By Direct Insertion

Preparing the Sample Flame and plasma sources are best suited for the analysis of samples in solution and liquid form. Although solids can be analyzed by direct insertion into the flame or plasma, they usually are first brought into solution by digestion or extraction. 

The third class of mechanisms is that originated by Pichler and Schulz in which chain growth is accomplished by direct insertion of an absorbed CO molecule into a carbon-metal bond produced by hydrogenation of a surface carbonyl (89). A complete representation of this mechanism (see... 

A second method uses permethylation of the dephosphated (48% aqueous HF, 48 h, 4°C) and 2H-reduced fipid A. This approach allowed the assignment of amide-bound fatty acids linked to GlcN(I) and GlcN(II), as well as the identification of the backbone structure as a HexpN disaccharide (85). Mass-spectrometric analysis of the products was performed by using either a short g.l.c. column (0.3 X 5 cm) or by direct insertion-probe analysis (87). In the case of C. violaceum (85), the mass spectra obtained from the permethyl-ated HexpN disaccharide bearing attached TV-methylacyl residues revealed unequivocally that both amino groups carried 12 0(3-OH). 

Functionalized organozinc halides are best prepared by direct insertion of zinc dust into alkyl iodides. The insertion reaction is usually performed by addition of a concentrated solution (approx. 3 M) of the alkyl iodide in THF to a suspension of zinc dust activated with a few mol% of 1,2-dibromoethane and MeaSiCl [7]. Primary alkyl iodides react at 40 °C under these conditions, whereas secondary alkyl iodides undergo the zinc insertion process even at room temperature, while allylic bromides and benzylic bromides react under still milder conditions (0 °C to 10 °C). The amount of Wurtz homocoupling products is usually limited, but increases with increased electron density in benzylic or allylic moieties [45]. A range of poly-functional organozinc compounds, such as 69-72, can be prepared under these conditions (Scheme 2.23) [41]. 

Scheme 2.23. Preparation of functionalized zinc reagents by direct insertion of zinc.

Benzylic organomanganese reagents prepared by direct insertion of activated manganese metal display the same behavior (Scheme 2.60) [131]. Excellent results are also obtained for 1,4-additions of organomanganese reagents to unsaturated esters in the presence of CuCI (3 mol%) [127]. 

LIF methods can be applied in-line, at-line and on-line for real-time monitoring as discussed throughout this chapter. In-line or in situ intrinsic LIF is by far more prevalent in real-time applications such as PAT as it is nondestructive and simple to deploy along with attractive analytical merits. In-line application can be accomplished by direct insertion in situ probes or flow cells. This type of monitoring is utilized for realtime analyte quantification monitoring and detection of process endpoints and faults. 

This section reviews those methods for constructing a C—C bond by direct insertion into an unactivated C-H bond that show synthetically useful selectivity. Both inter- and intramolecular reactions are considered. 

ICP-AES has been used to analyse a wide variety of sample types. It is usually necessary to present the sample in the form of a liquid, although solids can be analysed directly in the form of slurries, by direct insertion, laser ablation or electrothermal vaporization (see Chapter 7). 

The products were tetrafluoropropene and tetrafluorocyclopropane, and the pressure dependence of the product ratio indicated that tetrafluoropropene was formed only by isomerization of tetrafluorocyclopropane and not by direct insertion of CH2 into a CF bond. 

The above results, which are not strongly dependent on the particular value chosen for s, show that about 10% of the trimethylene diradicals lead to propylene, and that the limiting yield of cyclopropane is about 90%. Additional propylene may of course be formed by direct insertion into carbon-hydrogen bonds. 

Furthermore, the lower rate of heating (resulting from the insulating effect of the charcoal) assists in preventing the election of solid particles, which can occur when lower rank coals (in 10- to 20-mL platinum crucibles) are heated at the higher rate by direct insertion into the hot furnace. There is, therefore, no need for a modification of the method when it is applied to the lower-rank coals (an advantage), since in borderline cases, the result may be up to 2% lower (i.e., 32% volatile matter instead of 34% volatile matter) when the modification (the lower heating rate) is employed. 

The mass spectra of atenolol and compound were obtained by direct insertion of the sample into CEC 21-Ho B mass spectrometer. Characteristics of these mass spectra are summarized in Tables 5. and 6, and Pig. 5 The ion source temperature was 15o°C and 2oo-25o°C, respectively, and the ionizing electron beam energy was 7o eV. 

The most significant obstacle to be overcome in the preparation of organozinc halides by direct insertion of zinc metal into an organic halide is the intrinsic lack of reactivity of commercially available zinc metal. This is primarily due to a surface coating, for example of zinc oxide, which prevents direct reaction with an organic substrate. The success of attempts to insert zinc metal into an organic halide is entirely dependent upon the care with which the zinc metal is... 

Before Nobel s work/ black powder was ignited (not detonated) by direct insertion of a fired match or something similar into the main powder mass. Cannoneers used a fired wick, and sappers had to light the fuzes on their breeching charges. The only slight concession or transition was the advent of percussion caps, a blow to which would set off the main charge. 

Organometallics by transmetallation pyridylzinc chlorides can be accessed either by transmetallation of a pyridyllithium with anhydrous zinc chloride <2001EJ04207> or by direct insertion of zinc into carbonhalogen bonds using Rieke zinc in THF under reflux <2003SL852>. 

There are three general classes of mechanism most often encountered in alkane reactions (i) radical (ii) electrophilic and (iii) carbenoid. The C—bond-lneaking st in (i) and (ii) are shown in equations (2) and (3). Carbenoid reactions can go either by direct insertion into the C—bond (equation 4), which tends to happen when the carbene in question has singlet character, or by a two-stqi process (equations 5 and 6), in which H-atom abstraction precedes collapse of the radical pair, a pathway which is characteristic of triplet carbenes. ... 

Vaporize compounds of varying volatility. This is accomplished in the inlet system. Introduction of the sample is done by direct insertion probe, reservoir inlet, or following a chromatographic separation (GC, HPLC, and CE). As mentioned earlier, to introduce the LC flow to the mass spectrometer on-line, we need an appropriate interface. Development of appropriate interfaces was the utmost for evolution of the LC-MS coupling. 

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