Sources deuterium

Radiation from a xenon or deuterium source is focussed on the flow cell. An interchangeable filter allows different excitation wavelengths to be used. The fluorescent radiation is emitted by the sample in all directions, but is usually measured at 90° to the incident beam. In some types, to increase sensitivity, the fluorescent radiation is reflected and focussed by a parabolic mirror. The second filter isolates a suitable wavelength from the fluorescence spectrum and prevents any scattered light from the source from reaching the photomultiplier detector. The 90° optics allow monitoring of the incident beam as well, so that dual uv absorption and fluorescence... 

You can keep the spectrometer happy by adding a deuterium source to the sample. On the other hand, you probably don t want to do this otherwise you would have selected a deuterated solvent in the first place Nonetheless it is still an option in some cases. Note that if you only add a small amount of the deuterium source, you may struggle to achieve lock because the signal is too weak. 

Tetralin. Therefore, either trans-Decalin was formed on the surface of the coal with deuterium from the solvent or gas, or it was formed by isomerization from cis-Decalin with accompanying isotopic exchange with a deuterium source. Because the protium content of the cis-Decalins is much greater than the trans-Decalins, cis-trans isomerization is not very important. 

We now turn to examine several reports of hydrogen exchange in the benzene ring in which the deuterium source is either heavy water or a... 

To summarize, the use of heavy water as a deuterium source has provided a wealth of experimental information. Evidence for the associative ir-adsorption of benzene [species (I) J is secure (2). Evidence for hydrogen exchange in the benzene ring by an abstraction-addition mechanism is less well established, partly because of uncertainties that surround the mode of chemisorption and reaction of water at metal surfaces. Nevertheless, it would be wrong to deny that Scheme 6 is consistent with a large body of experimental work. 

The application of deuterated ammonium formate as a deuterium source in transfer deuteration reactions of aromatic heterocycles has been reported by Derdau (Scheme 6.173 c) [329]. It was found that the reaction time could be reduced from 12-18 h (50 °C, oil bath) to 20 min at 80 °C by employing microwave irradiation, using deuteriomethanol as solvent and 10% palladium-on-charcoal as a catalyst. 

A plethora of compounds (solutes) present in the mobile-phase on being passed as column effluent through a cell irradiated with Xenon or Deuterium source first absorb UV radiation and subsequently emit-radiation of a longer wavelength in two different manners, namely ... 

Radiation from a Xenon-radiation or a Deuterium-source is focussed on the flow cell through a filter. The fluorescent radiation emitted by the sample is usually measured at 90° to the incident beam. The second filter picks up a suitable wavelength and avoids all scattered light to reach ultimately the photomultiplier detector. 

The photodiode array detector (PDAD) measures absorption of light waves by a sample. This is considered the most powerful of the ultraviolet spectrophotometric detectors. The optical system focuses light from a deuterium source through the sample flow cell onto several photodiodes. These act as capacitators by holding a fixed amount of charge. When light strikes the photodiodes, they discharge a certain amount of current. 

UV detector—replace deuterium source and clean/rebuild detector flow cell if contaminated. 

Interestingly, Cp Ir(NHC) complexes were also shown to be efficient catalysts for the deuteration of organic molecules using CD3OH or (CD3)2CO as deuterium sources (Scheme 3.17). A wide set of organic molecules (including ketones, alcohols, olefins and ethers) were deuterated in high yields [15]. 

For P-C-T relationships involving deuterium, a similar procedure was followed. However, studies were limited to the range 0 < D/M 0.01 where D/M represents the deuterium-to-metal atom ratio, and only a 10-Torr, full-scale transducer was used. Deuterium was supplied to the system from a metal deu-teride that was prepared in this laboratory. An alloy of composition TiFeo.gs M11002 (mass 200 g) was activated thoroughly, then outgassed completely at 500° C. The alloy was exposed to deuterium (ultrapure) at 1000 psi for 4 hr, cooled to —196°C, and evacuated. The deuteride reservoir was closed, warmed to room temperature, and moved to the absorption manifold where it served as a high-purity deuterium source. 

Asymmetric transfer hydrogenation of benzaldehyde-l-d with (R,R)-28 and (CH3)3COK in 2-propanol gave (R)-benzyl-l-d alcohol quantitatively in 98% ee (Scheme 41) [114], Introduction of electron-donating and electron-accepting groups at the 4 position had little effect on the enantioselectivity. Catalytic deuteration of benzaldehydes was achieved by use of the same complex (R,R)-28 and a 1 1 mixture of formic acid-2-d and triethylamine to give the S deuter-io alcohols in up to 99% ee (Scheme 42) [114], The dt content in the product alcohol was >99%. Only a stoichiometric amount of deuterium source is required to complete the reaction. 

Fiber-optic UV-vis spectrophotometers are well suited to a clean-in-place application. For analytes with signals in the deep UV, best results will be obtained with a deuterium source and short fiber runs. Further out in the UV and visible regions, a xenon flash lamp... 

The reductive epoxide opening can also be carried out using substoichiometric quantities of Cp2TiCl in the presence of collidine hydrochloride. Moreover, with D20 deuterium-labeled alcohols can easily be obtained using relatively cheap D20 as deuterium source [79]. 

Prepare an absorbance spectrum of this solution in the above spectrophotometer operating between the wavelengths of 240 and 500 nm. Caution should be taken to change the light source at 340 nm from the tungsten to the deuterium source. Failure to do this will result in a very erratic spectrum below this wavelength. 

R,R)-TsDPEN-RuCl(p-cymene) complex catalyzes the deuteration of benzalde-hydes by using only a stoichiometric amount of the deuterium source, DCOOD/ N(C2Hs)3, to give the S deuterio alcohols in up to 99% e.e. [285]. The dj content in... 

Phosphonium ions exchange with acidic deuterium sources to form P—D bond-containing products. Alkylphosphoniums react with D O as ... 

A recent article by Swenton et al.I04 reported deuterium incorporation via the reduction of halides with a zinc-copper couple. They found that freshly prepared zinc-copper couple in dry ether solvents with heavy water as the deuterium source effects clean reduction of dibromocyclopropanes to their monobromo derivatives. In a second system, they104 found that dichloroketene adducts underwent clean reduction to the corresponding cyclobutanones... 

Fortunately, methods for background correction are now a part of most modem AAS and the most commonly used background correctors are a deuterium source, the Zeeman effect and the Smith-Hiefte effect. 

Ring-opened products A second electron transfer transforms the trimethylene radical anion 80a into the l,3- dianion 81a. In the absence of a proton (deuterium) source 81a eliminates hydride as a function of time (Table 4) to give the allyl anion 83a. Protonation of 83 a leads to 84a. Protonation of 81 a gives 82 a, as mentioned earlier. 

Sensitivity is specified by baseline noise. For years, noise specification has been benchmarked at 1.0 x 10 absorbance unit (AU) (Figure 4.9b). A wavelength range of 190-600 nm is typical, though sensitivity is substantially lower >400 nm due to a lack of energy of the deuterium source in the visible region. Many detectors allow a secondary tungsten source to increase sensitivity in... 

For the ultraviolet region, a low-pressure hydrogen or deuterium discharge tube is generally used as the source. Each of these can be used from 185 to about 375 nm, but the deuterium source has about three times the spectral output of the hydrogen source. Ultraviolet sources must have a quartz window, because glass is not transparent to ultraviolet radiation. They are frequently water-cooled to dissipate the heat generated. 

The optical layout (Figure 6.21) is similar to the conventional fluorimeter in that the detector is placed at right angles to the primary incident beam which is supplied from a xenon or deuterium source. However, due to the flow-cell dimensions and orientation only a small amount of the fluorescent energy will fall on the photodetector. Increased sensitivity is provided by the... 

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