1.00000

Diagram of atom numbering for #2:

Interatomic distances (Angstroms):1 and 16: 4.612142 and 16: 5.166503 and 16: 5.105474 and 16: 4.472635 and 16: 3.736346 and 16: 3.847851 and 14: 3.381022 and 14: 3.610593 and 14: 3.327184 and 14: 2.723645 and 14: 2.317226 and 14: 2.73360

25

#3 Front view:

#3 Side view:

#3

Annihilation of the first spin contaminant: S**2 before annihilation 0.9982, after 0.7986 Standard orientation: --------------------------------------------------------------------- Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z --------------------------------------------------------------------- 1 6 0 0.038970 -0.699564 -0.154033 2 6 0 1.291603 -1.243914 -0.139532 3 6 0 2.468569 -0.428255 0.001556 4 6 0 2.251298 0.988739 0.124957 5 6 0 0.993195 1.519055 0.108701 6 6 0 -0.179900 0.710742 -0.029828 7 1 0 -0.828535 -1.326182 -0.255417 8 1 0 1.438327 -2.306303 -0.233310 9 1 0 3.121762 1.613610 0.230173 10 1 0 0.843811 2.580197 0.201020 11 8 0 3.613916 -0.921029 0.016675 12 8 0 -1.340084 1.231708 -0.039494 13 1 0 -2.720148 0.480274 -0.277112 14 8 0 -3.634233 0.111977 -0.378547 15 8 0 -3.551964 -1.088985 0.355482

26

16 1 0 -3.738709 -0.791789 1.230793 ---------------------------------------------------------------------Zero-point correction= 0.120154 (Hartree/Particle) Thermal correction to Energy= 0.130180 Thermal correction to Enthalpy= 0.131124 Thermal correction to Gibbs Free Energy= 0.080943 Sum of electronic and zero-point Energies= -530.122654 Sum of electronic and thermal Energies= -530.112627 Sum of electronic and thermal Enthalpies= -530.111683 Sum of electronic and thermal Free Energies= -530.161865

27

Table T3. Bond dissociation energies of H-O-O-H at 298 K

Dissociation energy (kJ/mol) Dissociation energy (kcal/mol)O-O bond 213.8 ± 2.1a 50.7H-O bond 374.5 ± 8.4b 89.1aT. L. Cottrell, The Strengths of Chemical Bonds, 2d ed., Butterworth, London, 1958; B. deB. Darwent, National Standard Reference Data Series, National Bureau of Standards, no. 31, Washington, 1970; S. W. Benson, J. Chem. Educ. 42:502 (1965); and J. A. Kerr, Chem. Rev. 66:465 (1966).bWagman, D. D., Evans, W. H., Parker, V. B., Halow, L., Bailey, S. M., and Schumm, R. H., Selected values of chemical thermodynamic properties. Part 3. Tables for the first thirty-four elements in the standard order of arrangement, Nat. Bur. Stand. (U.S.), Tech. Note 270-3 (1967) and Part 4, Tables for Elements 35 through 53 in the standard order of arrangement, Nat. Bur. Stand. (U. S.), Tech. Note 270-4 1969).

28

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static-content.springer.com10.1007... · Web viewThermal correction to Gibbs Free Energy= 0.080943 Sum of electronic and zero-point Energies= -530.122654 Sum of electronic and thermal