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YARKINA et al.
45
40
35
30
25
20
15
10
5
1362.96, and 2869.76 cm−1 and antisymmetric vibra-
tions at 1462.86 cm−1 (δ CH3), 829.73 cm−1 (1,4-sub-
stitution), and 1709.09 and 1016.02 cm−1 (ν O–H).
5
4
7
6
The oxidation of PTBC was performed under
atmospheric pressure in a semibatch unit [4]. The oxi-
date was analyzed for the HP content by iodometric
titration [4]. N-hydroxyphthalimide (and its deriva-
tives) obtained by reacting phthalic anhydride or its
derivative with hydroxylamine hydrochloride accord-
ing to a known procedure [4] was used as the catalyst.
3
2
Para-tert-butylcumene hydroperoxide (PTBC
1
HP) obtained in the work was a white crystalline solid,
1
mp 72°C. H NMR (400 MHz), δ, ppm (J, Hz):
7.42 m (4H, 4CH (arom.)), 7.28 s (1H, O–O–H),
4
0
10
20
30
Time, min
40
50
60
1.63 d (6H, 2CH3 (isopropyl), J = 1.7), 1.35 d (9H,
3CH3, 4J = 1.1).
Fig. 1. Influence of temperature and the catalyst structure
on the liquid-phase oxidation reaction of PTBC in the
presence of N-HPI. The catalyst concentration is 2.0 wt %.
The catalysts are (1–5) N-HPI, (6) 4-phenyl-N-HPI, and
(7) 4-methyl-N-HPI. Temperatures are (1) 100,
(2) 110,(3, 6, 7) 120, (4) 130, and (5) 140°C.
RESULTS AND DISCUSSION
The liquid-phase oxidation of PTBC was initially
studied using PTBC HP as the initiator in the tem-
perature range from 100 to 120°C. It is seen from
Table 1 that varying the process conditions (tempera-
ture, duration, and initiator concentration) could not
increase the PTBC conversion above 20–25% at the
selectivity for hydroperoxide of no more than 80–
85%.
It turned out to be possible to increase the PTBC
oxidation rate and the selectivity for tert-PTBC HP to
90–95% with the use of N-hydroxyphthalimide (N-
HPI), which can substantially increase the effective-
ness of oxidation of sec-alkylarenes to HPs [1, 5–10].
As is seen from Table 1 and Fig. 1, in the presence
of 2.0 wt% N-HPI, increasing the temperature from
100 to 140°C leads to a uniform increase in the PTBC
oxidation rate; however, at 130–140°C, the decompo-
sition of the HP starts after 1 h of the reaction, which
leads to a decrease in the HP selectivity. The maxi-
mum conversion of the hydrocarbon (40–43%) is
achieved over 75 min of the reaction at 140°C. The
selectivity for tert-PTBC HP was at least 95–97% in
all the experiments. Thus, the use of N-HPI made it
possible to increase the PTBC conversion by two to
three times and the PTBC HP selectivity from 80–85
to 95–98%, in comparison with the oxidation in the
presence of the PTBC HP as the initiator.
Apparently, the proposed PTBP synthesis method
has substantial advantages over the method for prepar-
ing PTBP via phenol alkylation with isobutylene [2–4]
because it is based on the available petrochemical
feedstock (isopropylbenzene) and on the well-tested
technology of the synthesis of phenol and acetone by
the “Cumene” process and excludes the formation of
the m- and p-isomers of tert-butylphenol. The field of
application of PTBP, a valuable product of basic
organic and petrochemical synthesis, constantly
broadens, covering the manufacture of antioxidants;
pesticides; rubbers; varnishes; paints; macrocyclic
compounds (calixarenes); and, since recently, phar-
maceuticals [2, 3].
EXPERIMENTAL
Para-tert-butylcumene with an assay of 98.5%
obtained by the alkylation of cumene bytert-butyl
alcohol according to a known procedure [4] and hav-
ing the following constants: bp 217°C;1H NMR
(400 MHz), δ, ppm (J, Hz): 7.28 d (2H (arom.), H-2,
3
3
H-6, J = 8.1), 7.14 d (2H (arom.), H-3, H-5, J =
8.1), 2.8–2.9 septet (1H, CH (isopropyl)), 1.25 s (9H,
C(CH3)3), 1.18 d (6H, 2CH3 (isopropyl), 3J = 6.8) was
used in this work. The spectra were recorded using a
Bruker DRX 400 NMR spectrometer (400.4 MHz). A
DMSO-d6–CCl4 mixture was used as the solvent.
Tetramethylsilane was used as the internal standard.
IR spectrum of PTBC: 3000 cm−1 (C–H bonds in the
aromatic ring), 1611.94 and 1513.85 cm−1 (C=C bonds
It is also seen from the data presented in Table 1
that increasing the catalyst concentration from 1.0 to
4.0 wt % makes it possible to increase the rate of for-
mation of PTBC HP at 120°C from 8–10 to 35–40%
over 1 h. However, the use of N-HPI in an amount of
1–1.5 wt % is quite sufficient for the effective oxida-
tion of PTBC to the HP.
As is seen from Table 1, the joint use of N-HPI as
the catalyst and PTBC HP as the initiator also has a
of the benzene ring), 827.54 cm−1 (substitution on the positive effect on the PTBC oxidation parameters.
benzene ring), symmetric vibrations at 1393.87, Thus, using a 2 wt % N-HPI concentration of and
PETROLEUM CHEMISTRY
Vol. 59
No. 11
2019
Yarkina
