流动注射(FI)在线沉淀ICP-AES法测定碘

利用在酸性介质中碘离子与硝酸银反应生成沉淀,加入乙醇降低沉淀的溶解度,加入氨水,ＣＯ２－３ 、ＳＯ２－３ 、Ｃ２Ｏ２－４ 等离子不干扰测定,建立了流动注射在线沉淀ＩＣＰ－ＡＥＳ法测定碘的新方法。方法的线性范围为５～５０ μｇ／ｍ Ｌ,进样速率４０ 次／ｈ,加标回收率为９８．７％ ～１００．１％ ,分析结果满意。     

示波指示技术在动力学分析中的应用(Ⅲ)——示波双安培催化动力学法测定铜和碘

双安培法是一种灵敏度很高的分析方法,近年来已有许多应用.作者曾将双安培示波法用于确定氧化还原滴定的终点.本文将双安培示波技术用于催化动力学分析获得成功.在动力学分析中,加入不同浓度的催化剂,用本法测出指示组分达到一定浓度的时间,即可测得催化剂的浓度.因为示波器很稳定,测定电流的灵敏度很高,且不受试液的颜色或沉淀的影响,所得结果的重现性好,线性范围较宽,所以此法比光度法优越.     

Synthese und Konstitution von HIS2O8

Synthesis and Constitution of HIS₂O₈ Novel HIS₂O₈ has been obtained by reacting iodic acid and oleum at 210 °C. According to the results of a X-ray structure determination (monoclinic, P2₁/c, a = 1172.0(2), b = 625.7(2), c = 956.0(2) pm, β = 106.50(2), Z = 4, 1083 reflections, R₁ = 0.037, wR² = 0.103) iodine is connecting a sulfate and a hydrogensulfate group, thus forming IO₂ bridges. This can be regarded as a condensation of hypothetical iodic acid (III), HIO₂, with sulfuric acid.     

α-Iodoalkyl–Iodine–Ate Complexes as Observable Intermediates in the Iodine– Magnesium Exchange Reaction

An intermediate with a half-life of 30 minutes has been observed in the iodine–magnesium exchange reaction of 1,1-diiodoalkanes in THF at −78°C. This intermediate is likely the ate complex 1 . Its characteristic chemistry calls for a mechanistic reconsideration of several features of the halogen–metal exchange reaction.     

邻联甲苯胺显色光度法测定微量碘的研究

研究了在盐酸介质中,利用碘酸钾氧化性使邻联甲苯胺显色,建立了光度法测定碘的方法。在选定的条件下,有色溶液的最大吸收波长为426nm,碘的含量在0~20μg/25mL范围内符合比耳定律,表观摩尔吸光系数为1.13×105L.mol-1.cm-1。方法简单、快速、准确、选择性好、灵敏度高,用于测定加碘食盐中的碘,结果满意。     

Catalytic,Regioselective 1,4-Fluorodifunctionalization of Dienes

A catalysis-based regioselective 1,4-fluorofunctionalization of trifluoromethyl substituted 1,3-dienes has been developed to access compact, highly functionalized products. The process allows E,Z-mixed dienes to be processed to a single E-alkene isomer, and leverages an inexpensive and operationally convenient I(I)/I(III) catalysis platform. The first example of catalytic 1,4-difluorination is disclosed and subsequently evolved to enable 1,4-hetero-difunctionalization, which allows δ-fluoro-alcohol and amine derivatives to be forged in a single operation. The protocol is compatible with a variety of nucleophiles including fluoride, nitriles, carboxylic acids, alcohols and even water thereby allowing highly functionalized products, with a stereocenter bearing both C(sp³)−F and C(sp³)−CF₃ groups, to be generated rapidly. Scalability (up to 3 mmol), and facile post-reaction modifications are demonstrated to underscore the utility of the method in expanding organofluorine chemical space.     

Simple and Versatile Nitrooxylation: Noncyclic Hypervalent Iodine Nitrooxylating Reagent

Organic nitrates are broadly applied as pharmaceuticals (acting as efficient nitric oxide donor), energetic materials, building blocks in organic synthesis, etc. However, practical and direct methods to access organic nitrates efficiently are still rare, mainly due to the lack of powerful nitrooxylating reagents. Herein, we report bench-stable and highly reactive noncyclic hypervalent iodine nitrooxylating reagents, oxybis(aryl-λ³-iodanediyl) dinitrates (OAIDNs, 2 ), which are prepared just by using aryliodine diacetate and HNO₃. The reagents are used to achieve a mild and operationally simple protocol to access diverse organic nitrates. By employing of 2 , zinc-catalyzed regioselective nitrooxylation of cyclopropyl silyl ethers is realized efficiently to access the corresponding β-nitrooxy ketones with high functional-group tolerance. Moreover, a series of direct and catalyst-free nitrooxylations of enolizable C−H bonds are carried out smoothly to afford the desired organic nitrates within minutes by just mixing the substrates with 2 in dichloromethane.     

Stereospecific Photoredox-Catalyzed Vinylations to Functionalized Alkenes and C-Glycosides**

We report an efficient radical-mediated C−C coupling through photoredox-catalyzed reactions of 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO). This transition-metal-free and mild photocatalytic method has excellent functional group tolerance and affords vinylated products in good yields, with complete retention of the alkene configuration. The utility of the methodology is demonstrated by the diastereoselective synthesis of C-vinyl glycosides. Preliminary mechanistic studies suggest that the C−C bond formation is stereospecific and proceeds through a concerted radical coupling transition state.     

Synthesis of N-Monosubstituted Sulfondiimines by Metal-free Iminations of Sulfilimium Salts

Sulfondiimines are marginalized entities among nitrogen-containing organosulfur compounds, despite offering promising properties for applications in various fields including medicinal and agrochemical. Herein, we present a metal-free and rapid synthetic procedure for the synthesis of N-monosubstituted sulfondiimines that overcomes current limitations in their synthetic accessibility. Particularly, S,S-dialkyl substrates, which are commonly difficult to convert by existing methods, react well with a combination of iodine, 1,8-diazabicyclo[5.4.0]undec-7-en (DBU), and iminoiodinanes (PhINR) in acetonitrile (MeCN) to furnish the corresponding sulfondiimines in yields up to 85 % (25 examples). Valuable “free” NH-N′H-sulfondiimines can then be accessed by N-deprotection under mild reaction conditions. Several experimental observations suggest a mechanistic pathway diverging from the common radical-based iodine/iminoiodinane mechanism. Based on the experimental results in combination with data obtained by ¹H NMR spectroscopy, ESI mass spectrometry, and crystallographic analysis we propose a direct amination from PhINNs and a reaction path via a cationic iodonitrene.     

Synthesis of Trifluoromethylated Alkenes: Hypervalent Iodine Meets High-Valent Copper

The first trifluoromethylation of vinylbenziodoxolones (VBX) is reported herein. The synthetic method is based on the use of bench-stable, high-valent copper(III) species, and the reaction can be initiated under thermal conditions and/or irradiation (365 nm) giving access to trifluoromethylated alkenes in a stereoselective fashion. Various VBX reagents derived from tyrosine, cysteine, small peptides, thiols and amides can be used as precursors. The obtained alkenes could be further functionalized by reduction or epoxidation of the trifluoromethylated double bond. Furthermore, the method could be applied in a large-scale batch/flow synthesis and could be conducted under visible light irradiation.