Functional groups carboxylic esters

The user should bear in mind that the pairs of functional groups alcohol, ester carboxylic acids, ester amine, amide and carboxylic acid, amide can be interconverted by simple reactions. Compounds of the type... 

Cyanoborohydride and its modified reagents have been used for reductive dehalogenations. Thus, the combination of sodium or tetrabutylammonium cyanoborohydride, sodium or potassium 9-cyano-9-hydro-9-borabicyclo[3.3.1]nonanate [9-BBNCN] (2) or polymeric cyanoborane (3) in HMPA furnishes an efficient and mild system for the reduction of alkyl halides. The reagents are selective in that other functional groups, including ester, carboxylic acid, amide, cyano, alkene, nitro, sulfone, ketone, aldehyde and epoxide, are essentially inert under the reduction conditions thus, the reduction procedure is attractive for synthetic schemes which demand minimum damage to sensitive portions of the molecule. 

NaBHi is a much milder reducing agent than LiAlH,. In hydroxylic solvents it reduces aldehydes and ketones rapidly at 25° but is essentially inert to other functional groups epoxides, esters, lactones, carboxylic acids and salts, nitrile and nitro groups. Acid chlorides are reduced rapidly in diglyme or dioxane. 

A useful reaction of borane is the reduction of carboxylic acids to alcohols, which occurs very readily and can be achieved selectively in the presence of other functional group, including esters. For example, 4-nitrobenzoic acid is reduced... 

Acrylate and Methacrylate Polymers. Poly(ethyl acrylate) and poly(butyl acrylate) solutions and emulsions are important raw materials for pressure-sensitive adhesives. Copolymers of various esters, which give films of tailor-made hardness and which may additionally contain functional groups (carboxyl, amide, amino, methylol, hydroxyl), are used for pressure-sensitive adhesives to improve the adhesion properties or to enable the adhesive layer to be cross-hnked to a limited extent. 

The pairs of functional groups, alcohol-ester, carboxylic acid-ester, amine-amide, carboxylic acid-amide, can be interconverted by quite trivial reactions. When a member of these groups is the desired product or starting material, the other member should of course also be consulted in the text. 

Unsymmetrically substituted dipyrromethanes are obtained from n-unsubstitued pyrroles and fl(-(bromomethyl)pyiToIes in hot acetic acid within a few minutes. These reaction conditions are relatively mild and the o-unsubstituted pyrrole may even bear an electron withdrawing carboxylic ester function. It is still sufficiently nucleophilic to substitute bromine or acetoxy groups on an a-pyrrolic methyl group. Hetero atoms in this position are extremely reactive leaving groups since the a-pyrrolylmethenium( = azafulvenium ) cation formed as an intermediate is highly resonance-stabilized. 

Many compounds contain more than one functional group Prostaglandin Ei a hormone that regulates the relaxation of smooth muscles con tains two different kinds of carbonyl groups Classify each one (aldehyde ketone carboxylic acid ester amide acyl chloride or acid anhydride) Identify the most acidic proton in prostaglandin Ei and use Table 1 7 to estimate its pK ... 

The chemistry of carboxylic acids is the central theme of this chapter The impor tance of carboxylic acids is magnified when we realize that they are the parent com pounds of a large group of derivatives that includes acyl chlorides acid anhydrides esters and amides Those classes of compounds will be discussed m Chapter 20 Together this chapter and the next tell the story of some of the most fundamental struc tural types and functional group transformations m organic and biological chemistry... 

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... 

Fingerprint region (Section 13 20) The region 1400-625 cm of an infrared spectrum This region is less character istic of functional groups than others but varies so much from one molecule to another that it can be used to deter mine whether two substances are identical or not Fischer esterification (Sections 15 8 and 19 14) Acid cat alyzed ester formation between an alcohol and a carboxylic acid... 

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