bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Oxidative Solvolysis of Durohydroquinone Monobenzoates. A Study of the Mechanism
Authors: Takagi Makoto , Tazaki Masato , Matsuda Tsutomu 
Published: July 2006

Abstract
Durohydroquinone mono(p-substituted benzoate)s (1a–1e) were oxidized by DDQ, in CH3OH/CH2Cl2 at room temperature. The products were duroquinone dimethyl acetal 4 and p-substituted benzoic acids (5a–5e). None of the methyl esters 3 was formed. The details of the mechanism of a series of reactions, which start with the one-electron oxidation of 1, is elucidated by the isolation and characterization of the intermediates as well as by a kinetic study in an acetonitrile solution. The relation between the mode of oxidation, whether it is a one-electron or two-electron process, and the activation of the acyl group was explicitly discussed in terms of the mechanism. Two-electron oxidation is suggested to offer a better chance for acyl activation. Some generalization of the mechanism is made for other oxidation-induced acyl, phosphoryl and sulfuryl activating systems.
The Temperature and Solvent Effects on the AlCl3-catalyzed Cyclization of 3,3′-Diphenyl-2,2′-biindenyl-1,1′-dione
Authors: Toda Fumio , Todo Yozo 
Published: July 2006

Abstract
Upon the AlCl3-catalyzed cyclization of the title biindenone (1) into benz[c]indeno[2,1-a]fluorene-13,14-dione (2) and 3,3′: 3,3′-di(o-phenylene)-2,2′-biindenylidene-1,1′-dione (3), the 2:3 ratio increased when the reaction temperature was raised and decreased when the polarity of the solvent was increased.
Studies of Pyrazines, I. Pyrolyses of Substituted Pyrazines and Their Thermal Stabilities
Authors: Konakahara Takeo , Takagi Yukio 
Published: July 2006

Abstract
The pyrolyses and thermal stabilities of 2,5-dialkylpyrazines (1a–e), 2,5-diethoxypyrazine (2), chloropyrazine (3), alkoxypyrazines (4a–c), alkylthiopyrazines (5a, b), and alkylaminopyrazines (6a–d) were studied by means of a mass spectrometer, by which the pyrolysates in the sample reservoir were analyzed. The temperature dependence of the molecular ions and/or fragment ions was also discussed. The thermal dehydrogenation from two α-methine groups makes the 1d molecule thermally sensitive. The other 2,5-dibutylpyrazines were more stable than it, except for the t-butyl derivative, 1e. Hydroxy- and aminopyrazine, 4a and 6a, were very stable. The alkoxypyrazines, 4b and 4c, and alkylthiopyrazines, 5, underwent the thermal elimination of olefine to yield hydroxy- and mercaptopyrazine respectively. The latter disproportionated to form dipyrazinyl sulfide (11). At 280 °C, no analogous reactions of alkylaminopyrazines 6b–d could be observed. The relative thermal stabilities of the compounds were as follows:
2, 4a, 6a, 4b&gt;1c&gt;1e&gt;1b&gt;6c, 5a&gt;3&gt;6b&gt;1d&gt;1a&gt;6d, 5b&gt;4c
Preparation and the Properties of π-Allylic Palladium(II) Complexes of Amino Acid
Authors: Nakagawara Yoshihiro , Kikukawa Kiyoshi , Takagi Makoto , Matsuda Tsutomu 
Published: July 2006

Abstract
The preparation of π-allylic and related organopalladium(II) complexes with amino acid anions as bidentate ligands is described. The complexes were characterized by means of 1H NMR.
Relations between the Thermodynamic Properties of Alkali Halides at the Melting Point
Authors: Kanno Hitoshi 
Published: July 2006

Abstract
Two new empirical formulas are presented for alkali halides at the melting point. There is a set of linear relations between the initial slope of melting curve (dTm⁄dP) and the solid volume (Vs) for the sequences LiX, NaX, KX, and RbX (X=F, Cl, Br, and I).
Studies of Lignoids in Lauraceae. III. A New Lignan from the Heart Wood of Cinnamomum Camphora Sieb.
Authors: Takaoka Daisuke , Imooka Minoru , Hiroi Mitsuru 
Published: July 2006

Abstract
From the heart wood of Cinnamomum Camphora Sieb., a new lignan, (−)-trans-2-(3,4-dimethoxybenzyl)-3-(3,4,5-trimethoxybenzyl)butyrolactone [I] and 3-hydroxy-5,7-dimethoxy-3′,4′-methylenedioxyflavan [IV], were isolated, and their structures were determined.
Preparation of Mannich Bases from 6-Methoxy-2H-pyran-3(6H)-one and Its Epoxide
Authors: Torii Sigeru , Tanaka Hideo , Takao Hisasi 
Published: July 2006

Abstract
4-Morpholinomethyl-2H-pyran-3(6H)-ones 3 and 8 were prepared directly from 6-methoxy-2H-pyran-3(6H)-one (1) and its epoxide 4 by treatment with morpholine and aqueous 37% formalin in methanol in 70–88% yield. The mechanisms of the reaction have been discussed on the basis of the intermediates 5,6-dimethoxytetrahydropyran-3-one (2), 2,6-dimethoxy-5-hydroxytetrahydropyran-3-one (5), 2,6-dimethoxy-2H-pyran-3(6H)-one (6), and 2,5,6-trimethoxytetrahydropyran-3-one (7).
Aryl Alkanehydrazonates and Their Thio Analogs. Synthesis of Some 2-Alkyl Derivatives of 4H-1,3,4-Benzoxadiazines and 4H-1,3,4-Benzothiadiazines
Authors: Shawali Ahmad Sami , Hassaneen Hamdi Mahmoud 
Published: July 2006

Abstract
Synthesis of some p-nitrophenyl alkanethiohydr azonates, RC(SC6H4NO2-p)=NNHC6H3BrNO2(2, 4−), and p-nitrophenyl alkanehydrazonates, RC(OC6H4NO2p=NNHC6H3BrNO2(2,4−) is described. Upon treatment with triethylamine in ethanol at reflux the thiohydrazonates give directly 2-alkyl-4-(p-nitrophenyl)-7-nitro-4H-1,3,4-benzothiadiazines, whereas the hydrazonates yield the hydrazides, RCONHN(C6H4NO2-p)C6H3BrNO2(2,4−). The latter hydrazides can be cyclized, under stronger basic conditions, into 2-alkyl-4-(p-nitrophenyl)-7-nitro-4H-1,3,4-benzoxadiazines by displacement of the 2-bromine atom.
A Study of the Behavior of Surface Oxygen of V2O5 Catalysts by the Use of the 18O-Tracer
Authors: Kera Yoshiya 
Published: July 2006

Abstract
By the use of highly concentrated 18O-carbon dioxide, both the rate of the isotopic exchange of CO2 and the surface oxygen of a powderd V2O5 catalyst and that of the isotopic equilibration of CO2 on the surface were determined simultaneously in the temperature range from 330 to 450 °C. The rate of the isotopic exchange on the thin-plate crystallines, in which the (010) plane of V2O5 crystal was mainly exposed, was also determined. The equilibration rate was 30–40 times faster than the exchange rate. The exchange process on the thin-plate crystallines was found to be extremely rapid, although such a phenomenon has never been found on the powdered catalyst. Based on these results, the relationship of the reaction steps of the isotopic exchange and the isotopic equilibration with those on the triangular scheme of CO-oxidation, previously proposed, was discussed in detail. A small cycle of alternate reduction-oxidation on the top of the surface, especially on the (010) plane, was conclusively confirmed.
The Determination of the Critical Volume for the Free Motion of Solute Entities in an Aqueous Solution
Authors: Fujiwara Shizuo , Nagashima Kozo , Morita Hiroshi , Kanaoka Yasushi 
Published: July 2006

Abstract
A certain volume of a solution, (20–30 Å)3 per unit of solute entity, designated the “molecular space,” is assigned as the necessary volume for the free motion of the solute. By the use of ESR, the actual size of the molecular space has been determined for the cupric ion and 2,2,5,5-tetramethyl-3-carbamoylpyrollidin-1-oxyl. It is pointed out that the concentrations of the important solutions in nature, such as sea water or human serum, may correspond to the moleuclar space of ions.
31P Magnetic Relaxation in Polynucleotides
Authors: Akasaka Kazuyuki , Yamada Atsuko , Hatano Hiroyuki 
Published: July 2006

Abstract
Phosphorus-31 nuclear spin-lattice relaxation times and nuclear Overhauser enhancement upon nonselective proton saturation were measured on polyriboadenylic acid, polyribocytidylic acid, and polyribouridylic acid. A method is described to separate dipolar contribution from the contribution of chemical shift anisotropy for the phosphorus relaxation by the combined use of T1 and NOE data. Chemical shift anisotropies (δ⁄⁄−δ⊥) of phosphorus in these polynucleotides in solution are estimated to be in the range 120–165 ppm. The molecular motion of the phosphorus moiety becomes faster in the order, poly(A)&lt;poly(C)&lt;poly(U), the thermal activation processes being characterized by single activation energies, i.e., 5.1, 5.3–6.0, and 7.2–8.1 kcal/mol for poly(U), poly(C), and poly(A), respectively.
Electronic States of the Crystals of TCNE Complexes with Hexamethylbenzene, Acenaphthene, and Dibenzofuran
Authors: Tanaka Masashi 
Published: July 2006

Abstract
The polarized reflection spectra were measured on crystals of tetracyanoethylene and its charge-transfer complexes, and the absolute intensity of the absorption parallel to the crystalline axes has been obtained by the Kramers-Kronig transformation. The charge-transfer degree and the stabilization energy in the ground state were estimated for each complex by analyzing the charge-transfer bands in the crystalline state. In the TCNE–hexamethylbenzene(HMB), acenaphthene, and dibenzofuran complexes, the charge-transfer degrees are 9.05, 12.3, and 4.95% respectively in the ground state.
The Two-Photon Excitation Spectrum of Phenanthrene Crystal
Authors: Otokozawa Hiroshi , Inomata Shigehiro , Mikami Naohiko , Ito Mitsuo 
Published: July 2006

Abstract
The two-photon excitation spectrum of phenanthrene crystal was measured and compared with the corresponding usual one-photon absorption spectrum. It was found that the two-photon spectrum consists of a one-photon like system and a system characteristic of a two-photon process. The vibronic couplings in phenanthrene were discussed on the basis of the observed results.
A Method for the Analysis of Halogenated Organic Compounds in Tap Water by Means of Mass Fragmentography of GC-MS
Authors: Fujii Toshihiro 
Published: July 2006

Abstract
A simple, sensitive and practical method for the halogenated organic compound analysis of tap water is reported. A pentane extraction procedure using a ten fold increase in concentration by volume (without further concentration) followed by mass fragmentography of GC-MS was used. As little as 0.05 ppb concentration of each compound was detectable. Five simple halogenated organic compounds, including CCl4 and CHBr3 whose concentrations are relatively small, were determined for tap water in Japan.
The Synthesis of α-Aminonitriles Starting from the Corresponding Amino Acids. I. Use of o-Nitrophenylsulfenyl as an N-Protecting Group
Authors: Kawashiro Katsuhiro , Yoshida Hideyuki , Morimoto Shiro 
Published: July 2006

Abstract
N-o-Nitrophenylsulfenylamino acid amides of glycine, alanine (Dl and l), leucine (Dl and l), methionine (Dl), phenylalanine (Dl and l), and proline (l) were dehydrated in POCl3-pyridine. The N-protected α-amino-nitriles obtained were treated with anhydrous HCl affording the corresponding α-aminonitrile hydrochlorides. The optical purity of the l-α-aminonitriles was well retained.
Proton Magnetic Resonance Studies of cis-trans Equilibria of Some N-(2,5-Dichlorophenyl)-3-aminocrotonamides
Authors: Kondo Michio 
Published: July 2006

Abstract
The 1H NMR spectra of 3-(alkylamino)crotonamides indicate that these substances exist in solution as a mixture of the geometric isomers, cis and trans, in which the chelated cis form is predominant. Unsubstituted 3-aminocrotonamide appears to exist in the cis form only, and N,N-disubstituted derivatives in the trans form. In the case of 3-(alkylamino)crotonamide it is found that the cis-trans equilibrium is solvent dependent and that the apparent rate of interconversion between the isomers is very slow in chloroform-d, fast in dimethyl-d6 sulfoxide, and intermediate in acetone-d6 and methanol-d4. It seems that the cis-trans equilibrium is almost independent of both temperature and concentration, and that the replacement of the olefinic H by D proceeds through enamine\ightleftharpoonsimine tautomerization.
Stereochemical Studies of the Electrolytic Reactions of Organic Compounds. IV. Electrolytic Reduction of Optically-active 1-Pyridylalkanols to the Corresponding Substituted-alkyl Pyridines
Authors: Nonaka Tsutomu , Ota Tetsuro , Fuchigami Toshio 
Published: July 2006

Abstract
The mechanism of electrolytic reduction of 1-pyridylalkanol to the corresponding substituted-alkyl pyridine was examined by electrolyzing several optically-active 1-pyridylalkanols in an aqueous sulfuric acid solution in the vicinity of a mercury cathode. The alkyl pyridine from 1-(2-pyridyl)alkanol showed optical rotation, while that from 1-(4-pyridyl)alkanol was almost racemized.
The Ullmann Condensation Reaction of Haloanthraquinone Derivatives with Amines in Aprotic Solvents. II. The Presence of an Induction Period in the Condensation with 2-Aminoethanol
Authors: Arai Sadao , Hida Mitsuhiko , Yamagishi Takamichi , Ototake Satoshi 
Published: July 2006

Abstract
An induction period was present in the Ullmann condensation reactions of 1-bromoanthraquinone(AQBr) with 2-aminoethanol(AE) in the presence of CuBr or CuI in aprotic solvents under a nitrogen atmosphere, while there was no induction period in the reaction systems of 1-iodoanthraquinone(AQI)–AE–CuBr, AQI–AE–CuI, and AQBr–AE–[Cu(CH3CN)4]ClO4. In the condensation system with a copper(I) catalyst, the Cu(I) species was oxidized to the Cu(II) species by means of an electron transfer from Cu(I) to haloanthraquinone as the reaction proceeded. By adding copper(II) bromide, the induction period vanished in the reaction system of AQBr–AE–CuBr. The copper(II) species increased the catalytic activity of the copper(I) species. The formation of the copper(II) species was responsible for the presence of an induction period and played an important role in the Ullmann condensation reaction of haloanthraquinones with amines in the presence of copper(I) salt as a catalyst.
Excited-State Dipole Moments of Picrates of Pyridine, 2-Methylpyridine, 3-Methylpyridine, and 4-Methylpyridine
Authors: Sedoyama Osamu , Higashi Miwako , Akimoto Yoshinori , Yamaguchi Hiroyuki 
Published: July 2006

Abstract
Measurements of the excited-state dipole moments for picrates of pyridine and methylpyridines have been carried out by spectrophotometry. The contribution of the dative structure Ψ(D+A−) in the excited state of these picrates is larger than the contribution of Ψ(D+A−) in the ground state.
Studies of Heterocyclic Compouds. XII. Structures of Acetylated Products of 5-Hydroxy-4-(2-hydroxyethyl)-3-methylpyrazole
Authors: Ochi Hisao , Miyasaka Tadashi , Arakawa Kiichi 
Published: July 2006

Abstract
Acetylation of 5-hydroxy-4-(2-hydroxyethyl)-3-methylpyrazole (1) produced five acetyl derivatives: 4-(2-acetoxyethyl)-5-hydroxy-3-methylpyrazole (2), 4-(2-acetoxyethyl)-2-acetyl-5-hydroxy-3-methylpyrazole (3), 4-(2-acetoxyethyl)-1-acetyl-5-hydroxy-3-methylpyrazole (4), 5-acetoxy-4-(2-acetoxyethyl)-2-acetyl-3-methylpyrazole (5), and 1-acetyl-5-hydroxy-4-(2-hydroxyethyl)-3-methylpyrazole (6). The partial hydrolysis of 3 and 5 in aq acetic acid gave the monoacetate (2). The triacetate (5) afforded 3 by heating in a mixture of pyridine and meththanol. Migration of the acetyl group from the N1-position to the C5-O- and to the side chain-O-position is suggested. It is also suggested that the triacetate (5) may be effective for acetylation of amines.
The Photocyclization of 3,3′-Diphenyl-2,2′-bi-1H-indene-1,1′-dione
Authors: Toda Fumio , Todo Yozo 
Published: July 2006

Abstract
The photocyclization of the title compound afforded 14-hydroxy-4b-phenylbenz[c]indeno[2,1-a]fluoren-13-(4bH)-one, which is easily isomerized to 4b,13b-dihydro-4b-phenylbenz[c]indeno[2,1-a]fluorene-13,14-dione. The hydrogenation of both compounds gave anti-4b,8b,13a,13b-tetrahydro-4b-phenylbenz[c]indeno[2,1-a]fluorene-13,14-dione.
The Synthesis and Properties of Diacyl Selenides
Authors: Ishihara Hideharu , Sato Shigeyuki , Hirabayashi Yoshio 
Published: July 2006

Abstract
Diacyl selenides were synthesized in good yields by the deselenization of diacyl diselenides, which have conveniently been prepared from acyl chlorides and sodium hydroselenide. The reaction of dibenzoyl selenide with piperidine at 0 °C formed a fairly stable piperidinium salt. The methanolysis of distearoyl selenide gave selenostearic acid as an unstable intermediate.
Nuclear Magnetic Resonance Study of Exchanging Systems. IX. The Slow Rotation of the Methyl Group in Sterically Overcrowded Compounds
Authors: Nakanishi Hiroshi , Yamamoto Osamu 
Published: July 2006

Abstract
In order to obtain information about the slow rotation of methyl groups, the 1H NMR spectra of 9-t-butylethenoanthracene and 9-t-butyltriptycene derivatives were measured at very low temperatures. It was found that the signals of the two methyls of the t-butyl group in these compounds show a considerable line broadening at low temperatures, and it was made clear that the rotation of the methyl groups in these compounds is strongly restricted.
Chemical Transformation of Seldomycin 5 into 3′-Episeldomycin 5 and Its Antibacterial Activity
Authors: Matsushima Hideo , Kitaura Kozo , Mori Yasuki 
Published: July 2006

Abstract
3′-Episeldomycin 5 (7) was synthesized from seldomycin 5. Reaction of hexa-N-ethoxycarbonylseldomycin 5 (2) with o-nitrobenzenesulfonyl chloride gave penta-N-ethoxycarbonylseldomycin 5-2′,3′-epicyclic carbamate (3) in one step. Hexa-N-ethoxycarbonyl-3′-O-tosylseldomycin 5 or hexa-N-ethoxycarbonyl-3′-O-mesylseldomycin 5, prepared from 2, was also converted into 3 by being heated in weakly basic solvents such as N,N-dimethylformamide or pyridine. Compound 3 was hydrolyzed to give 7. Structure of 7 was confirmed by PMR, CMR, MS, and Δ[M] values. Compound 7 was found to be active against resistant bacteria which carry 3′-O-phosphorylating enzymes. Δ[M] values for vicinal amino groups were shortly discussed.
The C–Se Stretching Vibrations and Molecular Conformations of Dialkyl Selenides
Authors: Ohno Keiichi , Hirokawa Takeshi , Aono Seiro , Murata Hiromu 
Published: July 2006

Abstract
The Raman spectra of dialkyl selenides were measured in the liquid and solid states. The most intense Raman lines observed in the 500–700 cm−1 region were assigned to the C–Se stretching vibrations. Correlations of the C–Se stretching frequencies to the molecular conformations were found.
The Separation of Aluminium(III) and Chromium(III) as Their AcAc(acetylacetone)-Complexes, and of Cobalt(II), Copper(II), Magnesium(II), Manganese(II), Nickel(II), and Lead(II) as Their TTA(thenoyltrifluoroacetone)-Complexes, by Extraction Chromatography
Authors: Honjo Takaharu , Honda Yoshio , Matsumoto Tetsu , Honda Ryumon , Kiba Toshiyasu 
Published: July 2006

Abstract
The liquid-liquid extraction behavior of the Al(III) and Cr(III)–AcAc(acetylacetone)–CHCl3 system and of the Mg(II), Pb(II), Mn(II), Co(II), Ni(II), and Cu(II)–TTA(thenoyltrifluoroacetone)–MIBK (isobutyl methyl ketone) system have been studied, and the results have been applied to the separation of these metals as their AcAc and TTA-complexes by extraction chromatography.
Studies of Nitrogen-Phosphorus Compounds. XXVIII. The Thermal Decomposition and Fireproofing Effect of Trimeric and Tetrameric Phosphorus Diamide Nitride
Authors: Kobayashi Etsuro , Kanayama Tadao 
Published: July 2006

Abstract
The thermal decomposition of N3P3(NH2)6·H2O and N4P4(NH2)8·H2O and their fireproofing effects for cellulose have been investigated by means of DTA and TG. These compounds dehydrated at 113 and 124 °C and deammonated at 265 and 271 °C. The activation energies of the dehydration and deammonation were 27 and 42 kcal/mol in the trimer, and 37 and 40 kcal/mol in the tetramer. The cellulose impregnated with either of these compounds flamed up at lower temperatures than did the pure cellulose, but its carbonized product remakably resisted combustion.
Convenient Synthesis of α-Mercaptoalkanoic Acid Esters Using S-Cyanomethyl Thiocarbamates
Authors: Masuyama Yoshiro , Ueno Yoshio , Okawara Makoto 
Published: July 2006

Abstract
The reaction of cyanomethyl dithiocarbamate and S-cyanomethyl thiocarbamate with alkyl halides in aqueous medium selectively gave mono- and di-alkylated products. The treatment of the alkylated products with coned sulfuric acid gave α-mercaptoalkanoic acid esters.
A Phenomenological Description of Electron Paramagnetic Double-Resonance Relaxation of Organic Free Radicals in Solution. I. Theory of ENDOR Based on the Spin-Population Number Method
Authors: Shikata Hideo 
Published: July 2006

Abstract
ENDOR enhancement is phenomenologically described, applying the method of Lloyde and Pake. Emphasis is placed on the effect of incomplete hf separation. It is shown that fractional ENDOR enhancement can approximately be expressed as the product of that which Freed has formulated when the effect is absent, and an modified Allendoerfer-Maki type correlation, T2e2Δω2⁄(c+T2e2Δω2), where c is a constant dependent on the microwave power. Also, a simplified method is proposed for calculating the fractional ENDOR enhancement for a multilevel system consisting of several sets of equivalent protons, when Wn&lt;&lt;We, and it is proven that the week rf power irradiated leads to an ENDOR enhancement proportional to the number of equivalent protons, in the absence of the effect of incomplete hf separation.
Electronic Absorption Spectra of Pyrene and Hydropyrenes
Authors: Yoshinaga Tetsutaro , Hiratsuka Hiroshi , Tanizaki Yoshie 
Published: July 2006

Abstract
Vibronic π-π* transition bands of pyrene, 4,5-dihydropyrene (DHP), and 4,5,9,10-tetrahydropyrene (THP) were assigned by means of dichroism analysis using stretched poly(vinyl alcohol) films. The absorption spectra of the samples in the non-stretched films were divided into two component spectra polarized along the long (x) and short (z) axes of the molecular plane. For pyrene, in addition to the four conventionally-assigned band systems (1Lb, 1La, 1Bb, and 1Ba), some forbidden bands were found in the respective band regions. Most of the vibronic DHP and THP bands were also reasonably well assigned from comparisons with the calculated results for phenanthrene and biphenyl, respectively.
The Effect of Temperature on the Mass Spectra of 1-Alkenes. II
Authors: Hoshino Hiroko , Tajima Susumu , Isogai Fusako , Tsuchiya Toshikazu 
Published: July 2006

Abstract
The mass spectra of 1-alkenes ranging from C5 to C10 were measured at temperatures of the ion source 120–250 °C. Fragmentation M+\oversetm28→(M–28)+ and M+\oversetm28→(M–29)+, where m28 and m29 denote the metastable peaks of the fragmentations, were studied. The behavior of the curve of the intensity ratios R′28=m28⁄F28 and R′29=m29⁄F29(F28 and F29 denote the intensities of the (M–28)+ ion and the (M–29)+ ions, respectively), versus temperature T of the ion source of the mass spectrometer is explained by the quasi-equilibrium theory (QET).
Application of INDOR Method to a Relatively Slow Exchange System. OH Protons of the 1,3-Dihydroxyacetone Dimer in Dimethyl-d6 Sulfoxide
Authors: Kuroda Yoshihiro 
Published: July 2006

Abstract
The nuclear magnetic multiple-resonance method developed by Forsén and Hoffman for the study of exchange rates has been applied to the two different types of OH protons of the 1,3-dihydroxyacetone dimer in dimethyl-d6 sulfoxide, i.e., OH (α) and CH2OH (β). Here, “decay” and “recovery” curves were obtained using the so-called “INDOR” method, instead of a rapid repetitive scan method. Since the INDOR method continuously monitors a peak height, decay and recovery curves as fast as 1 s can be drawn by storing them in a computer after a single scan. The concentration dependence was examined as a two-site exchange system by neglecting the small amount of water (γ) contained in the dimethyl sulfoxide solvent. Both the lifetime, τ, and the longitudinal relaxation time, T1 obtained from this assumption correlate well with the concentration variation of the 1,3-dihydroxyacetone dimer. The difference in the types of OH protons on the concentration dependence is clearly seen for the latter parameter, T1. From the triple-resonance experiments including γ, it was found that the β proton is more “labile” than the α.