Simple substituents

The groups attached to the principal chain are called substituents, and these may be simple or complex. Simple substituents are formed directly from parent hydrides when a simple substituent is itself substituted, it becomes complex as a consequence. Normal alkyl groups are simple substituents branched alkyl groups are complex substituents. However, as exceptions the names isopropyl, isobutyl, jec-butyl, tert-butyl, isopentyl, tert-pentyl and neopentyl are taken to refer to simple substituents. 

Basic multiplicative prefixes di-, tri-, tetra-, etc. are used with the names of simple substituents and retained names. Different or modified prefixes are used with complex substituents bis-, tris-, tetrakis- from tetrakis- onwards the ending -kis is attached to the basic multiplicative prefix, giving pentakis-, hexakis-, etc. (compare the use in coordination nomenclature). 

The letter R in the following illustrations is widely used as a symbol for a generic group. It may stand for simple substituents such as H- or CH3-, or for complex groups composed of many atoms of carbon and other elements. 

Asymmetric sulfoxidation by Mb mutants are also applicable to other sulfides bearing simple substituents. Table III shows examples of asymmetric sulfoxidation catalyzed by wild-type and L29H/H64L Mb (48). For a wide range of substrates, L29H/H64L Mb exhibits high activity and selectivity. 

Enthalpies of formation of tetrazoles containing simple substituents <1990ZFK656> are presented in a review <1999TI IS(3)467>. Names of compounds and the values of A//[° (gas) (kcal rnol ) (in parentheses) are as follows ... 

The diazotization of 5-aminotetrazole as a general preparative method for 5-substituted tetrazoles with versatile simple substituents is still important. For instance, the preparation of N-unsubstituted 5-nitrotetrazole 397 through 5-nitrotetrazole sodium salt tetrahydrate <1997RJ01771> is a significant achievement of the last decade and demonstrates new features of the amino group reactivity in 5-aminotetrazole derivatives (Scheme 46). 

Using an empirical expression for the amplification capacity, Micskei et al. found that the amplification strength of the Soai reaction fluctuates over a wide range when the structure of the aldehyde is varied [32]. The authors excluded the possibility of simple substituent effects but rather assumed that important changes in the reaction mechanism are taking place. 

These have not been widely studied, but simple substituents on the carbocyclic rings appear to behave normally in all respects. For this reason the treatment of such groups in this section is intended to be illustrative rather than exhaustive. 

Me3C6H)2, E(Si(SiMe3)3)(2,4,6-(CF3)3C6H2), E(NR2)2, E(PR2)2. None of these series is complete. Obviously, the same substituents reveal their effects to a different extent, depending on the nature of the divalent atom. Unfortunately, there are no UV data on labile stannylenes and plumbylenes with relatively simple substituents. 

Figure 6 Imyanitov s methodology (a) simple substituents and (b) complex substituents...

Dibromomethyl) is an example of a complex substituent, one that is made up of two or more simple substituents. A complex substituent requires enclosing parentheses, and is alphabetised at its first letter, regardless of the origin of this letter, e.g., b from (bromomethyl), d from (dibromomethyl), and t from (tribromomethyl). 

Bulky (ethyl, allyl) substituents in the testosterone series also significantly decrease the activity by causing protrusion exceeding the ordinary distances of simple substituents in the plane of the molecule. 

The principal difficulty in predicting the position of highest electron density in the aromatic nucleus is that it is not yet possible to compare quantitatively the relative magnitudes of permanent polarization, resonance, and the polarizability of conjugated systems when they operate in opposition to each other. In Table 1 are summarized the electrical factors which operate for a number of simple substituents and the observed orientation which these groups exert when they are attached to a benzene ring. 

We are concerned here with several types of stereochemical reaction cycles. Cycles that involve simple substitution reactions on tetrahedra are discussed in the second section. Cycles composed of simple substituent exchange reactions of atropisomers occupy the third section. In the fourth we treat the effect on cycles of associative substitution reactions of tetrahedra that involve rearrange-able trigonal bipyramids as intermediates. 

O chemical shifts of phenols hydrogen bonded to heteroaromatic nitrogens in systems like o-hydroxypyridines or similar compounds with one or more nitrogens or hydroxy groups show OH chemical shifts that are very similar (94-97 ppm), with the exception of a para-substituted methoxy derivative (90 ppm) , but this can be ascribed to a simple substituent effect (see above). 

An ideal artificial enediyne prodrug should be stable toward cycloaromatization. Therefore the ASE must be considerably higher than that calculated for 10-11. This can be realized by designing structural constraints that increase the steric strain of the product much more than that of the enediyne. Simple substituents are not, in general, able to diminish the reactivity adequately thus, stabilized enediyne analogs are typically ortho-fused or bridged bicyclic or polycyclic compounds. 

To name the compound, put the whole branched substituent name in parentheses and then number and alphabetize as if a simple substituent. 

The attachment of simple substituents such as alkyl or methoxy groups to the backbone of PPy s is well known to markedly enhance their solubility in organic solvents and, consequently, their processability (see the preceding text). Covalent binding of more sophisticated substituents to PPy can provide a wide range of other attributes. A number of these are discussed in the following text, with particular emphasis on the synthesis of derivatized PPy s with sensing capabilities. 

The dipicolinic acid platform has proven to be extremely versatile, leading to numerous applications of its tris-complexes with Eu and Tb, in particular in analytical and bioanalytical chemistry (see Section 2.5 for photophysical properties and Section 6.2 for bioanalytical applications). As a consequence, researchers have invented ways of modulating the photophysical properties, principally by introducing substituents on the para position of the pyridine ring, a relatively easy synthetic procedure. Simple substituents (e.g.. Cl, Br, NH2, NHCOCH3) are introduced by substitution of the hydroxyl function of chelidamic acid under... 

Arts. The nine-carbon group attached to the cyclohexane ring is not one of the simple substituents and has no simple name. Instead, we name the cyclic portion as a substituent attached to the acyclic ptortion of the molecule. 

Ethers with simple substituents such as methyl, ethyl, propyl, butyl, and phenyl are known by their common names. The common name is obtained by placing the names of the substituents before the word ether. For example, compounds I and III in Problem 13.22 are diethyl ether and ethyl phenyl ether, respectively. 

There is more than one system for naming amines. For amines with simple substituents, the preferred nomenclature system names the substituents, without spaces between them, followed by the suffix -amine. This is often referred to as the common nomenclature system. 

In the search for Improved potency, a group of simple substituents was first examined as shown in Table I. In this table the results of the PCA test are shown as a percent inhibition at the intravenous dose tested. For those compounds which were sufficiently active to test several doses, an IDso, or a dose which gives a 50% inhibition of the PCA reaction, was calculated. The mean percent inhibition was evaluated using a one-sided Student "t" test and p is 0.01 unless otherwise noted. The column labeled piso is a calculated value used for QSAR work and is defined as log (1/IDso). The obvious difficulties in estimating the IDso from a single dose experiment are discussed in the following paper. The IDso of DSCG as determined in our system is included as compound 13 for reference purposes. 

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