Flow tube techniques

The kinetics of these oligomerizations initiated by a-lithio-methylisobutyrate (monomeric living polymethyl methacrylate) was reported by Muller et al. 50). A modified flow-tube technique, that permits to follow the polymerization for times as short as 0.02 s, was employed in this study. The reaction was performed in THF at... 

Some of the earliest experimental studies of neutral transition metal atom reactions in the gas phase focused on reactions with oxidants (OX = O2, NO, N2O, SO2, etc.), using beam-gas,52,53 crossed molecular beam,54,55 and flow-tube techniques.56 A few reactions with halides were also studied. Some of these studies were able to obtain product rovibrational state distributions that could be fairly well simulated using various statistical theories,52,54,55 while others focused on the spectroscopy of the MO products.53 Subsequently, rate constants and activation energies for reactions of nearly all the transition metals and all the lanthanides with various oxidant molecules... 

In obtaining experimental information about the isomeric forms of ions, a variety of techniques have been used. These include ion cyclotron resonance (ICR),31 flow tube techniques, notably the selected ion flow tube (SIFT),32 and the selected ion flow drift tube (SIFDT)32 (and its simpler variant33), collision induced dissociation (CID),10,11 and the decomposition of metastable ions in mass spectrometers.13 All of these techniques are mentioned in the text of Section in whore they have provided data relevant to the present review. 

Figure 8 Changes in the DMS (mle = 62) reactant and CH3SFCH2 (m/e = 80) product ion currents as a function of reaction time using the flow tube technique to study the reaction of DMS with F2. (Reprinted with permission from Ref. 7. Copyright 1991 American Chemical Society.)...

Description of the SIFT (selected ion flow tube) technique, which allows detection of gas traces in real time. 

Anions (9), (10a) and (11) derived from cycloctatetraene have been studied using the selected ion flow tube technique and MO calculations, as a continuation of previous work on the structures and energetics of eight-membered-ring species, CgH and... 

It would appear today, however, that the acid-base equilibrium of diazomethane with its anion is better known in the gas-phase than in solution The same group (DePuy et al., 1989) investigated reactions of the diazomethyl anion with CS2, COS, CO2, SO2, and with a series of a,)ff-unsaturated aldehydes and ketones — all in the gas phase using a flowing afterglow apparatus (DePuy and Bierbaum, 1981) and selected ion flow tube techniques (Van Doren et al., 1987). 

The distance covered by the reaction mixture in the tube is a measure of the time elapsed since the start of the reaction. If we observe the reaction at different positions along this tube using, for example, a moveable spectrophotometer, we see the mixture at different times of the reaction. The temporal coordinate of the reaction process is thereby mapped onto the spatial coordinate along the flow tube. When highly efficient mixing chambers are used, the flow tube technique is applicable for fast reactions with reaction times down to the millisecond range. 

Bertram and Thornton recently introduced a method for performing direct aerosol flow tube uptake studies on ambient aerosol particles [148, 149]. They are able to correlate observed N2O5 reactive uptake coefficients with simultaneous measurements of aerosol composition using other techniques. When the flow tube technique of Bertram and Thornton is coupled with a technique capable of detecting the presence of surface-active organics in the aerosol, potential exists for the influence of these organics on N2O5 uptake by ambient aerosol to be inferred. 

Seeley, J.V., Jayne, J.T., Molina, M.J. Kinetic studies of chlorine atom reactions using the turbulent flow tube technique. J. Phys. Chem. 100, 4019-4025 (1996b)... 

N3 +H2. The rate constant k 2 x 10 cm molecule" s for the reaction N3 + H2 - N2H + NH was determined using a selected-ion flow tube technique. Only branching into the N2H product channel was observed [2]. 

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