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1.
Karima Boubekri Junko Yano Satoru Ueno Kiyotaka Sato 《Journal of the American Oil Chemists' Society》1999,76(8):949-955
Polymorphic transformations of sn-1,3-distearoyl-2-ricinoleyl-glycerol (SRS) have been studied with differential scanning calorimetry, X-ray powder diffraction
(XRD), synchrotron radiation X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR) techniques by using a 99.8%
pure sample. Four polymorphs, α, γ, β′2, and β′1, were isolated. The thermal behavior of the four forms showed that the fusion of α at 25.8°C was followed by the crystallization
of γ which melts at 40.6°C, and β′2 and β′1 revealed melting peaks at 44.3 and 48.0°C, respectively. No β form was observed, even when the two β′ forms were annealed
around their melting points over one week. The XRD long spacing indicates that α packs into a double chain-length structure;
however, γ and the two β′ phases pack into a triple chain-length structure. The polarized and nonpolarized FTIR spectra in
methylene scissoring and methylene rocking regions indicated a parallel subcell packing in γ, and a mixture of orthorhombic
perpendicular and parallel or hexagonal subcells in the β′2 and β′1 phases. Consequently, SRS exhibits quite a unique polymorphic behavior, compared to tristearoyl glycerol and sn-1,3-distearoyl-2-oleoyl-glycerol. 相似文献
2.
M. Takeuchi S. Ueno E. Flöter K. Sato 《Journal of the American Oil Chemists' Society》2002,79(7):627-632
The binary phase behavior of SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SLS (1,3-distearoyl-2-linoleoyl-sn-glycerol) was examined by using DSC and conventional and synchrotron radiation X-ray diffraction. The solid-solution phases
were observed in the metastable α and γ forms in all concentration ranges. Results indicated that the miscible γ form did
not transform to the β′ form when the mixtures were subjected to simple cooling from a high-temperature liquid to a low-temperature
solid phase. However, and α-melt-mediated transformation into β′ and β2 resulted in the formation of immiscible phases in concentration ranges of SLS below 30%. By contrast, at SLS concentration
ranges above 30%, the α-melt-mediated transformation caused crystallization of only the γ form, and β′ and β2 crystals did not appear. These results show that the specific interactions between SOS and SLS are operative in the phase
behavior of the mixture states of SOS and SLS. 相似文献
3.
Satish K. Singh Ali Fathe Jalali Maggie Aldén 《Journal of the American Oil Chemists' Society》1999,76(4):499-505
The transformations of tristearin were examined by modulated temperature differential scanning calorimetry (MTDSC) in order
to study the effect of operational parameters on the nature of information obtained from this technique. Tristearin has been
used as a model polymorphic system showing metastable phases and complicated transformation routes occurring at relatively
slow rates. The parameters examined were underlying heating/cooling rates and the amplitude of modulation. The first conclusion
is that MTDSC enables overlapping α-melting and β-crystallization events to be separated, thus increasing the information
obtained compared to normal thermal analysis. Other general conclusions are that observation of reversible processes is strongly
influenced by the underlying heating rate; low to moderate heating rates are recommended. Amplitude of modulation has a complicated
effect on the phenomenon being studied; when studying systems that exhibit metastable or polymorphic transitions, it is recommended
that a range of amplitudes be tested to enable confirmation of whether an observed ‘recrystallization’ effect is a new phase
or the same phase as the one melting. Cooling with modulation disturbs the crystallization process, possibly leading to smaller
or imperfect crystals; however, the phases obtained are not different compared to normal DSC. The usefulness of MTDSC in analyzing
these types of complicated systems is primarily qualitative at the moment. Some recommendations have been made as to the combinations
of parameters for studying such systems. 相似文献
4.
T. D. Simpson D. P. Hockett L. Harris 《Journal of the American Oil Chemists' Society》1984,61(5):883-886
Differential scanning calorimetry is used to obtain specific heats of the α, β′2, β′1 and β phases of trimargarin and tristearin in the temperature range from 190–350 K. Unequal specific heats are observed for
β′ phases of the 2 lipids in contrast to nearly coincident values for their respective α and β phases. These results are discussed
on the basis of odd vs even chain length triglycerides. 相似文献
5.
A. Minato S. Ueno J. Yano K. Smith H. Seto Y. Amemiya K. Sato 《Journal of the American Oil Chemists' Society》1997,74(10):1213-1220
Thermodynamic and polymorphic behavior of POP (sn-1,3-dipalmitoyl-2-oleoylglycerol) and OPO (sn-1,3-dioleoyl-2-palmitoylglycerol) binary mixtures was examined using differential scanning calorimetry and conventional and
synchrotron radiation X-ray diffraction. A molecular compound, βC, was formed at the 1:1 (w/w) concentration ratio of POP and OPO, giving rise to two monotectic phases of POP/compound and
compound/OPO in juxtaposition. βC has a long-spacing value of 4.2 nm with a double chainlength structure and the melting point of 31.9°C. A structural model
of the POP-OPO compound is proposed, involving the separation of palmitoyl and oleoyl chain leaflets in the double chainlength
structure. In the polymorphic occurrence of the POP-OPO mixtures, the POP fraction transformed from α to β′ with no passage
through γ, then transformed to β. The presence of OPO in POP promoted the β′-β transformation of POP during the melt-mediated
crystallization. 相似文献
6.
K. Sato T. Arishima Z. H. Wang K. Ojima N. Sagi H. Mori 《Journal of the American Oil Chemists' Society》1989,66(5):664-674
The polymorphic modifications of POP and SOS were identified with X-ray diffraction (XRD), DSC and Raman spectroscopy by using
pure samples (99.9%). In POP, six polymorphs, α,γ, pseudo-β′2, pseudo-β′1, β′2 and β′1, were obtained, whereas five polymorphs, α, γ, pseudo-β′, β2 and β1, were isolated in SOS. Thermodynamic stability increased from α to β1 straightforwardly both in POP and SOS, because the polymorphic transformation went monotropically in the order described
above. Additionally, the 99.2% sample of POP crystallized another form, δ, but the 99.9% sample did not, implying subtle influences
of the impurity. The four forms, α, γ, β2 and β1, of POP, revealed XRD and DSC patterns identical to the four forms of SOS designated by the same symbols. The chain length
structure was double inα and triple in the other three forms in both POP and SOS. Peculiarity of POP was revealed partly in the chain length structure
of pseudo-β′2 and pseudo-β′1 which were double, whereas pseudo-β′ of SOS was triple. This apparently showed contrast to the facts that the three forms
revealed rather similar XRD short spacing patterns. Another peculiarity of POP was revealed in enthalpy value of the melt
crystallization of α: ΔHc (α) = 68.1 kJ/mol which was much larger than that of SOS (47.7 kJ/mol), and also than AOA and BOB. These peculiarities mean
that the double chain length structures of POP are more stabilized than the others. Raman bands of CH2 scissoring mode of SOS indicated parallel packing in γ, β2 and β1, and orthorhombic perpendicular packing in pseudo-β′. The polymorphic transformation mechanisms were discussed based on the
proposed polymorphic structure models.
Presented at the AOCS annual meetings in New Orleans, Louisiana in May 1987 and Phoenix, Arizona in May 1988. 相似文献
7.
The polymorphism of single fatty acid odd triglycerides, C11 through C17 has been reinvestigated, with extension of the study to C9, C19 and C21. With study of the even glycerides C8, C20 and C22 it has been possible to review the whole series (odd and even) C8 through C22. The odd glycerides resemble the even in showing three distinct melting levels. Lowest melting forms are α. Stable forms
are β except for C9 and C11 which show a different structure type. Intermediate melting β′ forms of odd glycerides are substantially more stable than
their even counterparts as well illustrated by differential thermal analysis. There are no vitreous forms. Alternation in
mp (between odd and even) is confirmed for stable phases and nonalternation for α and (within experimental error) for β′.
Both β′ and β long spacings show alternation but not α. Alternation is evident in the short spacings of β′ and β forms. While
short spacings of β′ forms of even triglycerides are much alike especially for C14 through C22, those of odd glycerides show a fortuitous 4-carbon cycle. This appears to involve no significant structural variation as
chain length increases but simply an approximate 4-carbon cycle of variation in diffraction details derived from the presumed
unvarying 0 ⊥ type subcell structure. 相似文献
8.
Paul J. M. W. L. Birker Sijmen de Jong Eli C. Roijers Ton C. van Soest 《Journal of the American Oil Chemists' Society》1991,68(12):895-906
To reveal the structure ofβ′ triacylglycerols in detail, LML (C12C14C12) was purified by a zone-melting procedure, and twinned crystals ofβ′ stable LML were obtained from a melt,β′ LML crystallizes in the monoclinic space group C2, with eight molecules in the unit cell. A powder X-ray diffraction study of solid compounds of 1:1 mixtures of selected triacylglycerols
led to the conclusion that the triacylglycerol molecules in theβ modification have a 1,2 chair-conformation (i.e., the fatty acid chains on glycerol positions 1 and 2 are adjacent, with the chain on the 3-position forming the back rest
of the chair). Packing studies and the positions of two-fold axes and two-fold screw axes in the unit cell require that the
molecules are bent at the glycerol site. The fatty acid chains make an angle of 25° with the long axis of the unit cell. Electron
micrographs and precession photographs indicate that the twinning results from the stacking of a large number of thin crystalline
platelets in two distinct orientations. 相似文献
9.
Polymorphism of stabilized and nonstabilized tristearin,pure and in the presence of food emulsifiers 总被引:1,自引:0,他引:1
Paola Elisabettini Amélia Desmedt François Durant 《Journal of the American Oil Chemists' Society》1996,73(2):187-192
The polymorphism of tristearin (SSS) was studied by means of differential scanning calorimetry and powder X-ray diffraction.
The influence of 5% in weight of different food emulsifiers—i.e., 1-monostearin, sorbitan tristearate, and sugar monostearate—was
also studied. Because polymorphism is sensitive to thermal treatment, two thermal conditionings were applied. According to
the dynamic process (melting, quenching, and heating at 5°C/min), SSS showed three polymorphic forms: α, β′, and β1. The presence of the emulsifiers hindered the β′→β transformation, and a destructured β2 form was recorded. According to the stabilization process (stabilization at 57°C for various periods of time), SSS showed
two β′ forms: β
2
′
and β
1
′
. Three hours of stabilization were necessary to recover the whole triglyceride under the β form. The emulsifiers slowed down
the polymorphic transition rates. Indeed, after six hours of stabilization, mixtures of β′ and β were observed. Sugar monostearate
seemed to have the most powerful effect on the transition kinetics because large amounts of α form were detected.
Presented at the 86th AOCS Annual Meeting & Expo, in San Antonio, Texas, in May 1995. 相似文献
10.
J. F. Toro-Vazquez M. Briceño-Montelongo E. Dibildox-Alvarado M. Charó-Alonso J. Reyes-Hernández 《Journal of the American Oil Chemists' Society》2000,77(3):297-310
This study investigates the crystallization kinetics of palm stearin (PS), a palm oil fraction, in blends with sesame seed
oil. The results indicate that the crystallization behavior of PS in sesame oil is mainly associated with the crystallization
of tripalmitin. Therefore, crystallization of blends of 26, 42, 60, and 80% (wt/vol) PS in sesame oil was described by equations
developed for simpler systems (e.g., Fisher and Turnbull equation). The isothermal crystallization, melting profile, and fitting
of the kinetics of nucleation to the Fisher and Turnbull equation showed that the 26, 42, and 60% PS/sesame oil blends crystallized
mainly in the β1′ polymorph state. In contrast, the 80% blend crystallized in two different polymorph states (i.e., β1′ at T⪯307.6 K and β1 at T≽308.2 K). The data indicated that, in spite of the higher concentration of PS in the 80% PS/sesame oil system, crystallization
in the β1 state required more free energy for nucleation (δG
c
) than β1′ crystallization in the 26, 42, and 60% PS/sesame oil. At the low cooling rate used (1 K/min) it was observed that, for a
particular PS blend, the higher the effective supercooling the higher the viscosity of the oil phase and the smaller the induction
time of crystallization (Ti). Additionally, the β1′ crystals from PS, developed at the highest effective supercooling investigated, were smaller than the β1 crystals obtained at lower effective supercooling. 相似文献
11.
T. Koyano I. Hachiya T. Arishimo K. Sato N. Sagi 《Journal of the American Oil Chemists' Society》1989,66(5):675-679
Melt crystallization of the polymorphs of SOS, α,γ, pseudo-β′, β2 and β1. and of POP, α,γ, pseudo-β′2 pseudo-β
1, β2andβ
1was examined using pure samples (99.9%). Induction time τ for newly occurring crystals in the melt phase was measured with
a polarizing microscope equipped with a temperature-controlled growth cell. Rate of crystallization, 1/τ, was obtained for
each polymorph of POP and SOS whose identification was done with X-ray diffraction and differential scanning calorimetry (DSC).
Two modes of crystallization, melt-cooling and melt-mediation, yielded approximately the same results for POP and SOS: (a)
The rates of crystallization were always higher in less stable than in more stable forms,β
2only crystallized via a γ-melt mediation, butβ
1did not occur by the melt crystallization; (b) the rate of meltmediated crystallization was always higher than the simple
melt-cooling as examined at the same crystallization temperature; (c) the occurrence behavior of the polymorphs differed between
the simple-cooling and meltmediation. The results were related to the solidification behavior of the polymorphs of cocoa butter.
Presented at the AOCS Annual Meeting in Phoenix, Arizona in May 1988. 相似文献
12.
Arjen van Langevelde Kees van Malssen Ed Sonneveld René Peschar Henk Schenk 《Journal of the American Oil Chemists' Society》1999,76(5):603-609
From a homologous series of C
nCn+2Cn (n = even) triacylglycerols which are β′-stable, Guinier X-ray powder diffraction photographs were used to determine cell parameters
and space groups. The powder diffraction patterns are consistent with a pseudo-orthorhombic unit cell with space group lc2a. Only one axis is changing as a function of chain lengthening. The experimental results were used to propose a β′-crystal
packing for triacylglycerols. In contrast to earlier proposed β′-crystal structures, the acyl chains of this structure are
not tilted with respect to the methyl-end group plane. Furthermore, with only one molecule in the asymmetric unit, overall
orthogonal chain packing is obtained when the intramolecular acyl zigzag planes are parallel. 相似文献
13.
M. Takeuchi A. Ueno J. Yano E. Floter K. Sato 《Journal of the American Oil Chemists' Society》2000,77(12):1243-1250
Polymorphic transformation behavior of sub-α1, sub-α2, α, and γ in 1,3-distearoyl-sn-2-linoleoyl-glycerol (SLS) has been studied with X-ray diffraction, differential scanning caloremetry, and Fourier-transform
infrared spectroscopy. Synchrotron radiation X-ray beam was employed to observe rapid transformation processes from the sub-α
and α forms to the γ form. The chain length structures were double in sub-α1, sub-α2, and α, whereas γ was of triple chain-length structure. The subcell packing was pseudohexagonal for the two sub-α forms,
hexagonal for the α form, and parallel type for the γ form. In comparison with 1,3-distearoyl-sn-2-oleoyl-glycerol (SOS), the occurrence behavior of sub-α, α, and γ of SLS was the same as that of SOS. However, the absence
of β′ and β was unique for SLS. The chain-chain interactions between the linoleoyl moieties may stabilize the γ form, prohibiting
the transformation into β′ and β forms. The presence of two cis double bonds may cause this stabilization, revealing the disordered chain conformation of the unsaturated chains. 相似文献
14.
T. Arishima N. Sagi H. Mori K. Sato 《Journal of the American Oil Chemists' Society》1991,68(10):710-715
Polymorphic behavior of 1,3-rac-palmitoyl-stearoy 1-2-oleoylglycerol, 99.9% purity (POS) was examined by X-ray diffraction (XRD), differential scanning calorimetry
(DSC), solubility measurements and optical microscopy in comparison with 1,3-dipalmitoyl-2-oleoylglycerol (POP) and 1,3-distearoyl-2-oleoylglycerol
(SOS). Melt crystallization and solvent crystallization were examined for the occurrence of metastable and stable polymorphs.
The number of independent polymorphs was four; α,δ, pseudoβ′ andβ. The lowest melting form, α, was identical to that commonly observed in POP and SOS lowest melting forms. As to the highest
melting form,β, the XRD shortspacing pattern was identical toβ
1 of POP and SOS. This is consistent with crystal habit:β single crystals of POS showed the same shape as those of β1 of POP and SOS. However, the melting point ofβ (POS), 35.9°C, was lower than those ofβ
1 of POP, 36.7°C, and of SOS, 43.0°C. Correspondingly, solubility ofβ of POS was lower than that of β1 of POP below about 13°C, but higher above 13°C. POS did not possessβ
2
, which is the second stable form in POP and SOS. Two forms of6 and pseudoβ′ occurred, the latter being more stable. The structural properties ofδ showed thatδ is not identical toγ previously observed in POP and SOS. Transformation behavior from the metastable to stable polymorphs of POS showed some differences
from those of POP and SOS.
Presented at the AOCS annual meeting in Cincinnati, Ohio, in May 1989. 相似文献
15.
T. M. Eads A. E. Blaurock R. G. Bryant D. J. Roy W. R. Croasmun 《Journal of the American Oil Chemists' Society》1992,69(11):1057-1068
Deuterium nuclear magnetic resonance (NMR) quadrupole echo spectra of deuterated acyl chains and the glyceryl moiety of tripalmitin
were found to depend on the crystal form. At 20°C, which is below melting points, line shapes indicate that molecular motions
in theβ form (triclinic subcell) are more restricted than inβ′ (orthorhombic) orα (hexagonal). Motional rates in excess of about 20 kHz are responsible for the line shapes. Spin-lattice relaxation, sensitive
to motional frequencies in the tens of megahertz range, is much faster for methyl (CD2) groups inα orβ′ than inβ, indicating that fast motions are also governed by crystal form. General theoretical considerations suggest that motion of
methylene groups is dynamically heterogeneous and that motion of methyl (CD3) groups may be averaged by motions other than rotation about the terminal C-C bond. The isothermal solid-state transition
fromα toβ, induced by increasing the temperature to 35°C, was accompanied by NMR lineshape changes consistent with immobilization.
The reversible transition ofα to “sub-α” upon cooling, accompanied by orthorhombic-like Bragg spacings and other changes in the X-ray pattern and by corresponding
changes in the infrared spectrum, also produced a marked restriction in NMR-detected mobility of the kind seen inβ′ relative toα. The advantages of2H NMR for studies of motions and transitions in solid glycerides are discussed.
Presented at the 80th Annual Meeting of AOCS in Cincinnati, May 1989, and at the 81st Annual Meeting in Baltimore, May 1990. 相似文献
16.
Isothermal crystallization of tripalmitin in sesame oil 总被引:1,自引:0,他引:1
Elena Dibildox-Alvarado Jorge F. Toro-Vazquez 《Journal of the American Oil Chemists' Society》1997,74(2):69-76
Crystallization of tripalmitin (TP) in sesame oil was investigated under isothermal conditions at a cooling rate similar to
the one achieved in industrial crystallizers (1 K/min). The results obtained indicated that, at TP concentrations <0.98%,
triacylglycerides of sesame oil developed mixed crystals with TP. However, at concentrations within the interval of 0.98 to
3.44%, tripalmitin crystallized independently from sesame oil. Within this concentration interval, discontinuities were observed
in the behavior of the induction time of TP crystallization (T
i) in sesame oil as evidenced by differential scanning calorimetry, polarized microscopy studies, and determination of the
Avrami index (n). In general, the discontinuities in T
i were associated with different polymorph states developed by TP in sesame oil as a function of its concentration and crystallization
temperature. Thus, TP crystals obtained at temperatures above 296 K with 1.80 and 2.62% TP solutions had n values close to 3 and developed lamellar-shaped crystals that are characteristic of β tripalmitin. In contrast, the crystals
obtained at temperatures of 296 K and below with 1.80% and 2.62% TP solutions provided n values close to 3. Axialite-shaped β′ TP crystals were obtained under these conditions. For the 0.98% TP solution, simultaneous
production of α and β′ crystals occurred below 291 K. However, at temperatures above 291 K, a crystallization process with
n=3 was obtained, and it developed a different polymorph state, i.e., β, with lamellar-shaped TP crystals. 相似文献
17.
James W. Hagemann John A. Rothfus 《Journal of the American Oil Chemists' Society》1988,65(9):1493-1501
Intermolecular energy calculations were performed on theoretical triarachidinα-form structures as selected bond rotations converted them intoβ′-forms with a chain-tilt change in the glycerol region. Interactions across the methyl gaps amounted to only 2-3% of the total
energy in initialα- and finalβ′-forms, but computer generated energy profiles duringα- toβ′-phase transitions revealed highly repulsive regions due to the close approach of methyl groups. This methyl gap interaction,
plus additional repulsive interactions in the lateral packing of molecules during rigid chain rotations, necessitated modification
of certain chain movements during phase transition to reduce excessive repulsive energy. These results suggest that phase
transitions proceed in a particular sequence of events that either distribute energy to promote further phase excitation or
that lead to collapse into the stable polymorphic form. Phase transition energy curves also reveal that secondaryα- andβ′-forms are possible and are dependent on the startingα-forms, the direction of chain rotation and the subcell arrangement. 相似文献
18.
Jacco van de Streek Paul Verwer René de Gelder Frank Hollander 《Journal of the American Oil Chemists' Society》1999,76(11):1333-1341
The structural elements of the β′-2 polymorph of 1,3-dilauroyl-2-myristoylglycerol as found by Birker et al. (J. Am. Oil Chem. Soc. 68:895–906, 1991) were also observed in the crystal structures of other long-chain compounds. This analogy led to the assembly
of a β′-2 structure at the atomic level from known crystallographic data. The structure was optimized by molecular mechanics
and was consistent with experimental data, including satisfactory reproduction of the X-ray powder pattern. To the best of
our knowledge, this is the first β′ structure with a 1,2 configuration and an intramolecular orthorhombic subcell which is
fully optimized by molecular mechanics to date. It shows all structural elements found earlier by Birker et al. 相似文献
19.
The solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre-exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized
at temperatures (T
Cr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (T
M
o) and the supercooling (i.e., T
Cr
o−T
M
o) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [T
M
o=65.8°C (±3.0°C)] than in the CB/canola oil blend [T
M
o=33.7°C (±4.9°C)]. Therefore, under similar T
Cr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of T
Cr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from
DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with T
M
o explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′eq and σ* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′eq and σ* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of
small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′eq and σ* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we
could not find a particular relationship that described the overall behavior of G′eq and σ* as a function of D and independent of the system investigated. 相似文献
20.
T. Arishima K. Sugimoto R. Kiwata H. Mori K. Sato 《Journal of the American Oil Chemists' Society》1996,73(10):1231-1236
The cross-polarization and magic-angle spinning nuclear magnetic resonance (CP/MAS-NMR) technique has been used to analyze
the polymorphic forms of three triacylglycerols, 1,3-dipalmitoyl-2-oleoyl glycerol (POP), 1, 3-racpalmitoyl-stearoyl-2-oleoyl glycerol (POS), and 1,3-distearoyl-2-oleoyl glycerol (SOS). Specific attention has been paid to
glycerol, carbonyl, olefinic, and methyl end carbon resonances. Many distinct differences were observed in each polymorphic
form of SOS. In the α form, the saturated and unsaturated acyl chains exhibit liquid state-like conformations. However, olefinic
conformations of the γ and β′ forms were asymmetric with respect to thecis double bond. Spectral difference between β2 and β1 was observed only for the methylene carbon, and not in the other regions. Spectra of corresponding polymorphic forms of POP
and POS were almost identical to those of SOS. However, some spectral differences were observed in the glycerol and methyl
regions of γ and β′. From the chemical shifts of the methylene carbons, the crystal structures of the polymorphic form have
been discussed, particularly in terms of the subcell structures. 相似文献