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Transition metal-catalyzed hydrogenation
Published in Ilya D. Gridnev, Pavel A. Dub, Enantioselection in Asymmetric Catalysis, 2016
Both TSs are stabilized by series of weak C–H…π interactions between substrate and BINAP π–electrons. Slightly longer N–H and B–H distances in the unfavorable TS might be an indication of increased repulsive intermolecular forces and its higher energy, respectively. The origin of these forces could be repulsive interaction between aromatic ring of naphthalene and aromatic ring of one C6F5 group. Note that with respect to benzene the quadrupole moment is reversed for hexafluorobenzene.94 The gas-phase optimized geometries predict a difference of 0.9–2.0 kcal/mol between the most stable transition states leading to the (R) and (S) product enantiomers depending on the calculation method. The sense of stereoselection is predicted correctly (preference for (R)-product), however, the computed enantiomeric excess (65%–93.8%) is lower than that observed experimentally for this reaction (99%). Thus, it is possible that solvent effect also contribute to the reaction enantioselectivity.
Polymeric Second-Order Nonlinear Optical Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
One of the most interesting π–π aromatic interactions for the self-assembly of chromophore glass is the arene–fluoroarene (Ar–ArF) interactions. Since organic materials based on the Ar–ArF interactions are not widely known yet, we will explain the interaction in more detail here. Benzene and hexafluorobenzene are known to co-crystallize with a melting point more than 18°C higher than either component in nearly parallel alternating molecular stacks with an interplanar distance of 3.4–3.7 Å [37]. The stabilization energy of the benzene-hexafluorobenzene dimer from both computational and experimental studies was estimated to be between 4 and 5 kcal/mol. The interaction can be rationalized mostly based on the complementary quadrupole moments of benzene (−29.0 × 10−40 Cm−2) and hexafluorobenzene (+31.7 × 10−40 C m−2) that are similar in magnitude but opposite in sign [38]. The formation of parallel alternating infinite molecular stacks is a common structural feature of all molecular Ar–ArF complexes reported (Figure 16.24).
Practical Laboratory Data
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Name Heptane Hexafluorobenzene Hexane 1-Hexanol Hydrogen fluoride Iodomethane Isobutane Isopropylbenzene Methanol Methyl acetate N-Methylaniline N-Methylformamide Methyl formate Nitrobenzene Nitromethane 1-Nonanol Pentane 1-Pentanol Phenol Propane 1-Propanol 2-Propanol Pyridine Pyrrole Pyrrolidine Styrene Sulfur dioxide Tetrachloroethene Tetrachloromethane Toluene Trichloroethene Trichloromethane Trimethylamine Water o-Xylene m-Xylene p-Xylene
The study on gas phase dehydrogenation reactions of transition metal cation and ethylene
Published in Molecular Physics, 2023
Wei Li, Ning Ding, Xunlei Ding, Xiaonan Wu
Many experimental and theoretical studies have been carried out on the reactions of ethylene with the first, the second-row and the third-row transition metal in the gas phase. Their study showed reaction paths for the H2 elimination reaction: M+ + ethylene = first intermediate MC2H4+ = insertion product = dihydrido complex = M-C2H2 + H2 [3,6,8,9]. The most important steps are the transfer of the hydrogen atom (HAT) from ethylene, especially the second HAT, which is affected by the electronic structure [17–22]. In addition, the rate of reaction is also an important index of C–H activation process. The reaction ability of Os+ and Ir+ is significantly higher than those of Pt+ for the reactivity of M+ with methane, hexafluorobenzene, methyl fluoride et.al. However, the reaction ability of Os+ and Ir+ are uncertain for different reactions [3,23–25].
2D constraint modifies packing behaviour: a halobenzene monolayer with X3 halogen-bonding motif
Published in Molecular Physics, 2021
Jonathan A. Davidson, Stephen J. Jenkins, Fabrice Gorrec, Stuart M. Clarke
1,3,5-triiodo-2,4,6-trifluorobenzene (TITFB) is a fluorinated analogue to triiodomesitylene (Figure 2) and hence may show promise in the rational design of halogen bonding systems. It has already been utilised in several studies on halogen bonding in bulk co-crystals [39–41]. At the surface, it has been observed to interact with halogen-bond bases to form ordered structures under applied potential from an STM tip. Intriguingly, however, the structure of the single component TITFB monolayer has thus far resisted analysis [42,43]. Related molecules have been examined using low temperature STM on metal surfaces, including hexabromobenzene on gold (77 K) [44] and hexafluorobenzene on silver (5 K) [45]. To the present authors' knowledge, however, no STM images of small perfluorinated aromatic molecules on graphite have previously been reported. It is possible that comparatively weak binding to the surface renders the layer prone to perturbation by the STM tip, or that the electronic properties of molecules of this type are unfavourable for high-resolution imaging.
The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6···(HF)1–4 complexes
Published in Molecular Physics, 2018
Hamidreza Jouypazadeh, Hossein Farrokhpour, Mohammad Solimannejad
The concept of aromaticity was introduced for the first time to explain the high stability and low reactivity of the compounds containing aromatic cycles in their structures [1]. The aromaticity can be defined as a result of the electron delocalisation in a closed cycle which leads to the energy stabilisation [2]. The intermolecular interactions involving the aromatic compounds have a main role in the understanding of biological and chemical processes, especially in the drug design and new materials with special functionality [3]. Although there are many published works in the literature on the aromaticity of the compounds [4], there are limited studies in the literature on the effect of intermolecular interaction on the aromaticity [5–8]. Miao et al. performed a systematic study on the aromaticity of borazine and its fluoroderivatives in the cation–π and anion–π interactions [5]. In another study, Rodríguez-Otero et al. studied the change in the aromaticity of benzene, pyrrol, triazine and hexafluorobenzene due to the cation–π and anion–π interactions using nucleus-independent chemical shift (NICS) methodology [6]. Foroutan-Nejad studied the aromaticity of C6H6 in the presence of an aluminium cluster (Al4) [2–7]. Recently, Sánchez-Sanz investigated the effect of π–π stacking interaction on the aromaticity in the polycyclic aromatic hydrocarbon/nucleobase complexes [8]. Also, Bloom and Wheeler studied the effect of aromaticity on cation–π, anion–π and π–stacking interactions [9].