Other functional groups

Chemical methods used for the determination of hydroxyl groups or alcoholic constituents in polymers are based on acetylation [16-18], phthalation [18], and reaction with phenyl isocyanate [18,19] or, when two adjacent hydroxy groups are present in the polymers, by reaction with potassium periodate [9,17]. Alcoholic hydroxyl groups may be found in the following polymers (1) poly(ethylene terephthalate) (PET) [20], (2) poly(methyl acrylate), [21], (3) poly(methyl methacrylate) [21], and (4) polyhydric alcohols in hydrolysates of poly(ester) resins [22]. 

These hydroxyl groups in polymers are also usually determined by acetylation [9,21] or bromination [23]. However, it should be noted that acetylation with acid anhydrides and acyl chlorides that only total hydroxyl groups in these resins can be determined [7], Aromatic sulfonyl chlorides, however, react selectively with phenolic hydroxyls [26]. 

For detection and quantitative determination of small quantities of epoxy groups, these groups may be reacted with dinitroarene sulfonic acids [7,20,21,24], which react nearly as rapidly as hydrogen halides. 

Anderson [25] determined the distribution of olefinic bonds in elastomers after derivitization with 2,4-dinitrobenzenesulfonyl chloride using a gel permeation chromatograph equipped with a photometer operating at 254 nm. It is also possible to determine olefinic linkages with a preliminary epoxidation, followed by a method to analyze for the epoxy [26], 

The residual double bonds of poly(methyl acrylate) have been determined by bromination [9,27]. Bromination is accomplished through the addition of potassium bromide to potassium bromate in acidic medium [9]. Styrene-butadiene copolymers contain residual double bonds. The butadiene content of the copolymer has been determined by an iodine monochloride titration procedure [9], 

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Alcohols are key functional groups in synthesis because their synthesis can be plaimed by an important disconnection and because they can be converted into a whole family of other functional groups. List three types of molecule you might make from an alcohol by FGI. 

Since (A) does not contain any other functional group in addition to the formyl group, one may predict that suitable reaction conditions could be found for all conversions into (A). Many other alternative target molecules can, of course, be formulated. The reduction of (H), for example, may require introduction of a protecting group, e.g. acetal formation. The industrial synthesis of (A) is based upon the oxidation of (E) since 3-methylbutanol (isoamyl alcohol) is a cheap distillation product from alcoholic fermentation ( fusel oils ). The second step of our simple antithetic analysis — systematic disconnection — will now be exemplified with all target molecules of the scheme above. For the sake of brevity we shall omit the syn-thons and indicate only the reagents and reaction conditions. 

Alkyl halides are such useful starting materials for preparing other functional group types that chemists have developed several different methods for converting alcohols to alkyl halides Two methods based on the inorganic reagents thionyl chloride and phosphorus tnbromide bear special mention... 

This method is widely used for the resolution of chiral amines and carboxylic acids Analogous methods based on the formation and separation of diastereomers have been developed for other functional groups the precise approach depends on the kind of chem ical reactivity associated with the functional groups present m the molecule... 

Alkynes are hydrocarbons that contain a carbon-carbon triple bond Sim pie alkynes having no other functional groups or rings have the general formula C H2 -2 Acetylene is the simplest alkyne... 

The importance of the Diels-Alder reaction is in synthesis It gives us a method to form two new carbon-carbon bonds m a single operation and requires no reagents such as acids or bases that might affect other functional groups m the molecule... 

The carbon-carbon bond forming potential inherent m the Claisen and Dieckmann reac tions has been extensively exploited m organic synthesis Subsequent transformations of the p keto ester products permit the synthesis of other functional groups One of these transformations converts p keto esters to ketones it is based on the fact that p keto acids (not esters ) undergo decarboxylation readily (Section 19 17) Indeed p keto acids and their corresponding carboxylate anions as well lose carbon dioxide so easily that they tend to decarboxylate under the conditions of their formation... 

Postreactions of polyacrylamide to iatroduce anionic, cationic, or other functional groups are often attractive from a cost standpoiat. This approach can suffer, however, from side reactions resulting ia cross-linking or the iatroduction of unwanted functionahty, such as carboxyl groups from hydrolysis. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Akylsilanes are more reactive than vinylskanes in Friedel-Crafts reactions, as shown in the selective acylation of 2,3-disilylalkenes. The akylsilanes, a-skyloxyakyltrialkylsilanes, have been used as enolate equivalents in the preparation of 1,4-diketones (178). The mild reaction conditions required for these reactions tolerate many other functional groups, providing valuable synthetic routes. 

Ketenes are oxo compounds with cumulated carbonyl and carbon—carbon double bonds of the general stmcture R R2C—C—O, where and R2 may be any combination of hydrogen, alkyl, aryl, acyl, halogen, and many other functional groups. Ketenes with R = sometimes called aldoketenes,... 

Substitution. Substitution products retain the same nuclear configuration as naphthalene. They are formed by the substitution of one or more hydrogen atoms with other functional groups. Substituted naphthalenes of commercial importance have been obtained by sulfonation, sulfonation and alkah fusion, alkylation, nitration and reduction, and chlorination. 

One class of aromatic polyethers consists of polymers with only aromatic rings and ether linkages ia the backbone poly(phenylene oxide)s are examples and are the principal emphasis of this article. A second type contains a wide variety of other functional groups ia the backbone, ia addition to the aromatic units and ether linkages. Many of these polymers are covered ia other articles, based on the other fiinctionahty (see Polymers containing sulfur, POLYSULFONES). 

Miscellaneous Curing Reactions. Other functional groups can react with the thiol terminal groups of the polysulfides to cross-link the polymer chains and build molecular weight. For example, aldehydes can form thioacetals and water. Organic and inorganic acids or esters can form thioesters. Active dienes such as diacrylates can add to the thiols (3). Examples of these have been mentioned in the Hterature, but none have achieved... 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

As seen in Figure 1, the organo sulfur compounds are methylated at the boiling point (90°C) of dimethyl carbonate, whereas methylation (or alkylation with other alkyl groups) of other functional groups requites higher temperatures. This has resulted in the selective methylation of sulfhydryl groups of compounds that contain other substituents that can be alkylated. The other substituents can then be alkylated at elevated temperatures (63). 

Melting points, boiling points, densities, and refractive indexes for carboxyUc acids vary widely depending on molecular weight, stmcture, and the presence of unsaturation or other functional groups (Tables 1,2,3, and 5). In addition, some useful constants for alkanoic acids are Hsted in Table 1. Some constants for selected unsaturated and substituted acids are given in Table 7. 

The presence of other functional groups ia an acetylenic molecule frequendy does not affect partial hydrogenation because many groups such as olefins are less strongly adsorbed on the catalytic site. Supported palladium catalysts deactivated with lead (such as the Liadlar catalyst), sulfur, or quinoline have been used for hydrogenation of acetylenic compound to (predominantiy) cis-olefins. 

In addition they may contain ether, amide, carbonyl, sulfone, or other functional groups. References 28 and 29 provide excellent reviews of polyimide chemistry. 

The other analytical methods necessary to control the typical specification given in Table 5 are, for the most part, common quality-control procedures. When a chemical analysis for purity is desired, acetylation or phthalation procedures are commonly employed. In these cases, the alcohol reacts with a measured volume of either acetic or phthalic anhydride in pyridine solution. The loss in titratable acidity in the anhydride solution is a direct measure of the hydroxyl groups reacting in the sample. These procedures are generally free from interference by other functional groups, but both are affected adversely by the presence of excessive water, as this depletes the anhydride reagent strength to a level below that necessary to ensure complete reaction with the alcohol. Both procedures can be adapted to a semimicro- or even microscale deterrnination. 

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