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ether has to be removed carefully to prevent bubbling of the
solution.
Pentaiodonitrobenzene C6I5NO2
The reaction was carried out, as reported in ref. 22. Periodic acid
(23.85 g, 0.10 mol) was dissolved in conc. sulfuric acid (375 mL).
Pounded iodine (78.00 g, 0.30 mol) was added to the clear
solution, and then stirred using an overhead stirrer for half an
hour. The reaction mixture was then placed in an ice-bath.
Distilled nitrobenzene (7.0 mL, 0.067 mol) was added over 15
minutes. The mixture was then stirred for one day at room
temperature and then for one day at 95 ꢀC. Aer heating the
Phenol 1 obtained aer sublimation is slightly hygroscopic;
therefore, let the sublimation nger to warm up before scraping
off the product. Yield from pentaiodonitrobenzene (it has been
taken into account the content of tetraiodo nitrobenzenes from
HPLC-UV-vis measurements – 57%) of phenol 1 is 58% (1.45 g,
0.003 mol). M.p. 88–90 C (lit. 88–90 C)13,16
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19F NMR spectrum of crude reaction mixture (Reaction I,
Spectrum S2‡) shows that there are 64% 2,3,4,5-(CF3)4-C6HNO2
and 36% 2,3,5,6-(CF3)4-C6HNO2 (percentages are converted to
100% leaving out 1a). Aer distillation, according to 19F NMR
spectrum, the ratio is changed to 54 and 46%, respectively
(Spectrum S3‡). The content of symmetrical nitrobenzene has
increased. There were no considerable amounts of 2,3,4,5-
(CF3)4-C6HNO2 in the cold-trap. It is possible that some of the
CF3 substituted nitrobenzene decomposed during the
distillation.
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reaction mixture to 95 C for one day, the iodine sublimed on
the top of the ask. The solution was then carefully poured onto
ice. The yellow suspension was then ltered. The residue was
not washed with ethanol as described in ref. 22 because the
product is soluble in this solvent. Pentaiodonitrobenzene on
the lter was instead recrystallized using a continuous extractor
(Soxhlet extractor may be used as well) from AcOEt (400 mL).
One batch of the product was ltered. The volume of the AcOEt
was then reduced to 200 mL and the solution was placed into
refrigerator. The yellow precipitate obtained was ltered again,
the two batches were combined, washed with hexane (200 mL)
and dried in a vacuum (10ꢁ3 Torr) at 50 ꢀC for six hours. 36.4 g
of a mixture of penta- (57%) and tetraiodonitrobenzenes (43%)
was obtained.
The distillate was worked up as follows: water (25 mL)
was added to the distillate (100 mL) and extracted with pentane
(3 ꢂ 50 mL). Pentane was removed by rotary evaporation; and
the ask was kept cold to prevent the sublimation of
compounds. To the obtained oily substance, 2 mL of water was
added, and crystals formed into this solution. The solution was
ltered and the solid on the lter was recrystallized from
pentane (25 mL). The obtained solid is the mixture of 2,3,4,5-
(CF3)4-C6HNO2 (51%) and 2,3,5,6-(CF3)4-C6HNO2 (49%) (Spectra
S6 and S21‡).
According to the 1H NMR spectrum and HPLC-ESI-MS-UV-vis
measurements, recrystallization twice from benzene and
ethanol24 gave the substance that has no aromatic hydrogens.
The recrystallization yield was 22%.
Acknowledgements
Pentakis(triuoromethyl)phenol C6(CF3)5OH 1
The reaction was carried out as described for C6I5Cl in ref. 16. This study was supported by the Estonian Science Foundation
Instead of C6I5Cl, C6I5NO2 (may contain C6I4HNO2 derivatives) (grants nos 8720 and 8162), the Estonian Research Council
was used: Dispersion of CuBr (9.71 g, 0.050 mol) and DMF (grant no. PUT182), the targeted nancing project of the Esto-
(50 mL) was cooled to 0 ꢀC, triuoromethyltrimethylsilane (9.50 nian Ministry of Education and Science (grant no. SF0180089
mL, 0.067 mol) was added. Aer that, KF (3.86 g, 0.066 mol) was s08), the Estonian Centre of Excellence (HIGH-TECHMAT
added slowly via solid addition funnel. Then, NMP (10 mL) was SLOKT117T) and by the Estonian National R & D infrastruc-
included, and the reaction mixture was stirred on a ice-bath for ture development program of Measure 2.3 “Promotion of
1.5–2 hours to form active CuCF3. C6I5NO2 (7.70 g, contains development activities and innovation” (Regulation no. 34)
0.006 mol pentaiodonitrobenzene, and 0.005 mol isomers of funded by the Enterprise Estonia foundation.
tetraiodonitrobenzenes) and additional NMP (40 mL) was
added. The reaction mixture was stirred overnight, and solvents
with other volatile substances were distilled off. The residue
References
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into diethyl ether (3 ꢂ 70 mL). Ether was evaporated, the
obtained solid was transferred into sublimation apparatus,
conc. H2SO4 (8 mL) was added and phenol 1 sublimed at
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41900 | RSC Adv., 2014, 4, 41895–41901
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