Paper
Photochemical & Photobiological Sciences
reported.9a,11b,12 The structures of the resulting photoproducts data were collected and analyzed on a Dell Dimension 2300
1
were confirmed by spectral analysis of H-NMR, which are in computer with appropriate GPC software from Viscotek. Two
good agreement with those reported.
ViscoGEL HR high-resolution columns (styrene-divinylbenzene
and
3-Ethylphenyl(phenyl)methanone (6).12 1H-NMR (300 MHz, columns) in series were used: G3000 HR 60
k
CDCl3) δ 7.76–7.72 (m, 2 H), 7.59 (m, 1 H), 7.55–7.48 (m, 2 H), GMHHR-MMixed Bed 4 M columns. The molecule weight dis-
7.44–7.29 (m, 4 H), 2.65 (q, J = 7.6 Hz, 2 H, –CH2–), 1.20 (t, J = tribution for the PMA polymer was determined from GPC data
7.6 Hz, 3 H, –CH3); The structure of 6 was confirmed by using an algorithm from Viscotek, which relies on LALS detec-
1H-NMR and in good agreement with the reported one.
2-Methyl-xanthen-9-one.9a 1H NMR (300 MHz, CDCl3) δ 8.33
(dd, J = 8.0, 1.6 Hz, 1 H), 8.11 (d, J = 1.6 Hz, 1 H), 7.70 (ddd, J =
7.6, 7.8, 1.6 Hz, 1 H), 7.53 (dd, J = 8.4, 2.4 Hz, 1 H), 7.47 (dd,
J = 8.4, 0.7 Hz, 1 H), 7.40–7.33 (m, 2 H), 2.45 (s, 3 H, –CH3).
3-Methylbenzophenone.11b 1H NMR (300 MHz, CDCl3)
δ 7.82–7.78 (m, 2 H), 7.63–7.56 (m, 3 H), 7.51–7.45 (m, 2 H),
7.41–7.33 (m, 2 H), 2.35 (s, 3 H, –CH3).
tion from a 670 nm diode laser source.
Laser flash photolysis (LFP)
Ketoprofen samples at concentration ranging from 0.2 to
2 mM were prepared in neat CH3CN in either the presence or
absence of a base. The base concentration used was always at
least 10 fold higher than that of KP to ensure complete dis-
sociation of the acid. 0.1 M sodium hydroxide aqueous solu-
tion was used. The laser flash photolysis systems were
conducted using a Nd:YAG laser with a pulse width of 10 ns
and excitation wavelength of 355 nm. All the transient spectra
and kinetics were recorded by employing a flow system with a
quartz cell with a 2 mL capacity. Samples were purged with
nitrogen or oxygen for 30 min prior to measurements. The
quenching rate constants were obtained with static cells
(0.7 cm). The optical density at 355 nm was 0.18.
Procedure for trapping the Michael adduct 7
To a solution of 10 mg (0.039 mmol) of 1 in 50 mL of 0.25%
v/v NaOH(aq)/CH3CN (0.1 M NaOH(aq) solution was used) was
added 10 equiv. of freshly purified MA (0.35 mL, 0.39 mmol),
followed by purging with argon gas for 20 min prior to
irradiation. The mixture solution in a Pyrex tube was then ir-
radiated at 350 nm for 5 min under an argon atmosphere. The
mixture was washed with 1% HCl and then extracted with
50 mL CH2Cl2. The organic layer was dried over MgSO4 and
concentrated in vacuo. The remaining crude residue was puri-
fied by preparative TLC plate (35% ethyl acetate/n-hexanes as
the eluent) to give rise to 6 as a major product in a relative
yield of 83% and trapped Michael adduct 7 as a minor in a
relative yield of 11% as determined by 1H-NMR. Deuterium
incorporation experiment was carried out under the same reac-
tion conditions but using 0.1 M NaOD/D2O aqueous solution
instead to give rise to a mixture of deuterated 6 and 7, and
PMA, where 7-D was purified by using a preparative TLC plate
as shown in Fig. 2.
Acknowledgements
We thank the Natural Sciences and Engineering Research
Council (NSERC) of Canada and the University of Victoria for
financial support.
Notes and references
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Methyl
4-(3-benzoylphenyl)pentanoate
(7). 1H-NMR
(500 MHz, CDCl3) δ 7.78 (d, J = 8.4 Hz, 2 H), 7.62 (s, 1 H),
7.61–7.56 (m, 2 H), 7.47 (t, J = 8.4 Hz, 2 H), 7.40–7.38 (m, 2 H),
3.61 (s, 3 H, OMe), 2.73 (sextet, 1 H), 2.24 (m, 2 H), 1.85 (m, 2
H), 1.28 (d, J = 6.9 Hz, 3 H, Me); 13C NMR (125 MHz; CDCl3)
δ 196.9 (CvO), 174.0 (methyl ester CvO), 146.3, 145.1, 137.8,
137.7, 134.3, 132.0, 130.3, 130.1, 128.6, 128.3, 51.5 (OMe), 39.3,
33.2, 32.5, 21.9 (Me); IR (CHCl3, cm−1) 3115, 3110, 2998, 2967,
1746 (CvO), 1643 (CvC), 1475, 1407, 1210, 855; MS (EI) m/z
319 [M + Na]+; HRMS, calcd for C20H14ONa: 319.1310; Found
319.1305.
Gel permeation chromatography (GPC) analyses
GPC measurements were performed using a Viscotek model
302 liquid chromatography system equipped with refractive
index (RI), low-angle light scattering (LALS, θ = 7°), right-angle
light scattering (RALS, θ = 90°), and UV detectors. THF was
used as the eluent at a flow rate of 1 mL min−1, and the
column temperature was set at 35 °C. All polymer solutions
were filtered through membrane filters with a nominal pore
size of 0.45 μm before injection into the GPC column. The
6 (a) G. Cosa, Pure Appl. Chem., 2004, 76, 263; (b) M.-D. Li,
J. Ma, T. Su, M. Liu, L. Yu and D. L. Phillips, J. Phys. Chem.
Photochem. Photobiol. Sci.
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