Experimental and Theoretical Study on Dissociative Photoionization of Cyclopentanone

The dissociative photoionization of cyclopentanone was investigated by means of a reflectron time-of-flight mass spectrometer (RTOF-MS) with tunable vacuum ultraviolet synchrotron radiation in the photon energy range of 9.0-15.5 eV. The photoionization efficiency (PIE) curves for molecular ion and fragment ions were measured. The ionization energy of cyclopentanone was determined to be 9.23\begin{document}$\pm$\end{document}0.03 eV. Fragment ions from the dissociative photoionization of cyclopentanone were identified as C\begin{document}$_5$\end{document}H\begin{document}$_7$\end{document}O\begin{document}$^+$\end{document}, C\begin{document}$_4$\end{document}H\begin{document}$_5$\end{document}O\begin{document}$^+$\end{document}, C\begin{document}$_4$\end{document}H\begin{document}$_8^+$\end{document}/C\begin{document}$_3$\end{document}H\begin{document}$_4$\end{document}O\begin{document}$^+$\end{document}, C\begin{document}$_3$\end{document}H\begin{document}$_3$\end{document}O\begin{document}$^+$\end{document}, C\begin{document}$_4$\end{document}H\begin{document}$_6^+$\end{document}, C\begin{document}$_2$\end{document}H\begin{document}$_4$\end{document}O\begin{document}$^+$\end{document}, C\begin{document}$_3$\end{document}H\begin{document}$_6^+$\end{document}, C\begin{document}$_3$\end{document}H\begin{document}$_5^+$\end{document}, C\begin{document}$_3$\end{document}H\begin{document}$_4^+$\end{document}, C\begin{document}$_3$\end{document}H\begin{document}$_3^+$\end{document}, C\begin{document}$_2$\end{document}H\begin{document}$_5^+$\end{document} and C\begin{document}$_2$\end{document}H\begin{document}$_4^+$\end{document}. With the aid of the ab initio calculations at the \begin{document}$\omega$\end{document}B97X-D/6-31+G(d, p) level of theory, the dissociative mechanisms of C\begin{document}$_5$\end{document}H\begin{document}$_8$\end{document}O\begin{document}$^+$\end{document} are proposed. Ring opening and hydrogen migrations are the predominant processes in most of the fragmentation pathways of cyclopentanone.     

Syntheses of Novel Asymmetric Cyclopentanone Dyes and Measurement of Two－photon Absorption Cross－section

A simple synthesis route with a high yield of novel asymmetric cyclopentanone dyes 3a—3e and their highly two-photon up-converted fluorescences are reported. The dyes have good solubilities in most of ordi-nary solvents, a wide UV absorption wavelength range from 380—540 nm, and high fluorescence quantum yields. The two-photon absorption cross-sections of dyes 3a—M were measured in chloroform by a two-pho-ton induced fluorescence method. All of these properties of the new dyes make them suitable for being used as two-photon fluorescent probes.     

Probing fuel-specific reaction intermediates from laminar premixed flames fueled by two C5 ketones and model interpretations

The flame chemistry was explored for two C₅ ketones with distinct structural features, cyclopentanone (CPO) and diethyl ketone (DEK). Quantitative information for numerous species, including some reactive intermediates, was probed from fuel-rich (?= 1.5) laminar premixed flames fueled by the ketones with a photoionization molecular-beam mass spectrometer (PI-MBMS). Furthermore, a new kinetic model was proposed aimed at interpreting the high-temperature combustion chemistry for both ketones, which could satisfactorily predict the current flame speciation measurements. Experimental observations in combination with modeling analyses were used to reveal the similarities and differences between the compositions of the species pools of the two flames, with emphasis on the effects of the carbonyl functionality on pollutants formations. Besides some primary species which preserve fuel-specific features produced from initial steps of fuel consumptions, basic C₁C₄ intermediates also differ much between the two flames. More abundant intermediates were observed in the CPO flame because the cyclic fuel structure enables ring-opening processes followed by formations of C₃ and C₄ hydrocarbons which cannot be easily produced from the two isolated ethyl moieties in DEK under flame conditions. The consumptions of C₃C₄ hydrocarbons in the CPO flame further lead to larger C₅C₆ species which were under the detection limit in the DEK flame. In both flames, the tightly bonded carbonyl groups in the fuels tend to be preserved, leading to carbon monoxide through α-scissions of fuel-related acyl radicals. The carbonyl moieties in most detected C₁C₃ aldehydes and ketones form through oxidations of hydrocarbon species rather than directly originating from the fuels.     

Solvent-Free Crossed Aldol Condensation of Cyclic Ketones with Aromatic Aldehydes Assisted by Microwave Irradiation

Summary. A fast alumina-promoted crossed aldol-condensation reaction of aldehydes and cyclic ketones under microwave irradiation is described. This process is simple, efficient, and environmentally benign and proceeds in fairly high yield without any self-condensation.     

铜镍双金属催化剂上糠醛水相选择性偶联加氢-重排制环戊酮

生物质资源高效催化转化制备高附加值化学品具有重要的科学意义与工业应用潜力.生物质基糠醛催化加氢-重排制备环戊酮是一条具有吸引力的"非石油"制备路线,但该过程面临副产物多、环戊酮选择性难以提高等难题,除糠醛外,中间物种也很容易发生多种聚合副反应.因此,探索中间物种聚合副反应的条件和作用机制,是提高目标产物环戊酮的选择性和收率的关键.本文制备了CuNi/Al-MCM-41双金属纳米过渡金属催化剂,通过精确调控介质水的pH值和原料浓度,实现了糠醛加氢-重排耦合制备环戊酮的高选择性和高收率.在2.0 MPa H2,160oC和近中性条件下反应5 h,糠醛的转化率为99.0％,环戊酮的选择性达到97.7％;其催化性能远远高于单组份铜或镍催化剂以及其它分子筛载体(MCM-41,SBA-15,HY,ZSM-5)负载的CuNi双金属催化剂.研究结果表明,高度分散在MCM-41上的少量Al组分,有利于Cu,Ni金属组分相互均匀分散.XPS结果表明,双金属催化剂CuNi/Al-MCM-41中Cu和Ni具有明显的电子结合能偏移,表明Ni向Cu转移电子;耦合催化反应性能的提高可能与CuNi双金属协同作用及电荷转移效应有关.傅立叶变换红外光谱和质谱结果表明,聚合副反应对反应体系的pH值敏感.在酸性条件下,中间产物糠醇在反应体系中容易发生聚合,导致糠醇重排生成3-羟基环戊烯酮的选择性降低;在碱性条件下,3-羟基环戊烯酮转化为4-羟基-环戊-2-烯酮后,容易进一步发生聚合副反应.在近中性条件下可有效避免中间体的聚合,提高加氢重排生成环戊酮的选择性.此外,降低原料糠醛的初始浓度,有利于降低聚合等副反应,能够进一步提高目标产物环戊酮的收率.本文为研制双金属纳米过渡金属催化剂以及利用双金属协同作用等方面提供新的启示,为解决生物质原料转化过程中普遍存在的聚合副反应和碳平衡降低等问题提供了新思路.     

Synthesis and spectroscopic characterization of novel 2-amino-4,5,6,7-tetrahydro-3H-cyclopenta[d]pyrimidine and pyrimido[1,2-a]pyrimidine derivatives

2-Aminocyclopenta[d]pyrimidines 3a-c were achieved via a one-pot, three-component reactions of cyclopentanone 1, aromatic aldehyde and guanidine hydrochloride (1:2:1 molar ratio). Also, cyclization of 2,5-bis-(arylmethylidene)cyclopentanones 2 with guanidine hydrochloride (1:1 molar ratio) in methanol in the presence of sodiummethoxide afforded cyclopenta-[d]pyrimidines 3. Compound 3a has been shown to be a useful building block for the synthesis of some novel pyrimido[1,2-a]pyrimidines 5, 7 and 12. The structures of the newly synthesized compounds were confirmed on the basis of analytical and spectral data.     

Synthesis of Pyrimidinone and 5‐unsubstituted 4, 6‐diarylpyrimidine‐2(1H)‐ones by Using Nano Magnetic Catalyst under Solvent Free Condition

Nano magnetic‐supported sulfonic acid is found to be a powerful and reusable heterogeneous catalyst for the efficient synthesis of pyrimidinones. In this study we use various ketones such as acetophenone and cyclopentanone instead of β‐keto ester in one‐pot synthesis of pyrimidinone at biginelli like reaction. Our objective is to improve conditions for the synthesis of multicomponent reactions using nano magnetic catalyst under solvent free condition. A number of excellent and significant results have been developed that lead our perspective understanding the effect of the magnetic nanoparticles when they are used as catalysts.     

Trimethylaluminium-induced diastereoselective methylation onto ethyl 2-oxocyclopentane-1-carboxylate and isomerization between the dimethylaluminium-alkoxide products

Methylation of α-disubstituted cyclopentanone 1 with Me₃Al in CH₂Cl₂ at 0 °C for 30 min gave diastereoselectively a mixture of (1R*,2S*)-2 and (1R*,2R*)-2 in a 96:4 ratio and 83% total yield. When the same methylation was carried out at 0 °C for 1 h and then at room temperature for 120 h, a diastereomeric mixture of (1R*,2S*)-2 and (1R*,2R*)-2 was obtained in a 12:88 ratio and in 88% total yield. The stereochemistry of the two diastereomers was determined by the results of acetalization of their diol derivatives 3 and 5. Isomerization between the Me₂Al-alkoxides of (1R*,2S*)-2 and (1R*,2R*)-2 and its possible mechanism were investigated by HPLC analysis of the methylation reaction process at 0 °C for 1 h and then at room temperature for 56 h and also by their mutual epimerization reactions.     

Synthesis of 2-Heterocyclomethyl-5-diphenylmethylenecyclopentanone Hydrochlorides and their Inhibitory Effect on Tumor Cell Growth

A large number of natural diterpenes and sesquiterpenes have remarkable bioactivity. The presence of α-methylenec?yclopentanone in diterpenes and α-methylene-γ-lactones in sesquiterpenes plays a significant role to mediate anti-tumour activities by directly interacting with sulfhydryl enzymes. However, it has been recognized that the therapeutic value of these natural compounds was limited due to their indiscriminating toxicity. To increase the selectivity and cytotoxicity to tumor cells, w…