Substituents classification

Stone filter funnel, 150 Stoneware, 365 Substituents, classification, 50 Suction filter, 19 Sulfanilic acid, 126, 262 diazotization, 24 261 pure for analysis, 384... 

Figure 3-18. A different classification of substituents at the reaction site.

A familiar feature of the electronic theory is the classification of substituents, in terms of the inductive and conjugative or resonance effects, which it provides. Examples from substituents discussed in this book are given in table 7.2. The effects upon orientation and reactivity indicated are only the dominant ones, and one of our tasks is to examine in closer detail how descriptions of substituent effects of this kind meet the facts of nitration. In general, such descriptions find wide acceptance, the more so since they are now known to correspond to parallel descriptions in terms of molecular orbital theory ( 7.2.2, 7.2.3). Only in respect of the interpretation to be placed upon the inductive effect is there still serious disagreement. It will be seen that recent results of nitration studies have produced evidence on this point ( 9.1.1). 

The material in the succeeding chapters describes both the synthesis of the indole ring and means of substituent modification which are especially important in indole chemistry. The first seven chapters describe the preparation of indoles from benzenoid precursors. Chapter 8 describes preparation of indoles from pyrroles by annelation reactions. These syntheses can be categorized by using the concept of bond disconnection to specify the bond(s) formed in the synthesis. The categories are indicated by the number and identity of the bond(s) formed. This classification is given in Scheme 1.1. 

Most chapters contain tables giving an inventor> of all known derivatives of the family concerned. The classification of substituents in these tables is made according to the following hierarchy ... 

The classification of hydrocarbons as aliphatic or aromatic took place m the 1860s when It was already apparent that there was something special about benzene toluene and their derivatives Their molecular formulas (benzene is CgHg toluene is C7Hj ) indicate that like alkenes and alkynes they are unsaturated and should undergo addition reac tions Under conditions m which bromine for example reacts rapidly with alkenes and alkynes however benzene proved to be inert Benzene does react with Bi2 m the pres ence of iron(III) bromide as a catalyst but even then addition isn t observed Substitu tion occurs instead ... 

Classification of Substituents in Electrophilic Aromatic Substitution Reactions... 

This natural classification, with the number of substituents R increasing regularly from two to eight (the unsubstituted l-pyrazoline-3,4,5-trione is unknown), is useful for redox studies, but in order to be consistent with other parts of this work the following classification will be used throughout the chapter. 

An overview of the most important quaternary ammonium salts tested for possible applicability in zinc-bromine batteries is presented in Table 2. A rough classification has been applied according to the substance classes of the substituents attached to the nitrogen. 

We will conclude this section on theory with such a case. In Section 8.3 it was shown that the influence of substituents on the rate of dediazoniation of arenediazonium ions can be treated by dual substituent parameter (DSP) methods, and that kinetic evidence is consistent with a side-on addition of N2. We will now discuss these experimental conclusion with the help of schematic orbital correlation diagrams for the diazonium ion, the aryl cation, and the side-on ion-molecule pair (Fig. 8-5, from Zollinger, 1990). We use the same orbital classification as Vincent and Radom (1978) (C2v symmetry). 

The other structural parameters, such as the ester group content, the presence, nature, and position of substituents on monomer units, and the number and nature of comonomers, are of less importance and do not modify this classification of hnear polyesters. 

Amines are important industrial chemicals which are involved in everyday life [3, 4]. Apart from the usual classification into primary, secondary, and tertiary amines, the distinction is often made between lighf amines (less than six-carbon substituents) and fatty amines. light amines are intermediates for the synthesis of drugs, herbicides, cosmetics, etc. [3]. They also find use as vulcanization accelerators and extraction agents. Fatty amines are involved in the synthesis of corrosion inhibitors and cationic surfactants, which are used in ore flotation processes and are good fabric softeners and antistatic agents [4—6],... 

Carbene reactivity is strongly affected by substituents.117 Various singlet carbenes have been characterized as nucleophilic, ambiphilic, and electrophilic as shown in Table 10.2 This classification is based on relative reactivity toward a series of both nucleophilic alkenes, such as tetramethylethylene, and electrophilic ones, such as acrylonitrile. The principal structural feature that determines the reactivity of the carbene is the ability of the substituent to act as an electron donor. For example, dimethoxycarbene is devoid of electrophilicity toward alkenes because of electron donation by the methoxy groups.118... 

Chloramphenicol was the first orally active, broad-spectrum antibiotic to be used in the clinic, and remains the only antibiotic which is marketed in totally synthetic form. Its initial popularity was dampened, and its utilization plummeted when it was found that some patients developed an irreversible aplastic anemia from use of the drug. Of the hundreds of analogues synthesized, none are significantly more potent or certain to be safer than chloramphenicol itself. Two analogues have been given generic names and fall into this chemical classification. It was found early in the game that activity was retained with p-substituents, and that... 

Metallocenes with substituted cyclopentadienyl rings. Metallocenes with methylated rings were among the first heavy alkaline earth metallocenes to be structurally characterized, but many other substituents have been incorporated into bis(cyclopentadienyl) complexes. Under this classification are included compounds with indenyl ligands, which in... 

For reaction of benzoyl chlorides in water, reactivity follows the electronreleasing ability of p-substituents, and there are striking differences in the micellar effects (Table 7). With electron-withdrawing substituents k+/k > 1, but its value progressively decreases with increasing electron release from a p-substituent. Thus an increase in electron release changes k+/k from values characteristic of a carbonyl addition reaction to values characteristic of SN reactions at saturated carbon. This classification also... 

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