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111.
通过气相色谱、红外光谱分析和量子化学计算,探究溶于二甲基亚砜(DMSO)中乙酸保留时间发生波动的原因。 结果显示,乙酸保留时间变化与DMSO体积等量递增呈线性关系,R2=0.99301;根据红外光谱分析得出,DMSO和乙酸之间生成了氢键,以DMSO-乙酸分子的形式通过色谱柱;根据Gaussian09程序计算结果,DMSO电子密度大的部分给予电子,与乙酸之间形成了氢键,而DMSO电子密度小的部分容易获得电子与具有强偶极矩的色谱柱固定液聚乙二醇产生作用力,吸附在固定液上。因此,在上述一系列复杂的分子间作用力的共同影响下,乙酸保留时间发生了波动,且随着溶剂DMSO体积比增加,乙酸保留时间不断延长。 相似文献
112.
113.
Detection of oxygen addition peaks for terpendole E and related indole–diterpene alkaloids in a positive‐mode ESI‐MS 下载免费PDF全文
Yayoi Hongo Takemichi Nakamura Shunya Takahashi Takayuki Motoyama Toshiaki Hayashi Hiroshi Hirota Hiroyuki Osada Hiroyuki Koshino 《Journal of mass spectrometry : JMS》2014,49(6):537-542
This report describes that a regular positive electrospray ionization mass spectrometry (MS) analysis of terpendoles often causes unexpected oxygen additions to form [M + H + O]+ and [M + H + 2O]+, which might be a troublesome in the characterization of new natural analogues. The intensities of [M + H + O]+ and [M + H + 2O]+ among terpendoles were unpredictable and fluctuated largely. Simple electrochemical oxidation in electrospray ionization was insufficient to explain the phenomenon. So we studied factors to form [M + H + O]+ and [M + H + 2O]+ using terpendole E and natural terpendoles together with some model indole alkaloids. Similar oxygen addition was observed for 1,2,3,4‐tetrahydrocyclopent[b]indole, which is corresponding to the substructure of terpendole E. In tandem MS experiments, a major fragment ion at m/z 130 from protonated terpendole E was assigned to the substructure containing indole. When the [M + H + O]+ was selected as a precursor ion, the ion shifted to m/z 146. The same 16 Da shift of fragments was also observed for 1,2,3,4‐tetrahydrocyclopent[b]indole, indicating that the oxygen addition of terpendole E took place at the indole portion. However, the oxygen addition was absent for some terpendoles, even whose structure resembles terpendole E. The breakdown curves characterized the tandem MS features of terpendoles. Preferential dissociation into m/z 130 suggested the protonation tendency at the indole site. Terpendoles that are preferentially protonated at indole tend to form oxygen addition peaks, suggesting that the protonation feature contributes to the oxygen additions in some degrees. © 2014 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons, Ltd. 相似文献
114.
Efficient Copper‐Catalyzed Direct Intramolecular Aminotrifluoromethylation of Unactivated Alkenes with Diverse Nitrogen‐Based Nucleophiles 下载免费PDF全文
Dr. Jin‐Shun Lin Ya‐Ping Xiong Can‐Liang Ma Li‐Jiao Zhao Prof. Dr. Bin Tan Prof. Dr. Xin‐Yuan Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1332-1340
A mild, convenient, and step‐economical intramolecular aminotrifluoromethylation of unactivated alkenes with a variety of electronically distinct, nitrogen‐based nucleophiles in the presence of a simple copper salt catalyst, in the absence of extra ligands, is described. Many different nitrogen‐based nucleophiles (e.g., basic primary aliphatic and aromatic amines, sulfonamides, carbamates, and ureas) can be employed in this new aminotrifluoromethylation reaction. The aminotrifluoromethylation process allows straightforward access to diversely substituted CF3‐containing pyrrolidines or indolines, in good to excellent yields, through a direct difunctionalization strategy from the respective acyclic starting materials. Mechanistic studies were conducted and a plausible mechanism was proposed. 相似文献
115.
Metal‐Free Oxidative Radical Addition of Carbonyl Compounds to α,α‐Diaryl Allylic Alcohols: Synthesis of Highly Functionalized Ketones 下载免费PDF全文
Xue‐Qiang Chu Hua Meng You Zi Prof. Dr. Xiao‐Ping Xu Prof. Dr. Shun‐Jun Ji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):17198-17206
A metal‐free direct alkylation of simple carbonyl compounds (ketones, esters, and amides) with α,α‐diaryl allylic alcohols is described. The protocol provides facile access to highly functionalized dicarbonyl ketones by a radical addition/1,2‐aryl migration cascade. The regioselectivity of the reaction was precisely controlled by the nature of the carbonyl compound. 相似文献
116.
Isolation of a Neutral Boron‐Containing Radical Stabilized by a Cyclic (Alkyl)(Amino)Carbene 下载免费PDF全文
Dr. Philipp Bissinger Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Ivo Krummenacher Dr. Ashwini K. Phukan Dr. Krzysztof Radacki Shun Sugawara 《Angewandte Chemie (International ed. in English)》2014,53(28):7360-7363
Utilizing a cyclic (alkyl)(amino)carbene (CAAC) as a ligand, neutral CAAC‐stabilized radicals containing a boryl functionality could be prepared by reduction of the corresponding haloborane adducts. The radical species with a duryl substituent was fully characterized by single‐crystal X‐ray structural analysis, EPR spectroscopy, and DFT calculations. Compared to known neutral boryl radicals, the isolated radical species showed larger spin density on the boron atom. Furthermore, the compound that was isolated is extraordinarily stable to high temperatures under inert conditions, both in solution and in the solid state. Electrochemical investigations of the radical suggest the possibility to generate a stable formal boryl anion species. 相似文献
117.
建立了采用气相色谱-质谱(GC-MS)同时测定水果中9种保鲜剂残留量的分析方法。水果样品用正己烷/乙酸乙酯(1/1,v/v)混合提取剂超声提取,经Florisil层析柱净化后用正己烷/乙酸乙酯(1/3,v/v)混合洗脱剂洗脱,以磷酸三苯脂(TPP)为内标物,采用GC-MS的全扫描方式(SCAN)和选择离子监测方式(SIM)对9种保鲜剂进行定性与定量分析。实验结果表明,9种保鲜剂的检出限(LOD)为0.10~2.16μg/kg,在50、100、200μg/kg添加水平下的回收率为75.3%~128%,相对标准偏差为1.57%~11.6%。本分析方法样品前处理简便,净化效果明显,在SIM谱图中分析目标物响应值大、灵敏度高,定量准确可靠,能够满足保鲜剂痕量残留的检测要求。 相似文献
118.
Dr. Ming-Yu Wu Jong-Kai Leung Li Liu Dr. Chuen Kam Dr. Kelvin Yuen Kwong Chan Prof. Dr. Ronald A. Li Prof. Dr. Shun Feng Dr. Sijie Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10413-10417
The chromosome periphery (CP) is a complex network that covers the outer surface of chromosomes. It acts as a carrier of nucleolar components, helps maintain chromosome structure, and plays an important role in mitosis. Current methods for fluorescence imaging of CP largely rely on immunostaining. We herein report a small-molecule fluorescent probe, ID-IQ , which possesses aggregation-induced emission (AIE) property, for CP imaging. By labelling the CP, ID-IQ sharply highlighted the chromosome boundaries, which enabled rapid segmentation of touching and overlapping chromosomes, direct identification of the centromere, and clear visualization of chromosome morphology. ID-IQ staining was also compatible with fluorescence in situ hybridization and could assist the precise location of the gene in designated chromosome. Altogether, this study provides a versatile cytogenetic tool for improved chromosome analysis, which greatly benefits the clinical diagnostic testing and genomic research. 相似文献
119.
Soliman Mohamed A. Mohamed Nader M. A. Takamiya Koichi Sekimoto Shun Inagaki Makoto Oki Yuichi Ohtsuki Tsutomu 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(3):1099-1107
Journal of Radioanalytical and Nuclear Chemistry - To assess the capability of Kyoto University Research Reactor to supply the domestic needs of medical isotopes, its neutron flux has been fully... 相似文献
120.
Inagaki Makoto Sekimoto Shun Tadokoro Takahiro Ueno Yuichiro Kani Yuko Ohtsuki Tsutomu 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(2):681-686
Journal of Radioanalytical and Nuclear Chemistry - Amount estimation of production of 99Mo required for medical applications was carried out by utilizing an electron linear accelerator with... 相似文献