共查询到20条相似文献,搜索用时 453 毫秒
1.
G. Knothe M. O. Bagby D. Weisleder R. E. Peterson 《Journal of the American Oil Chemists' Society》1995,72(6):703-706
Several novel allylic mono- and dihydroxy fatty compounds were synthesized from Δ5, Δ7-, Δ8-, and Δ10-monounsaturated fatty
acids with the selenium dioxide/tert-butyl-hydroperoxide. Chainlengths were C19 for Δ7 and Δ10, and C20 for Δ5 and Δ8 compounds. With a full range of Δ5- to Δ11-unsaturated allylic monohydroxy fatty compounds available, position-dependent
effects in the13C-nuclear magnetic resonance spectra of these compounds are discussed. The olefinic carbon shift differences in monohydroxy
compounds, where the OH group is located between the double bond and the terminal methyl group, were plotted as a function
of double-bond distance from C1. This plot is presumably a rational function. During SeO2-based hydroxylation, lactonization of the hydroxy groups, located between the double-bond and the carboxyl group, also occurs
for Δ5 unsaturation. 相似文献
2.
Using a combination of selective irradiation1H nuclear magnetic resonance experiments and two-dimensional1H−13C correlation spectroscopy spectral analysis of homoallylic andbis homoallylic substituted (azido, acetoxy, chloro and oxo) fatty ester derivatives, the carbon shifts of the ethylenic carbon
atoms were determined. In the case of methyl 12-azido-9Z-octadecenoate (homoallylic), the carbon chemical shifts of the ethylenic C-9 and C-10 carbon nuclei are 133.092 and 124.596
ppm, respectively. In methyl 9-azido-12Z-octadecenoate (bis homoallylic), the carbon chemical shift of the ethylenic C-12 and C-13 carbon nuclei are 128.118 and 131.243 ppm, respectively. 相似文献
3.
Isolation and characterization of the monounsaturated long chain fatty acids ofMycobacterium tuberculosis 总被引:2,自引:0,他引:2
The positions of double bond in the monounsaturated C15−C32 fatty acids ofMycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives.
The monounsaturated C15−C21 fatty acids had the double bond primarily at the Δ9 position while the monounsaturated longer chain fatty acids (C22−C32) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex
isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follow: C22, Δ4; C24, Δ5; C26, Δ7 and Δ9; C28, Δ9; C30, Δ11 and Δ13; C32, Δ13 and Δ15. 相似文献
4.
Robert L. Wolff William W. Christie Frédérique Pédrono Anne M. Marpeau Nanzad Tsevegsüren Kurt Aitzetmüller Frank D. Gunstone 《Lipids》1999,34(8):855-864
The fatty acid compositions of the seed lipids from four Ephedra species, E. nevadensis, E. viridis, E. przewalskii, and E. gerardiana (four gymnosperm species belonging to the Cycadophytes), have been established with an emphasis on Δ5-unsaturated polymethylene-interrupted
fatty acids (Δ5-UPIFA). Mass spectrometry of the picolinyl ester derivatives allowed characterization of 5,9- and 5,11–18∶2;
5,9,12–18∶3; 5,9,12,15–18∶4; 5,11–20∶2; 5,11,14–20∶3; and 5,11,14,17–20∶4 acids. Δ5-UPIFA with a Δ11-ethylenic bond (mostly
C20 acids) were in higher proportions than δ5-UPIFA with a δ9 double bond (exclusively C18 acids) in all species. The total δ5-UPIFA content was 17–31% of the total fatty acids, with 5, 11, 14–20∶3 and 5, 11, 14,
17–20∶4 acids being the principal δ5-UPFIA isomers. The relatively high level of cis-vaccenic (11–18∶1) acid found in Ephedra spp. seeds, the presence of its δ5-desaturation product, 5, 11–18∶2 acid (proposed trivial name: ephedrenic acid), and of
its elongation product, 13–20∶1 acid, were previously shown to occur in a single other species, Ginkgo biloba, among the approximately 170 gymnosperm species analyzed so far. Consequently, Ephedraceae and Coniferophytes (including
Ginkgoatae), which have evolved separately since the Devonian period (≈300 million yr ago), have kept in common the ability
to synthesize C18 and C20 δ5-UPIFA. We postulate the existence of two δ5-desaturases in gymnosperm seeds, one possibly specific for unsaturated acids
with a δ9-ethylenic bond, and the other possibly specific for unsaturated acids with a δ11-ethylenic bond. Alternatively,
the δ5-desaturases might be specific for the chain length with C18 unsaturated acids on the one hand and C20 unsaturated acids on the other hand. The resulting hypothetical pathways for the biosynthesis of δ5-UPIFA in gymnosperm seeds
are only distinguished by the position of 11–18∶1 acid. Moreover, 13C nuclear magnetic resonance spectroscopy of the seed oil from two Ephedra species has shown that δ5-UPIFA are essentially excluded from the internal position of triacylglycerols, a characteristic
common to all of the Coniferophytes analyzed so far (more than 30 species), with the possibility of an exclusive esterification
at the sn-3 position. This structural feature would also date back to the Devonian period, but might have been lost in those rare angiosperm
species containing δ5-UPIFA. 相似文献
5.
Gas chromatography-mass spectrometry of methyl esters of unsaturated oxygenated fatty acids 总被引:5,自引:0,他引:5
Silylation of hydroxyl groups in methyl esters of unsaturated hydroxy acids provides compounds that give mass spectra which
can be readily interpreted, whereas spectra of underivatized esters are extremely difficult to evaluate. The relationship
of the double bond(s) to the trimethylsiloxy (TMS) group results in specific mass spectral patterns. In esters that have the
TMS group separated from the double bond by one methylene group, the ions caused byα-cleavage at the TMS group on the side closest to the olefinic group are much more abundant than those produced fromα-cleavage on the other side of the TMS group. In esters that have the TMS group and the double bond separated by two methylene
groups,α-cleavage ions are approximately equal. When the TMS group and the double bond are allylic, no fragmentation results between
them. Cleavage does occur on either side of this system, and those ions resulting from cleavage alpha to the TMS group are
in greatest abundance. Silylation of esters that have a conjugated diene or ene-yne system adjacent to a hydroxyl group also
gives derivatives amenable to gas chromatographymass spectrometry. In these esters, large peaks are observed that arise fromα-cleavage at the TMS group and at the other end of the olefinic system. No fragmentation between the TMS group and the sites
of unsaturation occurs. Unsaturated epoxy methyl esters produce spectra difficult to interpret. When the epoxide is converted
to methoxy-hydroxy derivatives by BF3-methanol, the spectrum locates the position of the epoxide group. Silylation of the hydroxyl group produces a compound that
gives a less complicated spectrum which also locates the original epoxy group. Mass spectrometry of a series of unsaturated
keto-esters, without derivatization, provides spectra that are easily interpretable.
Presented at the AOCS Meeting, Los Angeles, April 1972.
N. Market. Nutr. Res. Div., ARS, USDA. 相似文献
6.
Most saturated diacyl phosphatidylcholines C(X):C(Y)PC (saturated 1,2-diacyl-sn-glycero-3-phosphocholine with X carbons in thesn-1 acyl chain and Y carbons in thesn-2 acyl chain), in excess water, can self-assemble into lamellae which, upon heating, may undergo multiple thermotropic phase
transitions at well-defined, discrete temperatures. The transition temperature corresponding to the main or the gel to liquid-crystalline
phase transition (Tm) is known for many bilayers of fully hydrated phosphatidylcholines. In this study, we have analyzed the Tm values of 44 molecular species of phosphatidylcholines in terms of their structural and packing characteristics in the gel-state
bilayer. Two general equations are thus derived: Tm=162.26−3651.71 (1/N)−88.42 (ΔC/N) for C(X):C(Y)PC with X≥Y, and Tm=157.68−3525.44 (1/N)−93.28 (ΔC/N) for C(X):C(Y)PC with X<Y. Here, N is the minimal hydrophobic thickness of the dimeric C(X):C(Y)PC
in the gel-state bilayer and ΔC is the effective chain length difference between thesn-1 andsn-2 acyl chains for the monomeric C(X):C(Y)PC in the gel-state bilayer. The advantage of these two equations in predicting
the Tm values for phosphatidylcholines with ΔC/CL values in the range of 0.07 to 0.40 is their simplicity. A figure containing a
total of 173 calculated Tm values is also presented. 相似文献
7.
Claudia Gerdes Julia Schuppan Arnd-Rüdiger Grimmer Michael Bolte Wolfgang Saak Detlev Haase Thomas Müller 《SILICON》2010,2(4):217-227
The structure and bonding of 7-silanorbornadienes was investigated using X-ray Diffraction (XRD), solid-state NMR spectroscopy
and density functional calculations. The solid state structures of four benzo-7-silanorbornadienes (4a, c, d, e) and of one dibenzo-7-silabenzonorbornadiene (5a) are reported and compared with the results of previous structural investigations. The most prominent features of the molecular
structures of all 7-silanorbornadienes are very long Si-C(bridgehead) bonds (d(SiC) = 190.6–196.8 pm) and very acute CSiC
bond angles α (α(CSiC) = 78.7–83.9°). All newly investigated 7-silanorborndienes show for tetracoordinated silicon nuclei
extremely deshielded 29Si NMR resonances (δ29Si = 65.6–31.6). Solid State NMR investigations for 7-silanorbornadienes anti-4a, b reveal highly anisotropic chemical shift tensors of axial or nearly axial symmetry (4a: δ11 = 161, δ22 = δ33 = −11; 4b: δ11 = 113, δ22 = 14, δ33 = −15). The dominating, strongly deshielding δ11 component is oriented almost perpendicular to the plane spanned by the two bridgehead carbon atoms and the bridging silicon
atom. The DFT calculations suggest that the origin of the strong deshielding is a small energy difference between the frontier
orbitals, which are strongly localized at the silicon atom. In addition the computations reveal that both the long SiC bonds
and the strongly deshielded 29Si NMR chemical shift are direct consequences of the bonding situation in 7-silanorbornadienes which are characterized by
through space interaction of the C=C double bonds and by hyperconjugation between the SiC σ-bonds and the unoccupied orbitals
of the C=C double bonds. 相似文献
8.
A. Grandgirard J. M. Bourre F. Julliard P. Homayoun O. Dumont M. Piciotti J. L. Sebedio 《Lipids》1994,29(4):251-258
During heat treatment, polyunsaturated fatty acids and specifically 18∶3n−3 can undergo geometrical isomerization. In rat
tissues, 18∶3 Δ9c, 12c, 15t, one of thetrans isomers of linolenic acid, can be desaturated and elongated to givetrans isomers of eicosapentaenoic and docosahexaenoic acids. The present study was undertaken to determine whether such compounds
are incorporated into brain structures that are rich in n−3 long-chain polyunsaturated fatty acids. Two fractions enriched
intrans isomers of α-linolenic acid were prepared and fed to female adult rats during gestation and lactation. The pups were killed
at weaning. Synaptosomes, brain microvessees and retina were shown to contain the highest levels (about 0.5% of total fatty
acids) of thetrans isomer of docosahexaenoic acid (22∶6 Δ4c, 7c, 10c, 13c, 16c, 19t). This compound was also observed in myelin and sciatic nerve, but to a lesser extent (0.1% of total fatty acids). However,
the ratios of 22∶6trans to 22∶6cis were similar in all the tissues studied. When the diet was deficient in α-linolenic acid, the incorporation oftrans isomers was apparently doubled. However, comparison of the ratios oftrans 18∶3n−3 tocis 18∶3n−3 in the diet revealed that thecis n−3 fatty acids were more easily desaturated and elongated to 22∶6n−3 than the correspondingtrans n−3 fatty acids. An increase in 22∶5n−6 was thus observed, as has previously been described in n−3 fatty acid deficiency.
These results encourage further studies to determine whether or not incorporations of suchtrans isomers into tissues may have physiological implications.
Presented in part at the 32nd International Conference on the Biochemistry of Lipids, 1991, Granada, Spain.
Delta nomenclature (Δ) is used fortrans polyunsaturated fatty acids to specify the position and geometry of ethylenic bonds. Polyunsaturated fatty acids containingtrans double bonds are abbreviated giving the locations of thetrans double bonds only; e.g., 20∶5 Δ17t 20∶5 Δ5c,8c,11c,14c,17t; 22∶5 Δ19t, 22∶5 Δ7c,10c,13c,16c,19t; 22∶6 Δ19t 22∶6 Δ4c,7c,10c,13c,16c,19t. 相似文献
9.
Fatty acyl groups (16∶1 and 16∶0) liberated from purified sulfoquinovosyl diacylglycerols produced by the unicellular marine
microalga,Heterosigma carterae (formerlyH. akashiwo), were converted to either the corresponding alcohols or methyl esters. Nicotinate derivatives of the alcohols were examined
by combined gas chromatography/mass spectrometry, and the methyl esters were examined by nuclear magnetic resonance (NMR)
spectroscopy after separation by high-performance liquid chromatography. Three different hexadecenoyl fatty acyl groups were
identified, one of which wascis 13-hexadecenoyl (16∶1n−3). Both the configuration and the n−3 position of the double bond in thecis 13-hexadecenoyl moiety were unequivocally established by NMR analysis of the corresponding methyl ester. The nicotinate derived
from the alcohol of the 16∶1n−3 fatty acyl moiety gave a characteristic fragmentation series in the electron impact msss spectrum
which, by careful interpretation, was consistent with, but not unambiguous for, the assigned location of the double bond.
Tandem mass spectrometry experiments on a sulfoquinovosyl monoacylglycerol containing thecis 13-hexadecenoyl group in thesn-2 position, using negative-ion liquid secondary ion mass spectrometry, also gave a fragmentation pattern which was consistent
with the positional assignment of the double bond. 相似文献
10.
Conifer (pine) seeds are a potential source of dietary oils, but their safety and nutritional properties are not well established.
Conifer seed oils differ from common edible vegetable oils in having a series of unusual polyunsaturated fatty acids (PUFA)
with a polymethylene-interrupted (PMI) double bond system and a double bond at the Δ5 position. A rat study was conducted
to assess whether Δ5 PMI-PUFA of conifer seeds could alter the levels of n−6 and n−3 long-chain polyunsaturated fatty acids
(LC-PUFA) in mothers' milk and the developing brain of fetuses and pups. Feeding maritime pine (Pinus pinaster) seed oil (MPO) diet with a Δ5 PMI-PUFA content of 1.4 g/100 g throughout pregnancy and lactation resulted in a large incorporation
of Δ5 PMI-PUFA in mothers' milk (5.1±0.5% of total fatty acids). The fetus (17 d old) and pup (22 d) brains, however, accumulated
very little (0.6 and 0.4% of total fatty acids, respectively) Δ5 PMI-PUFA. Mother's milk and pup's brain of the MPO group
contained normal levels of 20∶4n−6, 22∶4n−6, and 20∶5n−3 compared to a reference group of rats fed a fat blend of sunflower,
high-oleic sunflower, and canola oils. The level of 22∶6n−3, however, was slightly but significantly (P<0.05) higher in milk and pup brain of the MPO group. These results show that Δ5 PMI-PUFA of MPO exert no negative effect
on the levels of n−6 and n−3 LC-PUFA in rat brain during its early development. 相似文献
11.
Ethyl acetate extracts from heartwood of seven western conifer trees and individual volatile compounds in the extracts were
tested for antimicrobial activity against Phytophthora ramorum. Extracts from incense and western redcedar exhibited the strongest activity, followed by yellow-cedar, western juniper,
and Port-Orford-cedar with moderate activity, and no activity for Douglas-fir and redwood extracts. Chemical composition of
the extracts varied both qualitatively and quantitatively among the species with a total of 37 compounds identified by mass
spectrometry. Of the 13 individual heartwood compounds bioassayed, three showed strong activity with a Log10 EC50 less than or equal to 1.0 ppm (hinokitiol, thymoquinone, and nootkatin), three expressed moderate activity ranging from 1.0–2.0 ppm
(nootkatol, carvacrol, and valencene-11,12-diol), four compounds had weak activity at 2.0–3.0 ppm [α-terpineol, valencene-13-ol,
(+)-β-cedrene, (−)-thujopsene], and three had no activity [(+)-cedrol, δ-cadinene, and methyl carvacrol]. All of the most
active compounds contained a free hydroxyl group, except thymoquinone. The importance of a free hydroxyl was demonstrated
by the tremendous difference in activity between carvacrol (Log10 EC50 1.81 ± 0.08 ppm) and methyl carvacrol (Log10 EC50 >3.0 ppm). A field trial in California, showed that heartwood chips from redcedar placed on the forest floor for 4 months
under Umbellularia californica (California bay laurel) with symptoms of P. ramorum leaf blight significantly limited the accumulation of P. ramorum DNA in the litter layer, compared with heartwood chips from redwood. 相似文献
12.
The rates of rat liver microsomal and mitochondrial activation of the Δ4 to Δ17
cis-octadecenoate positional isomers have been investigated. The fatty acid to protein ratios required for maximum activation
of the Δ8, Δ9 and Δ10 isomers were much lower than the corresponding ratios required for maximum activation of thecis-octadecenoates with double bonds at either end of the fatty acid molecule. Also, as the incubation temperature was raised
from 22–38 C the Δ8 and Δ9 isomers exhibited little change in their rates of activation, while large increases in activation rates of the isomers with
the double bond at either end of the fatty acid chain were observed. Differential inhibition of the activation of the various
positional isomers was observed when anionic, cationic, or nonionic detergents were included in the incubation medium. The
different responses to fatty acid concentration, temperature and detergents are attributed to enzyme specificity and to differences
in solution properties of thecis-octadecenoates, rather than to the presence of separate rat liver enzymes that catalyze acyl-CoA ester formation of the various
positional isomers. 相似文献
13.
Octadecapentaenoic acid (all-cis δ3,6,9,12,15–18∶5; 18∶5n−3) is an unusual fatty acid found in marine dinophytes, haptophytes, and prasinophytes. It is not
present at higher trophic levels in the marine food web, but its metabolism by animals ingesting algae is unknown. Here we
studied the metabolism of 18∶5n−3 in cell lines derived from turbot (Scophthalmus maximus), gilthead sea bream (Sparus aurata), and Atlantic salmon (Salmo salar). Cells were incubated in the presence of approximately 1 μM [U-14C] 18∶5n−3 methyl ester or [U-14C]18∶4n−3 (octadecatetraenoic acid; all-cis δ6,9,12,15–18∶4) methyl ester, both derived from the alga Isochrysis galbana grown in H14CO3
−, and also with 25 μM unlabeled 18∶5n−3 or 18∶4n−3. Cells were also incubated with 25 μM trans δ2, all-cis δ6,9,12,15–18∶5 (2-trans 18∶5n−3) produced by alkaline isomerization of 18∶5n−3 chemically synthesized from docosahexaenoic acid (all-cis δ4,7,10,13,16,19–22∶6). Radioisotope and mass analyses of total fatty acids extracted from cells incubated with 18∶5n−3 were
consistent with this fatty acid being rapidly metabolized to 18∶4n−3 which was then elongated and further desaturated to eicosatetraenoic
acid (all-cis δ8,11,14,17,19–20∶4) and eicosapentaenoic acid (all-cis δ5,8,11,14,17–20∶5). Similar mass increases of 18∶4n−3 and its elongation and further desaturation products occurred in cells
incubated with 18∶5n−3 or 2-trans 18∶5n−3. We conclude that 18∶5n−3 is readily converted biochemically to 18∶4n−3 via a 2-trans 18∶5n−3 intermediate generated by a Δ3, Δ2-enoyl-CoA-iso-merase acting on 18∶5n−3. Thus, 2-trans 18∶5n−3 is implicated as a common intermediate in the β-oxidation of both 18∶5n−3 and 18∶4n−3. 相似文献
14.
One of the main compounds formed from 13L-hydroperoxy-9cis,11trans-octadecadienoic acid anaerobically at 100 C in aqueous ethanol was found to bethreo-11-hydroxy-12,13-epoxy-9-octadecenoic acid. The major part (ca. 90%) of this compound was formed from the fatty acid hydroperoxide
in a reaction involvingcis-addition to the Δ11 double bond of the proximally linked hydroperoxide oxygen and hydroxyl ion or hydroxyl radical from the solvent. A small
part (ca. 10%) was formed bycis-addition of the two hydroperoxide oxygens to the Δ11 double bond. 11-Hydroxy-12,13-epoxy-9-octadecenoic acid and its isomer, tentatively identified as 11-hydroxy-9,10-epoxy-12-octadecenoic
acid, also were isolated from a sample of autoxidized linoleic acid. 相似文献
15.
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
16.
Moghis U. Ahmad M. Shamim Ahmad S. M. Osman 《Journal of the American Oil Chemists' Society》1978,55(5):491-495
Methyltrans-2-hexadecenoate (1b) on allylic bromination with N-bromosuccinimide (NBS) (0.5 mole) yielded methyl 4-bromo-trans-2-hexadecenoate (2b) in 50% yield. Reaction with 2.0 moles of NBS afforded the allylic bromide (2b, δ 80%) as well as the dibromide (3b). Alkaline hydrolysis of the bromo ester (2b) yielded 4-hydroxy-trans-2-hexadecenoic acid (4a, δ 70%) and an unexpected product, 4-oxo-hexadecanoic acid (5a, δ 30%). A mechanism involving rearrangement is proposed to account for this unusual product. The effect of the ester carbonyl
adjacent to the double bond in2b was found to suppress dehydrobromination (elimination) reaction and favors only substitution (SN2), unlike the allylically brominated derivatives of internal olefinic compounds. The CrO3-pyridine oxidation of4b yielded the corresponding unsaturated ketone (7b). The structures of individual reaction products were established by elemental analyses as well as by spectral studies. 相似文献
17.
Jung Hoon Park Edoardo Magnone Jong Pyo Kim Soo Hyun Choi 《Korean Journal of Chemical Engineering》2012,29(2):235-242
The effect of minor surface modification on the performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ
membrane was evaluated in the temperature region from 700 to 850 °C. Oxygen permeation experiments were conducted according
to membrane thickness (1.0mm and 1.6 mm) and oxygen partial pressure (0.21, 0.42, and 0.63 atm) in the absence and in the
presence of carbon dioxide (300 and 500 ppm). The oxygen permeation flux of Ba0.5Sr0.5Co0.8Fe0.2O3−δ
membrane increased with increasing temperature and decreasing membrane thickness. The oxygen permeation flux through the
membrane of 1.0 mm thickness with Ba0.5Sr0.5Co0.8Fe0.2O3−δ
-modified surface was ca. 1.23 ml/cm2·min at 850 °C under air feeding condition. It was found that the Ba0.5Sr0.5Co0.8Fe0.2O3−δ
-modified Ba0.5Sr0.5Co0.8Fe0.2O3−δ
membrane has better oxygen permeation flux than the pristine Ba0.5Sr0.5Co0.8Fe0.2O3−δ
membrane. In summary, it has been demonstrated that the surface morphology is an important factor in determining the oxygen
permeation fluxes through Ba0.5Sr0.5Co0.8Fe0.2O3−δ
membrane under mixed-control conditions. 相似文献
18.
p-nitrobenzyl triphenyl phosphonium ylide initiated radical polymerisation of MMA in 1-4 dioxane at 65 ± 1°C for 2 h under
a nitrogen blanket, follows ideal kinetics with bimolecular termination. The overall activation energy and average value of
k
p
2/k
t are 75.7 kJ mol and 1.14 × 102 l mol−1 s−1. FTIR Spectroscopy confirms a band of 1,729 cm−1 of the ester group. 1H NMR and 13C NMR confirms methoxy protons at 3.8 δ ppm and 52 δ ppm, respectively. E.S.R studies confirm a free radical mode of polymerisation. TGDTA analysis confirms the atactic nature
of polymer and its thermal stability up to 120°C. Ylide dissociates to give a phenyl radical which is responsible for polymerisation. 相似文献
19.
Three distinct pairs of HETEs can be distinguished on the basis of their UV spectra. We used hydroxy-linoleates (hydroxy-octadeca-cis-trans-dienoates) as a base for comparisons; both the 9- and 13-hydroxy isomers have identical chromophores with λmax near 234 nm. The presence of a double bond three carbons removed from the conjugated diene (the chromophore of 9- and 11-HETE)
causes a shift in the observed λmax to near 235 nm. A double bond β to the chromophore (5- and 15-HETE) gives a further shift of 1.5 nm, giving a λmax between 236–236.5 nm. With double bonds in both these positions (8- and 12-HETE), the λmax is observed near 237 nm. It is apparent that the exact λmax of thecis-trans diene chromophore is influenced in a consistent way by the adjacent methylene interruptedcis double bonds.
hydroxylinoleate, describes the two primary products of linoleate oxygenation, more properly named 9-hydroxy-octadeca-10trans,12cis-dienoate and 13-hydroxy-octadeca-9cis,11trans-dienoate. Hydroxylinoelaidate refers to the correspondingall-trans dienes. RH-HPLC, reversed-phase high pressure liquid chromatography; SP-HPLC, straight-phase high pressure liquid chromatography. 相似文献
20.
Sterols were analyzed from four phytoplankton strains which are under investigation as possible sources of food for oysters
in culture. One strain ofPyramimonas contained only 24-methylenecholesterol as a major sterol component.Pyramimonas grossii, Chlorella autotrophica andDunaliella tertiolecta each contained a complex mixture of C28 and C29 sterols with Δ7, Δ5,7 and Δ5,7,9(11) nuclear double bond systems. Sterols were found both with and without the C-22 side chain double bond. Ergosterol and 7-dehydroporiferasterol
were the principal sterols in each of the latter three species, which also contained the rare tetraene sterols, 24-methylcholesta-5,7,9(11),22-tetraen-3β-ol
and 24-ethylcholesta-5,7,9(11),22-tetraen-3β-ol. 相似文献