Supporting Information
Nucleophilic Addition of Nitrogen to Aryl Cations: Mimicking Titan
Chemistry
Anyin Lia, Fred P. M. Jjunjua, and R. Graham Cooksa, *
a
Chemistry Department, Purdue University, West Lafayette, IN 47907, USA
* Address reprint requests to: Professor R. Graham Cooks,
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907.
Telephone: (765) 494-5262. Fax: (765) 494-9421 email: cooks@purdue.edu
Table of contents
Section 1 Additional Data on Reactivity of Aryl Ions with Molecular Nitrogen
Figure S1.
Figure S2.
Figure S3.
Table S1.
Table S2.
Table S3.
Nitrogen addition, three different ion activation pathways, two different pressures
Nitrogen addition reactivity using two different collision gases
Reactivity of para-substituted phenyl cations toward nitrogen addition
Thermochemistry for fragmentation and reaction of the aryl cations
Comparison of energy requirements for nitrogen activation via different routes
Heteroatoms in aromatic ring block the nitrogen addition reactivity
Section 2 Reactivity of Aryldiazonium Ions with Other Molecules
Figure S4.
Figure S5.
Figure S6.
Figure S7.
Table S4.
p. 2 - p.8
Reaction between the phenyldiazonium ion with acetonitrile
Fragmentation pattern of the acetonitrile reaction product
Reaction between the phenyldiazonium ion with aniline
Reaction between the phenyldiazonium ion with 3-octyne
Fragmentation patterns of model compounds
Section 3 Full Citation for Gaussian 03
p. 2
p. 4
p. 5
p. 6
p. 8
p. 8
p. 9 – p. 13
p. 9
p. 10
p. 11
p. 12
p.13
p.14
1
Section 1. Additional Data on Reactivity of Aryl Ions with Molecular Nitrogen
Figure S1 Reactivity of phenyl cation (m/z 77) generated from protonated aniline (m/z 94), toward
nitrogen addition (m/z 105), in three different ion activation pathways under two different pressures as
elucidated by multiple stage mass spectrometry: (a) Phenyl cations generated by helium CID were
isolated and directed into the octopole where they were allowed to react with N2 for 30 msec. Then all
ions were injected into the Orbitrap for mass analysis. (b) Phenyl cations generated by helium CID
without isolation with injection of all resulting ions into the Orbitrap by passing through the C-trap (~ 0.1
Pa N2) where nitrogen addition reactions took place prior to Orbitrap mass analysis. (c) Phenyl cations
generated by high energy collision-induced dissociation at 505 Pa N2 in the octopole cell, where the
nitrogen addition reaction took place after formation of the reactive cations. After 30 msec of collisional
activation and reaction time, all the ions were injected into the Orbitrap for mass analysis. Comparison of
these three spectra each normalized against the remaining reagent ion (m/z 77.038), shows that direct high
energy collisions give the highest yield of nitrogen addition product. The higher reactivity of the hotter
ions suggests the presence of activation barriers for the reaction.
2
Figure S2 (a) The ion fragmentation/reaction pathway depicted in Figure 5 took place only when
fragmentation occurred in the linear ion trap (CID using helium). (b) High energy collisional dissociation
(HCD) does not produce the fragment ion C8H5+, seen in the linear ion trap CID, however it produces
abundant phenyl cations which also undergo nitrogen addition.
3
Figure S3 Reactivities of para-substituted phenyl cations toward nitrogen addition. The reactivity was
evaluated by normalizing the peak height of the substituted addition product (P’) to the unreacted
𝑷′
substituted phenyl cation (R’). These initial reactivity values ([𝑹′]) were divided by the ratio for the
𝑷
unsubstituted phenyl cation ([𝑹]) to obtain a final normalized reactivity. The log (ratio/ratio) values are
plotted (y axis) against the Hammett inductive parameters (σI, x axis) and the plot displays fair linearity.
This suggests that inductive effects have a consistent, dominant influence on the nitrogen addition
reactivity. Note that better linearity would be obtained within each set of substituent groups (e.g. the
halides) and that the ethyl group falls off the trend line, indicating that other factors also significantly
influence the reaction. Note that plots of substituent effects for diazonium compounds against any single
set of substituent constants show scattered plots [1].
4
Table S1. Thermochemistry for Precursor Fragmentation and Addition Reaction of Substituted
Phenyl and other Aryl Cations
Substituent
Phenyl cation
a
Position
Cl
Br
CH3
C2H5
OH
OCH3
NH2
b
T-S gap
c
ΔHaddition
kJ/mol
kJ/mo
kJ/mol
281.5
77.5
-139.3
2-
341.5
5.0
-191.8
3-
291.7
47.4
-143.9
4-
304.5
30.5
-167.5
2-
318.4
19.2
-168.3
3-
287.8
42.3
-141.6
4-
298.2
25.1
-160.8
2-
315.3
18.0
-161.2
3-
281.5
35.3
-138.5
4-
290.1
17.4
-158.9
2-
255.6
66.5
-128.8
3-
264.9
62.6
-131.6
4-
277.6
44.7
-147.7
2-
248.2
66.9
-123.6
3-
262.5
62.6
-127.8
4-
275.3
41.4
-145.6
2-
326.5
-23.2
-186.5
3-
294.5
17.8
-134.6
4-
292.3
-9.5
-175.8
2-
311.3
-30.9
-179.5
3-
265.8
16.1
-124.2
4-
286.4
-18.8
-174.1
2-
293.4
-54.6
-163.4
3-
254.5
-7.6
-111.6
4-
283.5
-44.4
-179.4
H
F
ΔHFrag
5
Naphthyl cation
1-
252.3
-0.3
-135.6
Naphthyl cation
2-
260.8
-0.3
-140.6
Ethynylphenyl
cation
2-
N. A.
12.9
-89.0
Anthracenyl cation
1-
237.8
-57.6
-130.1
Anthracenyl cation
2-
240.7
-51.2
-128.0
a
Reaction enthalpy to break C-N bond of protonated amine to form the aryl cation
Energy difference between triplet ground state and singlet ground state aryl cation
c
Reaction enthalpy for N2 addition to aryl cation to form corresponding diazonium ion
b
6
Table S2. Comparison of Energy Requirements of First Steps of Nitrogen Activation via
Different Routes
Method of nitrogen activation
Energy
(kJ/mol)
Equivalent
photon
wavelength
(nm)
50.9
85.2
59.1
121.6 (Ly-α) 1
95.9 2
N+ from N2
2345
+
N2 from N2
1402
+
N3 from N2
2021
Methane(CH + N2 + M  HCN2)
>983 1
Phenylium from benzene
1245
Phenylium from protonated
346
345.2 2
aniline
1
Active CH was generated from methane by Ly-α photon irradiation. The energy of this process was not
reported, but longest wavelength of Ly-α photons is 121.6 nm.[2]
2
Aromatic structure allows absorption of multiple photons of longer wavelengths (similar to the slow
heating collisional activation is used in our MS experiment). In comparison, nitrogen is transparent to
photons > 120 nm, which makes it inaccessible to low energy activation
Table S3. Heteroatoms in Aromatic Ring Block the Nitrogen Addition Reactivitya
Heteroatom on the
Phenyl cation Ring
b
Position
T-S gap
c
ΔHaddition
kJ/mol
kJ/mol
N
2
167.6
-100.4
(dehydropyridine
cation)
3
101.4
-111.6
4
87.5
-51.1
a
Thermochemistry stays relatively constant. Nitrogen addition reaction blocked but water addition
product was observed for these ion
7
Section 2. Reactivity of Aryldiazonium Ions with Other Molecules
Dinitrogen reacts with the phenyl cation to generate the phenyldiazonium ion which reacts
readily with nitriles, alkynes and amines as demonstrated by the three experiments shown in
Figure S4, S6 and S7. The fact that the acetonitrile and alkyne products are covalently bound is
shown by the collision induced dissociation products seen in the MS/MS spectrum (Figure S5)
and by the fragmentation evident in Figure S7.
Figure S4. MS/MS product ion spectrum recorded at low energy and showing reactions of the
phenyldiazonium ion with acetonitrile in the octopole ion trap of an Orbitrap mass spectrometer.
Proposed structures are nominal but are supported by exact mass measurements and by the CID
fragmentation in Figure S5. Calculations indicate the proposed ring formation reaction to be exothermic
by ~220 kJ/mol.
8
Figure S5. Collision-induced dissociation (in the HCD cell) at nominal collision energy 70%
(mnfg’s units) in an Orbitrap mass spectrometer of the product ion generated in the ion/molecule
reaction shown in Figure S1. Major neutral fragment losses are ·CH3 (to give m/z 131.048) and
loss of N2 (to give m/z 118.066). This fragmentation behavior indicates that the reaction product
of the phenyl diazonium ion with acetonitrile in covalently bound, not a weak adduct. Note that
the ion structure proposed cannot currently be tested by generating it by other means. However,
the proposed structure is supported by the fact that CID loss of methyl radical from even electron
ions is quite rare and happens to parent ion with (-CH3) groups bonded to nitrogen-containing
rings or to parent with (-NCH3) bonded to aromatic rings (see Table S4.). In the of the
acetonitrile reaction product, only the first case is reasonable.
9
Figure S6. Ion/molecule reaction between phenyl diazonium and aniline as observed using product ion
MS/MS scan using 0% collision energy in the HCD cell of an Orbitrap mass spectrometer. Calculations
indicate the proposed reaction giving the azobenzene to be exothermic by ca. 200 kJ/mol. Ion structures
shown are nominal but molecular formulas agree with exact mass measurements to better than 0.7 ppm.
Protonated pyridine, m/z 94, is likely formed by a competitive side reaction.
10
Figure S7. Ion/molecule reaction between the phenyl diazonium cation and 3-octyne as observed using
product ion MS/MS scan using 0% collision energy in the HCD cell of the Orbitrap mass spectrometer.
Calculations indicate the proposed cyclization reaction to be exothermic by ca. 460 kJ/mol. This high
exothermicity may provide enough energy to facilitate loss of butene to form the fragment ion at m/z
159.091. Ion structures shown are nominal but molecular formulas agree with exact mass measurements
to better than 0.6 ppm.
11
Table S4. Fragmentation patterns of model compounds with sub-structures and neutral losses
similar to reaction product in Figure S4 and Figure S5. The loss of methyl radical from even
electron ions is quite rare and happens to parent ion with (-CH3) group bonded to nitrogen
containing rings or to parent with (-N-CH3) bonded to aromatic rings. In the case of the
acetonitrile reaction product, only the first case is reasonable.
m/z of [MH]+
MS2
5-methylcarbazole
182
182  167
[-15 ·CH3]
2-methylindole
132
132  117
[-15 ·CH3]
2,5-dimethylaniline
122
4,4'-methylenebis(N,Ndimethylaniline)
255
122  107, 105
[-15 ·CH3]
[-17 NH3]
255  240, 239
[-15 ·CH3]
[-16 CH4]
4-azido-N,N,Ntrimethylbenzenaminium
177 (M+)
177149
[-28 N2]
Benzotriazole
120
12092
[-28 N2]
Name
Structure
12
Section 3. Full Citation for Gaussian 03
Gaussian 03, Revision C.02, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, Jr., J. A.; Vreven, T.; Kudin, K. N.; Burant, J. C.;
Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.;
Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.;
Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.;
Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P.
Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.;
Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; AlLaham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.;
Chen, W.; Wong, M. W.; Gonzalez, C.; and Pople, J. A.; Gaussian, Inc., Wallingford CT, 2004.
Abbreviated as (Gaussian 03, Revision C.02, Frisch, M.J. et al; Gaussian, Inc., Wallingford CT,
2004.) in the main text.
References
1.
Patai, S.: The chemistry of diazonium and diazo groups; J. Wiley: New York, 1978.
2.
Trainer, M.G., Jimenez, J.L., Yung, Y.L., Toon, O.B., Tolbert, M.A.: Nitrogen
incorporation in ch(4)-n(2) photochemical aerosol produced by far ultraviolet irradiation.
Astrobiology 12, 315-326 (2012)
13