Functional group analysis in coal and on coal surfaces by NMR spectroscopy

The reaction of Cl{ovr POCH{sub 2}CH{sub 2}O} (2) with moisture in pyridine extracts of Argonne standard coal samples has been found to give results comparable with the ASTM D3302 moisture analyses of these samples. Differences in the two sets of results are discussed. Some exceptionally large solvent effects on {sup 31}P chemical shifts of model compounds derivatized with 2 and 8 have been discovered. Initial experiments aimed at labile hydrogen functional group analysis of solid coal samples with 2 and Me{sub 2}N{ovr POCH{sub 2}CH{sub 2}O} (15) are described. 17 refs., 1 fig., 6 tabs

A novel approach to catalytic desulfurization of coal. Semi-annual report

A gas chromatographic method has been developed for the quantitation of sulfur removed from coal as tributyl phosphine sulfide. The method also works well for quantitating the products of sulfur removed compounds such as dibenzothiophene

Heteronuclear probes of coal structure and reactivity. Semi-annual report

Efforts toward quantitation of the sulfur removed from coal in the reaction Coal(S) + excess PBu{sub 3} with heat {r_arrow} Coal + SPBu{sub 3}/PBu{sub 3} by column chromatography of the products followed by weighing the SPBu{sub 3} and vacuum distillation of the SPBu{sub 3}/PBu{sub 3} mixture followed by gas chromatographic analysis are described. The first method failed, but the latter is more successful. It has been discovered that para-chloro phenol catalyzes the removal of sulfur from dibenzothiophene by PBu{sub 3} under mild conditions

Functional group analysis in coal and on coal surfaces by NMR spectroscopy

An accurate knowledge of the oxygen-bearing labile hydrogen functional groups (e.g., carboxylic acids, phenols and alcohols) in coal is required for today's increasingly sophisticated coal cleaning and beneficiation processes. Phospholanes (compounds having the general structure -POCH{sub 2}CH{sub 2}O (1)) are being investigated as reagents for the tagging of liable hydrogen functional groups in coal materials with the NMR-active {sup 31}P nucleus. Of twelve such reagents investigated so far, 2 (2-chloro-1,3-dioxaphospholane, ClPOCH{sub 2}CH{sub 2}O) and 8 (2-chloro-1,3-dithiaphospholane, ClPSCH{sub 2}CH{sub 2}S) have been found to be useful in identifying and quantitating, by {sup 31}P NMR spectroscopy, labile hydrogen functional groups in an Illinois No. 6 coal condensate. Reagent 2 has also been used to quantitate moisture in pyridine extracts of Argonne Premium Coal Samples. Preliminary {sup 119}Sn NMR spectroscopic results on model compounds with the new reagent CF{sub 3}C(O)NHSnMe{sub 3} (N-trimethylstannyltrifluoroacetamide, 14) suggest that labile hydrogen functional groups in coal materials may be more precisely identified with 14 than with phospholanes. 14 refs., 2 figs., 2 tabs

Coal liquefaction process streams characterization and evaluation: Estimation of total phenol concentrations in coal liquefaction resids by [sup 31]P NMR spectroscopy

In this study, Iowa State University researchers used [sub 31]P-tagged reagents to derivatize the labile hydrogen functional groups in the THF-soluble portion of 850[degrees]F[sup +] distillation resid materials and the THF-soluble portion of process oils derived from direct coal liquefaction.[sup 31]P-NMR was used to analyze the derivatized samples. NMR peak assignments can be made by comparison to model compounds similarly derivatized. Species can be quantified by integration of the NMR signals. Different [sup 31]P-NMR tagged reagents can be used to produce different degrees of peak resolution in the NMR spectrum. This, in turn, partially dictates the degree of speciation and/or quantification of species, or classes of compounds, that can be accomplished. Iowa State chose a [sup 31]P-tagged reagent (ClPOCMe[sub 2]CMe[sub 2]O) which was shown previously to be particularly useful in the derivatization of phenols. The derivatized samples all exhibited a small group of peaks attributed to amines and a broad group of peaks in the phenol region. The presence of paramagnetic species in the samples caused the NMR signals to broaden. Electron paramagnetic resonance (EPR) spectra confirmed the presence of paramagnetic organic free radicals in selected samples. Various methods were employed to process the NMR data. The complexity and broadness of the phenol peak, however, made speciation of the phenols impractical

Structure-basicity relations among phosphate and phosphite esters. CNDO/2 and protonation studies

Protonation in HFSO; at -50 O C o f the phosphite triesters 1"'-5"' revealed a steady increase in ' J ~(H826 -928 Hz) upon increased constraint of the alkoxy groups. CNDO/2 calculations showed a concomitant rise in the positive charge on phosphorus and the phosphorus-bound hydrogen in the protonated species, but no trend was observed in the P hybridization. A plot of the cube of the sum of these charges vs. 'JpH (correlation coefficient 0.92) suggests that the charge contribution is probably dominant in the Fermi contact term. These results are consistent with stereochemically dependent orbital effects proposed earlier. A similar rise in the calculated negative charges at the ring oxygens of the phosphate analogues 1"-4" along with smaller differences in the protonation energies of the phosphoryl oxygen on constraint parallels the decreased hydrogen bonding tendency of the phosphoryl oxygen as shown by phenol shift experiments. A minor reversal in basicity of the first two members of the phosphite series is indicated by the BH stretching frequency trend of the BH; adducts 1*-5* and is rationalized in terms of the greater polarizing power of the proton than BHj

Protonation as a driving force for pentacoordination of phosphorus

CNDO/2 calculations are reported on four caged phosphorus compounds, Y-P(OCH2CH2)3X (X = N, CH; Y = O, OH+, H+). Structures with and without a transannular bond between P and X were taken into account; the influence of this bond on the stability of the compounds was examined. For X = N and Y = H+ the lowest-energy structure corresponds with the geometry found by X-ray analysis. If X = CH, formation of a transannular bond proves to be unlikely, as expected. The calculations predict the formation of a P-N bond upon protonation of the phosphate (X = N, Y = O). The net atomic charges in the protonated phosphite were used to calculate its NMR coupling constant, 1JPH, which correlates well with the value found experimentally

Enantio- and diastereoselective synthesis of gamma-amino alcohols

Contains fulltext : 149737.pdf (publisher's version ) (Open Access

Phosphatranes as unusual stabilizing structures for hypervalent phosphorus: 10-P-5 mono- and divalent cations

'H, I3C, and 'IP NMR evidence are presented for the formation of the hypervalent hosphorus mono- and divalent cations [HYP(OCH2CH2)3N]+,[ H2YP(OCH2CH2)3N]2+a,n d [R2YP(OCH2CH2)3N]2+(Y = 0, S; R = Me, Et). These new IO-P-5 cations are apparently stabilized by the presence of three five-membered rings chelating the phosphorus and also by the strong basicity of the apical chalcogen arising from its participation in the three-center, four-electron bonding system along the axis of the trigonal-bipyramidal structure