Molecular structure,vibrational spectroscopic and chemical reactivity of nematogenic p-n-alkylbenzoic acids: A comparative computational analysis

Molecular structure and vibrational spectroscopic studies of higher homologous series nematogenic p-n-alkylbenzoic acids (nBAC) that have 6 (6BAC) and 7 (7BAC) carbon atoms in the alkyl chain have been investigated using the Density Functional Becke3-Lee-Yang-Parr (B3LYP) level with the basis set 6-31++G (d.p) and Hartree Fock (HF) with the same basis set. The observed vibrational spectra has been resolved and assigned in detail for comparision with both the molecules. These results indicate that DFT and HF values are slightly different at both the levels. A comparision of chemical reactivity such as HOMO (E_H), LUMO (E_L) energies, energy gap (E_g), ionization energy (I), electron affinity (A), electro negativity (χ), chemical hardness (η), electronic chemical potential (μ), electrophilicity index (ω), and softness (S) has been made. It has been observed that the decrement has occurred in the energy band gap value of isolated molecule with increment in alkyl chain length. This provides valuable information regarding enhancing the stability of liquid crystal materials by maintaining the conductivity.     

A HF Loaded Lewis-Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

The very strong Lewis acid aluminium chlorofluoride (ACF) was loaded with anhydrous HF. The interaction between the surface of the catalyst and HF was investigated using a variety of characterization methods, which revealed the formation of polyfluorides. Moreover, the reactivity of the HF-loaded ACF towards the hydrofluorination of alkynes was studied.     

Hydroxylation of the silica in microfabricated thin layer chromatography plates as probed by time‐of‐flight secondary ion mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

Microfabricated silica thin layer chromatography (TLC) plates have previously been prepared on patterned carbon nanotube forests. The high temperatures used in their fabrication reduce the number of hydroxyl groups on their surfaces. Fortunately, silica can be rehydroxylated. In diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), a silanol peak below 3740 cm^?1 indicates a well‐hydroxylated silica surface that is fit for chromatography. Hydroxylations of our materials with HF are so effective that it is not possible to discern the position of this peak. In contrast, this signal is discernable when the plates are treated with NH₄OH. To find a more convenient method for studying the surfaces of TLC plates, time‐of‐flight secondary ion mass spectroscopy (ToF‐SIMS) was considered. ToF‐SIMS is advantageous because multiple microfabricated TLC plates must be scraped to obtain enough silica for one DRIFT analysis, while static SIMS can be performed on very small regions (500 × 500 µm² or less) of individual plates. Ratios of the SiOH⁺ and Si⁺ ToF‐SIMS signals for microfabricated TLC plates correlated well with ~3740 cm^?1 silanol peaks from DRIFT. Thus, SIMS allows direct analysis of all of our treated and untreated plates, including those hydroxylated with HF. The best hydroxylation condition for HF, which was better than any studied for NH₄OH, was around 150 ppm at room temperature. The best hydroxylation condition for NH₄OH was 50 °C for 72 h. ToF‐SIMS versus DRIFT results of commercial TLC plates were also obtained and evaluated. Copyright © 2014 John Wiley & Sons, Ltd.     

The extended Hulburt–Hirschfelder‐long‐range oscillator model for direct‐potential‐fit analysis

In the present work, an extended Hulburt–Hirschfelder oscillator model is proposed as a means of simplifying potential energy functions for direct‐potential‐fit analyses. The new potential energy function is joined smoothly to the long‐range inverse‐power dispersion energy expression. The new model is employed in direct‐potential‐fits using spectroscopic line positions that involve the ground electronic states of the principal isotopologues of hydrogen iodide and carbon monoxide, and the ground and first singlet‐sigma excited states of hydrogen fluoride and hydrogen chloride. The present methodology is found to lead to compact, flexible, and robust representations for the potential energy that compare favorably with the results of past work where more complicated models were employed.     

Simulation of proppant transport at intersection of hydraulic fracture and natural fracture of wellbores using CFD-DEM

Proppants transport is an advanced technique to improve the hydraulic fracture phenomenon, in order to promote the versatility of gas/oil reservoirs. A numerical simulation of proppants transport at both hydraulic fracture (HF) and natural fracture (NF) intersection is performed to provide a better understanding of key factors which cause, or contribute to proppants transport in HF–NF intersection. Computational fluid dynamics (CFD) in association with discrete element method (DEM) is used to model the complex interactions between proppant particles, host fluid medium and fractured walls. The effect of non-spherical geometry of particles is considered in this model, using the multi-sphere method. All interaction forces between fluid flow and particles are considered in the computational model. Moreover, the interactions of particle–particle and particle–wall are taken into account via Hertz–Mindlin model. The results of the CFD-DEM simulations are compared to the experimental data. It is found that the CFD-DEM simulation is capable of predicting proppant transport and deposition quality at intersections which are in agreement with experimental data. The results indicate that the HF–NF intersection type, fluid velocity and NF aperture affect the quality of blockage occurrence, presenting a new index, called the blockage coefficient which indicates the severity of the blockage.     

改性三氧化二铬催化1,1,3,3-四氯丙烯氟化高选择性合成反式-1-氯-3,3,3-三氟丙烯研究

反式-1-氯-3, 3, 3-三氟丙烯 (HCFO-1233zd (E))是近年来正在研发的第四代发泡剂,其大气臭氧消耗潜能值为0.00024,温室效应潜能值为7.0,毒性低,常态下不燃,使用安全;它也是合成含氟精细化工品的中间体,以及合成氟树脂和氟弹性体的单体。本论文制备了Al,Zn,Co改性的Cr2O3催化剂,将其成功应用于1, 1, 3, 3-四氯丙烯（HCC-1230za）与氟化氢反应中,高选择性地合成HCFO-1233zd (E),复合催化剂Zn / Cr2O3显示高稳定性,其中HCC-1230za转化率高达99.4％,HCFO-1233zd（E）的选择性高达98.2％。反应条件诸如反应物HF / HCC-1230za 的摩尔比和反应温度等对产物分布有显着影响。在相对较低的温度（200?C）和较大的HF / HCC-1230za 摩尔比（10：1）下,对HCFO-1233zd（E）的选择性有利。通过XRD,XPS,BET和V70吡啶吸附红外光谱技术对复合催化剂Zn / Cr2O3进行了表征。 XRD结果表明,催化剂中大多数无定形Cr2O3和高度分散微晶相Cr2O3共同导致催化剂的高活性和高稳定性。HCC-1230za的转化率与预氟化处理催化剂Zn / Cr2O3的比表面积有关,催化剂的比表面积越高,催化活性越高。XPS光谱表明,在预氟化过程中,表面铬氧化物可能与F原子强烈相互作用,从而导致Cr原子的化学环境发生广泛变化。V70吡啶吸附红外光谱和氨-程序升温脱附技术结果证明尚未失活的催化剂Lewis 酸和Br?nsted酸中心的数目和强度与新制备的催化剂相比明显提高。     

非链式化学HF（DF）激光器工作气体中电子分离的非稳定性和气体放电等离子体的自组织现象

报道了放电引发的非链式HF（DF）激光器中的激活介质由电子碰撞负离子分离引起的电离非稳定性。这种非稳性出现在电极空间分离、脉冲CO2激光加热的基于sF6的混合气体的大体积放电中。实验研究了自引发体放电过程中由激光加热引起的放电等离子体的自组织现象以及由此在放电间隙的大部分区域形成的准周期等离子体结构。重点分析了等离子体结构随气体温度和注入能量的变化,讨论了等离子体自组织对电子碰撞分离不稳定性所产生的影响,解释了混合气体中由于电子碰撞使负离子消失导致的单等离子体通道移动的产生机理。     

Comment on the assignments of some vibrational bands of oxalyl fluoride

In view of existing contradictory assignments of the symmetrical stretching vibrations associated with the formal C-C and C-F bonds of trans/cis oxalyl fluoride, an additional theoretical analysis of the corresponding calculated wavenumbers was preformed on trans-C₂O₂F₂ and cis-C₂O₂F₂ based on previously calculated ab initio scaled force fields at the HF/6-31G computational level and new force fields calculated at the MP2/aug-cc-pVTZ level. This novel analysis included computational data from the isotopic shifts brought about by incorporating ¹³C and ¹⁴C atoms into the structure. A detailed examination of the calculated wavenumbers made it possible to validate the assignments of the ν₂ and ν₃ wavenumbers in the trans-C₂O₂F₂ and cis-C₂O₂F₂ molecules as the formal C-C bond stretching and the formal C-F bond symmetrical stretching vibrations, respectively.     

Products formed at intermediate stages of electrochemical perfluorination of propionyl and n-butyryl chlorides. Further evidence in support of NiF3 mediated free radical pathway

The partially fluorinated HF soluble intermediates formed during the electrochemical perfluorination of propionyl chloride (PC) and n-butyryl chloride (n-BC) were analyzed after passing 0%, 25%, 50%, 75% and 100% of theoretical charge required for the fluorination of PC and n-BC. The acid fluorides formed were converted to their corresponding sodium salt by alkali treatment and were separated by methanol extraction. The methanol was subsequently removed from the extract by vacuum distillation and the residue containing partially fluorinated sodium carboxylates was analyzed using ¹⁹F and ¹H NMR spectra. Initial perfluorination on activated electrode surface indicates the operation of ‘zipper-mechanism’. Formation of partially fluorinated product mixture, initial selectivity towards primary and secondary carbon, carbon chain isomerization and formation of cleaved and coupled products support the general operation of free radical pathway in the overall electrochemical process.