Molecular traps

Fluoride ion selective spectrometry was used to determine the stability constants for zinc fluoride complexes in water at 25 °C, giving values j3i[ZnF(aq)]+ = 3.5 0.1 and /l2[ZnF2(-aq)] = 3.8 0.5.643 These results demonstrate that the complexation of fluoride is very weak and in aqueous chemistry no species beyond ZnF+ is of much importance. Organotitanium fluorides have been used as matrices for trapping molecular ZnF2 and MeZnF. 4... 

Witchel, H.J., Dempsey, C.E., Sessions, R.B., Perry, M., Milnes, J.T., Hancox, J.C. and Mitcheson, J.S. (2004) The low-potency, voltage-dependent HERG blocker propafenone-molecular determinants and drug trapping. Molecular Pharmacology, 66, 1201—... 

Hydrogen blistering blistering of steel caused by trapped molecular hydrogen formed as atomic hydrogen during corrosion of steel by hydrogen sulfide. 

This means that direct dissociation is sterically hindered at the Pt(l 1 1) surface so that it becomes a two-step process. First the molecule is trapped molecularly in the chemisorption well where it equilibrates. At sufficiently high surface temperatures dissociation will then be induced by thermal fluctuations which make the 02 molecules enter the dissociation channel. 

MS analysis was conducted on the deactivated catalysts from the MAT reactors using a VG instrument in which the probe was heated from ambient to 500 C at a rate of 20 C min1 and spectra over the mass range 50-600 were recorded every 5s. Spectra were recorded in both electron impact (El) and chemical ionisation (Cl, with ammonia) modes. A number of deactivated samples have also been analysed after extraction in chloroform to remove physically-trapped molecular species. 

Oils used in mechanical pumps have significantly higher vapor pressures than the oils used within diffusion pumps. Therefore, it is important to prevent backstreaming of mechanical pump oils into the diffusion pump. This barrier can be done either with liquid nitrogen cold traps, molecular sieves, water-cooled thimbles, or chevron baffles. 

Coaxial Traps Molecular Sieve Particulate Traps ... 

Spectra were recorded in both electron impact (El) and chemical ionisation (Cl, with ammonia) modes. A number of deactivated samples have also been analysed after extraction in chloroform to remove physically-trapped molecular species. 

Lipoxygenase enzymes are known to oxidize arachidonic acid at six possible positions. The chemical requirement for this oxidation (Eq. 4.1) appears simply to be a skipped cis diene which can produce (via the enzyme) a stabilized allylic radical, which then traps molecular oxygen to form a conjugated cis-trans diene hydroperoxide. Chart 4.1 shows the six possible mono-oxidation products as members of the HETE family. All of these compounds have been shown to be natural products. Only in the cases of 8 and 9 HETEs is the absolute stereochemistry not definitively known. Nevertheless, it is speculated that 8-HETE has the alcohol in the (5)-configuration and 9-HETE is of the (R) absolute... 

A current research theme concerns the preparation of adsorbents having a marked affinity for a particular type of compound. For this, polymers are synthesized which possess recognition sites in the form of surface deformations, appropriate for trapping molecular targets. The principle resembles that of immuno-extraction, which is even more selective, as explained in the next paragraph. 

Clathrate Well-defined chemical compounds consisting of a caged (trapped) molecular species contained in a lattice of a second type of molecule. 

Spin-lattice relaxation measurements of H and have uncovered the existence of trapped molecular hydrogen (H2) in many films of a-Si H. This molecular hydrogen is trapped at sites where it is more stable during annealing experiments than most of the bonded hydrogen. One important question that remains unanswered is the nature of the trapping site. 

Fig. 4 A dendritic box has been shown to trap molecular guests (i.e., 22), while fluorinated constructs (23) show promise as phase-transfer catalysts.

Wright, K.C. Blades, M.W. Fluorescence emission spectroscopy of trapped molecular ions, Pmc. 51st ASMS Conf. on Mass Spectrometry and Allied Topics, Montreal, Canada 2003. 

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