Addition route

In the presence of sulphuric acid this route to the nitric acidium ion is almost entirely dominant, the additional route of protonation via the... 

Scheme 64 shows the key steps in two additional routes leading to the penam ring system <79JCR(S)157, 76ACS(B)377). 

With contact temperature measurement, placing the measurement probe in contact with the object of measurement (duct, surface, etc.) produces an additional route for heat conduction to or from the object. This perturbation error changes the initial temperature field in the vicinity of the contact point and creates measurement errors. 

If a second solute Q is added that is able, in a second-order reaction, to make available an additional route for return to the ground state, we can write... 

In the presence of Q the quantum yield <5 is smaller because of the additional route ... 

Apart from the carbene-1,2-addition route starting from 1,3-dienes, vinylcyclo-propanes may be obtained from 1,4-dienes through a di-n-methane rearrangement. 

Another Michael addition route for synthesis of the pyrrolizidine alkaloide trachelan-thamidin is shown in Scheme 10.18.118... 

It is clear that a complex hydrocarbon polymer chemistry must exist in the atmosphere of Titan involving polyyne species, polynitrile species and mixtures of the two, and additional routes to polyaromatic hydrocarbon formation. This presents a significant problem for the gas chromatography/mass spectrometry instruments on the Huygens probe. There should be hydrocarbon fragments, producing perhaps... 

It was shown in the previous section that hydrocarbon oxidation catalyzed by cobalt salts occurs under the quasistationary conditions with the rate proportional to the square of the hydrocarbon concentration and independent of the catalyst (Equation [10.9]). This limit with respect to the rate is caused by the fact that at the fast catalytic decomposition of the formed hydroperoxide, the process is limited by the reaction of R02 with RH. The introduction of the bromide ions into the system makes it possible to surmount this limit because these ions create a new additional route of hydrocarbon oxidation. In the reactions with ROOH and R02 the Co2+ ions are oxidized into Co3+, which in the reaction with ROOH are reduced to Co2+ and do not participate in initiation. 

These reactions result in an additional route of chain propagation, which allows one to exceed the rate limit due to the mechanism of action of only variable-valence ions. In fact, the initial rate of RH transformation in the presence of the cobalt bromide catalyst is determined by the rate of two reactions, namely, R02 with RH (kp) and R02 with Co2+ (kp), followed by the reactions of Co3+ with Br and Br with RH. The general scheme proposed by Zakharov includes the following steps (written in the simplified form) [206] ... 

A wide variety of five-membered zirconacydes 8 may be formed by the formal co-cycliza-tion of two 7i-components (3 and 6 alkene, alkyne, allene, imine, carbonyl, nitrile) on zir-conocene ( Cp2Zr ) (Scheme 3.2) [2,3,8]. The co-cydization takes place via the r 2-complex 5 of one of the components, which is usually formed by complexation of 3 with a zircono-cene equivalent (path a) ( Cp2Zr itself is probably too unstable to be a true intermediate) or by oxidation on the metal (cyclometallation/p-hydrogen elimination) (path b). Two additional routes to zirconocene r 2-complexes are by the reverse of the co-cyclization reaction (i. e. 8 reverting to 5 or 9 via 7), and by rearrangement of iminoacyl complexes (see Section... 

Additional routes to a-allenic-a-amino acids were described more recently and utilize radical [136] or transition metal-catalyzed [137] allenylations, in addition to copper-promoted Michael additions [15b]. Thus, sterically demanding amino acid derivatives (e.g. 151) are accessible via a 1,6-addition reaction of lithium di-tert-butyl-cyanocuprate with acceptor-substituted enynes of type 150 (Scheme 18.48). 

Free-radical-catalysed additions have also been reported, and provide a genuine alternative to the more familiar base-catalysed addition routes. Thus the secondary diphosphine (28) readily adds to diphenylvinylphosphine in the presence of AIBN to give (29).25 Similarly, addition of di(pentafluorophenyl)phosphine to diphenylvinylphosphine affords26 the diphosphine (30). Sequential addition of silanes and secondary phosphines to terminal aco-dienes under the influence of u.v. light affords the silylalkylphosphines (31), which may be anchored via silicon to the surface of inorganic oxides and used as polymeric catalysts.27... 

An additional route consists of using the reconstruction ability of some LDH materials after a moderate thermal treatment. This is a pecuharity of LDH systems called the memory effect the LDH lamellar framework is reconstructed in the presence of the polymer with concomitant intercalation. Finally, a post-synthesis hydrothermal treatment can be applied in all cases, which may improve the inter- and intralamellar organization of the LDH/polymer nanocomposites. 

The oxidative solvolysis steps (Eq. 31/30) have previously been demonstrated to occur, and the room temperature rate constant given (kj = 3.5 x lO s" ) is in good agreement with that measured on producing the -chloroalkyl radical by the addition route (Eq. 29). 

The abstraction of a hydride is an additional route for the preparation of ben-zimidazolium salts Treatment of 2,3-dihydro-1 /f-benzimidazoles with tritylium tetrafluoroborate generates the benzimidazolium salt and triphenylmethane [Eq. (6)].44... 

Figure U. Gel permeation chromatogram of polymerized acetone-aniline condensation products. Key 3 5- and 6-TMDQ oligomers and 1,2- and U-ollgomeric series from a different addition route.

This default value was considered, in most cases, to be sufficient to account for additional routes of intake, i.e., inhalation and dermal absorption of contaminants in water. 

The o-quinodimethane (40) may also be generated by fluoride-induced 1/4/elimination of trimethyl(2-[(trimethylsilyl)methyl]-benzyl) ammonium iodide (43). When this elimination is carried out at low temperature, the reaction conditions are ecjually compatible with the presence of 27, and this provides an additional route to 42. ... 

A large number halogenated cycloproparenes is known, in particular the 1,1 -di-halogeno derivatives, which are available by the cycloaddition approach mentioned above. The 2- and 3-halogenobenzocyclopropenes 202 and 204 are conveniently synthesized by the carbene addition route from the appropriate precursors 201 and 203, respectively. 

The capability of NO to reduce nitrates, providing a pathway for the production of ammonium nitrite and thus of nitrogen, has also been demonstrated recently by Weitz and co-workers, mainly on the basis of IR data collected over BaNa-Y zeolite [75] however, according to a parallel additional route NO would also react with NO2 to form N2O3 and then nitrogen [reactions (13.25) and (13.26)], as already discussed. The oxidation of NO by surface nitrates over a Pt-Ba/Al2O3 catalyst has also been reported by Olsson et al. [76], whereas the formation of surface nitrates from NO2 on bare AI2O3 has been reported by Apostolescu et al. [77] and previously observed in our laboratories also [78]. 

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