Thiophene bonding capacity

The thermodynamic properties of thiophene,2-methylthiophene, ° and 3-methylthiophene have been computed from careful measurements of the heat capacity of the solid, liquid, and vapor states, the heat of fusion, the heat of vaporization, and the heat of combustion. From the heat of combustion of thiophene and from thermochemical bond energies, the resonance energy of thiophene has been re-estimated to be only 20 kcal/mole. 

The TpRe(CO)(PMc3) fragment is isoelectronic with [CpRe(NO)(PPh3)]+ and yet considerably more electron rich. This stronger tt basic character is reflected in its capacity to bind naphthalene, diasterospecifically, in a r] -coordination mode, to prefer ) -thiophene over ) -thiophene coordination and form stable tt complexes with acetone rather than the more common a-bonded species in, for example, [CpRe(NO)(PPh3 )(acetone)]+. 

Tetrahydrobenzo[/i]thiophenes 34 and 35 possess moderate affinity for the dopamine receptors. In order to potentially increase their affinity for the dopamine receptors, substituents were introduced on the 2-position of the tetrahydrobenzo[/1]thiophenes. The extra interaction point and the fact that these substituents have better hydrogen bond forming capacities than a... 

Ag-exchanged faujasite was claimed for thiophene removal (Michhnayr, 1980). Curiously, the preferred temperature for adsorption was 200-350 °C, and the sorbent was not dehydrated by heat-treatment prior to adsorption. Consequently, the sulfur capacities were very low, at 0.07-0.15 wt % for Ag-Y. The highest sulfur capacity (of 0.2 wt %) was obtained with the lowest Ag content, using USY zeolite. This sorbent was apparently intended for bonding the sulfur atom with Ag. It was clearly not intended for r-complexation (Michhnayr, 1980). 

As indicated from the vapor-phase isotherm results, NaY has similar total capacities for thiophene and benzene as CuY and AgY, because their pore volumes are similar. NaY, however, does not form a rr-complexation bond with thiophene, and hence does not have selectivity for thiophene. The lack of selectivity for thiophene results in the premature breakthrough of thiophene, shown in Figure 10.60. Hence a high-purity n-octane product cannot be obtained with NaY as the sorbent. With AgY and CuY and feeds containing 2000 and 500 ppmw thiophene, on the contrary, the sulfur content in the effluent was below the... 

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