Chet R. Jablonski

Comparison of standard and NMR methodologies for assessment of oxidative stability of canola and soybean oils

The oxidative stability of refined, bleached and deodorized canola and soybean oils was evaluated over a 30-day dark storage period at 65 °C. Peroxide value (PV), conjugated diene (CD) and triene (CT) contents, 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton absorption pattern of the fatty acids of oils during storage. Canola oil showed higher PV, CD, CT and TBARS as compared with those for soybean oil. The ratio of aliphatic to olefinic protons in both oils, determined by NMR spectroscopy, increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils.

Fast atom bombardment mass spectra of [(diars)Fe(CO)2(C(O)Me)(P-donor)]+ BF4− salts☆

Abstract Characteristic fast atom bombardment (FAB) mass spectra (8 keV, argon, glycerol matrix) have been obtained for an isostructural series of organometallic cations of the form cis,trans [(diars)Fe(CO) 2 (C(O)Me)L] + Bf 4 (L = phosphorus donor). The fast atom bombardment mass spectra (FABMS) obtained show relatively abundant fragments corresponding to the cationic portion of the complex [C + ]. Extensive fragmentation also occurs via successive CO loss, phosphorus donor ligand cleavage, and ligand decomposition. Evidence for a rearrangement fragmentation corresponding to the process [Fe(C(O)Me)] + → [FeMe] + + CO is presented.

Preparation of an ambident S-Sulfinate complex from dicarbonyl (η5-cyclopentadienyl)ferrate and sulfur dioxide

Abstract Nucleophilic addition of K + (η-C 5 H 5 )Fe(CO) 2 − rather than the corresponding sodium salt to THF solutions of sulfur dioxide precipitates K + (η-C 5 H 5 )Fe(CO) 2 S(O) 2 − , the first example of an isolable transition metal sulfinate anion. Reaction of the ambident sulfinate ion with CH 3 I or CH 3 OSO 2 F leads to S or O alkylated products respectively.

Preparation, crystal structure, absolute configuration, and conformational analysis of (−)436-(S)-(−)-diphenyl-1-phenylethylaminophosphine(η5-pentamethylcyclopentadienyl)-(dimethylphosphonato)cobalt(III)

Reaction of Cp★CoI2(P(OMe)3) 8 with the chiral aminophosphine (S)-(−)-diphenyl-phenylethylaminophosphine affords the diastereomeric phosphonate complexes (R,S)Co,SC-Cp★CoI(P(0)(OMe)2)(PPh2NHC★H(Me)Ph) (10a,10b) via Arbuzov dealkylation. 10a,10b are separable and configurationally stable in solution for extended periods. The structure and absolute configuration of the lower Rf diastereomer (−)-436-10b were determined via single-crystal X-ray diffraction. It crystallizes as a toluene solvate in space group P21 with a 13.194(6), b 9.062(4), c 17.023(5) A, β 108.78(3)°, Z = 2, and was refined to R = 0.067 for 6318 reflections. Spectroscopic and structural evidence demonstrate a strong 1,6 intramolecular NH ⋯ OP hydrogen bond between the aminophosphine NH and the basic phosphoryl oxygen, which establishes a quasi-boat conformation. Proton nuclear Overhauser difference spectra show that the conformation in solution is the same as that observed in the solid state.

Metallocenyl di-carbonium ions -13C and1H NMR spectra of 1,1′-di(1-methyl-l-ethylium)ferrocene dication

Abstract 13 C and 1 H NMR data for a heteroannular ferrocenyl α,α-di-carbonium ion are presented. The results are consistent with increased localization of positive charge on C α compared to related ferrocenyl mono-carbonium ions.

Rate-structure correlations for migratory CO insertion. Steric acceleration for the octahedral iron(II) case

Abstract The kinetics of the migratory insertion reaction of cis , cis -[(diars)- Fe(CO) 2 L(Me)] + , (Ia–Ig), (L = C 6 H 11 O 3 P (ETPB), P(OMe) 3 , PhP(OMe) 2 , PMe 3 , PhPMe 2 Ph 2 OMe) or Ph 2 PMe) in the presence of excess L′ (L′ = P(OMe) 3 or i-C 3 H 7 NC) in methylene chlorine- d 2 to form [(diars)- Fe(CO)LL′(C(O)Me)] + , (IIa–IIg), follow the rate law: Rate = k insert [(I)]. The first order rate constant, k insert , depends primarily on steric factors and shows an overall increase of a factor of 270 (at 290 K) as L varies from ETPB (cone angle 101°) to Ph 2 PMe (cone angle 136°). The pronounced steric acceleration of insertion rate is in accord with a unimolecular rate determining insertion step which requires neither inter- nor intramolecular nucleophilic participation.