Fourier transform Raman spectral measurements of powdered quaternary mixtures of organic compounds: Exceptional pure component spectral reconstruction using band-target entropy minimization (BTEM)

Fourier transform Raman spectra of eight mixtures of four organic solids, namely dicyandiamide, melamine, acetamide and urea were measured. Matrices formed from these spectra were first subjected to singular value decomposition to obtain the right singular vectors. The right singular vectors were then subjected to blind source separation using band-target entropy minimization (BTEM), thus no a priori information (i.e. involving the nature of the components present, their spectra, nor their concentrations) was included in the analysis. The recovered pure component spectra are of exceptionally high quality and are consistent with pure reference spectra. Various empirical and statistical tests, such as the Euclidean norm and target transform factor analysis, were employed to assess the quality of the recovered spectra. The present results indicate the applicability of combined Raman and BTEM analysis for solid mixtures.     

Chemoselective N-acetylation of primary aliphatic amines promoted by pivalic or acetic acid using ethyl acetate as an acetyl donor

The combination of pivalic or acetic acid as a promoter and EtOAc as a solvent and acetyl donor proved to be efficient for the chemoselective N-acetylation of primary aliphatic amines to afford the corresponding acetamides. We developed a simple and convenient approach, which requires mild reaction conditions. Competitive inter- and intramolecular reactions between aliphatic amines, alcohols, and aromatic amines were examined, and chemoselectivity was achieved by adjusting the conditions of the reaction.     

Mild and Useful Method for N-Acylation of Amines

Iodine is found to promote quantitative N-acylation of primary and secondary amines (aliphatic and aromatic) in a very short time with an equimolar amount of acetyl chloride and benzoyl chloride under solvent-free conditions at room temperature. This catalytic acylation of amines offers an additional useful method for the acetylation using acetyl chloride instead of acetic anhydride and other acetylating agents. This method is also useful in the N-acylation of heterocycles. Mild reaction condition, high selectivity, efficiency, and good yields are some of the major advantages of the procedure.     

高氯酸锂-乙酰胺新型二元熔盐电解质的谱学研究

高氯酸锂与乙酰胺在适宜摩尔配比范围内可形成热稳定性良好、电化学性能优良的室温熔盐.从分析LiClO4与乙酰胺形成熔盐的作用机制出发,通过红外、拉曼光谱的谱学分析并应用非局部密度泛函理论方法进行量化计算对二者的相互作用进行了讨论.发现乙酰胺通过Li－O键与LiClO4中的Li＋配位而破坏了LiClO4的离子键,形成很大的配位阳离子,削弱了阴阳离子间的库伦作用力;同时Li－O也导致乙酰胺分子间的氢键断裂,因而体系的共熔温度较之纯物质熔点显著降低,部分样品室温下以液体状态稳定存在.     

The use of Cr (CO)6 as an alternative CO source in Pd‐catalyzed C‐N bond formation: Synthesis of benzamides

An efficient strategy for the synthesis of benzamides from acetamides and aryl iodides using 1 mol% Pd (OAc)₂ as catalyst and Cr (CO)₆ as CO‐precursor is described. This new synthetic methodology displays high functional group tolerance on both substrates and avoids the need for ligands, reducing agents, or other additives. The corresponding products were obtained in good to excellent yields at atmospheric pressure under mild reaction conditions.     

Palladium-catalyzed phosphination and amination through CH bond functionalization on biphenyl: Amido-substituent as directing group

The formation of N-(2'-(diphenylphosphoryl)-[1,1′-biphenyl]-2-yl)-2,3,4,5,6-pentafluorobenzamide (3_eaaa) has been achieved through the palladium-catalyzed and Ag(I)-assisted CH functionalization of N-([1,1′-biphenyl]-2-yl)-2,3,4,5,6-pentafluorobenzamide (1_eaa) via phosphination and in the presence of diphenylphosphine oxide (2_a). The reaction was accompanied with small amount of carbazole derivative, (9H-carbazol-9-yl)(perfluorophenyl)methanone (4_eaa). Crystal structures of 3_eaaa and 4_eaa were both determined by X-ray crystal diffraction methods. Indeed, phosphination took place at the ortho-position of inter-annular ring of 1_eaa. Substituents with various electron-withdrawing/donating capacities on the amido-fragment of 1 were found to greatly affect the ratio distribution of products 3 and 4. By contrast, substituents on various locations of the biphenyl in 1 do not influence much on the outcome of the products distribution. A reaction mechanism is proposed to account for these experimental observations. Computational studies employing Density Functional Theory methods (DFT) on this proposed mechanism found that the electron density property of the palladium metal center in the intermediate II is critical to the formation of either 3 or 4. A relatively electron-poor palladium metal center favors the pathway of forming 3. On the contrary, the pathway of producing 4 will be prevailed while the palladium metal center is having fair amount of electron-density in the proposed intermediate II.     

高氯酸锂-乙酰胺/乙烯脲体系的二元熔盐电解质

制备了高氯酸锂与乙酰胺和乙烯脲形成的二元低温熔盐电解质，采用差示扫描量热法、交流阻抗法和循环伏安法分别对其热学、电化学性质进行了研究.测试结果表明,高氯酸锂-乙酰胺体系具有较好的热稳定性和高的电导性，配比n（LiClO4）:n（Acetamide）=1.0:5.5的样品室温（25 ℃）电导率为1.25×10－3 S•cm－1，80 ℃电导率为1.15×10－2 S•cm－1;其电化学稳定电位窗近3 V左右.     

Theoretical study on the reaction mechanism for the hydrolysis of esters and amides under acidic conditions

The mechanisms underlying the hydrolysis of methyl acetate and acetamide under acidic conditions were investigated using the MP2/6-311+G(d,p)//MP2/6-31+G(d,p) level of theory. It was necessary to include two water molecules as reactants to obtain a tetrahedral (TD) intermediate for the A_AC2 mechanism that Ingold classified for the hydrolysis of methyl acetate. This mechanism includes two TS structures, one for the formation of the TD intermediate and the other for its decomposition. Since the activation energies were calculated to be 15.7 and 18.3 kcal mol⁻¹, the second step determines the rate of hydrolysis. The calculated value was close to that observed at ∼16 kcal mol⁻¹. It was confirmed that the A_AC2 mechanism had a barrier lower by 9.9 kcal mol⁻¹ than the A_AL2 mechanism. The A_AC2 mechanism is also applicable to the acid-catalyzed hydrolysis of acetamide. It is not the TD intermediate with which the NH₃⁺ moiety forms, but one further step is required to produce the final products, acetic acid and ammonium ion.     

乙酰胺的分光光度检测

研究了乙酰胺的分光光度分析方法。该方法用溴水氧化酰胺 ,其氧化产物可把 I-氧化成 I2 ,I2 再和淀粉 -KI生成有色络合物来测定酰胺的含量 ,主要适用于伯酰胺的分析。方法在 5× 1 0 - 6 ～ 1× 1 0 - 4 g/ 2 5m L范围内符合比耳定律 ,表观摩尔吸光系数 ε5 76 nm=4 .5× 1 0 4L·mol- 1·cm- 1。该法灵敏、快速、重现性好。     

甘氨酸从水到有机物水溶液的迁移焓研究

蛋白质是各种生物形态结构和生命活动所依赖的物质基础,在水溶液中蛋白质天然结构的稳定性归结于氨基酸残基之间以及与溶液中其它组分的相互作用．天然环境中存在的众多物质对蛋白质的溶解度、变性行为和解缔等都有很大的影响．为深入了解蛋白质折叠与解折叠过程中的物理化学现象,以氨基酸、肽、酰胺及其衍生物作为蛋白质模型分子的热力学研究引起了广泛重视．