共查询到20条相似文献,搜索用时 78 毫秒
1.
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
2.
3.
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
4.
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
5.
6.
7.
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
8.
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
9.
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
10.
11.
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
12.
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
13.
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
14.
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
15.
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
16.
An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
17.
Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described. 相似文献
18.
用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在. 相似文献
19.
An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction. 相似文献
20.
The Diels-Alder reactivity of 1,2-heteroborines (H4C4B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed. 相似文献