Functional groups shapes

There are few but very interesting examples in the literature concerning the synthesis of large molecules with functional groups. Shape-selective halogenation of naphthalene is claimed to proceed over non-acidic zeolites, e.g. the selective monochlorination in the liquid phase with zeolite KL [48], usually carried out with typical Lewis acid catalysts, and the oxyiodination on zeolite KX to 2-iodo and 2,6-diiodonaphthalene [49]. 

Although there has been much study of the relationship between the structure and the sensory activity of odorous molecules, it frequently appears impossible to predict the odour from its chemical structure. In other words, very similar chemical structures can have quite different smells (e.g. the para versus the meta form, optical isomers). Contrarily, different compounds in terms of functional group, shape, etc can have similar smells [2]. 

Name of functional group Shape of functional group Hydrophobic vs. hydrophilic character Polar vs. nonpolar character Acidic vs. basic (pK ) character... 

Alcohols are abundant in nature and varied in structure (see, e.g.. Section 4-7). Simple alcohols are used as solvents others aid in the synthesis of more complex molecules. They are a good example of how functional groups shape the structure and function of organic compounds. 

Fig. 25. Schematic representation of imprinting (a) cross-linking polymerization ia the presence of a template (T) to obtain cavities of specific shape and a defined spatial arrangement of functional groups (binding sites. A—C) (b) cross-linked polymer prepared from the template monomer and ethylene...

Bulky, even if highly polari2able, functional groups or atoms that are attached anywhere but on the end of a rod-shaped molecule usually are less favorable for Hquid crystal formation. Enhanced intermolecular attractions are more than countered as the molecule deviates from the required linearity. For example, the inclusion of the bromine atom at position three of 4-decyloxy-3-bromoben2oic acid [5519-23-3] (9) prevents mesomorphic behavior. In other cases the Hquid crystal phases do not disappear, but their ranges are narrower. 

Relatively unambiguous monotonic SARs also occur where activity depends on the ionization of a particular functional group. A classic example (Fig. 5) is that of the antibacterial sulfonamides where activity is exerted by competitive inhibition of the incorporation of j -amin ohenzoic acid into foHc acid (27). The beU-shaped relationship is consistent with the sulfonamide acting as the anion but permeating into the cell as the neutral species. 

The living polymerization process offers enormous flexibiUty in the design of polymers (40). It is possible to control terminal functional groups, pendant groups, monomer sequencing along the main chain (including the order of addition and blockiness), steric stmcture, and spatial shape. 

Hydrogels are water-containing polymers, hydrophilic in nature, yet insoluble. In water, these polymers swell to an equiUbrium volume and maintain thek shape. The hydrophilicity of hydrogel is a result of the presence of functional groups such as —NH2, —OH, —COOH, —CONH2, —CONH—, —SO H, etc. The insolubihty and stabiUty of hydrogels are caused by the presence of a three-dimensional network. The scope, preparation, and characterization of hydrogels has been reviewed (107). 

The subunits which can be defined can include atoms or collections of atoms corresponding to functional groups. The subunits can be represented as regions of space defined by electon density. These representations correspond well with the qualitative concepts that arise from valence bond stmctures. The mathematical evaluation can assign shape and charge density to atoms. Table 1.17 gives the C and H charge densities in some... 

Alkenes are hydrocarbons that contain a carbon-carbon double bond. A carbon-carbon double bond is both an important structural unit and an important functional group in organic chemistry. The shape of an organic molecule is influenced by the presence of this bond, and the double bond is the site of most of the chemical reactions that alkenes undergo. Some representative alkenes include isobutylene (an industrial chemical), a-pinene (a fragrant liquid obtained from pine trees), and famesene (a naturally occuning alkene with three double bonds). 

The division of the molecular volume into atomic basins follows from a deeper analysis based on the principle of stationary action. The shapes of the atomic basins, and the associated electron densities, in a functional group are very similar in different molecules. The local properties of the wave function are therefore transferable to a very good approximation, which rationalizes the basis for organic chemistry, that functional groups react similarly in different molecules. It may be shown that any observable... 

Similarity effect on chemical events may be traced back to the old empirical rule that like dissolves like similia similibus solvuntur). This rule, however, implies the similarity between solute and solvent molecules in polarity or functional group, but not in molecular shape. 

The compounds with more complicated shapes and more than one functional group are described by a straightforward numbering system that you will learn in later chemistry courses. Other functional groups will be studied then too. 

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