Loss of CO2 from Perbenzoate Anions in the Gas Phase
3-Nitroperbenzoic acid.43 Procedure as for 2-nitroperbenzoic
acid. 3-Nitrobenzoic acid (5.0 g, 30 mmol), MsOH (14.4 g, 150
mmol), and H2O2 (3.6 g of 88%, 93 mmol) afforded the product as
pale yellow crystals (4.9 g, 89%), which was analyzed as 99.7%
peracid by iodometric titration: mp 80-82 °C; νmax/cm-1 3508
br, 3286 br, 1743 vs, 922; δH (CDCl3, 300 MHz) 7.77 (1H, t, J )
8.1 Hz), 8.34 (1H, ddd, J ) 7.6, 1.8, 1.2 Hz), 8.52 (1H, ddd, J )
8.1, 2.3, 1.2 Hz), 8.85 (1H, m), 11.55 (1H, br); δC (CDCl3, 75 MHz)
124.4, 127.1, 128.7, 130.3, 134.8, 148.3, 165.8; m/z (ESI) found
182.0128, calcd for C7H4NO5 (M - H)- 182.0089.
was analyzed as 68.2% peracid by iodometric titration. Further
purification by flash chromatography (Rf ) 0.3, cold CH2Cl2 on
silica) achieved a purity of 84.1%: δH (CDCl3, 500 MHz) 3.88
(3H, s), 6.97 (2H, d, J ) 8.8 Hz), 7.95 (2H, d, J ) 8.8 Hz), 11.62
(1H, br); δC (CDCl3, 125 MHz) 55.5, 114.2, 121.9, 131.5, 164.4,
167.9; m/z (ESI) found 167.0368, calcd for C8H7O4 (M - H)-
167.0344.
Electronic Structure Calculations. Geometry optimizations
were carried out with the B3LYP method46,47 using the 6-311++G-
(d,p) basis set within the GAUSSIAN03 suite of programs.48 All
stationary points on the potential energy surface were characterized
as either minima (no imaginary frequencies) or transition states (one
imaginary frequency) by calculation of the frequencies using
analytical gradient procedures. Frequency calculations provided
zero-point energies, which were added to the calculated electronic
energy. The minima connected by a given transition state were
confirmed by inspection of the animated imaginary frequency using
the MOLDEN package49 and by intrinsic reaction coordinate
calculation.50,51
4-Nitroperbenzoic acid.37,43 Preparation as for 2-nitroperbenzoic
acid. 4-Nitrobenzoic acid (5.0 g, 30 mmol), MsOH (14.4 g, 150
mmol), and H2O2 (3.6 g of 88%, 93 mmol) afforded the product as
yellow crystals (5.4 g, 93%) that were analyzed as 95.8% peracid
by iodometric titration. Further purification was achieved by
washing a CH2Cl2 solution (300 mL) of the crude product (5.3 g)
with aqueous NaOH (0.038 M, 50 mL) then water (50 mL). Drying
(MgSO4) and solvent removal at room temperature afforded material
of 98.8% purity: mp 139 °C (vigorous decomposition) (lit. 138
°C decomposition);37 max/cm-1 3503 br, 3283 br, 1741 vs; δH
ν
(CDCl3, 300 MHz) 8.20 (2H, dm, J ) 9.0 Hz), 8.37 (2H, dm, J )
9.0 Hz), 11.56 (1H, s); δC (CDCl3, 75 MHz) 123.7, 124.0, 130.6,
131.3, 166.1; m/z (ESI) found 182.0123, calcd for C7H4NO5 (M -
H)- 182.0089.
Acknowledgment. S.J.B. acknowledges the financial support
of the University of Wollongong (URC New Researcher Grant),
the Institute for Biomolecular Science, and the Australian
Research Council (DP0452849). We also acknowledge the
support of the Australian Partnership for Advanced Computing
(ANU, Canberra) for a generous allocation of supercomputing
time.
3-Methoxyperbenzoic acid.44 Although Swern and co-workers37
report that their procedure was unsuccessful in the synthesis of
3-methoxyperbenzoic acid, in our hands, slight changes to the
method permitted its preparation. Stirred 3-methoxybenzoic acid
(5.0 g, 33 mmol) in MsOH (14.7 g, 153 mmol) was cooled to 0
°C, and H2O2 (88%, 3.5 g, 91 mmol) was added dropwise at such
a rate to keep the temperature below 50 °C. After 4 h, ice (50 g)
was added, the mixture extracted with CHCl3 (3 × 50 mL), and
the combined organic extracts were washed with H2O (50 mL) and
dried (MgSO4). Removal of solvent in vacuo at room temperature
afforded a brown/yellow solid (3.7 g, 26% yield), 38% peracid by
iodometric titration. A small quantity was purified for characteriza-
tion by flash chromatography (Rf ) 0.34, CH2Cl2 on silica), and
upon cooling, the resulting colorless oil crystallized: mp 32-34
°C; νmax/cm-1 3516 br, 3265 br, 1732 vs, 925 w; δH (CDCl3, 300
MHz) 3.85 (3H, s), 7.18 (1H, ddd, J ) 8.3, 2.6, 1.0 Hz), 7.41 (1H,
t, J ) 7.9 Hz), 7.49 (1H, dd, J ) 2.6, 1.8 Hz), 7.59 (1H, dt, J )
7.6, ∼1.2 Hz), 11.62 (1H, s); δC (CDCl3, 75 MHz) 55.5, 113.6,
121.0, 121.6, 126.3, 130.0, 159.8, 168.0; m/z (ESI) found 167.0371,
calcd for C8H7O4 (M - H)- 167.0344.
Supporting Information Available: Electronic energies, zero-
point energies, and molecular geometries (as Cartesian coordinates)
for all stationary points discussed in the text. This material is
JO060730A
(46) Becke, A. D. J. Chem. Phys. 1993, 98, 1372.
(47) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. ReV. B: Condens. Matter
1988, 37, 785.
(48) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; 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.; Al-Laham,
M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian
03, revision C.02; Gaussian Inc.: Wallingford, CT, 2004.
4-Methoxyperbenzoic acid.45 A solution of freshly prepared
4-methoxybenzoyl chloride (3.0 g, 18 mmol) in CH2Cl2 (6 mL)
was added dropwise to a stirred suspension of aqueous H2O2 (93%,
3.0 g, 82 mmol) in CH2Cl2 (6 mL) at 0 °C. After 2.5 h at 0 °C, the
mixture was poured into ice water (15 mL), extracted with CH2Cl2
(3 × 15 mL), and the combined extracts were washed with cold
water (10 mL) and dried (MgSO4). Rotary evaporation of solvent
at room temperature yielded a white solid (3.1 g, yield 72%) that
(49) Schaftenaar, G.; Noordik, J. H. J. Comput.-Aided Mol. Des. 2000,
14, 123.
(50) Gonzalez, C.; Schlegel, H. B. J. Chem. Phys. 1989, 90, 2154.
(51) Gonzalez, C.; Schlegel, H. B. J. Phys. Chem. 1990, 94, 5523.
(43) Pande, C. S.; Jain, N. Synth. Commun. 1988, 18, 2123.
(44) Blake, R. C., II; Coon, M. J. J. Biol. Chem. 1980, 255, 4100.
(45) Konen, D. A.; Silbert, L. S. J. Org. Chem. 1971, 36, 2162.
J. Org. Chem, Vol. 71, No. 21, 2006 8005