Perdecanoic acid as a safe and stable medium-chain peracid for Baeyer-Villiger oxidation of cyclic ketones to lactones

Article abstract of DOI:10.1039/c9ra06087a

Stability studies dedicated to high-energy compounds for a series of linear peracids (C₆-C₁₂), including sensitivity to mechanical impulse (shock and friction), as well as electrical (spark) and thermal sensitivity (temperature and heat of decomposition), were presented in this work for the first time. Studies revealed that all peracids were insensitive to shock, while in the case of the other sensitivity tests sharp differences between results for C₈ and C₁₀ peracids were observed. Taking into account the relatively high initial temperature of decomposition (above 64 °C) perdecanoic acid was selected as a safe alternative to commonly used hazardous short-chain peracids. Next, a new method for the Baeyer-Villiger oxidation was presented. Oxidation of 2-adamantanone was chosen as a model reaction. Peroctanoic, perdecanoic and perdodecanoic acids were tested as oxidants. Peroctanoic acid was the most reactive but taking into account both safety and kinetic issues, perdecanoic acid was selected for the further studies. The influence of reaction conditions on reaction rate was investigated. Optimized reaction conditions were suggested (two-fold molar excess of peracid with respect to the ketone, toluene as a solvent, 35 °C). This exploratory study offers promise with regard to the development of safer alternatives to peracetic acid in industrial oxidation.

Full text of DOI:10.1039/c9ra06087a

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PAPER
Perdecanoic acid as a safe and stable medium-
chain peracid for Baeyer–Villiger oxidation of cyclic
ketones to lactones†
Cite this: RSC Adv., 2019, 9, 30012
a
a
b
c
Magdalena Sitko, Anna Szelwicka, Andrzej Wojewodka, Andrzej Skwarek,
´
c
c
c
Dariusz Tadasiewicz, Lech Schimmelpfennig, Krzysztof Dziuba,
Magdalena Morawiec-Witczak and Anna Chrobok
c
a
*
Stability studies dedicated to high-energy compounds for a series of linear peracids (C
6
–C12), including
sensitivity to mechanical impulse (shock and friction), as well as electrical (spark) and thermal sensitivity
temperature and heat of decomposition), were presented in this work for the first time. Studies revealed
that all peracids were insensitive to shock, while in the case of the other sensitivity tests sharp
(
differences between results for C
8
and C10 peracids were observed. Taking into account the relatively
ꢀ
high initial temperature of decomposition (above 64 C) perdecanoic acid was selected as a safe
alternative to commonly used hazardous short-chain peracids. Next, a new method for the Baeyer–
Villiger oxidation was presented. Oxidation of 2-adamantanone was chosen as a model reaction.
Peroctanoic, perdecanoic and perdodecanoic acids were tested as oxidants. Peroctanoic acid was the
most reactive but taking into account both safety and kinetic issues, perdecanoic acid was selected for
the further studies. The influence of reaction conditions on reaction rate was investigated. Optimized
reaction conditions were suggested (two-fold molar excess of peracid with respect to the ketone,
Received 5th August 2019
Accepted 15th September 2019
DOI: 10.1039/c9ra06087a
ꢀ
toluene as a solvent, 35 C). This exploratory study offers promise with regard to the development of
rsc.li/rsc-advances
safer alternatives to peracetic acid in industrial oxidation.
The shorter the alkyl chain the more unstable the peracid is.
This is the result of higher percentage share of active oxygen in
Introduction
Peracids are characterized by high oxidation potential and the molar mass of peracid. The average dissociation energy of
ꢁ1
therefore are very reactive oxidizing species. The peroxy bond is the peroxy bond of peracids is low (ca. 90 kJ mol ) which
weak and can be cleaved readily which results in low stability of causes the lowest stability in the group of organic peroxides.
peracids. Peracids can decompose spontaneously and explo- Perbenzoic acid caused skin tumors in mice but it is safer than
3
sively under thermal or mechanical stress (shock, impact, fric- peracetic or performic acid. However, there are no appropriate
tion), and can undergo uncontrolled decomposition which can results for safety measures for this species. Short-chain
1,2
be catalysed by organic or metal compounds. Therefore, per- aliphatic peracids are miscible with water while the longer-
acids are treated as explosive materials and are covered by chain (C
special regulations for shipping and storage. Stabilising exhibited low toxicity on animals and longer-chain are non-toxic
6
and higher) are not. As a result short-chain peracids
1
compounds (metal salts and chelating agents) are very oen and non-irritant. A series of tests are performed to assess the
3
added to increase the storage ability of the peracid.
hazard with handling of peracids, such as detonation ability,
shock, heat and friction sensitivity. The most popular peracids
are the short-chain and the hazard with handling with these
hazardous materials limits their commercial application. For
example, the transport and storage of peracetic acid is
a
Department of Chemical Organic Technology and Petrochemistry, Silesian University
of Technology, Krzywoustego 4, 44-100 Gliwice, Poland. E-mail: Anna.Chrobok@polsl.
pl
2,4,5
prohibited.
b
In industrial practice performic or peracetic acid are very
Department of Inorganic Chemistry, Analytical Chemistry and Electrochemistry,
Silesian University of Technology, Krzywoustego 6, 44-100 Gliwice, Poland
oen generated in situ from adequate carboxylic acid or alde-
c
Grupa Azoty Zakłady Azotowe Puławy S.A., Tysi a˛ clecia Pa n´ stwa Polskiego 13, 24-110 hyde to increase process safety. Peracids are the commonly-
Puławy, Poland
applied oxidizing agents, used also in a standard protocol for
1
†
Electronic supplementary information (ESI) available: Elemental analysis,
H
6
Baeyer–Villiger oxidation of ketones to lactones. Lactones are
13
and
C
NMR spectra of peracids, detailed data concerning peracids

ne chemical products with many potential applications, e.g. in
sensitivities to friction, shock, electric spark, and thermal stability of peracids.
See DOI: 10.1039/c9ra06087a
7
–9
polymers, pharmaceuticals and agrochemicals industry.
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The production of the most important lactones in the
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1
13
H NMR spectra were recorded at 600 MHz, and C NMR
industry is still based on peracid acid, e.g. the production of spectra were recorded at 150 MHz using a Varian system.
useful monomer 3-caprolactone (world production 40–60 KTA). Samples were analysed in the form of solutions in CDCl and
3
3
-Caprolactone is manufactured by the oxidation of cyclohexa- TMS was used as an internal reference (d ¼ 0 ppm).
10
none with peracetic acid (Perstorp AB). The reaction is carried
The determination of carbon, hydrogen and nitrogen
out in two reactors: rst is used for peracetic acid synthesis and content in peracid molecules was carried out based on
in the second one the oxidation of cyclohexanone is carried out. elemental analysis using Vario MICRO cube automatic analyser.
Alternatively, BASF produces 3-caprolactone by the oxidation of For each peracid the analysis was performed three times using
cyclohexanone with peracetic acid generated in situ by the samples of approximately 3 mg.
aerobic oxidation of acetaldehyde in the same reactor to avoid
problems with peracetic acid safety issue.
Purity of peroxyacids, as well as the content of peroxy groups
in the post-reaction mixtures were determined by iodometric
11
The use of medium chain peracid (the most oen used titration. A weighted sample (ca. 0.100–0.200 g) and 20 mL of
perC ) is known from chemo-enzymatic Baeyer–Villiger oxida- glacial acetic acid were introduced to the 250 mL-Erlenmeyer
8
tion. In this variant, the carboxylic acid is oxidized to peracid in ask. The ask was purged with argon for 25 seconds and
situ in the presence of lipase B Candida antarctica and next the a pinch of sodium iodide was added. Aer closing, the ask was
12,13
freshly generated peracid oxidizes ketone to lactone.
placed in the dark for 30 minutes. Then 20 mL of distilled water
The only literature data concerning the application and and 5 drops of starch were added and the mixture was titrated
stability studies of longer chain peracids is the application of by the 0.1 M aqueous solution of sodium thiosulphate. A molar
dodecanebis(peroxoic acid) in the selective oxidation of content of peroxy groups was calculated according to an equa-
aliphatic amines to oxime or bromination of aminoanthracene- tion n ¼ 0.5cV [mol], where: 0.5 – coefficient calculated based
T
14,15
ꢁ
+
ꢁ
9,10-dione.
2
Nevertheless, high stability at room temperature on the stoichiometry of the reactions 2I + 3H + OOH / I +
2
ꢁ
1
2ꢁ
ꢁ
and non-shock sensitive in nature was conrmed only with 2H
DSC. of the titrant [mol L ], V
Herein, we present for the rst time stability tests for
2
O and I
2
+ 2S
2
O
3
/ S
4
O
6
+ 2I , c – molar concentration
– volume of the titrant [L].
ꢁ
T
The test for peracids shock sensitivity was carried out
medium-chain aliphatic peracids (C
6
–C12) which can be the safe according to the PN-EN 13631-4 standard using the BAM
alternative to very reactive short-chain analogues. Furthermore, apparatus equipped with 3 different weights: 1, 5, and 10 kg. A
the goal of this work was to design an innovative, safe process sample of the tested peracid was placed in the shock set. This
for the synthesis of lactones in Baeyer–Villiger oxidation based set was then placed centrally on the anvil and the specic weight
on extremely stable perdecanoic acid as oxidant. The studies was installed at the height, that corresponds to its appropriate
emerged the “forgotten oxidants” as very reactive but still safe potential energy. The weight was then released and it was
oxidants. Replacing of short-chain peracids with less hazardous observed whether there was any reaction (sound effects, ame).
medium-chain peracids may lead to an economically viable The test was continued until no reaction occurred in 6 consec-
process in the industry. Moreover, application of oxidant utive trials for a specic energy value.
analogue, which minimize the potential for chemical accidents,
The test for peracids friction sensitivity was carried out
including explosions, is in compliance with the idea of green according to the PN-EN 13631-3 standard using the Peters
chemistry.
apparatus, determining the upper limit of insensitivity, the
lower limit of sensitivity, and the value of E50 (energy under
which the tested substance is initiated with 50% probability).
The test was carried out by placing a small sample of peroxyacid
on a porcelain plate, then the plate was placed in the apparatus,
Experimental
Materials and methods
Ketones, hexanoic, octanoic, decanoic and dodecanoic acids and a stamp was placed at one end of the sample. During the
were purchased from Sigma-Aldrich. Toluene, dichloro- test the sample was moving under the stamp and it was
methane, acetonitrile, glacial acetic acid and H
were purchased from Chempur, while aqueous 50 wt% H
2
SO
4
95 wt% observed whether there was any reaction (bang, crack, ame,
visible mark on the plate). The test was started with the force of
2 2
O
solution in water, 0.1 M aqueous solution of sodium thio- 360 N and continued until no reaction occurred in 6 consecutive
sulphate and sodium iodide were purchased from Avantor trials for a specic force value.
Performance Materials.
The test for peracids electric spark sensitivity was carried out
GC analyses were performed using a PerkinElmer Clarus 500 using the apparatus consists of a source of a constant voltage,
equipped with an SPB™-5 column (30 m ꢂ 0.2 mm ꢂ 0.2 mm a system of capacitors, and two special electrodes. The capaci-

lm) and a ame ionization detector (FID). Yields were deter- tors of an adequate capacity were selected for the tests, and their
mined based on calibration curves; n-decane was used as an connection method and voltage values were changed to achieve
internal standard.
specic energy of the electric spark. The sample of tested per-
Melting points of peracids were determined using EZ-Melt oxyacid was placed in a special metal mold and covered with
ꢀ
apparatus (maximum temperature range: 20–400
C). a foil disc with an opening for the electrode needle. The sample
Measurements were performed in a capillary using 5 mg of each was placed on the bottom electrode, then the electrodes were
ꢀ
sample. Temperature range were set as 28–65 C in heating rate brought so close that the needle of the positive (top) electrode
ꢀ
ꢁ1
of 0.5 C min
.
touched the foil disc. When the energy value was selected, the
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capacitors were charged and the test was started, which caused ask, to which toluene (2 mL) and n-decane (0.10 mmol,
a ashover between the electrodes. It was observed whether external standard) were added. Then, peracid (1.34 mmol) was
a reaction occurred (presence of smoke, smell of burning, or added. The ask was equipped with a reux condenser, sealed
ꢀ
smudging of the mass of the sample). The test was continued with a septum and then mixed on magnetic stirrer at 25–45 C
until no reaction occurred in 6 consecutive trials for a specic for 10–120 min (1200 rpm), depending on the reaction rate.
energy value.
Periodically, during the reaction, 10 mL of the samples diluted
Thermal stability of peracids was determined by the differ- with dichloromethane were collected to monitor the progress of
ential scanning calorimetry method (DSC) using the Mettler- the reaction using GC. The yields of the lactone were in the
Toledo DSC 822e differential scanning calorimeter. Samples range 96–99%.
ꢀ
ꢀ
ꢁ
of approximately 3 mg were heated from ꢁ65 C to 150 C in
1
a nitrogen atmosphere with a ow rate of 60 mL min at
ꢀ
ꢁ1
a heating rate of 2, 5, and 10 C min
.
Results and discussion
Stability tests
Synthetic procedures
In order to study the stability of medium chain peracids, four
General procedure for the synthesis of peracids. Perhex- selected peracids of an even number of carbon atoms (C –C )
6
12
anoic, peroctanoic, perdecanoic, and perdodecanoic acids were were synthesized according to the procedure described in the
16
synthesized based on the procedure described in the literature. In the reaction of aliphatic acids with 50 wt%
16
literature.
aqueous solution of H O in the presence of 95 wt% of H SO as
2 2 2 4
Carboxylic acid (20.0 g, 0.10–0.17 mol) dissolved in 95 wt% catalyst and reaction medium the peracids were synthesized
sulphuric acid (40.0 g) was introduced into a high 250 mL with high yields (90–95%) and purities (100%). The only
beaker, equipped with a mechanic stirrer and placed in ice-bath exception was perhexanoic acid which was obtained as 86 wt%
ꢀ
to cool (10 C). Aer stabilization of the temperature, the solution in hexanoic acid with 75% yield. Unfortunately, aer
ꢀ
5
0 wt% aqueous solution of hydrogen peroxide (1.5 eq.) was two weeks of storage in 20 C the decomposition of perhexanoic
carefully dropwised for 10 min, taking care to not exceed the acid was observed up to 55 wt% (Table 1). The structure and
ꢀ
1
13
temperature of the mixture above 30 C. Aer addition of the purity of peracids were conrmed with H and C NMR
oxidant, the mixture was stirred at 1000 rpm for 50 min. Next, (Fig. S1–S6†) as well as elemental analysis (Table S1†).
ice water (ca. 150 mL) was slowly added to the beaker, and
Next, peracids were studied in a series of special tests dedi-
peracid crystallized as a white solid. The content of the beaker cated for high-energy compounds, including sensitivity to
was transferred to a separating funnel and extracted with mechanical impulse (shock and friction), as well as electrical
diethyl ether (5 ꢂ 30 mL). The organic phase was washed with (spark) and thermal sensitivity (temperature and heat of
water (20 mL) and dried over anhydrous MgSO . Aer ltration, decomposition).
4
the ltrate was carefully evaporated on a vacuum rotary evapo-
The test for sensitivity of peracids to friction was based on
ꢀ
rator at 25 C. Crude peracid was recrystallized from petroleum the observation of the effects of an explosive reaction (or lack
ꢀ
ꢀ
ether (10 mL/1 g of the peracid) at ꢁ20 C (ꢁ30 C for perhex- thereof) of the sample exposed to friction of a specic force
anoic acid). The product was then ltered off under vacuum and (Fig. S7, Tables S2–S5†). The test determining sensitivity of
washed with a cold petroleum ether (10 mL). The yields of peracids to shock was based on the observation of the effects of
peracids were in the range of 90–95%, except of perhexanoic an explosive reaction (or lack thereof) of the sample, which was
acid (75%).
Peroctanoic acid. H NMR (600 MHz, CDCl
exposed to shock of a specic energy (Tables S6–S9†). The
, TMS): d/ppm sensitivity of peracids to the electric spark was determined
1
3
0
7
.85–0.95 (m, 3H), 1.24–1.39 (m, 8H), 1.72 (dt, J ¼ 15.0 Hz, J ¼ based on the observation of the effects of an explosive reaction
.5 Hz, 2H), 2.43 (dd, J ¼ 8.7 Hz, J ¼ 6.3 Hz, 2H), 11.36 (s, 1H). (or lack thereof) of the sample, which was exposed to an electric
1
3
C NMR (600 MHz, CDCl , TMS): d/ppm 14.17, 22.70, 24.79, spark of a specic energy (Tables S10–S12†). For all types of tests
3
2
8.87, 29.04, 30.58, 31.69, 174.83.
Perdecanoic acid. H NMR (600 MHz, CDCl
both sensitivity and insensitivity limits were determined, as
, TMS): d/ppm samples were tested rst increasing and then decreasing the
1
3
0
2
.88 (t, J ¼ 6.8 Hz, 3H), 1.18–1.40 (m, 12H), 1.61–1.76 (m, 2H), intensity of each stimulus (Table 2).
13
.41 (t, J ¼ 7.5 Hz, 2H), 11.36 (s, 1H). C NMR (600 MHz, CDCl ,
3
TMS): d/ppm 14.23, 22.80, 24.79, 29.08, 29.20, 29.35, 29.46,
3
0.58, 31.98, 174.82.
Perdodecanoic acid. H NMR (600 MHz, CDCl
Table 1 Characteristics of synthesized peracids
1
3
, TMS): d/ppm
ꢀ
a
Peracid
Melting point ( C)
Purity (wt%)
0
2
.88 (t, J ¼ 6.8 Hz, 3H), 1.19–1.39 (m, 16H), 1.64–1.75 (m, 2H),
1
3
.41 (t, J ¼ 7.5 Hz, 2H), 11.36 (s, 1H). C NMR (600 MHz, CDCl
3
,
b
c
C
C
5
H
H
11COOOH (perC
15COOOH (perC
6
)
)
<RT
86 /55
TMS): d/ppm 14.25, 22.84, 24.79, 29.09, 29.21, 29.47, 29.50,
7
8
31.5–32.6
42.7–43.3
49.5–50.5
100
100
100
29.69, 29.73, 30.58, 32.05, 174.83.
C9H19COOOH (perC10)
11
C H23COOOH (perC12)
General procedure for the Baeyer–Villiger oxidation of cyclic
ketones in the presence of synthesized peracids. A ketone (0.67
mmol) was introduced into a two-neck 10 mL round-bottom
a
c
b
Calculated based on the iodometric titration. Just aer synthesis.
ꢀ
Aer 2 weeks of storage at ꢁ20 C, prior to stability analysis.
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Table 2 Sensitivities of peracids to shock, friction, and electric spark
Shock, energy/J
Friction, force/N
Electric spark, energy/J
Sensitivity
limit
Insensitivity
limit
Sensitivity
limit
Insensitivity
limit
Sensitivity
limit
Insensitivity
limit
Peracid
perC
perC
perC10
perC12
6
n/a
n/a
n/a
n/a
>50
>50
>50
>50
47
64
110
118
41
60
106
110
—
—
8
0.62
13.50
12.62
0.56
12.62
11.76
Thermal behavior of peroctanoic, perdecanoic and perdo-
decanoic acids was also tested, based on differential scanning
calorimetry (DSC) measurements. The results were depended
on the heating rate (Table S13†), but generally the thermograms
revealed narrow and sharp peaks of melting process with rela-
tively regular heat, followed by broad peaks of decomposition
with irregular heat (Fig. 1).
The temperature of decomposition of tested peracids
increased proportionally to their molar mass, and they
decomposed slowly at relatively high temperature (initial
ꢀ
ꢀ
temperature 64–70 C, maximum temperature 92–109 C). A
large amount of heat was released during decomposition, the
ꢁ1
highest for perdecanoic acid (more than 1000 kJ kg , Table 3).
Comparing to the literature data for 50 wt% aqueous solution of
peracetic acid, both lower temperatures and higher heat of
decomposition illustrate the dangerous nature of peracetic acid.
ꢀ
ꢁ1
.
Fig. 1 DSC of perdecanoic acid at a heating rate of 10 C min
17
According to the tests, all peracids are insensitive to shock The longer alkyl chain in peracid the higher stability and
energy of 50 J, which is the insensitivity limit for the high-energy usability in practice, e.g. as oxidation agent. Based on these
compounds. They are therefore resistant to this type of impulse. results the perdecanoic acid is the most promising for the
The results showed that peroctanoic acid has a signicantly application as safe oxidant in chemical reactions from the
lower limits for sensitivities to friction and electric spark than process safety point of view.
peracids with longer alkyl chain. In the case of friction the limit
is over two times lower, while for electric spark it is over twenty
times lower than for C10 and C12 peracids.
Interestingly, perdecanoic and perdodecanoic acids are
characterized by almost the same sensitivity limits for the tested
Baeyer–Villiger oxidation with peracids as oxidants
In order to demonstrate the reactivity of longer alkyl chain
peracids the Baeyer–Villiger oxidation of cyclic ketones to
lactones was chosen as a model reaction. For initial studies the
types of stimulus. Due to technical limitations determination of
sensitivity of perhexanoic acid to electric spark was not
oxidation of 2-adamantanone was tested (Scheme 1) started
possible; however, taking into account friction sensitivity as
with 2-fold molar excess of peracid as oxidation agent. The
well as decomposition during storage, this peracid cannot be
reaction was carried out at ambient temperature and toluene
considered as a safe compound, and was eliminated on this
was used as a solvent.
stage of studies.
The longer the alkyl chain in peracid the lower reactivity was
observed which is related to a decrease of percentage share of
active oxygen in the oxidant molecule. For peroctanoic acid the
Table 3 Thermal stability of peracids (recorded for the heating rate reaction was completed aer 40 min, while in the case of per-
ꢀ
ꢁ1
5
C min )
dodecanoic only 70% of lactone yield was obtained in the same
Heat of decomposition/kJ
Tmax/ C kg
ꢀ
ꢀ
ꢁ1
Peracid
perC
perC10
perC12
T
initial/ C
8
69.7
64.2
68.7
38.1
92.2
96.2
109.0
62.0
314
1036
734
a,17
5
0 wt% aq. perC
2
1503
a
ꢀ
ꢁ1
Heating rate 4 C min
.
Scheme 1 Model Baeyer–Villiger oxidation of 2-adamantanone to 4-
oxatricyclo[4.3.1.1 ]undecan-5-one.
3,8
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Fig. 4 The influence of the temperature for the model oxidation of 2-
adamantanone. Reaction conditions: 2-adamantanone (0.100 g, 0.67
mmol), perdecanoic acid (1.34 mmol), toluene (2 mL), 1200 rpm.
Fig. 2 The activity of peracids in the model oxidation of 2-ada-
mantanone. Reaction conditions: 2-adamantanone (0.100 g, 0.67
ꢀ
mmol), peracid (1.34 mmol), toluene (2 mL), 25 C, 1200 rpm.
excess of perdecanoic acid in respect to the ketone. Lower
amounts of oxidant caused a visible decrease of the reaction
rate, and only 86% (1.5 eq. of peracid) and 79% (equimolar
amount) yields of lactone were obtained in 30 minutes.
time. Taking into account both safety and kinetic issues, per-
decanoic acid was selected to the further studies (Fig. 2).
Additionally, the inuence of various solvents (dichloro-
methane, toluene and acetonitrile) for model reaction was
examined (Fig. 3). Lactone was obtained almost quantitatively
in 60 min at ambient temperature in each case, but the highest
initial reaction rate was observed when dichloromethane was
applied. However, because of environmental issues, toluene is
preferred.
Besides the reaction rate, the safety issues and the easy work
up are also the key factors which inuence the economic
aspects. The concentration of peracid in the post-reaction
mixture should be taken into the consideration. Due to the
safety reasons peroxy groups must be removed from the post-
reaction mixture prior to separation of the product. The
concentrations of peracid before and aer the oxidation of
ketone, depending on a molar ratio of ketone to peracid in
various temperatures were studied (Table 4). The higher
concentration of peracid led to the faster reaction but the
content of unreacted peroxy group also increased. The appli-
cation of molar ratio higher than 1 : 2 (ketone : peracid) is
unreasonable. For the experiments using a xed two-fold molar
Temperature of the oxidation process had a signicant
inuence on the reaction rate (Fig. 4). The reactions were
ꢀ
carried out at 25, 35, 45 and 55 C. High reaction rate, low
residence time creates possibility in the future to use contin-
uous ow reactor, instead of batch approach, what is of
signicant importance for industrial scale production.
In the next step molar ratio of the oxidant to the ketone was
studied (Fig. 5). The conversion of ketone to lactone was almost
ꢀ
full in 30 minutes at 35 C for the three- and two-fold molar
Fig. 5 The influence of molar ratio ketone : oxidant for the model
Fig. 3 The influence of the solvent for the model oxidation of 2- oxidation of 2-adamantanone. Reaction conditions: 2-adamantanone
ꢀ
adamantanone. Reaction conditions: 2-adamantanone (0.100 g, 0.67 (0.100 g, 0.67 mmol), perdecanoic acid, toluene (2 mL), 35 C,
ꢀ
mmol), perdecanoic acid (1.34 mmol), solvent (2 mL), 25 C, 1200 rpm. 1200 rpm.
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Table 4 The concentration of peroxy group before reaction (C
0
) and in the post-reaction mixture (C
1
) for the model oxidation of 2-
adamantanone
ꢀ
Molar ratio ketone : peracid
Temp./ C
C
0
/wt%
Time/min
Yield of lactone/%
1
C /wt%
1
1
1
1
1
1
1
1
1
1
: 1
: 1.5
: 2
: 3
: 2
: 2
: 2
: 2
: 2
: 2
35
35
35
35
25
35
45
55
60
6.6
9.8
60
60
45
30
90
60
30
15
88
96
99
99
99
99
99
99
99
99
0.7
3.2
6.5
12.3
6.6
6.5
6.5
6.1
6.0
5.6
1.1
12.2
17.5
12.3
12.3
12.4
12.3
12.4
12.4
45
30
45
a
a
70
60 in total
a
ꢀ ꢀ
0 min of the reaction at 45 C and then 30 min of mixing at 70 C.
3
ꢀ
excess of perdecanoic acid at the temperatures in the range of starts at 64.2 C. Slow decomposition of perdecanoic acid might
ꢀ
2
5 to 60 C the post-reaction peroxy group content was almost be useful to controlled removal of unreacted oxidant. An
ꢀ
on the same level till 45 C and started slightly decrease from experiment in which aer 30 minutes of oxidation of 2-ada-
5 C. It can be the result of initial decomposition of peracid. mantanone at 45 C, the mixing was continued by another 30
From DSC data thermal decomposition of perdecanoic acid minutes at 70 C, revealed that only minor quantity of perde-
canoic acid was determined in the post-reaction mixture (about
ꢀ
ꢀ
5
ꢀ
1
wt%).
a
Table 5 Oxidation of various ketones to lactones
Finally, the favourable reaction conditions were applied to
demonstrate the robustness of the method (Table 5). The
most reactive were cyclobutanone and 2-adamantanone, and
full conversion of ketones was reached aer 1 h. The oxida-
tion of more resistant cyclohexanones was completed in 5 h
while the norcamphor was converted in 3 h. Cycloheptanone,
which is extremely unreactive due to very stable structure,
Ketone
Lactone
Time
Yield/%
99
4
3
5 min
h
(
lack of ring strain) did not undergo oxidation under these
conditions.
95
1
9
h
94
97
Conclusions
0 min
Increasingly stringent environmental regulations of industrial
processes, mostly with regard to safety, forced the modication
of a number of chemical processes, specially oxidation
processes. The results discussed above expanded and developed
safe oxidants based on medium-chain peracids. The key devel-
opment was to perform stability tests for several linear peracids
4
5
h
h
94
97
4
5
h
h
93
96
6
(C –C12), which were used very rarely as oxidants. This work
delivered a new knowledge concerning sensitivity of studied
peracids to mechanical impulse (shock and friction), as well as
electrical (spark) and thermal sensitivity (temperature and heat
of decomposition). These fundamental stability studies resulted
in the emergence of safe oxidants. Perdecanoic acid was used as
oxidant in the Baeyer–Villiger oxidation for the rst time. Per-
acid was demonstrated to be very robust in terms of substrate
scope. High yields of lactones (up to 99%) were obtained aer
relatively short reaction times (45 min to 5 h), at near-ambient
4
5
h
h
94
96
5
h
3%
ꢀ
temperature (35 C). Moving onto the continuous ow system
could have signicantly inuenced the efficiency of the process,
a
Reaction conditions: ketone (0.67 mmol), perdecanoic acid (1.34
mmol), toluene (2 mL), 35 C, 1200 rpm; yield determined on GC.
ꢀ
but such experiments are beyond the scope of this paper.
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Paper
In summary, in this work it has been demonstrated how
stability studies can underpin rational design of oxidant that in
turn lead to a both safer and economically viable process.
4 H. Klenk, P. H. G ¨o tz, R. Siegmeier and W. Mayr, Peroxy
Compounds Organic, Ullmann's Encyclopedia of Industrial
Chemistry, 2000.
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T. Luukkonen and S. O. Pehkonen, Crit. Rev. Environ. Sci.
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This work was supported by The National Centre for Research
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30018 | RSC Adv., 2019, 9, 30012–30018
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