Thermal Decomposition of Percarboxylates
J . Org. Chem., Vol. 63, No. 12, 1998 3819
Ta ble 8. P r oton NMR Sp ectr a l Da ta for 1-4
3
3 or on a Beckmann Acculab spectrophotometer. NMR
spectra were recorded on a Varian T-60 spectrophotometer
CCl solvent, TMS internal standard), on a J EOL-J NM-MH-
00 spectrophotometer (CDCl solvent, TMS internal standard)
or on a J EOL-J NM-FX-60 spectrophotometer (CDCl solvent,
perester
δ values (ppm) (from TMS-CCl4 solvent)
(
1
4
1a
1.10 and 1.60 (m, 13H), 7.21 (s, 5H)
1.10 (m and s, 11H), 1.48 (m, 2H), 3.70 (s, 3H),
6.60-7.75 (AB q, J ) 8.7 Hz, 4H)
1.18 and 1.48 (s and m, 13H), 2.31 (s, 3H), 7.11
(m, 4H)
3
1
1
b
c
3
1
3
TMS internal standard for C NMR).
Kin etics. The kinetic procedures used in this study were
described previously.2 The same precautions and tests were
1
1
d
e
1.23 and 1.59 (s and m, 13H), 7.25 (s, 4H)
1.10 and 1.15 (s and m, 11H), 1.66 (m, 2H),
used to determine the accuracy and precision of the first-order
rate constants.
Ma ter ia ls a n d Solven ts. All hydrocarbon solvents used
for the reaction kinetics solutions were distilled prior to use,
with the forerun being discarded. Reagent grade solvents
7
.42-8.17 (AB q, J ) 8.5, 4H)
2
2
a
b
1.08 (s, 9H), 1.77-3.10 (m, 6H), 7.20 (s, 5H)
1.13 (s, 9H), 1.73-2.97 (m, 6H), 3.67 (s, 3H),
6.55-7.07 (AB q, J ) 8.5 Hz, 4H)
(2,2,4-trimethylpentane, dodecane and hexadecane) were pur-
2c
1.10 (s, 9H), 1.57-2.93 (m), 2.30 (s) (7H) and
7.03 (m, 4H)
chased from Aldrich Chemical and from Eastman Organic
Chemicals.
tert-Butyl hydroperoxide (Aldrich Chemical) was distilled
prior to use (30 °C at 30 Torr). A forerun and sizable amount
of distillation pot residue were discarded. Thionyl chloride
2d
2e
1.10 (s, 9H), 1.78-3.08 (m, 6H), 7.20 (s, 4H)
1.17 (s, 9G), 1.74-3.16 (m, 6H), 7.33-8.20 (AB q,
J ) 9.2 Hz, 4H)
3
3
a
1.00 (s, 9H), 1.57-2.23 (m, 6H), 2.40-2.83 (m, 2H),
7
.30 (m, 5H)
(Baker Chemical and Pfaltz and Bauer) was distilled im-
b
1.10 (s, 9H), 1.57-2.20 (m, 6H), 2.43-2,87
mediately before use in the preparation of acid chlorides. The
following solvents for syntheses were used as received: diethyl
ether (Mallinckrodt reagent grade), DMSO (Baker Chemical),
and diethylene glycol (Eastman Organic Chemicals). All
starting compounds were distilled prior to use, with the
exception of the purchased 1-arylcycloalkyl cyanides and
(
m, 2H), 3.77 (s, 3H),6.73-7.30 (AB q, J ) 8.5
Hz, 4H)
3
3
3
c
d
e
1.07 (s, 9H), 1.53-2.87 (m) and 2.33 (s) (11H),
7
.13 (m, 4H)
1.05 (s, 9H), 1.67-2.13 (m, 6H) 2.33-2.80 (m, 2H),
7
.27 (s, 4H)
1
-arylcycloalkyl carboxylic acids.
1.15 (s, 9H), 1.67-2.90 (m, 8H), 7.43-8.17 (AB q,
J ) 8.7 Hz, 4H)
1.07 (s, 9H), 1.33-2.67 (m, 10H), 7.20 (m, 5H)
1.10 (s, 9H), 1.65 and 2.43 (m and s, 13H), 7.23 (s, 4H)
1.19 (s, 9H), 1.70 and 2.45 (m, 10H), 4.38 (s, 4H)
1.15 (s, 9H), 1.68 and 2.44 (m, 10H), 7.40-8.25
(AB q, J ) 8.5 Hz, 4H)
The precursor organic chemicals for synthesis of the per-
esters in this study were all purchased from Aldrich Chemical
Co. These purchased compounds were all the para-substituted
4a
4c
4d
4e
1
-phenylcyclopropanecarboxylic acids (except for the p-nitro
compound), 1-(p-chlorophenyl)cyclobutanecarboxylic acid, 1-
phenylcyclobutanecarboxylic acid, 1-phenylcyclopentanecar-
boxylic acid, 1-(p-chlorophenyl)cyclopentanecarboxylic acid,
1
-(p-methoxyphenyl)cyclopentanecarboxylic acid, 1-(p-tolyl)cy-
instabilities of these compounds, special precautions were
taken to deliver the samples at temperatures below ambient.
The peresters are listed in decreasing order of analysis
accuracy. The less stable the perester, the less accurate the
carbon/hydrogen analysis. This suggests that some of the
peresters underwent some decomposition en route to the
elemental analyses.
clopentanecarboxylic acid, 1-(p-chlorophenyl)cyclohexanecar-
boxylic acid, 1-phenylcyclohexanecarboxylic acid, 1-phenylcy-
clobutanecarbonitrile, 1-p-tolylcyclohexanecarbonitrile, 1,3-
dibromopropane, p-tolylacetonitrile, p-methoxyphenylaceto-
nitrile, p-chlorophenylacetonitrile, and phenylacetonitrile.
P er ester s. Peresters were synthesized by the method
1
2,34
previously described.
Peresters were purified by column
Ca r boxylic Acid Ch lor id es. Carboxylic acid chlorides
were prepared from their corresponding corresponding acids
by adding 0.12 mol of freshly distilled thionyl chloride to 0.04
mol of carboxylic acid dissolved in 25 mL dry benzene. The
solutions were heated to reflux for 3-5 h. Benzene and excess
thionyl chloride were removed by distillation under reduced
pressure. Most of the acid chlorides were purified by distil-
lation under reduced pressure. The p-nitrophenyl alicyclic
carbonyl chlorides were not distilled, however, due to decom-
position at the distillation temperatures. The p-nitrophenyl
alicyclic peresters were the most readily purified by recrys-
tallization from hydrocarbon solvents. Yields of purified acid
chlorides ranged from 50 to 80%. IR and NMR spectra for all
the carboxylic acid chlorides prepared in this study were
consistent with the assumed structures. No impurities could
be detected in the IR and NMR spectra of the acid chlorides.
chromatography through silica gel or alumina and by recrys-
tallization from isooctane or hexane. The peresters were
pumped free of solvent by high vacuum pump. Note: A n ea t
sa m p le of p er ester 3b (p-m eth oxy su bstitu en t) exp er i-
en ced a r u n a w a y exoth er m , r esu ltin g in a n exp losion .
All n ea t sa m p les of th e p er ester s of th is stu d y sh ou ld
be k ep t cold a n d sh ou ld be h a n d led w ith a p p r op r ia te
p er son a l p r otective equ ip m en t a n d w ith ca u tion ! Yields
of peresters were typically 50-80% from the acid chlorides.
The remaining material balance from the acid chlorides could
be isolated as carboxylic acids.
Many of the peresters were liquids at room temperature.
The following melting ranges were measured for the solid
peresters: 1b (43.3-44.4 °C), 1c (77.9-79.3 °C), 1d (63.7-
6
4.2 °C), 1e (106.8-107.8 °C), 2d (33-35 °C), 2e (68.0-70.0
°
C), 3d (64.5-66.3 °C), 3e (33-36 °C), 4d (65.2-66.8 °C), and
IR carbonyl peaks for the acid chloride precursors to peresters
4
e (68.0-69.8 °C).
1a , 2a , 3a , and 4a matched published values.17
The infrared spectra of peresters 1a , 2a , 3a and 4a matched
1-(p-Nitr oph en yl)cycloalkan ecar boxylic Acids. A modi-
1
7
35
those previously published. Table 8 gives the proton NMR
fied method of Roberts was used to nitrate the benzene ring
spectral characteristics of the peresters in series 1-4.
of the 1-phenylcycloalkanecarboxylic acids. To a solution of
0.03 mol of 1-phenylcycloalkanecarboxylic acid in 35 mL of
acetic anhydride at 10 °C, was slowly added a solution of 17
mL of concentrated (96%) sulfuric acid and 15 mL of concen-
trated nitric acid (prepared cold, in small scale). It was found
that yields were generally higher if nitric acid from a freshly
opened bottle was used. The resulting solution was allowed
to stir for 2-3 h at 10 °C. To this solution 250 mL of distilled
water was carefully added, and the yellowish solid precipitate
was collected by suction filtration. The filtered solid was
stirred with 100 mL of distilled water and collected again by
1
3
Table 9 gives the C NMR spectral characteristics (500-
000 scans). Spectra were recorded under broad band decou-
1
pling mode, using a pulse width of 3 ms (flip angle of 40°),
pulse repetition rate of 2.8 s, and field width of 4 kHz. The
instrument was locked onto the deuterium of CDCl solvent.
3
Relative carbon intensities are given in parentheses. Chemical
shifts are relative to tetramethylsilane.
Table 10 lists carbon/hydrogen analyses for some of the
peresters. Analyses were performed by Integral Microana-
lytical Laboratories, Inc., Raleigh, NC. Because of the thermal
(34) Koenig, T.; Wolf, R. J . Am. Chem. Soc. 1967, 89, 2948.
(35) Roberts, D. D.; Watson, T. M. J . Org. Chem. 1970, 35, 978.