IR spectra of screened phenols, phenol radicals, quinone, and cyclohexadienone

Brodskii, A.I.; Kotorlenko, L. A.; Samoilenko, S. A.; Pokhodenko, V. D.

doi:10.1007/bf00605804

Cited by 6 publications

(7 citation statements)

References 7 publications

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“…At pH >, 9 the phenolic groups ionize (the δ region) to give the phenolate anion (−C−O − ) that subsequently transforms to the ketone (see Supporting Information) with a characteristic symmetric stretching mode at 1678 cm −1 (the ε region). 29 To summarize, there is a clear correlation between the changes seen in the infrared spectra and the ionization of the different functionalities present on GO with pK values of 4.3, 6.6, and 9.8. The pK values of 4.3 and 6.6 correspond to ionization of carboxylic groups, but the former have hydroxyl groups present in an ortho position that allows the carboxylate anion to be stabilized by H-bonding, and hence, these groups are more acidic.…”

mentioning

confidence: 83%

“…The position of this band is characteristic of a ketone group. 29 The broad trend in the changes of the infrared spectra with pH is more easily discerned by following the changes in the intensities of the bands in the shaded regions of Figure 4.…”

mentioning

confidence: 96%

“…At higher pH values, this band shifts to 1594 cm –1 . At pH >, 9 the phenolic groups ionize (the δ region) to give the phenolate anion (−C–O – ) that subsequently transforms to the ketone (see Supporting Information) with a characteristic symmetric stretching mode at 1678 cm –1 (the ε region) …”

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confidence: 99%

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Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements

Konkena

Vasudevan

2012

J. Phys. Chem. Lett.

776

572

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The chemistry underlying the aqueous dispersibility of graphene oxide (GO) and reduced graphene oxide (r-GO) is a key consideration in the design of solution processing techniques for the preparation of processable graphene sheets. Here, we use zeta potential measurements, pH titrations, and infrared spectroscopy to establish the chemistry underlying the aqueous dispersibility of GO and r-GO sheets at different values of pH. We show that r-GO sheets have ionizable groups with a single pK value (8.0) while GO sheets have groups that are more acidic (pK = 4.3), in addition to groups with pK values of 6.6 and 9.0. Infrared spectroscopy has been used to follow the sequence of ionization events. In both GO and r-GO sheets, it is ionization of the carboxylic groups that is primarily responsible for the build up of charge, but on GO sheets, the presence of phenolic and hydroxyl groups in close proximity to the carboxylic groups lowers the pKa value by stabilizing the carboxylate anion, resulting in superior water dispersibility .

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confidence: 83%

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confidence: 96%

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Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements

Konkena

Vasudevan

2012

J. Phys. Chem. Lett.

776

572

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“…The absorption bands at 1198, 1122, and 1105 cm –1 arise due to the stretching vibrations of C–O. The aromatic ring −CC– stretching vibrations appear as a broad singlet at 1604 cm –1 . Symmetric and asymmetric −CH stretching vibrations of the methylene groups are observed at 2865 and 2957 cm –1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The aromatic ring −C C− stretching vibrations appear as a broad singlet at 1604 cm −1 . 72 Symmetric and asymmetric −CH stretching vibrations of the methylene groups are observed at 2865 and 2957 cm −1 , respectively.…”

Section: Energy and Fuelsmentioning

confidence: 99%

Novel (Co-,Ni)-p-tert-Butylcalix[4]arenes as Dispersed Catalysts for Heavy Oil Upgrading: Synthesis, Characterization, and Performance Evaluation

Al‐Attas¹,

Zahir²,

Ali³

et al. 2018

Energy Fuels

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This study investigates the promotional effects of a potentially new class of oil-soluble dispersed catalyst precursors for upgrading of vacuum gas oil (VGO), that is metal-based p-tert-butylcalix[4]arenes (TBC[4]s). Co- and Ni-TBC[4] were synthesized, and the metal–ligand complexation was confirmed by scanning electron microscopy-energy dispersive X-ray, inductively coupled plasma, X-ray diffraction, UV–vis, Fourier transform infrared, and 1H NMR. The thermogravimetric and calorimetric behaviors of the synthesized complexes, which are key properties of dispersed hydrocracking catalysts, were also studied. The differential scanning calorimetry profile of Ni-TBC[4] and Co-TBC[4] showed that the organometallic structure has lower thermal stability compared with that of the parent TBC[4]. This apparent drawback can be positively exploited by employing TBC[4] as a carrier of the metal, where the active sites are formed in situ by the destruction of the organometallic complex on reaching the desired reaction conditions. The catalytic performance of the synthesized precursors was evaluated using a batch autoclave reactor with varying concentrations of catalyst precursors at 420–450 °C. The results show that the synthesized metal-based TBC[4] dispersed catalysts evidently enhanced the hydrogenation activity and reduced coke formation. The addition of 500 ppm Co and Ni as standalone dispersed catalysts produced distillate yields of 45.7 and 49.7 wt % and a coke laydown of 2.6 and 2.3 wt %, respectively. Increasing the concentration of catalyst precursors enhanced the conversion of VGO from 86.17% at 100 ppm Ni to 88.28% at 500 ppm Ni. Moreover, as the metal concentration increased from 100 to 500 ppm, the distillate yield increased from 36.87 to 49.66 wt %, while the yield of gases decreased from 20.48 to 17.12 wt % because the hydrogenation reactions were enhanced. In contrast, the yields of distillate and naphtha decreased by 14.12 and 15.36%, respectively, as the temperature increased from 420 to 450 °C.

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Study on thermal decomposition of calix[4]arene and its application in thermal stability of polypropylene

et al. 2011

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IR spectra of screened phenols, phenol radicals, quinone, and cyclohexadienone

Cited by 6 publications

References 7 publications

Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements

Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements

Novel (Co-,Ni)-p-tert-Butylcalix[4]arenes as Dispersed Catalysts for Heavy Oil Upgrading: Synthesis, Characterization, and Performance Evaluation

Study on thermal decomposition of calix[4]arene and its application in thermal stability of polypropylene

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IR spectra of screened phenols, phenol radicals, quinone, and cyclohexadienone

Cited by 6 publications

References 7 publications

Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pKa Measurements

Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pKa Measurements

Novel (Co-,Ni)-p-tert-Butylcalix[4]arenes as Dispersed Catalysts for Heavy Oil Upgrading: Synthesis, Characterization, and Performance Evaluation

Study on thermal decomposition of calix[4]arene and its application in thermal stability of polypropylene

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Product

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Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements

Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK_a Measurements