An infrared absorption study of autoxidized methyl linoleate

Summary A study has been made of the infrared absorption spectra of autoxidized methyl linoleate in samples ranging from PV 1 to PV 940 m.e./kg. Principal changes occur in the frequency range 3400–3550 cm⁻¹ where bonded−OH groups absorb and at 1650–1775 cm⁻¹ where >c=0 groups absorb. Two maxima were observed in oxidized samples in the −OH absorption range: one sharp and distinct at 3467–70 cm⁻¹ which increased in intensity with increase in PV and a broad band which increased with increasing PV until it resolved into a true maximum at 3430 cm⁻¹. Reduction of typical oxidized samples with KI reagent resulted in disappearance of the 3430 cm⁻¹ band and appearance of a new band above 3500 cm⁻¹. The band at 3430 cm⁻¹ was attributed to −OOH groups associated by hydrogen bridging. The band at 3467 cm⁻¹ and the band appearing above 3500 cm⁻¹ were attributed to −OH groups, the band at the higher frequency resulting directly from reduction of a hydroperoxide. Absorption due to ketone and aldehyde carbonyl groups appeared only as an indefinite shoulder on the band due to the ester carbonyl. These were resolved by using the intensity of the sample with PV 1 as I_o and that for the oxidized samples as I. A plot of Log I_o/I then revealed three maxima. These indicate the presence of two and possibly three carbonyl containing substances other than the ester carbonyl in autoxidized methyl linoleate. Absorption in the two critical frequency ranges of fractions of autoxidized methyl linoleate eluted from an adsorption column correlate with interpretations made from ultraviolet absorption studies of the same substances. This paper reports research undertaken in cooperation with the Quartermaster Food and Container Institute for the Armed Forces and has been assigned number 211 in the series of papers approved for publication. The views or conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or indorsement of the Department of the Army. Presented at the Fall Meeting of the American Oil Chemists’ Society, New York, Nov. 17, 1948.     

Studies on the radical polymerization of N-vinyl 2-pyrrolidone initiated by diphenyl ditelluride

N-vinyl pyrrolidone (NVP) was polymerized in dioxan at 60 ± 0.1°C for 1 h using diphenyl ditelluride as radical initiator. The system follows ideal kinetics i.e. R _p α [DPDT]^0.5[NVP]. The activation energy and dissociation constant is computed as 46 kJ mol⁻¹ and 1.1 × 10⁻¹¹ s⁻¹, respectively. The polymer was characterized with the help of FTIR, ¹H-NMR, ¹³C-NMR, ESR spectroscopy. The FT-IR spectrum showed bands at 1660–1680 cm⁻¹ due to combination of >C = O and C–N stretching. The gyromagnetic constant ‘g’ has been computed as 2.2203. The main product of this reaction were poly(N-vinylpyrrolidone)s with phenyl tellanyl ends. The presence of tellurium in polymer is confirmed by ICP analysis. The DSC shows the T _g of poly(N-vinylpyrrolidone) is 168°C due to rigid pyrrolidane group. The TGA showed that polymer was stable up to 380°C.The GPC studies showed that the weight average molecular weight decreases with increase of [DPDT].     

Infrared spectra of dinitrogen adsorbed on bimetallic lanthanide (Eu or Yb)–Ni/SiO2 catalysts

Bimetallic lanthanide (Ln: Eu or Yb)–Ni/SiO₂ catalysts prepared by the use of dissolution of lanthanide metals in liquid ammonia have been studied by infrared spectroscopy for dinitrogen adsorption. The infrared spectra were measured at 133–300 K using Ln–Ni/SiO₂ obtained when the Eu or Yb metal dissolved in liquid ammonia reacted with 20 mass% Ni/SiO₂ in different ratios. Infrared spectra for Eu–Ni/SiO₂ showed absorption bands at 2336, 2265, 2254 and 2227 cm⁻¹ at 133 K, which disappeared upon evacuation. The adsorbed state was found to be all molecular from the isotope shift using ²⁸N₂ and z³⁰N₂₈. The bands at 2254 and 2227 cm⁻¹ of them were assigned to new adsorbed dinitrogen species resulting from synergetic interactions between the europium and nickel metal. The concentration of adsorbed dinitrogen on Eu–Ni/² varied markedly with the Eu/Ni ratios, and particularly, it increased in the region of high Eu content. Upon introduction of ytterbium onto nickel, new bands at 2254 and 2226 cm^−- similarly appeared. However, the dependence of dinitrogen adsorption as a function of Yb content in Yb–Ni/SiO²> was somewhat different from that for Eu–Ni/SiO₂. The effects of lanthanide on the surface of Ln–Ni/SiO₂ were discussed in connection with the variation in catalytic properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

The dynamic surface chemistry during the interaction of CO with ceria captured by Raman spectroscopy

The interaction of CO with ceria under conditions typically used to measure the oxygen storage capacity (OSC) of automotive three way catalysts (TWC) has been investigated by in situ Raman spectroscopy. During exposure of the ceria to CO at 623 K vibrational bands at 1582–1600 and 1331–1340 cm⁻¹ appeared; these bands increased with increasing time of exposure to CO. The band positions are consistent with phonon modes of carbon; however, assignment to carboxylate species or carbonate species cannot be excluded. Subsequent exposure to O₂ at room temperature resulted in a decrease in the intensities of the 1582–1600 and 1331–1340 cm⁻¹ bands by more than 90%. As well, exposure to O₂ at room temperature also resulted in the appearance of Raman modes characteristic of formate and peroxide surface species. The mechanism by which formate forms upon room temperature O₂ exposure is discussed in the context of the assignment of the 1582–1600 and 1331–1340 cm⁻¹ bands to carbon phonon modes which result from the disproportionation of CO on reduced ceria.     

Interaction of hydrogen and n‐pentane with sulfated zirconia

Interaction of hydrogen with sulfated zirconia catalysts was studied in situ at 473 K. Interaction of hydrogen with the sample evacuated at 673 K leads to the formation of new hydroxyl groups (wide bands near 3330 cm⁻¹) and water (1620 cm⁻¹). In the case of the sample evacuated at 873 K, SOH groups (3660 cm⁻¹) and zirconium hydrides (1555 cm⁻¹) form. Adsorption of n‐pentane on sulfated zirconia catalysts in the range of 253–383 K was studied. It was shown that hydrides and protonated cyclopentadienes form at low temperatures. At higher temperatures, aromatic compounds are formed mainly. The reaction mechanism is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conjugated opto/electroactive ethynylene-carbazole polymers with TTF as pendant group

Three conjugated ethynylene-carbazole polymers with Tetrathiafulvalene (TTF) as pendant group (P1–P3) were synthesized by using sonogashira coupling reaction and characterized by ¹H NMR, GPC, CV, UV–Vis, FL, and TGA. CV and UV–Vis spectra showed that an intramoleular interaction existed between the electron-rich moiety TTF and electron-deficient moiety polyethynylcarbazole of the polymers. A strong fluorescence quench (ca. 99%) could be observed, compared to the polyethynylene-carbazole without TTF units, which could be ascribed to the photo-induced electron transfer (PET) interaction from TTF moiety to the polyethynylene-carbazole backbone. The observed onset decomposition temperatures (T _d) for P1–P3 varied from 256 to 298 °C. The polymers mentioned above exhibited good thermal properties and higher conductivity (neutral conductivity ~7–11 × 10⁻⁷ S cm⁻¹; doped conductivity ~6–11 × 10⁻⁴ S cm⁻¹).     

Analysis of oxidation states of vanadium in vanadia–titania catalysts by the IR spectra of adsorbed NO

Adsorption of NO on vanadia–titania samples pre-subjected to different reduction treatments has been studied by FTIR spectroscopy. When the NO adsorption is performed at 85 K on oxidized samples, antisymmetric NONO species, typical for V⁵⁺ sites, are detected and characterized by bands at 1779 and 1686 cm⁻¹. At ambient temperature, however, adsorption is negligible and only with time reactive adsorption occurs producing NO⁺ (2120 cm⁻¹), nitro/nitrato species (bands in the 1650–1100 cm⁻¹ region) and weakly adsorbed NO (broad band at 1915 cm⁻¹). Adsorption of NO at ambient temperature on reduced samples results in the formation of two types of species: (i) V⁴⁺(NO)₂ dinitrosyls characterized by ν_s(NO) and ν_as(NO) at 1903–1880 and 1769–1753 cm⁻¹, respectively, and (ii) V³⁺(NO)₂ complexes, which give rise to ν_s(NO) at 1834–1822 cm⁻¹ and ν_as(NO) at 1697–1685 cm⁻¹. At low temperature the dinitrosyls are transformed into species in which more than one (NO)₂ dimer is attached to one cationic site. Addition of O₂ to NO, preadsorbed on reduced vanadia–titania samples, results in a fast oxidation of the V³⁺(NO)₂ species, whereas the V⁴⁺(NO)₂ complexes are more stable and do not disappear completely in the presence of oxygen. The results obtained suggest that NO is a convenient probe molecule for the analysis of the oxidation state of vanadium in vanadia–titania catalysts. To prevent oxidation of reduced vanadium sites, low equilibrium pressures of NO and registration of the IR spectrum soon after the NO admission are recommended. This revised version was published online in August 2006 with corrections to the Cover Date.     

Skeletal Isomerization of Linear Butenes on Boron Promoted Ferrierite: Effect of the Catalyst Preparation Technique

Potassium and acid ferrierites were impregnated with boron species by wet and incipient wetness techniques. All samples display a medium-intensity band at 3,450–3,470 cm⁻¹ associated to Si−OH···O groups corresponding to boron-containing units. The 1,398–1,404 cm⁻¹ band assigned to the B–O stretching in BO₃ units does not appear on boron–potassium–ferrierite prepared by wet impregnation. Catalytic performance during the linear butene skeletal isomerization was measured. At 300 °C, boron impregnated by incipient wetness technique on acid ferrierite reduces both linear butene conversion at a short time and isobutene yield in all time range. Boron–potassium–ferrierite prepared by wet impregnation has a suitable acidity to promote isobutene production. At 450 °C, this sample shows the best performance, being the isobutene yield 1.7 times higher than the acid-ferrierite one and reaching the highest isobutene selectivity (92%). This performance is maintained with time. Both isobutene yield and by-product distribution are strongly affected by temperature; dimer intermediates are formed. Finally, both kinds of hydroxyl groups corresponding to 3,466 and 3,635 cm⁻¹ bands influence the isobutene production whereas BO₃ sites are inactive for this reaction.     

Detection of lard mixed with body fats of chicken, lamb, and cow by fourier transform infrared spectroscopy

Fourier transform infrared (FTIR) spectroscopy provides a simple and rapid means of detecting lard blended with chicken, lamb, and cow body fats. The spectral bands associated with chicken, lamb, and cow body fats and their lard blends were recorded, interpreted, and identified. Qualitative differences between the spectra are proposed as a basis for differentiating between the pure animal fats and their blends. A semiquantitative approach is proposed to measure the percent of lard in blends with lamb body fat (LBF) on the basis of the frequency shift of the band in the region 3009–3000 cm⁻¹, using the equation y=0.1616x+3002.10. The coefficient of determination (R ²) was 0.9457 with a standard error (SE) of 1.23. The percentage of lard in lard/LBF blends was also correlated to the absorbance at 1417.89 and 966.39 cm⁻¹ by the equations y=0.0061x+0.1404 (R ²=0.9388, SE=0.018) and y=0.004x+0.1117 (R ²=0.9715, SE=0.009), respectively. For the qualitative determination of lard blended with chicken body fat (CF), the FTIR spectral bands in the frequency ranges of 3008–3000, 1418–1417, 1385–1370, and 1126–1085 cm⁻¹ were employed. Semiquantitative determination by measurement of the absorbance at 3005.6 cm⁻¹ is proposed, using the equation y=0.0071x+0.1301 (R ²=0.983, SE=0.012). The percentage of lard in lard/GF blends was also correlated to the absorbance at 1417.85 cm⁻¹ (y=0.0053x+0.0821, with R ²=0.9233, SE=0.019) and at 1377.58 cm⁻¹ (y=0.0069x+0.1327, with R ²=0.9426, SE=0.022). For blends of lard with cow body fat (CBF) bands in the range 3008–3006 cm⁻¹ and at 1417.8 and 966 cm⁻¹ were used for qualitative detection. The equation y=−0.005x+0.3188 with R ²=0.9831 and SE=0.0086 was obtained for semiquantitative determination at 966.22 cm⁻¹.     

Synthesis of a novel amphiphilic polymer containing nucleobases in the self-organized nanospheres

A simple strategy to achieve molecular recognition in water is to make the polymers self-organized into nanospheres which could incorporate the functional groups containing hydrogen bonding sites into hydrophobic-lipophilic regions. A novel amphiphilic polymer, Poly(polyoxyethylene-600)-oxy-5-(6-(1-thymine)hexyl)) isophthaloyl (PPETHI), has been synthesized. The PPETHI polymer could self-organize into nanospheres in dilute aqueous solution, which were 150–300 nm in diameter as estimated by SEM. The isophthaloyl with side hexyl thymine of the polymer self-organized into hydrophobic regions and the PEG surrounded it. Molecular recognition between thymine in PPETHI polymer and adenine substrate has been studied by FT-IR. The FT-IR studies demonstrate that C₄=O of thymine has recognized with N-H of adenine through complementary nucleobases. It shows that the typical characteristic band at 3,352 cm⁻¹ of N-H stretching vibration of adenine shifted to 3,373 cm⁻¹ and the band at 1,685 cm⁻¹ of C₄=O of thymine shifted to 1,680 cm⁻¹. To confirm the formation of hydrogen bonds, the N-H band at 3,373 cm⁻¹ and C₄=O band at 1,680 cm⁻¹ have retrieved to 3,312 cm⁻¹ and 1,685 cm⁻¹ respectively upon heating to 115 °C or higher by means of variable temperature FT-IR. The formations of hydrogen-bonds between thymine in the polymer and adenine substrate in nanospheres were confirmed. It could enhance their interaction and loading capacity.     

Kinetic Studies on Oxirane Cleavage of Epoxidized Soybean Oil by Methanol and Characterization of Polyols

The kinetics of the oxirane cleavage of epoxidized soybean oil (ESO) by methanol (Me) without a catalyst was studied at 50, 60, 65, 70 °C. The rate of oxirane ring opening is given by k[Ep][Me]², where [Ep] and [Me] are the concentrations of oxiranes in ESO and methanol, respectively and k is a rate constant. From the temperature dependence of the kinetics thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), free energy of activation (ΔF) and activation energy (ΔE _a) were found to be 76.08 (±1.06) kJ mol⁻¹, −118.42 (±3.12) J mol⁻¹ k⁻¹, 111.39 (±2.86) kJ mol⁻¹, and 78.56 (±1.63) kJ mol⁻¹, respectively. The methoxylated polyols formed from the oxirane cleavage reaction , were liquid at room temperature and had three low temperature melting peaks. The results of chemical analysis via titration for residual oxiranes in the reaction system showed good agreement with IR spectroscopy especially the disappearance of epoxy groups at 825, 843 cm⁻¹ and the emergence of hydroxy groups at the OH characteristic absorption peak from 3,100 to 3,800 cm⁻¹.     

A Novel Dinucleating Ligand-Containing Hexabenzimidazoles and Its Dinuclear Zinc Complex Bridged by a Carboxylate Group for the Hydrolysis of 2-Hydroxypropyl-p-nitrophenyl phosphate

A dinuclear zinc(II) complex with the ligand bis{tris[2-(1-methylbenzimidazole-2-yl)ethyl]-methylamine}nitrilotriacetic acid sodium salt, L, was synthesized and characterized. Complex formation of L with Zn²⁺ in aqueous acetone was studied by Zn²⁺ titration using ¹H NMR and UV–vis spectroscopies. Analysis of the titration data indicates the formation of a dizinc complex. The ν_as(COO⁻) and ν_s(COO⁻) stretches were observed at 1572 and 1450 cm⁻¹, respectively. The low separation of the stretches, Δ_exp = 115 cm⁻¹, is an indication of chelating coordination of the carboxylate group between the two zinc(II) ions. The catalytic activity of [LZn₂]³⁺ 1, as a model for phosphatase that catalyze chemical transformation of phosphate ester, in the hydrolysis of the RNA model, 2-hydroxypropyl p-nitrophenyl phosphate, was examined in aqueous acetone buffer solution, pH 7.0–9.5. The mechanism of the catalytic hydrolysis suggests that the rate of acceleration is due to what is called double Lewis acid activation.     

Long-term behavior of oil-based varnishes and paints I. Spectroscopic analysis of curing drying oils

The curing of drying oils at 60°C has been investigated by Fourier transform infrared spectroscopy and Fourier transform Raman analysis of linseed oil and poppyseed oil. In the first step, hydroperoxides are formed (broad vibration band centered around 3425 cm⁻¹) with concomitant conjugation and cis-trans isomerization of the double bonds (disappearance of cis bands at 3011 and 716 cm⁻¹, appearance of trans conjugated and trans nonconjugated bands at 987 and 970 cm⁻¹). The subsequent decomposition of hydroperoxides in the presence of oxygen leads to the formation of alcohols (nitrite band at 779 cm⁻¹ after nitrogen monoxide treatment), aldehydes (bands at 2810 and 2717 cm⁻¹ in gas phase), ketones (saturated and unsaturated at 1720 and 1698 cm⁻¹, respectively), carboxylic acids (saturated and unsaturated acid fluorides identified at 1843 and 1810 cm⁻¹ after SF₄ treatment), and peresters or γ-lactones (near 1770 cm⁻¹). A rapid decrease in the double-bond concentration is recorded when curing continues, and the formation of epoxides, characterized by a vibration band at 885 cm⁻¹, is observed. Thermolysis experiments have suggested the proposal of a reaction of addition of peroxyl radicals on the conjugated double bonds as a probable mechanism. This mechanism explains both the rapid disappearance of conjugated double bonds and the formation of epoxides as intermediate products observed in the initial step of curing.     

Novel PEO-based solid composite polymer electrolytes with inorganic–organic hybrid polyphosphazene microspheres as fillers

Novel solid-state composite polymer electrolytes based on poly (ethylene oxide) (PEO) by using LiClO₄ as doping salts and inorganic–organic hybrid poly (cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) microspheres as fillers were prepared. Electrochemical and thermal properties of PEO-based polymer electrolytes incorporated with PZS microspheres were studied. Differential scanning calorimetry (DSC) results showed there was a decrease in the glass transition temperature of the electrolytes and the crystallinity of the samples in the presence of the fillers. Maximum ionic conductivity values of 1.2 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.5 × 10⁻⁴ S cm⁻¹ at 80° were obtained and lithium ion transference number was 0.29. Compared with traditional ceramic fillers such as SiO₂, the addition of PZS microspheres increased the ionic conductivity of the electrolytes slightly and led to remarkable enhancement in the lithium ion transference number.     

In vitro dynamic swelling behaviors of polyhydroxamic acid hydrogels in the simulated physiological body fluids

Summary Influence of some simulated physiological body fluids on the dynamic swelling behaviour of polyelectrolytic hydroxamic acid hydrogels (PHA) was investigated at 37 °C in vitro. The simulated physiological body fluids are distilled water, human sera, physiological saline (0.89 % NaCl), isoosmotic phosphate buffer at pH 7.4, gastric fluid at pH 1. 1, (gylicine-HCl buffer), urea (0.3 mol L⁻¹), and the aquatic solutions of K₂HPO₄ and KNO₃ (the sources of K+). The values of equilibrium swelling of PHA hydrogels varied in the range of 130–4625%, while the values of equilibrium fluid content of the hydrogels varied in the range of 57–97%. The initial rate of swelling, diffusional exponent, and, diffusion coefficient were calculated using swelling kinetics data. Diffusion of the fluids into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 0.6×10⁻⁶– 8.1×10⁻⁶ cm² s⁻¹. Received: 15 March 2000/Accepted: 18 December 2000     

Redox and transport behaviors of Cu(I) ions in TMHA-Tf<Subscript>2</Subscript>N ionic liquid solution

The redox and transport behavior of monovalent copper species in an ammonium imide-type ionic liquid, trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf₂N) were examined with a micro-disc electrode to clarify its applicability to, for example, electroplating. It was found that the diffusion coefficient of Cu(I) ions in TMHA-Tf₂N containing 12 mmol dm⁻³ Cu(I) ions was 1.2 × 10⁻⁶ cm² s⁻¹ and the redox potential of Cu(I)/Cu was in the potential range 0.1–0.2 V vs. I ⁻/I ₃⁻ at 50 °C. The diffusion coefficient was one order smaller than that of Cu(II) ions in aqueous solution due to the high viscosity of the ionic liquid. The diffusion coefficient of Cu(I) ion increased with rising temperature and was 1.0 × 10⁻⁵ cm² s⁻¹ at 112 °C, which was comparable to that of Cu(II) ions in aqueous CuSO₄ solutions at ambient temperature. This is accounted for by the drastic decrease in the viscosity of the ionic liquid solution with increasing temperature. The activation energy of diffusion was estimated to be 39 kJ mol⁻¹ in the ionic liquid solution.     

Preparation and physical properties of some C18 unsaturated fatty esters containingL-amino acid residues and methyl esters ofN-stearoylamino acids

A series of five C₁₈ unsaturated fatty esters (1–5) containing anL-amino acid residue (glycine, alanine, valine, leucine, phenylalanine) was prepared from methyl 12-amino-9-cis-octadecenoate and five methylN-stearoyl-amino acid ester derivatives (6–10) from stearoyl chloride and the sameL-amino acids. The infrared analysis of compounds 1–5 showed characteristic absorption bands at 3300 and 1665 cm⁻¹ for the amino and amido functions, while the amido function in compounds 6–10 gave absorption bands at 3300 and 1680 cm⁻¹. The position of the amido group (peptide linkage) in compounds 1–5 was readily determined by mass spectral analysis.¹H nuclear magnetic resonance (NMR) analysis showed a doublet at 7.15 ppm for the amide proton (NHCO) in compounds 1–5, while in compounds 6–10 the amide proton signal appeared at 6.0 ppm. In¹³C NMR, the amido carbonyl resonance appeared at 171–175 ppm. In compounds 1–5 the effect of the amide function on the ethylene carbon (C-9) gave a signal at 124.1–125.3 ppm, while the remaining ethylenic carbon appeared at 131.9–132.5 ppm. The methine carbon (C-12) of the alkenyl chain was shifted to 48.4–49.8 ppm, and the assignment of the various carbon nuclei in the amino acid residue was readily achieved. In the methylN-stearoylamino acid ester derivatives (6–10), the methine carbon adjacent to the amido system and alpha to the carbomethoxy group appeared between 41.2–57.0 ppm depending on the type of alkyl group present in the amino acid moiety. The phenyl system in compounds 5 and 10 was confirmed by the¹³C signals in the 127–136 ppm range and by the proton signals in the 7.0–7.27 ppm region.     

Milled rice surface lipid measurement by diffuse reflectance fourier transform infrared spectroscopy (DRIFTS)

Diffuse reflectance Fourier transform infrared spectroscopy was investigated as a method for rice surface lipid determination. Long- and medium-grain rice was milled at four degrees of milling to obtain samples with various levels of residual bran, and total lipids were determined by solvent extraction. Fourier transform infrared spectra were collected between 4000 and 400 cm⁻¹. Weighted regression analysis identified changes in surface chemical functional groups with bran removal. Groups typical of lipids increased with bran content whereas those typical of carbohydrates and protein decreased. Partial least squares (PLS) regression analysis showed a high degree of correlation between the spectra in the 4000–400 cm⁻¹ range and extracted lipids of long-grain rice (R ²=0.96) and medium-grain rice (R ²=0.96); a high degree of correlation was also observed when long- and medium-grain rice data were combined (R ²=0.96). There was a high positive correlation between the spectra and extracted lipids in the 1300–1000 cm⁻¹ range for the long-grain rice (R ²=0.98), medium-grain rice (R ²=0.98), and combined long-/medium-grain rice data (R ²=0.94). PLS selected spectral regions that correlated positively with functional groups of lipid/lipid oxidation products and negatively with functional groups of protein and carbohydrates.     

Formation and Migration of NCO Species on Ag/SiO2 Catalyst

The adsorption of HNCO has been investigated on Ag/SiO₂ catalyst by means of FTIR spectroscopy. Adsorption of HNCO on the reduced sample at 190 K produced an absorption band at 2,170 cm⁻¹ attributed to NCO bonded to Ag. Annealing the adsorbed layer under continuous degassing, the 2,170 cm⁻¹ band gradually attenuated and at the same time a spectral feature at 2,300 cm⁻¹ due to Si–NCO developed. From these spectral changes it was inferred that NCO bonded to Ag spilt over onto silica.     

Antioxidant activity of Magnolol, honokiol, and related phenolic compounds

The antioxidant activity of 10 Japanese and Chinese crude drugs (Kampo drugs) was determined in vitro. Extract of Magnolia cortex, which had the highest antioxidant activity, contained phenolic compounds magnolol and honokiol. However, inhibitory effects of these compounds on lipid oxidation were weaker than that of α-tocopherol as measured by thiobarbituric acid assay. The structure-activity relationship of phenolic compounds showed that antioxidant activities were in the order 4-allyl-2,6-dimethoxyphenol ≥ p,p′-biphenol > eugenol > 2-allyl-6-methylphenol > honokiol > magnolol > caffeic acid > p-ethylphenol > guaiacol. As expected, these results showed that an electron donor and/or bulky groups at the ortho- or para-position of the phenol were required for inhibition of lipid oxidation. Electron spin resonance spin trapping experiments showed that phenol compounds with an allyl substituent on their aromatic rings directly scavenged superoxide (O ₂ ⁻ ), and that only eugenol trapped hydroxyl radicals. These findings suggest that phenolic compounds that contain allyl groups may be effective antioxidants because of the scavenging ability of O ₂ ⁻ or hydroxyl radical, whereas other phenols, without an allyl moiety such as α-tocopherol, may play a role in the termination of free radical chain reactions.