supplementary materials for · 2014. 12. 17. · one-pot room-temperature conversion of cyclohexane...
TRANSCRIPT
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www.sciencemag.org/content/346/6216/1495/suppl/DC1
Supplementary Materials for
One-pot room-temperature conversion of cyclohexane to adipic acid by
ozone and UV light
Kuo Chu Hwang* and Arunachalam Sagadevan
*Corresponding author. E-mail: [email protected]
Published 19 December 2014, Science 346, 1495 (2014)
DOI: 10.1126/science.1259684
This PDF file includes:
Materials and Methods
Supplementary Text
Figs. S1 to S6
Tables S1 to S15 1H and
13C NMR Data
1H and
13C NMR Spectra
Full Reference List
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Materials and Methods
General procedure for oxidative C-H functionalization of cycloalkanes.
All reactions were conducted under an ozone atmosphere using oven-dried glass
wares. A 100 W Hg lamp was used as the light source without any filter. Ozone was
generated by an ozone generator (C-labsky series, model no. c-l010-DT)) using pure
oxygen gas as the source of oxygen. Starting materials (Aldrich) are commercially
available and were used as received. NMR spectra were recorded in CDCl3, DMSO or
CDCl3-DMSO mixture, 1H NMR at 600 MHz and
13C NMR at 150 MHz were used to
determine the structures of products. Data were reported as: s= singlet, d= doublet, t=
triplet, q= quartet, m= multiplet, b= broad.
A dry test tube of 20 mL capacity was charged with cyclohexane (6.5 mL) and
equipped with a Teflon septum and a magnetic stirrer bar. Ozone gas (flow rate= 0.45
mL per minute) was bubbled into the cyclohexane solution and simultaneously irradiated
under a 100 W Hg lamp (200 mW/cm2 at 310 nm) (distance between reaction vessel and
light is 5 cm) for 0.5-15 h at room temperature. The reaction vessel was equipped with
chilled water-methanol circulator (-5 to -10 oC) condenser to trap evaporating
reactants/intermediates and to improve the mass balance. Upon irradiation, white solid
was slowly formed and precipitated. After completion of reaction the crude product
(pasty wet solid) was collected and subjected to isolation/purification of the process. The
white solid was further dispersed in ethyl acetate-hexane (20:80) solution and stirred for
30 min at room temperature. The solid precipitate was collected by centrifugation and
dried under vacuum for 2 h at room temperature. Small amount of the collected dried
solid product was dissolved in d-chloroform for 1H NMR and
13C NMR measurements to
identify the reaction products and the purity of adipic acid. In 1H NMR, a quite clean
adipic acid spectrum was observed without the presence of cyclohexane, cyclohexanol
and cyclohexanone peaks. To be very cautious for the structure characterization, we
further grew crystals of the white solid precipitate in ethanol and adopted x-ray
crystallography for structure characterization of the solid precipitate product, since x-ray
crystallography is an absolute method for structure characterization of an unknown
compound. For recrystallization of the solid precipitate, 6.5 g of the solid dried
precipitate was added to 32 mL of absolute ethanol. The solid-ethanol solution was
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slowly heated to refluxing condition and continued stirring for 30 minutes. Then, heater
was turned off to allow slow cooling of the solution to room temperature. White
crystalline solids were slowly formed. The crystalline white solids were isolated by
filtration method (6.1g). The chemical structure of the white crystalline product was
determined by single crystal x-ray chromatography to be adipic acid.
In the current photo irradiation process, liquid reactant was gradually converted to solid
precipitate. At the late stage of reaction process, a small amount of liquid
reactant/intermediates were trapped in the solid precipitate. It is therefore inherently
difficult to reach more than 90% conversion. Nevertheless, the problem can be overcome
by designing a dynamic flow reactor allowing regular removal of solid precipitated
products from the bottom of the reactor when a large scale production of solid adipic acid
is concerned.
Procedure for determination of conversion, selectivity, and mass balance.
After ozone-uv irradiation, a known amount (in mole) of external standard, 1,4-
dicyanobenzene, was added to the final crude products solution. Once the external
standard was added, the molar ratios of all products relative to the external standard in the
final solution are fixed irrespective of the later experimental procedure. Then, the
absolute amounts of all products in the final solution can be determined by multiplication
of the relative molar ratios of all crude products to the external standard (determined by
1H NMR peak area ratio) with the mole of the external standard added. Since adipic acid
was formed and precipitated as solid precipitate, DMSO and d-chloroform were used to
fully dissolve the solid adipic acid for 1H NMR measurement so that the amount of adipic
acid in the crude product can be determined accurately. The mass balance was
determined by the sum of all products (in moles, including unreacted starting substrate)
divided by the initial mole of starting material. The selectivity of adipic acid (AA) was
determined by the mole of AA in the crude product (by 1H NMR) divided by the total
moles of all crude products. The conversion percentage was determined by the total
moles of all crude products divided by the initial mole of the starting material. From 1H
NMR spectra, only cyclohexanol, cyclohexanone and adipic acid were detected as final
products. No shorter chain acids or any other decomposition products were detected in
1H NMR measurements during the time course of reaction.
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Supplementary Text
General aspects: reproducibility, effects of pH, uv fluence, and ozone flow rate on
product yields. As shown in the Tables S1 and S2, all experiments were repeated at
least 3 times. The reproducibility of all experiments is within a reasonably good range.
The mass balance in the neat cyclohexane-dark system seems to be lower than others,
indicating that the -5 to -10 oC cooling condenser can only efficiently trap the vapors of
higher boiling point intermediates, cyclohexanol and cyclohexanone, but poorly for the
low boiling point starting cyclohexane substrate. Photo irradiation and addition of acidic
water can much more efficiently convert low boiling point cyclohexane to intermediates
(i.e., cyclohexanol and cyclohexanone) and product (i.e., adipic acid) of higher boiling
points, leading to higher adipic acid yields and higher mass balance values.
We also investigated the pH effect on the yield of adipic acid. Aqueous 0.5 M HCl or
0.5 M NaOH solution was added to the cyclohexane solution. The amount of water
added to cyclohexane solutions is 8 vol%. The results in Tables S1 and S3 show that
under the same condition, the presence of acidic water results in higher adipic acid yields
than those for both neutral and basic water systems in both light and dark conditions.
Since both ozone and singlet O(1D) can react with water to generate hydroxyl radicals,
the major oxidant switches from ozone or O(1D) to hydroxyl radical in the cyclohexane-
water systems (see below for the discussion of plausible reaction mechanisms). In the
literature, it is known that hydroxyl anion (i.e., a basic water condition) can react with
ozone molecules to generate non-hydroxyl radical product (32), and therefore disfavors
the formation of hydroxyl radical. Therefore, a low pH value will favor the formation of
more amounts of hydroxyl radical via suppression of hydroxyl radical concentration,
leading to more efficient and more rapid oxidative conversion of cyclohexane to adipic
acid and thereby higher adipic acid yield.
In the presence of acidic water and absence of uv light irradiation, one can obtain a
reasonably good yields (43~46%) of adipic acid (see Table S1). Exposure of the
cyclohexane-acidic water-ozone system to photo irradiation can further promote higher
yields (73~77%) of adipic acid and higher mass balance values under the same condition
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(see Table S1). Photo irradiation will efficiently convert ozone molecules to singlet
O(1D), which can either directly react with cyclohexane/ intermediates or react with water
to generate hydroxyl radical, and thus accelerate the oxidation of cyclohexane to generate
higher boiling point intermediate (i.e., cyclohexanone, see discussion below about
reaction mechanisms). Formation of higher boiling point intermediate can better prevent
evaporation of reactants and thus higher final mass balance values.
We also investigated the effects of uv fluence and ozone flow rate on the yields of
adipic acid (see Tables S4 and S5). Higher uv light intensity will in general lead to
higher adipic acid yields and higher mass balance values. Higher ozone flow rate will in
general lead to higher adipic acid yields, and simultaneously accelerate the
reactant/intermediate evaporation rate and thus lower the mass balance values. To
compromise the pros and cons, a 0.45 mL/min flow was found to be the best for our
current reactor design.
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Table-S1. Effects of water and light irradiation on the yields of adipic acid using
cyclohexane as the starting substrate. The light intensity is 200 mW/cm2 at 310 nm (with
the distance between the 100 W Hg lamp and the reactor being 5 cm. The ozone flow
rate is 0.45 mL/min. The reaction vessel was equipped with chilled water-methanol
circulator (-5 to -10 oC) condenser (to trap evaporating reactant and intermediates).
Note: 1d is cyclohexanone, and 2b is adipic acid.
Substrates Products
%Yield
2b 55
%Conversion
65
%Selectivity
for 2
851d +10
Condition No. of run
neat, rt,15h
h
4
2b 53 64 831d +115
2b 51 61 841d +106
1b
2b 13 28 461d +15neat,rt,15h
dark
1
2b 14 27 521d +132
2b 14 30 471d +163
Massbalance
65
64
61
53
55
52
2b 77 86 891d +9+ 8 vol% aqueous
0.5 M HCl, RT,
15 h, h
10
2b 74 82 901d +811
2b 73 81 901d +812
2b 45 58 781d +13+ 8 vol% aqueous 0.5 M HCl, RT, 15 h, dark
7
2b 46 56 821d +108
2b 43 50 841d +79
58
56
51
86
82
81
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Table-S2. Effects of water and light irradiation on the yield of adipic acid using
cyclohexanol and cyclohexanone as the starting substrates. The light intensity is 200
mW/cm2 at 310 nm (with the distance between the 100 W Hg lamp and the reactor being
5 cm. The ozone flow rate is 0.45 mL/min. The reaction vessel was equipped with
chilled water-methanol circulator (-5 to -10 oC) condenser (to trap evaporating
reactants/intermediates). Note: 1d is cyclohexanone, and 2b is adipic acid.
Substrates Products
%Yield
2b 83
%Conversion
93
%Selectivity
for 2b
891d +10
Condition No. of run
neat,rt, 8h
h
4
2b 85 91 931d +65
2b 83 96 871d +136
2b 26 42 621d +161
2b 27 41 661d +142
2b 22 38 581d +163
Massbalance
98
97
98
96
97
98
1c
neat,rt, 8h
dark
OH
2b 88 88 991d +8neat,rt,8h
h
4
2b 92 92 991d +55
2b 89 89 991d +56
2b 28 28 991d +671
2b 34 34 991d +612
2b 27 27 991d +673
96
97
95
95
95
94
neat,rt, 8h
dark
O
1d
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Table S3. pH effect on the yield of adipic acid in the cyclohexane-water-ozone-uv
irradiation system. The light intensity is 200 mW/cm2 at 310 nm with the distance
between the 100 W Hg lamp and the reaction vessel being 5 cm. The ozone flow rate is
0.45 mL/min. The reaction vessel was equipped with chilled water-methanol circulator (-
5 to -10 oC) condenser (to trap evaporating reactants/intermediates). Note: 1d is
cyclohexanone, and 2b is adipic acid.
Substrates Products
%Yield
2b 63
%Conversion
73
%Selectivity
for 2b
861d +10
Condition No. of run
+ 8 vol% neutral
H2O, RT, 15h, h
1
2b 65 73 891d +82
2b 66 73 901d +73
1b
2b 33 48 691d +15+ 8 vol% neutral H2O, RT, 15h, dark
1
2b 34 47 721d +132
2b 36 48 751d +123
Massbalance
80
78
77
55
57
58
2b 22 32 691d +10+ 8 vol% aqueous 0.5 M NaOH, RT 15 h, dark
1
2b 40 55 731d +151
58
78+ 8 vol% aqueous 0.5 M NaOH, RT
15 h, h
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Table S4. Effect of uv fluorence on adipic acid yield. The ozone flow rate is 0.45 mL
per minute. The reaction vessel was equipped with chilled water-methanol circulator (-5
to -10 oC) condenser (to trap evaporating reactants). Note: 1d is cyclohexanone, and 2b
is adipic acid.
Substrates Products
%Yield
%Conversion %Selectivity for 2b
ConditionUV-light power density
(mW/cm2 at 310 nm)
(distance)
1b 2b 68 80 851d + 12
200 (5 cm) 2b 75 83 901d +8
150 (14 cm)
2b 60 73 821d +13100 (22 cm)
Massbalance
80
83
73
+ 8 vol% aqueous
0.5 M HCl,RT, 15h
h
Table S5. Effect of ozone flow rate on the yield of adipic acid. The light intensity is 200
mW/cm2 at 310 nm with the distance between the 100 W Hg lamp and the reactor being 5
cm. The reaction vessel was equipped with chilled water-methanol circulator (-5 to -10 oC) condenser (to trap evaporating reactants/intermediates). Note: 1d is cyclohexanone,
and 2b is adipic acid.
Substrates Products
%Yield %Conversion %Selectivity
for 2b
Condition O3 flow rate
(mL / minute)
1b
2b 68 73 931d + 51.0
2b 75 83 901d +80.45
Massbalance
73
83
+ 8 vol% aqueous
0.5 M HCl,RT, 15h
h
2b 55 80 691d +250.15 93
Measurements of intermediate/product concentrations during the reaction time course:
The concentrations of reactant and products were measured as a function of reaction
time course for two different systems, i.e., (a) neat cyclohexane and (b) cyclohexane-8
vol% aqueous 0.5 M HCl under ozone treatment and uv irradiation condition (see Fig.
S3(a) & S3(b) shown below). In the experiments, a constant amount of reaction solution
was removed from the bulk solution every 15 min, and added a fixed amount of 1,4-
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dicyanobenzene solution as an external standard for 1H NMR determination of product
concentrations. As shown in Fig. S3(a) below, both cyclohexanol and cyclohexanone
were detected as reaction intermediates in the case of neat cyclohexane, whereas in the
presence of acidic water only cyclohexanone was detected as the primary intermediate
and no cyclohexanol was detected during the reaction time course. Such a result
indicates that the major reaction pathways might be different for these two systems. As
described in the main text for neat cyclohexane, cyclohexane was oxidized by O(1D) to
form cyclohexanol, which was further oxidized by O(1D) to generate cyclohexanone, and
then to adipic acid. This reaction scheme matches well with the observation shown in Fig.
S3(a).
When in the presence of acidic water, the variation in the concentrations of
cyclohexane and products was shown in Fig. S3(b). Cyclohexanone, instead of
cyclohexanol, was observed as the primary intermediate for oxidative conversion of
cyclohexane to adipic acid. The concentration of cyclohexanol was too low to be
detected by 1H NMR.
Reaction Mechanism for dark conversion of neat cyclohexane to adipic acid by ozone.
It was reported that ozone can abstract hydrogen atom from saturated hydrocarbons to
form [R. .OOOH] radical pair, which then collapses to form highly unstable alkyl
trioxides (ROOOH), as evidenced by low temperature (-40 C) 1H NMR (34). The RO-
OOH then decomposes to form ROH and HOOH. Ozonation of neat cyclohexane in
dark is likely to follow a similar chemical route to generate cyclohexanol. Subsequent
hydrogen atom abstraction at the weakest C-H bond adjacent to the carbonyl position by
ozone will generate ketone-alpha trioxide intermediate which, upon decomposition of the
O-O and C-C bonds, will generate acid-aldehyde. The aldehyde moiety of the acid-
aldehyde intermediate can be easily oxidized by ozone in dark to become carboxylic acid,
leading to the formation of dicarboxylic adipic acid.
Reaction Mechanism for light induced ozonolytic conversion of neat cyclohexane to
adipic acid. Upon photo irradiation, ozone molecule will decompose to generate singlet
O(1D) atom, which initiates oxidative conversion of cyclohexane to adipic acid. A
possible reaction pathway for the neat cyclohexane-ozone-uv system is proposed in Fig.
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S4(i) to account for formation of adipic acid via selective C-H bond oxidation of
cyclohexane by O(1D). First, direct C-H bond insertion of O(
1D) into cyclohexane would
lead to formation of cyclohexanol (21), which is further oxidized by O(1D) at the weakest
methine C-H bond to form a geminal diol, 1,1’-dihydroxycyclohexane. Geminal diols are
known to be very unstable and will rapidly undergo dehydration to form stable ketones
(22). The bonding energies of methine C-H, methylene C-H, and O-H bonds are ca. ~96,
~99, and ~105 kcal/mol, respectively (23). Insertion of O(1D) into a C-H bond in
cyclohexane requires cleavage of one C-H bond and formation of two bonds (i.e., C-O
and O-H), which is exothermic and thermodynamically favored. Subsequent insertion of
O(1D) into the methine C-H bond of cyclohexanol is also thermodynamically favored.
Both cyclohexanol and cyclohexanone were isolated as stable intermediates upon short
time uv irradiation of cyclohexane in the presence of ozone. The conversion of
cyclohexanone to adipic acid by reaction with singlet O(1D) atom probably proceeds via
di-hydroxylation at the alpha C-H bond adjacent to the ketone functionality, since the
alpha C-H bond is weaker than other remote methylene C-H bonds. Decomposition of
the 1,1’-dihydroxycyclohexanone may undergo different pathways (paths a and b) to
generate two possible intermediates, i.e., 1-formyl hexanoic acid and
cyclohexanediketone (see Fig. S4(i)). Control experiments show that 1-formyl hexanoic
acid (2.3 M in CCl4) can be quantitatively converted to adipic acid within 20 min. upon
ozone treatment and uv irradiation at room temperature, whereas under the same
condition cyclohexanediketone was converted to pentanedioic acid, instead of adipic acid
(path b). The control experiments suggest that the conversion of cyclohexane,
cyclohexanol, and cyclohexanone to adipic acid likely occurs via the pathway a.
Alternatively, cyclohexanone may undergo tautomerization to become the enol form (see
the path c in Fig. S4(i)), which can then react with ozone in the dark to generate adipic
acid. The above scheme is supported by kinetic measurements of intermediate/product
concentrations during the reaction time course (see Fig. S3(a) and discussion above).
Reaction mechanisms for cyclohexane-acidic water-ozone-uv irradiation reaction.
Both ozone and O(1D) (generated by uv irradiation of ozone) are reported to react with
water to form hydroxyl radical (.OH) (see, equations 3 & 4 in Fig. S4(ii))(24, 25)
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Hydroxyl radical is known to abstract hydrogen atoms from various hydrocarbons with
slow rates (~5 x 107 M
-1s
-1) in dipolar and aprotic solvents (33), and initiate peroxidation
chain reaction in the presence of molecular oxygen to generate hydroperoxides (34). It is
possible that hydroxyl radical abstracts a hydrogen atom from cyclohexane to generate
cyclohexyl radical, which then reacts with molecular oxygen, followed by hydrogen atom
abstraction from another cyclohexane molecule, and to produce cyclohexyl
hydroperoxide (see equation (5) in Fig. S4(ii)). The cyclohexyl hydroperoxide, unstable
in the presence of trace amounts of metal ions, could then decompose to generate
cyclohexanone directly as the primary product without forming cyclohexanol. Selective
hydrogen atom abstraction of hydroxyl radical toward cyclohexanone at the weakest
alpha C-H position adjacent to the carbonyl group will lead to formation of alpha-keto
hydroperoxide, which decomposes to generate carboxylic acid-aldehyde, and then to
adipic acid upon air or ozone oxidation of the aldehyde moiety (see equation (6) in Fig.
S4(ii)).. The above proposed reaction scheme for hydroxyl radical-mediated oxidative
conversion of cyclohexane to cyclohexanone, and finally to adipic acid was supported by
the variation in the concentrations of cyclohexane, cyclohexanone and adipic acid during
the reaction time course (see data in Fig. S3(b)). The presence of hydroxyl radical in
cyclohexane-acidic water-ozone-uv irradiation system was confirmed by EPR
measurements (see the EPR data in Fig. S5). Besides the above proposed mechanisms,
the possibility of having other (minor) reaction pathways is not excluded.
EPR measurements of hydroxyl radicals:
EPR spectra (X band, 9.8 GHz, room temperature) were taken from samples of
cyclohexane-5 vol% aqueous 0.5 M HCl under ozone bubbling and uv light irradiation
(by 100 W Hg lamp irradiation) in the presence a radical trapping reagent, 5,5-Dimethyl-
1-pyrroline-N-oxide (DMPO, 2.5 x 10-2
M). The parameters used in the simulation are
the followings: g= 2.0070, coupling constant AN= 7.2 G, and ArH= Ar’H= 4.1 G. All
measurements were done at room temperature. By using DMPO as a spin trapping
reagent, we have detected the presence of hydroxyl radical (see the EPR spectra shown
below in Fig. S5) in both dark and photo conditions in the case of cyclohexane-acidic
water-ozone system. The observed EPR spectra for both light and dark conditions match
well with the simulated spectrum and are also the same as those reported in the literature,
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where the hydroxyl radical-DMPO adduct was oxidized (possibly by ozone) to become
DMPOX (35). (No EPR signal was detected in neat cyclohexane-ozone system in both
dark and light conditions.).
Pros and Cons of four different reaction processes. In the manuscript, we are reporting
four different processes for the synthesis of adipic acid, namely, (a) neat cyclohexane-
ozone-dark, (b) neat cyclohexane-ozone-light, (c) cyclohexane-acidic water-ozone-dark,
and (d) cyclohexane-acidic water-ozone-light (see results in Table S1). The advantage of
the process (a) is simple, but the adipic acid yield is too low and the mass balance is also
quite low, which is due to easy evaporation of low boiling point of cyclohexane by the
ozone gas flow. Photo irradiation of the neat cyclohexane-ozone system (i.e., the process
(b)) can dramatically improve the adipic acid yield to ~50 mol%, and also improve the
mass balance. The disadvantage of the process (b) is that it requires a photo irradiation
setup and additional photo-electricity consumption. Addition of acidic water to neat
cyclohexane in the dark (i.e., the process (c)) is very promising process for synthesis of
adipic acid, since this process can generate ~45 mol% of adipic acid, approaching to that
obtained by photo irradiation of neat cyclohexane-ozone system (i.e., the process (b)), but
without the need of additional photo-electricity consumption. The process (c) is better
than both the processes (a) and (b) in terms of simplicity and the adipic acid yield. The
disadvantages of the process (c) are that the adipic acid yield is below 50 mol% and
nearly 40 mol% of starting substrate/intermediates was lost via evaporation.
Combination of acidic water and photo irradiation (i.e., the process (d)) leads to the
highest adipic acid yield (~75 mol%) and the highest mass balance value (~82 mol%)
among all. The disadvantage of this process is the same as that for the process (b), that is,
the need for additional photo irradiation setup and photo-electricity consumption. In
general, the electricity-to-light conversion efficiency is low, 10~15%, for high pressure
Hg lamp, but 30% for uv LEDs. If uv LEDs were used as the light source, the increase
in the production cost of the process (d) over the process (c) may not be a true
disadvantage. Overall, the process (d) will provide faster production and lower cost for
production of adipic acid. since the ~ 1.67 fold increase in the adipic acid yield under the
same experimental condition and operation time is quite significant.
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Fig. S1.
Ozonolytic conversion of cyclohexane to adipic acid under uv photo irradiation.
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Fig. S2
ORTEP diagram of the solid product (2b) isolated from the cyclohexane-O3-uv
irradiation system.
Table S6. Crystal data and structure refinement for TWIN5.
Identification code twin5
Empirical formula C6 H10 O4
Formula weight 146.14
Temperature 100(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group P 21/c
Unit cell dimensions a = 7.1627(10) Å
b = 5.1358(7) Å
c = 9.9772(18) Å
Volume 343.08(9) Å3
Z 2
Density (calculated) 1.415 Mg/m3
Absorption coefficient 0.120 mm-1
F(000) 156
Crystal size 0.30 x 0.25 x 0.25 mm3
Theta range for data collection 3.042 to 26.411°.
Index ranges -8
-
Table S7. Atomic coordinates ( x 104) and equivalent isotropic displacement
parameters (Å2x 103) for TWIN5. U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
________________________________________________________________________
x y z U(eq)
________________________________________________________________________
C(1) 3297(4) 9097(5) 8088(3) 20(1)
C(2) 2092(4) 8365(6) 6573(3) 21(1)
C(3) 509(4) 10346(5) 5790(3) 21(1)
O(1) 4778(3) 7483(4) 8697(2) 27(1)
O(2) 2937(3) 10982(4) 8693(2) 26(1)
Table S8. Bond lengths [Å] and angles [°] for TWIN5.
_____________________________________________________
C(1)-O(2) 1.216(3)
C(1)-O(1) 1.313(3)
C(1)-C(2) 1.498(3)
C(2)-C(3) 1.517(4)
C(2)-H(2A) 0.9900
C(2)-H(2B) 0.9900
C(3)-C(3)#1 1.525(5)
C(3)-H(3A) 0.9900
C(3)-H(3B) 0.9900
O(1)-H(1) 0.8400
O(2)-C(1)-O(1) 123.5(2)
O(2)-C(1)-C(2) 123.5(2)
O(1)-C(1)-C(2) 112.9(2)
C(1)-C(2)-C(3) 114.1(2)
C(1)-C(2)-H(2A) 108.7
C(3)-C(2)-H(2A) 108.7
C(1)-C(2)-H(2B) 108.7
C(3)-C(2)-H(2B) 108.7
H(2A)-C(2)-H(2B) 107.6
C(2)-C(3)-C(3)#1 111.8(3)
C(2)-C(3)-H(3A) 109.3
C(3)#1-C(3)-H(3A) 109.3
C(2)-C(3)-H(3B) 109.3
C(3)#1-C(3)-H(3B) 109.3
H(3A)-C(3)-H(3B) 107.9
C(1)-O(1)-H(1) 109.5
_____________________________________________________________
Symmetry transformations used to generate equivalent atoms: #1 -x,-y+2,-z+1
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Table S9. Anisotropic displacement parameters (Å2x 103) for TWIN5. The
anisotropic displacement factor exponent takes the form: - 2[ h2 a*2U11 + ... + 2 h k
a* b* U12 ]
________________________________________________________________________
U11 U22 U33 U23 U13 U12
________________________________________________________________________
C(1) 19(1) 23(1) 18(1) 0(1) 6(1) -2(1)
C(2) 22(1) 22(1) 16(1) -3(1) 5(1) -2(1)
C(3) 22(1) 23(1) 18(1) -3(1) 5(1) 0(1)
O(1) 27(1) 31(1) 17(1) -6(1) 0(1) 7(1)
O(2) 26(1) 30(1) 18(1) -6(1) 2(1) 6(1)
________________________________________________________________________
Table S10. Hydrogen coordinates ( x 104) and isotropic displacement parameters (Å2x
10 3) for TWIN5.
________________________________________________________________________
x y z U(eq)
________________________________________________________________________
H(2A) 1434 6672 6576 25
H(2B) 3008 8131 6037 25
H(3A) 1134 12086 5869 26
H(3B) -507 10434 6250 26
H(1) 5457 8030 9520 41
________________________________________________________________________
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Fig. S3
Concentrations of cyclohexane, cyclohexanol, cyclohexanone, and adipic acid as a
function of reaction time in (a) neat cyclohexane, and (b) cyclohexane-8 vol% aqueous
0.5 M HCl-ozone-uv irradiation at room temperature. The solid lines are smooth
interpolation between data points.
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O3 100 W Hg lamp
HO
hv
O3
H HOH
O
HOH
O
O
HOOH
O
O
OO
OH
(isolated)(isolated)
O (1D) +
1O2
O(1D)
O(1D)
H
O(1D)
OOH
H
OH
OOH
X
HO
O O
OHO3
- CO2
path a
path b
O3
OH
O
OHO OH
path c
O3 (in dark)
O (1D) +
H2O 2
.OH
O3 + H2O
(1)
(2)
(3)
2 .OH + O2
.OH
O2
(4)
O
- H2O
O
HO OH HO H
O
OHO
OHO
O.OH/O2 O3
(5)
(ii) cyclohexane-H2O-O3-uv
(i) neat cyclohexane-O3-uv
O
.
O-O.
OOH
(6)
- H2O
Fig. S4
Plausible reaction mechanisms for oxidative conversion of (i) neat cyclohexane and (ii)
cyclohexane-8 vol% aqueous 0.5 M HCl to adipic acid under uv photo-irradiation.
-
Fig. S5
EPR spectra detected from a cyclohexane-acidic water-ozone system under uv light
irradiation (top) and in dark (middle). The bottom EPR spectrum is a simulated one
using the following parameters: g= 2.0070, coupling constant AN= 7.2 G, and ArH= Ar’H=
4.1 G. The top equation illustrates the reaction of a spin trapping reagent, DMPO, with
hydroxyl radical, followed by ozone oxidation of the DMPO-OH adduct to become stable
DMPOX radical, which is responsible for the observed EPR signal. The observed
hydroxyl radical EPR spectra are the same as those reported in the literature (35)
-
Fig. S6
ORTEP diagram of the solid product (compound 2g) isolated from the cycloheptane-O3-
uv irradiation system
Table S11. Crystal data and structure refinement for 140404LT_0m.
Identification code 140404LT_0m
Empirical formula C7 H12 O4
Formula weight 160.17
Temperature 100(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group C 2/c
Unit cell dimensions a = 17.7023(8) Å a= 90°.
b = 4.7139(2) Å b= 106.831(2)°.
c = 9.6336(4) Å g = 90°.
Volume 769.46(6) Å3
Z 4
Density (calculated) 1.383 Mg/m3
Absorption coefficient 0.113 mm-1
F(000) 344
Crystal size 0.30 x 0.28 x 0.13 mm3
Theta range for data collection 4.378 to 26.388°.
Index ranges -22
-
Table S12. Atomic coordinates ( x 104) and equivalent isotropic displacement
parameters (Å2x 103) for 140404LT_0m. U(eq) is defined as one third of the trace of
the orthogonalized Uij tensor.
________________________________________________________________________ x y z U(eq)
________________________________________________________________________
O(1) 7576(1) 10484(2) 3876(1) 16(1)
O(2) 8358(1) 6734(2) 4685(1) 16(1)
C(1) 8217(1) 8953(2) 3999(1) 13(1)
C(2) 8767(1) 10305(2) 3269(1) 17(1)
C(3) 9393(1) 8373(2) 2977(1) 15(1)
C(4) 10000 10126(3) 2500 14(1)
________________________________________________________________________
Table S13. Bond lengths [Å] and angles [°] for 140404LT_0m.
_____________________________________________________
O(1)-C(1) 1.3214(12)
O(1)-H(1) 0.890(15)
O(2)-C(1) 1.2237(13)
C(1)-C(2) 1.4984(13)
C(2)-C(3) 1.5221(14)
C(2)-H(4) 0.9900
C(2)-H(5) 0.9900
C(3)-C(4) 1.5278(12)
C(3)-H(3) 0.9900
C(3)-H(2) 0.9900
C(4)-C(3)#1 1.5278(12)
C(4)-H(6) 0.9900
C(4)-H(7) 0.9900
C(1)-O(1)-H(1) 110.2(9)
O(2)-C(1)-O(1) 123.39(9)
O(2)-C(1)-C(2) 123.99(9)
O(1)-C(1)-C(2) 112.56(9)
C(1)-C(2)-C(3) 116.06(9)
C(1)-C(2)-H(4) 108.3
C(3)-C(2)-H(4) 108.3
C(1)-C(2)-H(5) 108.3
C(3)-C(2)-H(5) 108.3
H(4)-C(2)-H(5) 107.4
C(2)-C(3)-C(4) 110.17(9)
C(2)-C(3)-H(3) 109.6
C(4)-C(3)-H(3) 109.6
-
C(2)-C(3)-H(2) 109.6
C(4)-C(3)-H(2) 109.6
H(3)-C(3)-H(2) 108.1
C(3)-C(4)-C(3)#1 114.50(12)
C(3)-C(4)-H(6) 108.6
C(3)#1-C(4)-H(6) 108.6
C(3)-C(4)-H(7) 108.6
C(3)#1-C(4)-H(7) 108.6
H(6)-C(4)-H(7) 107.6
_____________________________________________________________
Symmetry transformations used to generate equivalent atoms: #1 -x+2,y,-z+1/2
Table S14. Anisotropic displacement parameters (Å2x 103) for 140404LT_0m. The
anisotropic displacement factor exponent takes the form: -2p2[ h2 a*2U11 + ... + 2 h k
a* b* U12 ]
________________________________________________________________________
U11 U22 U33 U23 U13 U12
________________________________________________________________________
O(1) 14(1) 17(1) 22(1) 3(1) 11(1) 2(1)
O(2) 15(1) 17(1) 20(1) 3(1) 9(1) 1(1)
C(1) 12(1) 16(1) 13(1) -3(1) 5(1) -1(1)
C(2) 15(1) 16(1) 22(1) 4(1) 11(1) 2(1)
C(3) 14(1) 16(1) 19(1) 0(1) 10(1) 0(1)
C(4) 12(1) 15(1) 17(1) 0 8(1) 0
________________________________________________________________________
Table S15. Hydrogen coordinates ( x 104) and isotropic displacement parameters (Å2x
10 3) for 140404LT_0m.
________________________________________________________________________
x y z U(eq)
________________________________________________________________________
H(4) 9037 11906 3878 20
H(5) 8448 11107 2333 20
H(3) 9140 6993 2208 18
H(2) 9660 7300 3867 18
H(6) 10283 11367 3314 17
H(7) 9717 11367 1686 17
H(1) 7291(8) 9730(30) 4409(15) 21
________________________________________________________________________
Spectroscopic Data:
-
Glutaric acid (2a)(36) (CAS No.: 110-94-1)
White solid; 1H NMR (600 MHz, DMSO): δ 12.019 (b, 2 H), 2.230-2.123 (m, 4 H),
1.677-1.627 (m, 2 H); 13
C NMR (150 MHz, DMSO): δ 174.2, 32.8 and 20.0. NMR data
is in agreement with authentic commercially available sample.
Adipic acid (2b)(36, 37) (CAS No.: 124-04-9)
White solid; 1H NMR (600 MHz, CDCl3-DMSO): δ 2.246-2.224 (m, 4 H), 1.603-
1.580 (m, 4 H); 13
C NMR (150 MHz, CDCl3-DMSO): δ 175.1, 33.2, and 23.8.
NMR data is in agreement with authentic commercially available sample
Pimelic acid (heptanedioic acid) (2e)(36, 38) (CAS No.: 111-16-0)
White solid; 1H NMR (600 MHz, CDCl3-DMSO): δ 2.148-2.111 (m, 4 H), 1.491-
1.440 (m, 4 H), 1.244-1.93 (m, 2 H); 13
C NMR (150 MHz, CDCl3-DMSO): δ
-
175.9, 33.5, 28.2, and 24.1. NMR data is in agreement with authentic commercially
available sample.
Suberic acid (octanedioic acid) (2f)(36, 39) (CAS No.: 505-48-6)
White solid; 1H NMR (600 MHz, CDCl3): δ 2.133 (t, J= 7Hz, 4 H), 1.484-1.460
(m, 4 H), 1.221-1.197 (m, 4 H); 13
C NMR (150 MHz, CDCl3-DMSO): δ 175.9,
33.7, 28.4 and 24.3. NMR data is in agreement with authentic commercially available
sample.
6-oxoheptanoic acid (3g)(40, 41) (CAS No.: 3128-07-2)
White solid; 1H NMR (400 MHz, CDCl3): δ 2.456-2.433 (m, 2H), 2.363-2.339 (m,
2 H), 2.130 (s, 3H), 1.621-1.598 (m, 4H); 13
C NMR (100 MHz, CDCl3): δ 208.6,
178.5, 43.1,33.5, 29.8, 24.0 and 23.0. NMR data is in agreement with authentic
commercially available sample.
-
6-oxooctanoic acid (3h)(42) (CAS No.: 4233-57-2)
White solid; 1H NMR (600 MHz, CDCl3): δ 2.394-2.382 (m, 2H), 2.369-2.300 (m,
4H), 1.584-1.561 (m, 4H), 0.993 (t, J= 7.2 Hz, 3H); 13
C NMR (150 MHz, CDCl3):
δ 211.5, 179.6, 41.7, 35.8, 33.7, 24.0, 23.0 and 7.7.
Cyclodecane-1,6-dione (2i)
White solid; 1H NMR (400 MHz, CDCl3): δ 2.42-2.31 (t, 2H), 2.31-2.20 (m, 2H),
2.0 (s, 3H), 1.50-153 (m, 4H); 13
C NMR (100 MHz, CDCl3): δ 209.0, 176.3,
43.10, 33.6, 29.7, 24.0, 22.9 33.4, 24.1; HRMS calcd for C7H12O3: 144.0786,
found: 144.0780.
3,4-dihydronaphthalen-1(2H)-one (2j)(43) (CAS No.: 529-34-0)
Brown liquid; 1H NMR (400 MHz, CDCl3): δ 8.003 (d, J= 7.8 Hz, 1H), 7.435 (t,
J= 15 Hz, 1 H), 7.272 (t, J= 15 Hz, 1 H), 7.226 (t, J= 15.6 Hz, 1 H), 2.936 (t, J= 12
Hz, 2 H), 2.626 (t, J= 13.2 Hz, 2 H), 2.130-2.088 ( m, 2 H); 13
C NMR (100 MHz,
-
CDCl3): δ 198.2, 144.4, 133.3, 132.5, 128.6, 127.0, 126.5, 39.0, 29.6 and 23.2.
NMR data is in agreement with authentic commercially available sample.
2,3-dihydro-1H-inden-1-one (2k)(44) (CAS No.: 83-33-0)
Brown solid; 1H NMR (600 MHz, CDCl3): δ 7.698 (d, J=7.8 Hz, 1 H), 7.530 (t, J=
15 Hz, 1 H), 7.424 (d, J= 7.8 Hz, 1H), 7.310 (t, J= 13.8 Hz, 1 H), 3.085 (t, J= 12
Hz, 2 H), 2.636-2.616 (m, 2 H); 13
C NMR (150 MHz, CDCl3): δ 206.8, 155.0,
136.9, 134.4, 127.1, 126.5, 123.5, 36.0 and 25.6. NMR data are in agreements with
commercially available authentic samples.
-
(2g)
O
OH
O
HO
-
(2g)
O
OH
O
HO
-
References and Notes
1. Y. Wen, X. Wang, H. Wei, B. Li, P. Jin, L. Li, A large-scale continuous-flow process for the
production of adipic acid via catalytic oxidation of cyclohexene with H2O2. Green Chem.
14, 2868–2875 (2012). doi:10.1039/c2gc35677e
2. “Adipic acid (ADPA): 2014 world market outlook and forecast up to 2018” (Merchant
Research and Consulting, Birmingham, UK, 2014).
3. S. Van de Vyver, Y. Roma’n-Leshkov, Emerging catalytic processes for the production of
adipic acid. Catal. Sci. Technol. 3, 1465–1479 (2013). doi:10.1039/C3CY20728E
4. A. Castellan, J. C. J. Bart, S. Cavallaro, Industrial production and use of adipic acid. Catal.
Today 9, 237–254 (1991). doi:10.1016/0920-5861(91)80049-F
5. A. Chauvel, G. Lefebvre, Petrochemical Processes: Major Oxygenated, Chlorinated and
Nitrated (Editions Technip, Paris, 1989).
6. L. Schneider, M. Lazarus, A. Kollmuss, “Industrial N2O projects under the CDM: Adipic acid
- A case of carbon leakage?” Working paper WP-US-1006, Stockholm Environment
Institute, Somerville, MA, 2010.
7. F. Cavani, J. H. Teles, Sustainability in catalytic oxidation: An alternative approach or a
structural evolution? ChemSusChem 2, 508–534 (2009). Medline
doi:10.1002/cssc.200900020
8. R. A. Reimer, C. S. Slaten, M. Seapan, M. W. Lower, P. E. Tomlinson, Abatement of N2O
emissions produced in the adipic acid industry. Environ. Prog. 13, 134–137 (1994).
doi:10.1002/ep.670130217
9. K. Sato, M. Aoki, R. Noyori, A “green” route to adipic acid: Direct oxidation of cyclohexenes
with 30 percent hydrogen peroxide. Science 281, 1646–1647 (1998). Medline
doi:10.1126/science.281.5383.1646
10. U. Schuchardt, D. Cardoso, R. Sercheli, R. Pereira, R. S. da Cruz, M. C. Guerreiro, D.
Mandelli, E. V. Spinacé, E. L. Pires, Cyclohexane oxidation continues to be a challenge.
Appl. Catal. A 211, 1–17 (2001). doi:10.1016/S0926-860X(01)00472-0
11. M. N. Timofeeva, O. A. Kholdeeva, S. H. Jhung, J. S. Chang, Titanium and cerium-
containing mesoporous silicate materials as catalysts for oxidative cleavage of
cyclohexene with H2O2: A comparative study of catalytic activity and stability. Appl.
Catal. A Gen. 345, 195–200 (2008). doi:10.1016/j.apcata.2008.04.039
12. Z. Bohström, I. Rico-Lattes, K. Holmberg, Oxidation of cyclohexene into adipic acid in
aqueous dispersions of mesoporous oxides with built-in catalytical sites. Green Chem. 12,
1861–1869 (2010). doi:10.1039/c0gc00032a
13. Y. Deng, Z. Ma, K. Wang, J. Chen, Clean synthesis of adipic acid by direct oxidation of
cyclohexene with H2O2 over peroxytungstate–organic complex catalysts. Green Chem. 1,
275–276 (1999). doi:10.1039/a908889j
14. K. M. Draths, J. W. Frost, Environmentally compatible synthesis of adipic acid from D-
glucose. J. Am. Chem. Soc. 116, 399–400 (1994). doi:10.1021/ja00080a057
http://dx.doi.org/10.1039/c2gc35677ehttp://dx.doi.org/10.1039/C3CY20728Ehttp://dx.doi.org/10.1016/0920-5861(91)80049-Fhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19536755&dopt=Abstracthttp://dx.doi.org/10.1002/cssc.200900020http://dx.doi.org/10.1002/ep.670130217http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9733504&dopt=Abstracthttp://dx.doi.org/10.1126/science.281.5383.1646http://dx.doi.org/10.1016/S0926-860X(01)00472-0http://dx.doi.org/10.1016/j.apcata.2008.04.039http://dx.doi.org/10.1039/c0gc00032ahttp://dx.doi.org/10.1039/a908889jhttp://dx.doi.org/10.1021/ja00080a057
-
15. H.-K. Fun, S. Chantrapromma, L.-H. Ong, First order temperature dependent phase transition
in a monoclinic polymorph crystal of 1,6-hexanedioic acid: An interpretation based on
the landau theory approach. Molecules 19, 10137–10149 (2014). Medline
doi:10.3390/molecules190710137
16. B. Barletta, E. Bolzacchini, L. Fossati, S. Meinardi, M. Orlandi, B. Rindone, Metal-free
functionalization of the unactivated carbon-hydrogen bond: The oxidation of
cycloalkanes to cycloalkanones with ozone. Ozone Sci. Eng. 20, 91–98 (1998).
doi:10.1080/01919519808547278
17. Y. Matsumi, F. J. Comes, G. Hancock, A. Hofzumahaus, A. J. Hynes, M. Kawasaki, A. R.
Ravishankara, Quantum yields for production of O(1D) in the ultraviolet photolysis of
ozone: Recommendation based on evaluation of laboratory data. J. Geophys. Res. 107,
10.1029/2001JD000510 (2002). doi:10.1029/2001JD000510
18. Y. Matsumi, M. Kawasaki, Photolysis of atmospheric ozone in the ultraviolet region. Chem.
Rev. 103, 4767–4782 (2003). Medline doi:10.1021/cr0205255
19. P. Michaud, R. J. Cvetanovic, Reaction of the excited oxygen atoms O(1D2) with
cyclopentane. J. Phys. Chem. 76, 1375–1385 (1972). doi:10.1021/j100653a027
20. T. H. Varkony, S. Pass, Y. Mazur, Reaction of oxygen atoms with saturated hydrocarbons in
the liquid state. J. Chem. Soc. Chem. Commun. 1975, 457–458 (1975).
doi:10.1039/c39750000457
21. M. D. Hoops, B. S. Ault, Matrix isolation study of the photochemical reaction of
cyclohexane, cyclohexene, and cyclopropane with ozone. J. Mol. Struct. 929, 22–31
(2009). doi:10.1016/j.molstruc.2009.04.003
22. I. Ignatyev, M. Montejo, P. G. R. Ortega, J. J. L. González, Effect of substituents and
hydrogen bonding on barrier heights in dehydration reactions of carbon and silicon
geminal diols. Phys. Chem. Chem. Phys. 13, 18507–18515 (2011). Medline
doi:10.1039/c1cp21580a
23. S. J. Blanksby, G. B. Ellison, Bond dissociation energies of organic molecules. Acc. Chem.
Res. 36, 255–263 (2003). Medline doi:10.1021/ar020230d
24. E. Reisz, W. Schmidt, H. P. Schuchmann, C. von Sonntag, Photolysis of ozone in aqueous
solutions in the presence of tertiary butanol. Environ. Sci. Technol. 37, 1941–1948
(2003). Medline doi:10.1021/es0113100
25. B. J. Finlayson-Pitts, J. N. Pitts Jr., Tropospheric air pollution: Ozone, airborne toxics,
polycyclic aromatic hydrocarbons, and particles. Science 276, 1045–1052 (1997).
Medline doi:10.1126/science.276.5315.1045
26. M. S. Chen, M. C. White, A predictably selective aliphatic C-H oxidation reaction for
complex molecule synthesis. Science 318, 783–787 (2007). Medline
doi:10.1126/science.1148597
27. T. Newhouse, P. S. Baran, If C-H bonds could talk: Selective C-H bond oxidation. Angew.
Chem. Int. Ed. 50, 3362–3374 (2011). Medline doi:10.1002/anie.201006368
28. H. M. L. Davies, T. Hansen, M. R. Churchill, Catalytic asymmetric C-H activation of alkanes
and tetrahydrofuran. J. Am. Chem. Soc. 122, 3063–3070 (2000). doi:10.1021/ja994136c
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=25019557&dopt=Abstracthttp://dx.doi.org/10.3390/molecules190710137http://dx.doi.org/10.1080/01919519808547278http://dx.doi.org/10.1029/2001JD000510http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14664632&dopt=Abstracthttp://dx.doi.org/10.1021/cr0205255http://dx.doi.org/10.1021/j100653a027http://dx.doi.org/10.1039/c39750000457http://dx.doi.org/10.1016/j.molstruc.2009.04.003http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21946669&dopt=Abstracthttp://dx.doi.org/10.1039/c1cp21580ahttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12693923&dopt=Abstracthttp://dx.doi.org/10.1021/ar020230dhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12775069&dopt=Abstracthttp://dx.doi.org/10.1021/es0113100http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9148793&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9148793&dopt=Abstracthttp://dx.doi.org/10.1126/science.276.5315.1045http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17975062&dopt=Abstracthttp://dx.doi.org/10.1126/science.1148597http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21413105&dopt=Abstracthttp://dx.doi.org/10.1002/anie.201006368http://dx.doi.org/10.1021/ja994136c
-
29. K. Chen, A. Eschenmoser, P. S. Baran, Strain release in C-H bond activation? Angew. Chem.
Int. Ed. 48, 9705–9708 (2009) and references therein. Medline
doi:10.1002/anie.200904474
30. H. Varkony, S. Pass, Y. Mazur, Reactions of ozone with saturated hydrocarbons. ozone-
hydrocarbon complexes. J. Chem. Soc. Chem. Commun. 1974, 437–438 (1974).
doi:10.1039/c39740000437
31. S. I. Chan, C. Y.-C. Chien, C. S.-C. Yu, P. Nagababu, S. Maji, P. P.-Y. Chen, Efficient
catalytic oxidation of hydrocarbons mediated by tricopper clusters under mild conditions.
J. Catal. 293, 186–194 (2012). doi:10.1016/j.jcat.2012.06.024
32. K. Sehested, H. Corfitzen, J. Holcman, C. H. Fischer, E. J. Hart, The primary reaction in the
decomposition of ozone in acidic aqueous solutions. Environ. Sci. Technol. 25, 1589–
1596 (1991). doi:10.1021/es00021a010
33. S. Mitroka, S. Zimmeck, D. Troya, J. M. Tanko, How solvent modulates hydroxyl radical
reactivity in hydrogen atom abstractions. J. Am. Chem. Soc. 132, 2907–2913 (2010).
Medline doi:10.1021/ja903856t
34. J. Cerkovnik, E. Erzen, J. Koller, B. Plesnicar, Evidence for HOOO radicals in the formation
of alkyl hydrotrioxides (ROOOH) and hydrogen trioxide (HOOOH) in the ozonation of
C-H bonds in hydrocarbons. J. Am. Chem. Soc. 124, 404–409 (2002). Medline
doi:10.1021/ja017320i
35. E. Finkelstein, G. M. Rosen, E. J. Rauckman, Spin trapping of superoxide and hydroxyl
radical: Practical aspects. Arch. Biochem. Biophys. 200, 1–16 (1980). Medline
doi:10.1016/0003-9861(80)90323-9
36. O. Cloarec, M.-E. Dumas, A. Craig, R. H. Barton, J. Trygg, J. Hudson, C. Blancher, D.
Gauguier, J. C. Lindon, E. Holmes, J. Nicholson, Statistical total correlation
spectroscopy: An exploratory approach for latent biomarker identification from metabolic 1H NMR data sets. Anal. Chem. 77, 1282–1289 (2005). Medline doi:10.1021/ac048630x
37. A. K. Patra, A. Dutta, A. Bhaumik, Mesoporous core–shell Fenton nanocatalyst: A mild,
operationally simple approach to the synthesis of adipic acid. Chemistry 19, 12388–
12395 (2013). Medline doi:10.1002/chem.201301498
38. L. Rokhum, G. Bez, Excellent synthesis of adipic acid. Synth. Commun. 41, 548–552 (2011).
doi:10.1080/00397911003629408
39. S. Das, E. R. Rani, M. K. Mahanti, Kinetics and mechanism of the oxidative cleavage of
ketones by quinolinium dichromate. Kinet. Catal. 48, 381–389 (2007).
doi:10.1134/S0023158407030068
40. S. Biswas, S. Maiti, U. Jana, An efficient iron-catalyzed carbon–carbon single-bond cleavage
via retro-Claisen condensation: A mild and convenient approach to synthesize a variety
of esters or ketones. Eur. J. Org. Chem. 2010, 2861–2866 (2010).
doi:10.1002/ejoc.201000128
41. K. Miyamoto, Y. Sei, K. Yamaguchi, M. Ochiai, Iodomesitylene-catalyzed oxidative
cleavage of carbon-carbon double and triple bonds using m-chloroperbenzoic acid as a
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19937877&dopt=Abstracthttp://dx.doi.org/10.1002/anie.200904474http://dx.doi.org/10.1039/c39740000437http://dx.doi.org/10.1016/j.jcat.2012.06.024http://dx.doi.org/10.1021/es00021a010http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=20146469&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=20146469&dopt=Abstracthttp://dx.doi.org/10.1021/ja903856thttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11792209&dopt=Abstracthttp://dx.doi.org/10.1021/ja017320ihttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6244786&dopt=Abstracthttp://dx.doi.org/10.1016/0003-9861(80)90323-9http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15732908&dopt=Abstracthttp://dx.doi.org/10.1021/ac048630xhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=24167824&dopt=Abstracthttp://dx.doi.org/10.1002/chem.201301498http://dx.doi.org/10.1080/00397911003629408http://dx.doi.org/10.1134/S0023158407030068http://dx.doi.org/10.1002/ejoc.201000128
-
terminal oxidant. J. Am. Chem. Soc. 131, 1382–1383 (2009). Medline
doi:10.1021/ja808829t
42. T. Ashkenazi, A. Widberg, A. Nudelman, V. Wittenbach, D. Flint, Inhibitors of biotin
biosynthesis as potential herbicides: Part 2. Pest Manag. Sci. 61, 1024–1033 (2005).
Medline doi:10.1002/ps.1075
43. B. Chen, F. Li, Z. Huang, T. Lu, Y. Yuan, J. Yu, G. Yuan, Self-assembled nanostructures of
Ag6[PV3Mo9O40] with N-donor ligands and their catalytic activity. RSC Advances 2,
11449–11456 (2012). doi:10.1039/c2ra21858e
44. Y. Shimada, K. Hattori, N. Tada, T. Miura, A. Itoh, Facile aerobic photooxidation of alcohols
using 2-chloroanthraquinone under visible light irradiation. Synthesis 45, 2684–2688
(2013). doi:10.1055/s-0033-1338420
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19133783&dopt=Abstracthttp://dx.doi.org/10.1021/ja808829thttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15937974&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15937974&dopt=Abstracthttp://dx.doi.org/10.1002/ps.1075http://dx.doi.org/10.1039/c2ra21858ehttp://dx.doi.org/10.1055/s-0033-1338420