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The single electron chemistry of coals

Description: Our work on single election transfer in coals led us to the knowledge that the energetics of bond cleavage in radical cations is 20-40 kcal/mole lower than the corresponding homolytic bond cleavage energies. Having made excellent progress in the other areas covered by this proposal, we are extending our studies to the investigation of the formation and cleavage reaction of radical cations in coals. The formation of a radical cation requires the transfer of an electron from a neutral molecule to an appropriate electron acceptor (oxidant). As a first step, we seek oxidants which will form radical cations from functional groups typical of those in coals. We must also study the decomposition behavior of bonds typical of those found in coals. Alkyl and alkoxy aromatic compounds were chosen as the electron donors because of their common occurrence in coals.
Date: January 18, 1991
Creator: Larsen, J. W. & Kaushal, P.

The single electron chemistry of coals

Description: TCNQ Charge Transfer Complexes with Coals. TCNQ can be readily deposited in coals from pyridine solution. IR spectra of TCNQ and TCNQ in Illinois No. 6 coal are shown in Fig. 1. It is clear that the stretching frequency has been shifted by the full 44 cm[sup [minus]1] caused by the transfer of a single electron. Similar behavior has been observed with a variety of coals, including lignites, subbituminous and a range of bituminous coals. There are two possible explanations for the observed shift. The simplest explanation is that there exist in coals structures which are excellent single electron donors capable of transferring an electron to TCNQ in the ground state. All of the TCNQ dissolved in the coal is shifted. No uncomplexed TCNQ remains in the sample, as demonstrated by the absence of the unaltered CN stretch at 2227 cm[sup [minus]1]. The spectrum shown is for TCNQ in coal in a molar concentration equivalent to approximately 20% of the PNA systems in this coal as deduced from the NMR studies of Solum et al. (1989). It is highly unlikely that 20% of the PNA systems in coal are such good electron donors that the charge transfer complex would have an electron transferred in the ground state. The second explanation is that cooperative interactions between the TCNQ and the aromatic systems in coal have led to the formation of an extended valance band structure, that the TCNQ LUMO is part of this band structure, and that the band is half filled.
Date: July 24, 1990
Creator: Larsen, John W. & Flowers, Robert A., II.

The single electron chemistry of coals, January 1, 1990--March 30, 1990

Description: The Wyodak, Upper Freeport and Pocahontas No. 3 samples containing DPPD display a decrease in spin density as compared to the starting coals. Coincident with this decrease is a loss or decrease of the narrow inertinite signal in the esr spectrum of these coals. The Pittsburgh No. 8 coal sample containing DPPD also displays a loss of spin density as compared to the starting coal but there is no change in the esr spectrum. These results compare well with earlier work involving 4-vinylpyridine and the same coal samples. We discovered the presence of poly(4-vinylpyridine) in our coal samples and a concurrent loss of inertinite radical density. It is possible that the inertinite radicals may initiate the polymerization or in the present work may abstract hydrogen from DPPD. No C=N stretch was displayed in the IR spectrum to substantiate this claim.
Date: April 16, 1990
Creator: Larsen, John W. & Flowers, Robert A., II

The single electron chemistry of coals. [Quarterly], April 1--June 30, 1992

Description: Depolymerization of coals at low temperatures may offer advantages over thermal bond cleavage. Because bond cleavage energies of radical cations are lower than the corresponding homolytic bond cleavage energies of the same bond, generation of radical cations in coal may make possible depolymerization at lower temperatures. We seek to investigate the above possibility using single molecules containing functional groups common in coals. Since the generation of a radical cation requires the removal of an electron from a neutral molecule, a primary focus of the study will be finding oxidants that will remove an electron from compounds with structural similarity to those typically found in coals. The study will also be concerned with the decomposition of radical cations and the products formed as a result of the decomposition.
Date: October 1, 1992
Creator: Larsen, John W. & Eskay, T. P.

The single electron chemistry of coals. [Quarterly] report, January 1, 1991--March 31, 1991

Description: The simplest explanation for these shifts in the infrared spectra is there exists in coal single electron donors which are capable of transferring an electron to TCNQ in the ground state. All of the TCNQ placed in the coal appears to be converted to the radical anion as displayed in the IR spectrum for all of the coals except for the 100% loading.
Date: April 22, 1991
Creator: Larsen, John W. & Flowers, Robert A., II

The single electron chemistry of coals. [Quarterly] report, January 1--March 31, 1993

Description: Following the position of the nitrile band and using the assumption that there is a linear relationship for between the extent of charge transfer and frequency, a 69% charge transfer was obtained and successfully replicates Flowers` results. If a Diels-Alder reaction occurred, we would expect the position of nitrile group to have shifted down field to the 2260-2240 cm{sup {minus}1} range for a saturated alkyl nitrile. There is no evidence for this type of reaction under these conditions since we obtained a shift upfield from 2229 cm{sup {minus}1} to 2200 cm{sup {minus}1}. There are some peaks of interest in the 1660-1300 cm{sup {minus}1} range of the deposited coals which will be investigated. The TCNE-Illinois No. 6 reaction mixture will be heated from room temperature to 180{degrees}C within the Harrick cell during IR analysis to see if a Diels-Alder or other additions reaction could occur.
Date: September 1, 1993
Creator: Larsen, John W. & Rothenberg, S. E.

The single electron chemistry of coals. [Quarterly] report, July 1, 1990--December 30, 1990

Description: Our work on single election transfer in coals led us to the knowledge that the energetics of bond cleavage in radical cations is 20-40 kcal/mole lower than the corresponding homolytic bond cleavage energies. Having made excellent progress in the other areas covered by this proposal, we are extending our studies to the investigation of the formation and cleavage reaction of radical cations in coals. The formation of a radical cation requires the transfer of an electron from a neutral molecule to an appropriate electron acceptor (oxidant). As a first step, we seek oxidants which will form radical cations from functional groups typical of those in coals. We must also study the decomposition behavior of bonds typical of those found in coals. Alkyl and alkoxy aromatic compounds were chosen as the electron donors because of their common occurrence in coals.
Date: January 18, 1991
Creator: Larsen, John W. & Kaushal, P.

The single electron chemistry of coals. [Quarterly] report, July 1--September 30, 1993

Description: Tetracyanoethylene (TCNE) and Tetracyanoquinodimethane (TCNQ) were used earlier in an attempt to determine the single electron donating ability of aromatic groups in coals. The extent of electron transfer from coals to these compounds was measured by determining the frequency shift of the nitrile stretching bands in the Diffuse Reflectance (DR) infrared spectra. Our addition to this work will be to study the interactions of coals, such as Illinois No. 6, with TCNE. We will determine whether a Diels-Alder reaction or other addition reactions are occurring.
Date: December 31, 1993
Creator: Larsen, John W. & Rothenberg, S. E.

The single electron chemistry of coals. Quarterly report, October 1, 1993--December 31, 1993

Description: The objective of this work is to investigate and characterize the single electron reactions of alkyl and alkoxy aromatic compounds in order to determine the role these reactions play in the chemistry of coal. The work here is concerned with the interactions of coals, such as Illinois No. 6, with tetracyanoethylene.
Date: August 1, 1994
Creator: Larsen, John W. & Rothenberg, S. E.

The single electron chemistry of coals. [Quarterly] report, October 1--December 31, 1992

Description: Radical cation generation in coal may make possible depolymerization at low temperature. This possibility was investigated using single molecules containing functional groups common in coals. Single- electron oxidations of 4,4{prime}-dimethoxybibenzyl (DMBB) by Fe(III) (1,10-phenanthroline){sub 3}(ClO{sub 4}){sub 3}, in refluxing CH{sub 3}CN, gave incomplete mass balances; an attempt was made to identify the additional products. Part of these products were deduced to be dimer, p-methoxybenzylated dimer of DMBB; mono, di, and tri-p- methoxybenzylated DMBB. Similar oxidations in CH{sub 2}Cl{sub 2} and sulfolane solvents gave similar results. Attempts to use other solvents were unsuccessful.
Date: December 31, 1992
Creator: Larsen, John W. & Eskay, T. P.