Functional group g

Carboxylic acid derivatives (or acyl derivatives), RC—G, have the OH replaced by another electronegative functional group, G. such that it can be hydrolyzed back to the acid ... 

Fig. 1 (a) Structure of a methylene-bridged cavitand 1 substituted with functional groups (G) at the upper rim. (b) General structure of cavitands with different bridging units (BU) and one example of an aryl-bridged cavitand [38], (c) Structure of calix[n]arenes 2 with functional groups (G) at the wider rim. (d) Conformations of calix[4]arenes... 

Because cavitands and calix[n]arenes with various functional groups (G) can be synthesized, a range of reactions can be applied to obtain substituted derivatives. Some of these molecules can be used as receptors for neutral molecules and ions, for the synthesis of stationary phases for chromatography and as catalysts for... 

Amines, Nitriles, and Other Nitrogen-Containing Functional Groups, G. Kneen, 1981, 1982, 1983, 1984, and S. G. Lister, 1986. This series of reviews deals partially with cyanocarbons. 

Disaccharides Like amino acids, monosaccharides can be linked together by a condensation reaction in which water is released. When two monosaccharides bond together, a disaccharide is formed, as shown in Figure 23.10. The new bond formed is an ether functional group (G-O-G). 

Functional group G valuef L (cal-cc) No. of functional groi 5)S in the polymer repeat unit Tbtal G value,, (cal-cc) ... 

Researchers have found that upon exposing polyethylene particles to the oxidating conditions of oxygen with transition metals or chromic acid alone, a network of large pores can be created [22]. These pores range in size from 900-5000 A. These supports which have a reported loading capacity in excess of 100 /xmole of functional groups/g were shown to be suitable for both batchwise and continuous flow solid phase synthesis. 

If a catalyst is to work well in solution, it (and tire reactants) must be sufficiently soluble and stable. Most polar catalysts (e.g., acids and bases) are used in water and most organometallic catalysts (compounds of metals witli organic ligands bonded to tliem) are used in organic solvents. Some enzymes function in aqueous biological solutions, witli tlieir solubilities detennined by the polar functional groups (R groups) on tlieir outer surfaces. 

Structural keys describe the chemical composition and structural motifs of molecules represented as a Boolean array. If a certain structural feature is present in a molecule or a substructure, a particular bit is set to 1 (true), otherwise to 0 (false). A bit in this array may encode a particular functional group (such as a carboxylic acid or an amidelinkage), a structural element (e.g., a substituted cyclohexane), or at least n occurrences of a particular element (e.g., a carbon atom). Alternatively, the structural key can be defined as an array of integers where the elements of this array contain the frequency of a specific feature in the molecule. 

In recent decades, much attention has been paid to the application of artificial neural networks as a tool for spectral interpretation (see, e.g.. Refs. [104, 105]). The ANN approach app]ied to vibrational spectra allows the determination of adequate functional groups that can exist in the sample, as well as the complete interpretation of spectra. Elyashberg [106] reported an overall prediction accuracy using ANN of about 80 % that was achieved for general-purpose approaches. Klawun and Wilkins managed to increase this value to about 95% [107]. 

Tran orm-based or long-range strategies The retrosynthetic analysis is directed toward the application of powerful synthesis transforms. Functional groups are introduced into the target compound in order to establish the retion of a certain goal transform (e.g., the transform for the Diels-Alder reaction, Robinson annulation, Birch reduction, halolactonization, etc.). 

A saturated alkyl group does not exhibit functionality. It is not a d -synthon, because the functional groups, e.g. halide or metal ions, are lost in the course of the reaction. It functions as an alkyl synthon. Alkenyl anions (R. West, 1961) on the other hand, constitute d -synthons, because the C = C group remains in the product and may be subject to further synthetic operations. 

Table 1. Reaciivicy of reducing agents towards functional groups (adapted from J. B. Hendrickson, O. J. Cram, and G. S. Hammond, Organic Chemistry, 3rd ed., McGraw-Hill 1970, with modi(icaiiotis. ...

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. 

Alcohols and alkyl halides are classified as primary secondary or tertiary according to the degree of substitution of the carbon that bears the functional group (Section 2 13) Thus primary alcohols and primary alkyl halides are compounds of the type RCH2G (where G is the functional group) secondary alcohols and secondary alkyl halides are compounds of the type R2CHG and tertiary alcohols and tertiary alkyl halides are com pounds of the type R3CG... 

---