Solid–liquid phase equilibria in the system K2SO4–MgSO4–H2O at 318 K

The polythermal solubility diagram of the system K₂SO₄–MgSO₄–H₂O presents the formation of three double salts, picromerite, leonite, langbeinite appearing in this order with increasing temperature. In the temperature range between 314.15 K and 320.65 K, picromerite and leonite ought to coexist. The search in the literature revealed a lack of isothermal phase equilibrium data within this temperature range. Therefore, the solubility in the system K₂SO₄–MgSO₄–H₂O was determined in the whole concentration range at 318 K. The solid phases, epsomite, leonite, picromerite and arcanite occur with increasing potassium sulfate concentration. A two-salt point of leonite and picromerite is established at 0.618 molal K₂SO₄ and 3.030 molal MgSO₄ at the temperature of investigation.     

Selective cyclization of alkynols and alkynylamines catalyzed by potassium tert-butoxide

Potassium tert-butoxide (t-BuOK) was found to be an effective catalyst for the cyclization of aromatic alkynols and alkynylamines. In the presence of 10 mol % t-BuOK, a range of alkynols were converted to the corresponding exo-cyclic enol ethers as pure Z-stereoisomers with 100% selectivity and moderate to excellent yields. Moreover, the cyclization of alkynylamines was also achieved to afford indoles and isoindolin-1-ones in good yields.     

K2S2O8-Mediated halogenation of 2-arylimidazo[1,2-a]pyridines using sodium halides as the halogen sources

A convenient halogenation of 2-arylimidazo[1,2-a]pyridines using sodium chloride/bromide/iodide as the halogen sources in the presence of K₂S₂O₈ as an easy-to-handle oxidizing agent was developed. The present work offers an efficient and rapid access to 3-chloro-, 3-bromo- and 3-iodo-2-arylimidazo[1,2-a]pyridines which can be readily converted to C3-substituted imidazo[1,2-a]pyridines by cross-coupling reactions.     

Coordination chemistry of alkali and alkaline earth cations. X-ray structural analysis of bis (benzo-15-crown-5) potassium nitrate monohydrate

The 1:2 charge separated KNO₃ complex with benzo-15-crown-5 (B15C5) has been crystallized from a 50% water-methanol solution. K(B15C5)₂NO₃·H₂O is monoclinic,P2₁/c,a=12.717(2),b=19.569(2),c=13.025(3) Å, =100.79(1)^o,Z=4,D _c =1.37 g·cm^–3. The X-ray structure was refined toR=0.052 for 3049 independent reflections withF ₀ ² 2.0(F ₀ ² ), collected with MoK radiation for a 2 -range of 4–44°. The K⁺ ion is coordinated tenfold in a crown sandwich through all five oxygen atoms of the macrocyclic ligand. Nitrate and water oxygens are not involved in the cation coordination sphere. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82031 (6 pages).     

动力学光度法测定维生素B1的研究

在氢氧化钠介质中,微量维生素B1对高碘酸钾氧化苯并红紫4B褪色反应有明显的催化作用,据此建立了测定维生素B1含量的动力学光度法.测定了反应动力学参数,方法的线性范围为0.01～0.4 mg·L-1,检出限为7.0×10-6g·L-1.用于小米粉和维生素B1片剂中维生素B1含量的测定.     

利用X射线衍射和拉曼光谱法对KCl和NaCl混合溶液微观结构的研究

利用X射线衍射法和拉曼光谱法系统研究了25 ℃下, 0-26%质量分数浓度范围内KCl和NaCl混合溶液的结构。通过分析X射线衍射法所得的混合溶液的差值结构函数F(Q)以及差值对分布函数G(r)发现,混合溶液组分中的K⁺的水化层半径及其水化数均大于Na⁺,从而揭示出常温下NaCl在水中的溶解度大于KCl的原因。在拉曼光谱的研究中,观察到溶液中水分子的四面体氢键受破坏程度随KCl浓度的增加和NaCl浓度的减少,先增大后减小,并结合X射线衍射法的结果,推断混合溶液中Na⁺对水溶液中氢键结构的破坏程度比K⁺严重,且加入适量的K⁺会使Na⁺由结构缔造者转变为打破结构者,对水溶液结构的破坏增强。     

吸光光度法测定碘酸钾的研究

研究了碘酸钾、碘化钾与孔雀石绿在盐酸介质中形成离子缔合物的最佳条件 ,并由此建立了一种测定碘酸钾的新方法。在试验条件下 ,碘酸钾浓度在 0～ 10 μg·ml- 1范围内服从比耳定律 ,线性相关系数为 0 .9991。方法具有简便、灵敏、准确的特点 ,可用于食盐中微量碘的测定。     

Synthesis of enantiomeric pure lithium and potassium benzamidinate complexes

A new synthesis leading to the chiral amidines (S,S)- and (R,R)-N,N-bis-(1-phenylethyl)benzamidine ((S)- and (R)-HPEBA) in good yields is presented. Further reaction of (S)-HPEBA with n-BuLi gave the chiral lithium salt (S)-LiPEBA. Treatment of KH with (S)-HPEBA in boiling THF afforded the corresponding potassium salt (S)-KPEBA. In contrast by performing the reaction in boiling toluene a fast racemization was observed. In the solid state racemic KPEBA formed a dimer, in which all four nitrogen atoms are in a plane. To each potassium atom a toluene molecule is η⁶-coordinated.     

Facile stereoselective synthesis of cis- and trans-3-alkoxyazetidin-2-ones

A highly stereoselective synthesis of cis- and trans-3-alkoxy-3-phenyl/benzylthioazetidin-2-ones is described. The reaction of α-chlorosulfide-β-lactams with various alcohols catalyzed by a Lewis acid such as ZnCl₂ in the presence of molecular sieves (3-4 Å) leads to cis-3-alkoxy-3-phenyl/benzylthio-β-lactams whereas treatment of potassium 2-alkoxy-2-phenylthioethanoate with appropriate Schiff's base using POCl₃ in the presence of triethylamine leads to the formation of trans-3-alkoxy-3-phenylthioazetidin-2-ones as major products.     

Mg diffusion in K(Ta0.65Nb0.35)O3 thin films grown on MgO evidenced by Auger electron spectroscopy investigation

The diffusion of Mg in pulsed laser deposited K(Ta_0.65Nb_0.35)O₃ thin films epitaxially grown on (1 0 0) MgO single crystal substrate were investigated by Auger electron spectroscopy (AES). A diffusion of Mg from the substrate into the whole thickness (400 nm) of the as-deposited K(Ta_0.65Nb_0.35)O₃ films was observed with an accumulation of Mg at the surface. Ex situ post-annealing (750 °C/2 h) has led to a homogeneous distribution of Mg in all the ferroelectric coating. This strong reaction between film and substrate promotes a doping effect, responsible for the reduction of K(Ta_0.65Nb_0.35)O₃ dielectric losses in comparison with films grown on other substrates.