Acetone— contact distances

With the long alkyl chain substitutions on the A-heterocyclic carbenes, lamella-structured silver(i) carbene complexes 27a and 27b (Figure 14) were isolated.74 It is interesting to note that the synthetic procedures for the two complexes are the same except for the use of different solvents of crystallization. The dinuclear 27a was obtained from recrystallization in dichloromethane- -hexane while the tetranuclear 27b was obtained from acetone. The structure of 27a could be interpreted as the dimeric form of [Ag(carbene)Br] bridged by intermolecular Ag-Br interactions. The Ag-G bond has a distance of 2.094(5) A. The tetranuclear 27b, on the other hand, could be regarded as two monocationic bis(carbene)silver(i) bridged by an [Ag2Br4]2 anion, with the presence of short Ag(cationic)-Ag(anionic) contact (3.0038(18) A) and comparable Ag-G bond distances (2.0945(5), 2.138(13) A). A related... 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

The planar structure was fabricated as follows the glass substrate was carefully cleaned as described above. A 300 nm metal layer was deposited onto the substrate by e-beam evaporation. Next, the metal layer was patterned by standard photolithography. After metal etching, the device structure contained two parallel metal stripes that served as contacts. The distance between the two stripes was 10 pm. Then, a Cu-stripe with a thickness of 70 nm was e-beam evaporated onto the contacts. Finally, the substrate was immersed into the TCNQ/acetonitrile solution. The device was kept in the TCNQ/acetonitrile solution until the Cu layer was completely converted into Cu(TCNQ). Finally, the substrate was rinsed with acetone and dried with nitrogen. Figure 27.10 shows a schematic drawing of the device. 

Planar SDs were fabricated using standard photolithography on 0, 3,4 and 5 min SiN samples (undoped). Before metallization, all samples were cleaned in acetone, methanol, and deionized (DI) water in an ultrasonic bath, followed by boiling aqua regia cleaning for 20 min and 5 min DI water rinse. Ti/Al/Ti/Au (30/100/30/100 nm) ohmic contacts were deposited by e-beam and thermal evaporation, followed by a 60 s rapid thermal annealing (RTA) at 900 °C in nitrogen ambient. Finally, 200 pm diameter Ni/Au (30/120 nm) SDs were deposited by e-beam evaporation. The distance between SDs and ohmic contacts was 50 pm. 

Trichloroethane is a volatile, colorless liquid and its vapor is heavier than air. It has a sweet, ethereal odor. It is poorly soluble in water but dissolves in other solvents, such as acetone, benzene, ethanol, and carbon tetrachloride. The vapors of I, I, I-trichloroethane are heavier than air and may travel a considerable distance from the evaporation source. In contact with water or humidity, trichloroethane decomposes slowly yielding corrosive acids. In normal working conditions... 

This treatment of ion association may not seem entirely satisfactory on two accounts (i) ion association ceases sharply at r = rf, and (ii) it is difficult to accept that ions up to / may be considered associated to the central ion (/ = 14 A for a (1-1) electrolyte in acetone at 25°C). Fuoss has suggested that only those ions which are in actual contact should be considered associated. The distance between two ions forming a pair is... 

By a reasoning not to be referred to here, Schul deduced from his results that the range of the forces between the solvent and the solute decreases less rapidly with the distance than Van der Waals-London attractions would, though the order of magnitude of the forces is equal. He assumed a dipole potential and a polarisation of the molecules of the solvent The potential of the forces would then be inversely proportional to the 3id or 4th power of the distance rather than to the 6th power, as for Van der Waals forces. This means that in the system nitrocellulose-acetone, acetone molecules at a distance of 30 A from the axis of the chains would still be attracted with 0.1 of the force which they undergo when in contact with the chain, whereas e.g. CO molecules in this distance would only exert 0.0005 of the mutual attraction at direct contact. This would mean that even in 5 —10% solutions nearly all the molecules of the solvent undergo attraction by the chain molecules (Solvation). 

Common sense tells us that coming in contact with a toxic chanical— touching it, inhaling it, ingesting it— makes us sick. The more contact, the sicker people are likely to get. For example, if a student spills acetone in his organic chanistry class, or if a homeowner spills paint thinner in her garage, those nearest the spiU inhale the most fumes, and they are more likely to feel nauseous or dizzy than those at a distance who inhale less fumes. At the same time, some people who are farther away and inhale less fumes may be particularly sensitive and end up feeling just as sick as those nearest the spill. 

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