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天然食品甜味剂甘草酸 总被引:1,自引:0,他引:1
从甘草中提取的甘草酸是一种高甜度、低热量、安全无毒的非热源性甜味剂,甜度约为蔗糖的200至250倍.甘草酸可用水、稀氨、醇氨等萃取;用硫酸或乙醇等进行精制;用2,4-二硝基苯肼鉴别;可在252nm的波长处紫外分光光度法测定其含量. 相似文献
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从甘草中提取的甘草酸是一种高甜度、低热量、安全无毒的非热源性甜味剂,甜度约为蔗糖的200至250倍.甘草酸可用水、稀氨、醇氨等萃取;用硫酸或乙醇等进行精制;用2,4-二硝基苯肼鉴别;可在252 nm的波长处紫外分光光度法测定其含量. 相似文献
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利用双水相体系的温度诱导效应萃取甘草酸 总被引:11,自引:0,他引:11
利用双水相分配技术结合温度诱导效应提取甘草酸,研究甘草酸单铵盐在环氧乙烷-环氧丙烷共聚物(EOPO)/混合磷酸钾(KHP)体系中的分配行为,通过实验确定了最佳体系:EOPO L64浓度为28(wt)%,K2HPO4浓度为32(wt)%。甘草酸单铵盐最大总收率达68.4%,为工业上采用双水相技术提取干草酸提供了一种新途径。 相似文献
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聚合物材料空化效应研究进展 总被引:2,自引:0,他引:2
综述了聚合物基材料中的各种空化现象,对橡胶增韧聚合物体系中的空化现象进行了详细讨论.同时讨论了聚合物基材料的形态、结构等因素对空化效应的影响,介绍了各种空化现象的原因及其对材料性能的影响和作用机理. 相似文献
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甘草酸的电化学行为研究 总被引:3,自引:0,他引:3
用循环伏安法、单扫描示波极谱法研究了甘草酸(glycyrrhizic,GA)在汞电极上的电化学行为及反应机理.证明甘草酸在pH=4~12的缓冲溶液(H3BO3+H3PO4+乙酸+NaOH)中有吸附峰,且示波极谱导数峰值与甘草酸浓度在8.3×10-5~1.2×10-6mol/L范围内成正比,使用悬汞电极(HMDE)线性扫描伏安法可使检测下限达2.4×10-6mol/L.根据实验结果首次提出了甘草酸在汞电极上的反应机理.该机理同时被紫外光谱证明,得到合理解释 相似文献
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单扫描示波极谱法测定甘草酸 总被引:3,自引:0,他引:3
本文报道测定甘草酸的单扫描法波极谱方法,在0.1mol/LNaAc-HAc(pH4.1±0.1)缓冲液中,甘草酸还原波峰电位为-1.38V(vs.SCE),峰高与其浓度在2.0×10^-6~1.0 ×10^-4mol/L范围内有线性关系,检测限为1.2×10^-6mol/L。甘氨酸,半胱氨酸等不干扰测定。应用本方法测定强力宁注射液中甘草酸含量,结果令人满意。本文还讨论了电极过程机理。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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