Reactions involving elimination

An example of cleavage ol the sulfur-oxygen bond in trifluoromethane-sulfonic ester has been reported Tnfluororaethyl triflate reacts with neutral or anionic nucleophiles with elimination of carbonyl difluoride and formation of trifluoromethanesulfonyl fluoride [57] (equation 32) The mechanism of this reaction involves elimination of fluoride ion, which is a chain carrier in the substitution of fluorine for the trifluoromethoxy group... 

The linking up of amino acids can be described as a polycondensation reaction involving elimination of water the result is the formation of peptide bonds. 

The chemistry of O-acyl derivatives of trinitromethane was studied in more detail. By analogy with O-silyl ethers of trinitromethane, for intermediate (120) (Scheme 3.103, Eq. 1) it was suggested (222a) that the reaction involves elimination of acetyl nitrate to form the very unstable N-oxide A, which adds acetyl chloride to give derivative (121). Saponification of the latter affords isolable oxime (122). 

When oligoisobutenes are formed from gaseous isobutene at ambient temperature by BF3 and H20 the initial group is CH3, formed by addition of a proton to the monomer [8]. The predominant terminal groups are double bonds [8] formed by transfer reactions involving elimination of a proton from the growing carbonium ion ... 

Figure 14-7 Some PLP-dependent reactions involving elimination of a y substituent. Replacement by another y substituent or by a substituent in the (3 position is possible, as is deamination to an a-oxo acid.

There are also a vast number of reactions known between alkoxides and non-trivial alcoholic reagents such as glycol, catechols, alkanolamines and hydroxylamines. The fundamental reaction involves elimination of alcohol, but with the reaction products complicated by the nature of chemistry of the other substituents.1... 

Elimination of alkenes has been already dealt with in Section II,F (oxidative addition-elimination), while other reactions involving elimination of dihydrogen may be found in that section and in Section II,E this latter section includes many cases in which metal hydride species are believed to act as intermediates. 

Related reactions involving elimination of hydrocarbons are also known, but appear much less general and this route has been used mostly for vanadium105, zinc241a,241b, cadmium2410 and mercury242 derivatives (equations 85-89). 

Similarly, other reactions involving elimination in which the organometallic compound acts as a strong base are rare compared with the corresponding reactions of organolithium compounds [1]. 

Another unusual anion is [MnVII(=N)(NBu )3]2, which is formed by a reaction involving elimination of isobutylene ... 

Silylated aminophosphinimines, R2N-P=NR (R = SiMes) are obtained from LiNR2 with PX3 (X = F, Cl, Br) or R2N-PF2, or in reactions involving elimination of chlorotrimethylsilane. They dimerize slowly to cyclic phosphazanes. ... 

A combination of 1-alkenylboronates and 1-halo-1,3-alkadienes is expected to lead to the same trienes, but this combination is generally not recommended because of the experimental problems related to the instability of dienyl halides and a side reaction involving elimination of hydrogen halides with bases to produce the corresponding enyne. 

Trimethyl-N-sulfinylsilananiine, McaSiNSO, obtained from the reaction of (Me3Si)3N with SOCI2 was first reported in 1966 but full details of the preparation have not been published. This compound provides a useful source of the NSO function by reactions involving elimination of MesSiCl, for example, in the formation of S(NSO)2, and it may be converted into a stable mercury salt Hg(NSO)2 by reaction with Hgp2. 

The alternative way in which a carbocation can be converted into a neutral product is by elimination of a cation, almost always a proton. Two important reactions involve elimination as the final step. 

B-Fluoroborazines have also been prepared by elimination of silyl fluorides. Facile cleavage of the Si—N bond renders silylamines very effective in the synthesis of these and other B-haloborazines, and they are extensively utilized. Reactions involving elimination of silyl halides have been found particularly useful in sterically hindered systems. ... 

Reactions involving elimination of amines or chloroalkanes have met with some success. Linear polymers (RNBPh) are products from the thermal decomposition (distillation) of (RNH)2BPh compounds when the amino substituents are sufficiently bulky (R = i-Bu, s-Bu, t-Bu or i-Pr). The degree of polymerization is inferred from viscosity measurements to be between 10 and 20. The products hydrolyze rapidly but are thermally stable to 350°C. 

Other low-yield photodecomposition reactions involving elimination of small molecules have been reported.144-14 ... 

Sometimes, although the first step in the reaction may be addition of hydrogen to carbonyl, the overall reaction involves elimination of the carbonyl oxygen as water ... 

H. Watts gave general equations for such reactions involving elimination of water ... 

Kinetics is the study of the speed of a chemical reaction or process and is a critical element in toxicology. Most processes described in the discipline follow zero- and first-order kinetics. Recall that rate laws are employed to determine concentrations as a function of time. Although there are other variables and factors, the elimination of a xenobiotic substance from the body is fundamentally dependent on the kinetics of the reactions involved. Elimination processes often involve catalysts (enzymes), the role of which is central in determining the overall speed of the elimination, since a catalyst reduces the energy of activation. Eg. 

Aromatic Amines Primary Amines Anilines in aqueous media p-substituted anilines react in the followitig way a coupling reaction involving elimination of the para- substituent to give... 

The participation of reactive groups at the active site provides specificity not only for the substrates that will bind, but also for the reaction that will be catalysed. For example, in a non-enzymic model system, an amino acid may undergo (X-decarboxylation to yield an amine, transfer of the a-amino group and replacement with an oxo-group (section 9.3.1.2), isomerization between the d- and L-isomers, or a variety of reactions involving elimination or replacement of the side-chain. In an enzyme-catalysed reaction only one of the possible reactions will be catalysed by any given enzyme. 

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