Reactions reaction sequences

Electrochemical and nonelectrochemical processes. A reaction is often designated by the letter E to mark it as an electrode reaction in contrast to C, a chemical (nonelectrodic) reaction. Reaction sequences can be marked accordingly as ECE, EEC, ECC, etc. 

In the successive protonation reactions (Reaction sequence 11), the degradation of the strong triple bond of dinitrogen is achieved neither by splitting nor saturating it directly. Rather, as protonation of... 

Oxidation of base oil in a free radical process in solution can be represented by the following series of reactions. Reaction sequence (3.2(i-vii)) [55] ... 

Bass LM, Cates RD, Jarrold ME, Kirchner NJ, Bowers MT. Ion-molecule association reactions reaction sequences initiated by protonated methanol (CKjOH ) in CH OH experiment and theory. J Am Chem Soc. 1983 105 7024-33. 

Example 2.5 tert-Butyl hydrogen sulfate is required as an intermediate in a reaction sequence. This can be produced by the reaction between isobutylene and moderately concentrated sulfuric acid ... 

Enzymes act by lowering the overall activation energy of a reaction sequence by involving a series of intermediates, or a mechanism, different from the spontaneous uncatalysed reaction. 

Derive the steady-state rate law corresponding to the reaction sequence of Eqs. XVIII-40-XVIII-44, that is, without making the assumption that any one step is much slower than the others. See Ref 234. 

Write a possible reaction sequence for the photochemical oxidation of aqueous CN ion on Ti02. 

Let us consider tire oxidation of Fe(s) to Fe (solvated), which can be described by tire following reaction sequence [36, 40] ... 

The reaction mechanisms of plasma polymerization processes are not understood in detail. Poll et al [34] (figure C2.13.6) proposed a possible generic reaction sequence. Plasma-initiated polymerization can lead to the polymerization of a suitable monomer directly at the surface. The reaction is probably triggered by collisions of energetic ions or electrons, energetic photons or interactions of metastables or free radicals produced in the plasma with the surface. Activation processes in the plasma and the film fonnation at the surface may also result in the fonnation of non-reactive products. 

Deposition of Si02 has been achieved by exposing the substrate to the binary reaction sequence SiCL-l-2H20 —> Si02+ 4HC1. This is divided into the following half-reactions in which species at the surface are inaicated by asterisks [95] ... 

George S M, Sneh O, Diiion A C, Wise M L, Ott A W, Okada L A and Way J D 1994 Atomic iayer controiied deposition of SiO, and Ai,0, using ABAB.. . binary reaction sequence chemistry Appl. Surf. Sc/. 82/83 460-7... 

Ott A W, McCariey K C, Kiaus J W, Way J D and George S M 1996 Atomic iayer controiied deposition of Ai203 fiims using binary reaction sequence chemistry App/. Surf. Sc/. 106 128-36... 

Ott A W, Kiaus J W, Johnson J M and George S M 1997 Ai203 thin fiim growth on Si(IOO) using binary reaction sequence chemistry Thin Solid Films 292 135-44... 

Once we have an idea which structure we should make to obtain the desired property, we have to plan how to synthesize this compound - which reaction or sequence of reactions to perform to make this structure from available starting materials (Figure 1-3). 

Figure 1-3. The design of a reaction or sequence of reactions to make a structure from available starting materials.

To become familiar with a knowledge-based reaction prediction system To appreciate the different levels in the evaluation of chemical reactions To know how reaction sequences are modeled To understand kinetic modeling of chemical reactions To become familiar with biochemical pathways... 

When reaction rate equations can be given for the individual steps of a reaction sequence, a detailed modeling of product development over time can be made ... 

We have already explored this route (frame 184) and found that the reaction sequence actually is ... 

Perhaps the most sensational synthesis of chiysanthemic add uses this strategy. You ma r remember that TM 31 is usually made from the adduct of acetylene and acetone. Draw out the stages of this reaction sequence. 

TrialkyIboranes (p. 9), which can be synthesized from olefins and diborane, undergo alkyl coupling on oxidation with alkaline silver nitrate via short-lived silver organyls. Two out of three alkyl substituents are coupled in this reaction. Terminal olefins may be coupled by this reaction sequence in 40 - 80% yield. With non-terminal olefins yields drop to 30 - 50% (H.C. Brown, 1972C, 1975). 

Cis-olefins or cis./rjns-dienes can be obtained from alkynes in similar reaction sequences. The alkyne is first hydroborated and then treated with alkaline iodine. If the other substituents on boron are alkyl groups, a cis-olefin is formed (G. Zweifel, 1967). If they are cir-alkenyls, a cis, trans-diene results. The reactions are thought to be iodine-assisted migrations of the cis-alkenyl group followed by (rans-deiodoboronation (G. Zweifel, 1968). Trans, trans-dienes are made from haloalkynes and alkynes. These compounds are added one after the other to thexylborane. The alkenyl(l-haloalkenyl)thexylboranes are converted with sodium methoxide into trans, trans-dienes (E. Negishi, 1973). The thexyl group does not migrate. 

N. Trachtenberg, 1969). products or even as the major 1958). The reaction sequence with SeOj, except that the C—< the dehydrogenation of C—C other reagents have also been quinones. 

The reaction sequence is successful because reverse, ring-contraction reactions are unlikely and because only the final product contains a secondary lactam group, which is depro-tonated under the reaction conditions. 

This reaction sequence is much less prone to difficulties with isomerizations since the pyridine-like carbons of dipyrromethenes do not add protons. Yields are often low, however, since the intermediates do not survive the high temperatures. The more reactive, faster but less reliable system is certainly provided by the dipyrromethanes, in which the reactivity of the pyrrole units is comparable to activated benzene derivatives such as phenol or aniline. The situation is comparable with that found in peptide synthesis where the slow azide method gives cleaner products than the fast DCC-promoted condensations (see p. 234). 

With the catalysis of strong Lewis acids, such as tin(IV) chloride, dipyrromethenes may aiso be alkylated. A very successful porphyrin synthesis involves 5-bromo-S -bromomethyl and 5 -unsubstituted 5-methyl-dipyrromethenes. In the first alkylation step a tetrapyrrolic intermediate is formed which cyclizes to produce the porphyrin in DMSO in the presence of pyridine. This reaction sequence is useful for the synthesis of completely unsymmetrical porphyrins (K.M. Smith, 1975). 

Enantiomerically pure tetroses, pentoses, and hexoses have been synthesized by the following reaction sequence (A.W.M. Lee, 1982 S.Y. Ko, 1983), which is useful as a repetitive two-carbon hotnologi-.ation in total syntheses of higher monosaccharides and other polyhydroxy compounds (1) Wittig reaction of a protected hydroxy aldehyde with (triphenylphosphor-... 

The two stage reaction sequence is called ozonolysis and is represented by the gen eral equation... 

Suggest reaction sequences and reagents suitable for carrying out each of the following con versions Two synthetic operations are required in each case... 

Deduce the identity of the missing compounds in the following reaction sequences Show stereochemistry in parts (b) through (d)... 

This reaction sequence is called the acetoacetic ester synthesis It IS a standard... 

Recognize too that the reaction sequence is one that is characteristic of p keto esters in general and not limited to just ethyl acetoacetate and its derivatives Thus... 

Ethyl acetoacetate behaves similarly to diethyl malonate in its reactivity toward a p unsaturated carbonyl compounds Give the structure of the product of the following reaction sequence... 

The acetoacetyl group is then transformed to a butanoyl group by the reaction sequence illustrated m steps 2 to 4... 

Hydrophilic (Section 19 5) Literally water loving a term applied to substances that are soluble in water usually be cause of their ability to form hydrogen bonds with water Hydrophobic (Section 19 5) Literally water hating a term applied to substances that are not soluble in water but are soluble in nonpolar hydrocarbon like media Hydroxylation (Section 15 5) Reaction or sequence of reac tions in which an alkene is converted to a vicinal diol Hyperconjugation (Section 4 10) Delocalization of a electrons... 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cycHzed mbber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenoHc stmcture renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxyHc acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubiHty is controUed by chemical and polarity differences rather than molecular size. 

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