碘化钾-甲基异丁基甲酮萃取电感耦合等离子体发射光谱法测定磷酸一铵、磷酸二铵中铊含量

通过对观测方式、测定波长、共存元素干扰等因素进行分析和条件优化,建立了测定磷酸一铵、磷酸二铵中铊含量的碘化钾-甲基异丁基甲酮（KI-MIBK）萃取电感耦合等离子体发射光谱法。实验表明,直接采用电感耦合等离子体发射光谱法进行测定时,磷酸一铵、磷酸二铵中的锰元素对分析结果有正干扰。通过萃取分离,干扰被排除,测定结果准确、可靠。在0～1.0 mg/L范围内,铊的质量浓度与光谱强度呈良好的线性关系,相关系数达1.0000。该方法检出限为0.0072 mg/kg,相对标准偏差为4.28%（n = 10）,加标回收率在97.00%～100.5%之间。     

Salts of 2,5-dimercapto-1,3,4-thiadiazole

Reaction of 2,5-dimercapto-1,3,4-thiadiazole with ammonia or pyridine gives monoammonium or monopyridinium slats, and the reaction with hydrazine hydrate gives both mono- and dihydrazine salts, which was confirmed by alkylation of the salts obtained. Difference in the chemical shifts of the SCH₂R groups was found in the¹H NMR spectra of the mono- and dialkyl-substituted 2,5-dimercapto-1,3,4-thiadiazoles.Institute of Chemistry, Vilnius LT-2600, LithuaniaTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 682–687, May, 2000.     

Simple and Efficient Method for the Synthesis of Benzimidazole Derivatives using Monoammonium Salt of 12‐Tungstophosphoric Acid

Benzimidazoles have been synthesized in very good yield from o‐phenylenediamine and aromatic aldehydes in the presence of monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀], an efficient heterogeneous catalyst. This catalyst has the advantages of simple workup procedure, water insolubility, and good activity with high yield for the synthesis of benzimidazole derivatives.     

Efficient Method for the Synthesis of 1,5‐Benzodiazepine Derivatives Catalyzed by Monoammonium Salt of 12‐Tungstophosphoric Acid

Monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] was found to be a practical, inexpensive, reusable, and efficient heterogeneous catalyst for the preparation of 1,5‐benzodiazepine derivatives of o‐phenylenediamine and ketones. The heteropolyacid‐based catalyst has the advantages of simple workup procedure, water insolubility with good activity, and high‐yielding reaction for the synthesis of 1,5‐benzodiazepine derivatives.     

A new polymorph of ammonium succinate – serendipity in action

Succinic acid has been known since 1546 and was first chemically identified in the mid‐19th century. In an attempt to prepare a molecular salt of succinic acid with (S)‐(?)‐α‐methylbenzylamine, we have obtained the second polymorph of the monoammonium salt of succinic acid, NH₄⁺·C₄H₅O₄^?. The crystal structure determination proves the structure of the ionic compound and the intimate role of the ammonium ion in the structure, which is compared to the earlier described polymorph.