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Modifications reaction

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). [Pg.139]

The aromatic ring of a phenoxy anion is the site of electrophilic addition, eg, in methylolation with formaldehyde (qv). The phenoxy anion is highly reactive to many oxidants such as oxygen, hydrogen peroxide, ozone, and peroxyacetic acid. Many of the chemical modification reactions of lignin utilizing its aromatic and phenoHc nature have been reviewed elsewhere (53). [Pg.143]

Surface Modification. Reaction or adsorption at the soHd surface can alter its properties and lead to a surface charge or steric stabilization... [Pg.546]

SAMs of OH-terrninated alkanethiols have been used in many surface modification reactions (Fig. 14). These reacted with OTS to yield a weU-ordered bdayer (322), with octadecyldimethylchlorosilane (323,324), with POCI3 (325—327), with trifluoroacetic anhydride (328), epichlorohydrin (329), with alkyhsothiocyanate (330), with glutaric anhydride (331), and with chlorosulfonic acid (327). [Pg.542]

Purification. Hemoglobin is provided by the red blood ceU in highly purified form. However, the red ceU contains many enzymes and other proteins, and red ceU membranes contain many components that could potentially cause toxicity problems. Furthermore, plasma proteins and other components could cause toxic reactions in recipients of hemoglobin preparations. The chemical modification reactions discussed herein are not specific for hemoglobin and may modify other proteins as well. Indeed, multifimctional reagents could actually couple hemoglobin to nonhemoglobin proteins. [Pg.166]

Compared to the chemical modification reactions of PS, alkylation and acylation reactions are preferred to other reactions, such as halogenation, nitrolation, sulfo-nation, amination, and chloromethylation, etc. because the obtained polyfunctional PS has higher physico-me-chanical properties. [Pg.263]

The mechanism of chemical modification reactions of PS were determined using toluene as a model compound with EC in the presence of BF3-0(C2H5)2 catalyst and the kinetics and mechanism of the alkylation reaction were also determined under similar conditions [53-55]. The alkylation reaction of toluene, with epichlorohydrin, underwent polymerization of EC in the presence of Lewis acid catalysis at a low temperature (273 K) as depicted in Scheme (9). [Pg.263]

Grafting reactions onto a polymer backbone with a polymeric initiator have recently been reported by Hazer [56-60]. Active polystyrene [56], active polymethyl methacrylate [57], or macroazoinitiator [58,59] was mixed with a biopolyester polyhydroxynonanaate [60] (PHN) or polybutadiene to be carried out by thermal grafting reactions. The grafting reactions of PHN with polymer radicals may proceed by H-abstraction from the tertier carbon atom in the same manner as free radical modification reactions of polypropylene or polyhy-droxybutyratevalerate [61,62]. [Pg.733]

Thomson, V Click Organic Interactive to predict products from degradation and modification reactions of simple peptides. [Pg.1031]

Recent progress of basic and application studies in chitin chemistry was reviewed by Kurita (2001) with emphasis on the controlled modification reactions for the preparation of chitin derivatives. The reactions discussed include hydrolysis of main chain, deacetylation, acylation, M-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, 0-carboxymethylation, N-carboxyalkylation, silylation, and graft copolymerization. For conducting modification reactions in a facile and controlled manner, some soluble chitin derivatives are convenient. Among soluble precursors, N-phthaloyl chitosan is particularly useful and made possible a series of regioselective and quantitative substitutions that was otherwise difficult. One of the important achievements based on this organosoluble precursor is the synthesis of nonnatural branched polysaccharides that have sugar branches at a specific site of the linear chitin or chitosan backbone [89]. [Pg.158]

Modification reactions Residues introduced/nm S-layer surface (SUM) BSA OVA CA MYO... [Pg.349]

Most of the subsequent steps of tetrapyrrole synthesis are identical in plants, animals, and bacteria. The pathway includes synthesis of the monopyrrole porphobilinogen from two molecules of ALA by the action of ALA dehydratase with the elimination of two molecules of water, followed by the assembling of a linear tetrapyrrole hydroxymethylbilane from fonr molecnles of porphobilinogen, ring closure and two modification reactions of side chains. This produces the first tetrapyrrole macrocycle, uroporphyrinogen HI. Therefore, eight molecules of ALA are necessary to form one tetrapyrrole. [Pg.34]

Surface modification reactions OTC (GC) 139 etching HCl i O leaching HCl 140 particle depcaition 143 whisker formation 142 Surfactant mobile phases (LC) 408... [Pg.518]

Surface modification reactions are used to improve the wettability of glass surfaces by polar stationary phases and to Improve the extent of deactivation by sllylation" [138-146,166]. Miaaiuua procedures have been investigated but only a few are in use. Of these, the most important reactions are etching by hydrogen chloride, leaching with aqueous hydrochloric acid, formation of whiskers and solution deposition of a layer of solid particles. Because of the high purity and thinness of the... [Pg.593]

An important polymer modification reaction is the grafting to or from a polymer backbone by some chemical method to produce a branched structure Q). The characterization of the products of these reactions is often somewhat less well defined than block copolymers (2) due to the complexity of the mixture of products formed. It is therefore useful to prepare and characterize more well defined branched systems as models for the less well defined copolymers. The macromonomer method (3 ) allows for the preparation of more well defined copolymers than previously available. [Pg.85]

In addition, the polymer modification reactions leading to acidic and ionomeric functionalities are described in detail. The derived ion-containing block copolymers may aid in the correlation of chemical architecture with ionomer morphology and properties. [Pg.258]

Not surprisingly, The amount of di-t-butylperoxide (DtBP) is an important factor affecting the outcome of the reaction. The level of incorporation increases in proportion to the amount of DtBP (compare samples 1, 2, 6). Too much of the radical promoter is deleterious, since sample 6 was partially orosslinked, and an attempted modification reaction using 6.53 mmol of DtBP produced a completely insoluble product, which apparently was highly crosslinked. [Pg.305]

When the modification reaction was attempted on high density polyethylene (HDPE), a very low level of incorporation was obtained (sample 9). The diminished reactivity probably results from a low solubility of HDPE in the reaction medium, limiting the reaction to the surface of a solid substrate. [Pg.305]


See other pages where Modifications reaction is mentioned: [Pg.145]    [Pg.141]    [Pg.423]    [Pg.538]    [Pg.178]    [Pg.164]    [Pg.748]    [Pg.463]    [Pg.263]    [Pg.267]    [Pg.852]    [Pg.59]    [Pg.59]    [Pg.346]    [Pg.348]    [Pg.284]    [Pg.286]    [Pg.188]    [Pg.852]    [Pg.77]    [Pg.576]    [Pg.593]    [Pg.1328]    [Pg.63]    [Pg.260]    [Pg.265]    [Pg.272]    [Pg.302]    [Pg.302]    [Pg.304]    [Pg.306]    [Pg.306]    [Pg.309]   


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Acyloin reaction Silicon modification

Allergic reactions modification

Aminoacyl-tRNA modification reactions

Bart reaction Scheller modification

Bart reaction modifications

Barton modification Hunsdiecker reaction

Base modification reactions

Click Reactions in Polysaccharide Modification

Coupling agent modification reaction process

Covalent modification reactions, table

Cristol-Firth modification, Hunsdiecker reaction

Curtius reaction, modification using

Curtius reaction, modification using mixed carboxylic-carbonic anhydrides

Cyclodextrins modification reactions

Enzymatic modification reactions, cyclodextrin

Enzymatic reaction modification

Enzymic reaction, controlled modification

Gattermann aldehyde reaction Adams modification

Homer-Emmons modification Wittig reaction

Horner-Wadsworth-Emmons reaction Still-Gennari modification

Horner-Wadsworth-Emmons reaction modification

Hypersensitivity reactions modification

Julia reaction Kocienski modification

Ketones Wittig reaction modification

Kindler modification of Willgerodt reaction

Kindler modification of the Willgerodt reaction

Kinetics polymer modification reaction

Knoevenagel reaction Doebner modification

Knoevenagel reaction Verley-Doebner modification

Kolbe-Schmitt reaction Marasse modification

Leuckart reaction Eschweiler-Clarke modification

Lysine modification, Maillard reaction

Meyers modification, Ramberg-Backlund reaction

Modification Reactions of Cyclodextrins

Modification chemical side reactions during

Modification cycloaddition reactions

Modification of Reaction Conditions

Modification of the Hertz-Langmuir Equation as Applied to Decomposition Reactions

Modification of the Thiele Modulus for a Reversible Reaction

Modification reaction with

Modification reaction, phenolysis

Modifications to the Chapter 6 CRE Algorithm for Multiple Reactions

Nonenzymatic reactions, modification

Other Modification Reactions Involving Group Transfer

Perkin reaction Oglialoro modification

Peterson olefination Wittig reaction modification

Polymer modification reactions

Polymer modification through reaction with acid

Polymer post-modification coupling reactions

Post-condensation Modifications of the Passerini and Ugi Reactions

Posttranslational modification reactions, biological

Precursor modification reactions

Primary side, modification reactions

Protein modification, Maillard reaction

Quantitative Determinations and Modification Reactions of Side Chain Groups

Reaction chemical modification

Reaction pathway modification

Reaction rate modification

Reactions Involving Modification of Ligands

Reactions of Polymers Polymer Modification

Reactions on Polymers Polymer Modification

Reactive processing chain modification reactions

Reduction reactions modifications

Scaffold modification epoxidation reactions

Scaffold modification oxygenation reactions

Schlosser modification of the Wittig reaction

Secondary side, modification reactions

Sharpless reaction modification

Surface Modification by Chemical Reaction

Surface Modification using CuAAC Reaction

Surface modification during reactions

Surface modification reactions

Surface modification, CuAAC reaction

Thiol-ene Reactions for Chemical Modifications after Polymerisation

Willgerodt reaction Kindler modification

Willgerodt reaction and the Kindler modification

Wittig Reaction modifications

Wittig reaction Schlosser modification

Wittig reaction Wadsworth-Emmons modification

Wittig reaction phosphonate modification

Wittig reaction, Horner-Emmons modification

Wolff-Kishner reaction Huang-Minlon modification

Woodward modification Prevost reaction

Woodward modification of the Prevost reaction

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