Sonochemical Reaction of Bifunctional Molecules on Silicon (111) Hydride Surface

While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established thermal reaction and sonochemical reaction of nucleophilic molecules (cyclopropylamine and 3-Butyn-1-ol) was performed on p-type silicon hydride (111) surfaces. The nature of surface grafting from these reactions was examined through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Cyclopropylamine, being a sensitive radical clock, did not experience any ring-opening events. This suggested that either the Si–H may not have undergone homolysis as reported previously under sonochemical reaction or that the interaction to the surface hydride via a lone-pair electron coordination bond was reversible during the process. On the other hand, silicon back-bond breakage and subsequent surface roughening were observed for 3-Butyn-1-ol at high-temperature grafting (≈150 °C). Interestingly, the sonochemical reaction did not produce appreciable topographical changes to surfaces at the nano scale and the further XPS analysis may suggest Si–C formation. This indicated that while a sonochemical reaction may be indifferent towards nucleophilic groups, the surface was more reactive towards unsaturated carbons. To the best of the author’s knowledge, this is the first attempt at elucidating the underlying reactivity mechanisms of nucleophilic groups and unsaturated carbon bonds during sonochemical reaction of silicon hydride surfaces.     

Synthetic Applications of the Direct Alkylation Reactions of 3-Sulfolenes

The readily available sulfolenes can be used as the 1-carbanion equivalent of the unsubstituted and substituted buta-1,3-dienes which can be directly alkylated. This convenient synthetic method is not only regiospecific, efficient and straight forward, but also favorable because the normally unstable molecules containing conjugated dienyl moiety can be prepared directly in their protected forms. The deprotection step is both clean and highly stereoselective. The applications of this type of reaction in organic synthesis include the trans-β-ocimene, α-farnesene and a series of hydroindans and hydronaphthalenes.     

Preparation,morphology, and thermoresponsive properties of poly(N‐isopropylacrylamide)‐based copolymer microgels

In this research, thermoresponsive copolymer latex particles with an average diameter of about 200–500 nm were prepared via surfactant‐free emulsion polymerization. The thermoresponsive properties of these particles were designed by the addition of hydrophilic monomers [acrylic acid (AA) and sodium acrylate (SA)] to copolymerize with N‐isopropylacrylamide (NIPAAm). The effects of the comonomers and composition on the synthesis mechanism, kinetics, particle size, morphology, and thermoresponsive properties of the copolymer latex were also studied to determine the relationships between the synthesis conditions, the particle morphology, and the thermoresponsive properties. The results showed that the addition of hydrophilic AA or SA affected the mechanism and kinetics of polymerization. The lower critical solution temperature (LCST) of the latex copolymerized with AA rose to a higher temperature. However, because the strong hydrophilic and ionic properties of SA caused a core–shell structure, where NIPAAm was in the inner core and SA was in the outer shell, the LCST of the latex copolymerized with SA was still the same as that of pure poly(N‐isopropylacrylamide) latex. It was concluded that these submicrometer copolymer latex particles with different thermoresponsive properties could be applied in many fields. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 356–370, 2006     

Ceramides from the Taiwan Red Alga Ceratodictyon Spongiosum and Symbiotic Sponge Sigmadocia Symbiotica

The structure of a mixture of ceramides ( 1 ) de rived from 2‐amino‐4(E)‐alkene‐1,3‐diol sphingenines with C₂₂, C₂₃, and C₂₄ saturated fatty acid residues from red alga Ceratodictyon spongiosum ZANARDINI (Rhodymeniaceae) containing the symbiotic sponge Sigmadocia symbiotica has been elucidated on the basis of spectroscopic and chemical evidence. In addition, one new sterol, n‐nonadecanoic acid 24‐ methylenecholesteryl ester ( 2 ), and six known sterols were also isolated from the marine organisms.     

异烷基膦酸1-甲庚基酯负载树脂分离原子吸收光谱法测定氧化钇中痕量铕铽铒和镱

异烷基膦酸1-甲庚基酯(代号5712)是在较低酸度下具有优良稀土分离性能的萃取剂。本文测定了15种稀土(Ⅲ)在5712-负载树脂与不同浓度的HNO_3之间的分配比。研究了5712-负载树脂柱分离Y、Tb、Dy、Ho、Er的最优条件。0.58mol/L HNO_3可使这5种元素分离良好。利用5712-负载树脂分离和富集高纯氧化钇中痕量Eu、Tb、Er和Yb,然后再以原子吸收光谱法测定。经过本法分离和富集,除去了大量基体,从而提高了测定的灵敏度。     

Synthesis and Spectral Properties of Phenyl‐Pyridin‐2‐Ylmethylene‐Amine Complex of Rhodium(III)

A new complex of [Rh(PA)₂Cl₂]Cl·H₂O (where PA = phenyl‐pyridin‐2‐ylmethylene‐amine) has been synthesized and characterized. The complex shows high intensity bands in the UV region, and these are assigned to spin‐allowed π‐π* transitions. The medium‐intensity absorption band profile in the lower energy region can be explained by convolution of spin‐allowed CT and d‐d* transitions. Emission spectrum at low temperature (77 K) of the complex in EtOH/MeOH (4:1 v/v) has also been investigated. It shows a broad, symmetric, and structureless red emission with micro second life time and hence is assigned as d‐d* phosphorescence. Voltammetric data have also been obtained for the complex. There were three reduction peaks observed for the complex. The first peak, including two reduction steps with elimination of two chlorides, is consistent with ECEC reaction.     

Easily Accessible 2‐(2‐Bromophenyl)‐4,4,5,5‐Tetramethyl‐[1,3,2]Dioxaborolane for Suzuki‐Miyaura Reactions

A simple and direct method has been developed for the preparation of the title compound from 1,2‐dibromobenzene. Suzuki‐Miyaura reactions of this compound with substituted bromoaryls proceeded smoothly to give 2‐bromobiphenyl derivatives in moderate to excellent yields. Instead of converting each of the bromoaryl compounds to the corresponding arylmetals followed by reacting with 2‐iodobromobenzene, the advantage of this protocol is that the substituted bromoaryls were used directly to couple with the title compound.     

Experimental and Computational Studies of the Isomerization between Z and E Isomers of Benzaldoximes

The isomerization between Z and E isomers of benzaldoximes in different solvents were measured by TLC method. The experimental results show that acid solvents catalyze this inter‐conversion process dramatically. Solution state NMR measurements also show very different spectra for Z and E isomers of benzaldoximes in different solvents. All this suggests that the acidity of solvent is a very important factor to affect the inter‐conversion process. Theoretical investigations of Z to E inter‐conversion of benzaldoximes in different solvents were carried out by DFT calculations at B3LYP/6–3 11+G** level. The calculations show that the barrier from Z to E in the presence of acid is much lower than that without acid. This agrees with the experimental data very well. The calculated structure in the transition state is helpful for the understanding of the inter‐conversion mechanism.