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101.
As a photocatalyst, mesoporous carbon nitride (mpg‐C3N4) shows higher photocatalytic activities in organic synthesis. Herein we report an mpg‐C3N4‐catalyzed oxidation of α‐hydroxy ketones to synthesize 1,2‐diketones using visible light. This transformation represents a green and highly efficient synthetic route to synthesize 1,2‐diketones for which catalytic approaches are scarce. 相似文献
102.
A pinch of sugar: The new bifunctional carbohydrate/cinchonine-based thiourea 1 has been designed for the asymmetric addition reaction of α-ketophosphonates and trimethylsilyl cyanide, the product of which can be hydrolyzed to afford tertiary α-hydroxy phosphonates with excellent enantioselectivities. 相似文献
103.
在磁性体磁化过程中, 决定其能够达到的最高温度, 对磁热材料的优化选取是重要的. 本文以钆镓石榴石(Gd3Ga5O12) 为例, 根据高磁场下趋近饱和定律的思想, 给出了低温、超强磁场下, Gd3Ga5O12晶体等效磁化率的定量形式. 在外磁场从0---40 T范围内, 计算了该晶体的磁熵变、声子熵变以及磁性体温度随外磁场的变化, 结果均与实验值符合较好. 利用声子熵变与饱和磁熵变曲线交点的唯一性, 给出了在磁性体磁化过程中, 确定其温度达到最大值的方法, 预言了Gd3Ga5O12晶体在绝热磁化过程中达到的最高温度为64.7K. 该方法还可以对所加外磁场大小进行预言或估计. 相似文献
104.
《Analytical letters》2012,45(4):263-272
Abstract The utility of hydroxy naphthol blue (HNB) as a spectrophotometric and fluorometric reagent for the uranyl ion has been investigated. In phthalate buffer (at a pH of 4.0), UO2 2+ forms a brown complex of low absorptivity with the red form of HNB. By following the decrease in HNB absorbance at 530 nm (which has ε = 4.1 × 103) uranyl ion can be determined to levels as low as 1.1 × 10?6 M (0.30 μg/ml). HNB also emits at 460 nm when excited at 365 nm at these pH values, while the UO2 2+ complex exhibits greatly reduced emission. Examination of the quenching of HNB emission by UO2 2+ allows the determination of uranyl ion to levels as low as 3.2 × 10?6 M (0.86 μg/ml). A 1:1 type complex was formed between UO2 2+ and HNB, and a formation constant of 9.77 × 103 (log K1 = 3.99) was measured for the complex. 相似文献
105.
以2-羟基苯甲醛和3-甲氧基苯乙酸为原料,经3步反应合成2-羟基-10,11-二氢-5H-二苯并[a,d]环庚烯-5-酮。 相似文献
106.
A procedure for pH-metric determination of the limiting adsorption of OH groups (A
OH) by FeIII, ZrIV, CrIII, and InIII oxyhydroxide hydrogels from 0.1 and 1.0 M solutions of NaCl is described. Data on the molecular area occupied by a single OH group on the hydrogel surface (S
OH) and the S
spec values, which were calculated from A
OH and S
OH, are presented. The S
spec value does not depend on the pH of hydrogel precipitation; the true S
spec value can be determined only from sorption of the OH groups at the actual point of zero charge of the hydrogel. The A
OH values for hydrogels were found to change only slightly during aging of hydrogels in electrolyte solutions. 相似文献
107.
蔗糖、葡萄糖对水溶液中丙酮、乙醇和乙腈活度的影响(298.1K) 总被引:1,自引:0,他引:1
用液上气相色谱法测定了298.1K下蔗糖和葡萄糖水溶液中丙酮、乙醇和乙腈的活度系数。对实验规律和3个非水组分活度数(lnγ)随糖浓度(m)的变化,从糖分子平伏羟基(e-OH)水化和溶剂混溶序及溶质与糖分子间相互作用的角度作了初步解释。 相似文献
108.
新显色剂1-羟基-2-(5-NO2-2-吡啶偶氮)-8-氨基-3,6-萘二磺酸与钯的显色反应 总被引:4,自引:0,他引:4
探讨了新显色剂1-羟基-2-(5-NO2-2-吡啶偶氮 )-8-氨基-3,6-萘二磺酸(简称5-NO2-PAH)与钯离子显色的适宜条件及其共存离子的影响,建立了5-NO2-PAH测定钯的新显色反应体系.结果表明,在pH 2.0~5.5范围内,钯与试剂形成稳定的1∶1配合物,其最大吸收峰位于712 nm, 表观摩尔吸光系数ε Pd=2.84×104 L*mol-1*cm-1,钯的浓度在0~20 μg/10 mL 范围内遵守比尔定律.方法已用于实际样品中钯的测定. 相似文献
109.
Timothy Biswick Alexandra Pacu?a Jerzy Podobinski 《Journal of solid state chemistry》2007,180(4):1171-1179
The steps associated with the thermal decomposition of Zn5(OH)8(NO3)2·2H2O and ZnOHNO3·H2O are re-examined. Previous reports have suggested that Zn5(OH)8(NO3)2·2H2O decomposes to ZnO via two intermediates, Zn5(OH)8(NO3)2 and Zn3(OH)4(NO3)2 whereas ZnOHNO3·H2O has been reported to decompose to ZnO via a Zn3(OH)4(NO3)2 intermediate. In this study, we demonstrate using TG, mass spectral analysis of evolved gases and in situ variable temperature powder X-ray diffraction analysis that, in fact, in the decomposition of Zn5(OH)8(NO3)2·2H2O an anhydrous zinc nitrate intermediate is also involved. We, additionally, show that the decomposition of ZnOHNO3·H2O to ZnO also involves the formation of an anhydrous zinc nitrate intermediate. The anhydrous zinc nitrate formed in both cases is poorly crystallised and this observation may explain why this phase could not be observed by PXRD analysis in the previous studies. 相似文献
110.
Carolina Aliaga Andrea Arenas Alexis Aspée Camilo López‐Alarcón Eduardo A. Lissi 《Helvetica chimica acta》2007,90(10):2009-2016
The pyraninoxyl radical is readily formed from the MnO2‐promoted oxidation of pyranine. The free radical can be formed in high concentrations (mM ), and presents a characteristic EPR spectrum that indicates a high spin‐density delocalization. It is relatively stable under nitrogen (half‐life ca. 50 min) but readily decays in presence of O2. In spite of its high stability, the radical readily reacts with antioxidants (phenols and ascorbic acid) with a partial recovery of the parent pyranine. High concentrations of the pyraninoxyl radical (ca. 9 μM ) are present when pyranine is exposed to a free radical source (10 mM 2,2′‐azobis[2‐amidinopropane], 37°). The fact that these radicals readily react with antioxidants (ascorbic acid and caffeic acid) supports the proposal that protection by antioxidants of peroxyl radical‐promoted pyranine bleaching is mainly due to the occurrence of a repair mechanism. 相似文献