Subject Scheme

Print indexes have been superceded to a large degree by their database counterparts on the Web, but they can stiU play an important role in access to those older materials not yet covered online. Records are usually arranged in some type of classed subject scheme or they can be alphabetically... 

The starting material for assembly of asar[ ]arene macrocycles is tetramethoxybenzene (12.31), which can be prepared from commercial dihydrojybenzoquinone (12.33) in abundant quantities. We subjected (Scheme 12.11) a mixture of tetramethojybenzene and paraformaldehyde to Friedel-Crafts alleviation conditions at 80 °C in chlorinated solvents, with BF3 OEt2 as the Lewis acid. Influenced by the prior work on the synthesis of pillar[n]arenes - where pillar[5]arene is formed primarily under similar reaction conditions - we were expecting this reaction mixture to form asar[5]ar-ene as the major product. To our surprise, we found, however, that the reaction mixture produced only asar[6]arene and not even a trace of asar[5]arene. It is most likely that the increased steric demand imposed on the macrocyclic framework by the two additional methojyl groups not present in pillar[ ]arenes is responsible for this striking difference in reactivity between the asar[ ]arene and pillar[ ]arene families of macrocycles. Soxhlet extraction of the crude reaction mixture with acetonitrile as the solvent was then used as a scalable method of purification to access pure asar[6]arene (12.32a) in bulk quantities. 

The treatment may be made more detailed by supposing that the rate-determining step is actually from species O in the OHP (at potential relative to the solution) to species R similarly located. The effect is to make fi dependent on the value of 2 and hence on any changes in the electrical double layer. This type of analysis has permitted some detailed interpretations to be made of kinetic schemes for electrode reactions and also connects that subject to the general one of this chapter. 

The first step in an inductive learning process is always to order the observations to group those objects together that have essential features in common and to separate objects that are distinctly different. Thus, in learning from individual reactions we have to classify reactions - we have to define reaction types that encompass a series of reactions with essential common characteristics. Clearly, the definition of what are essential common features is subjective and thus a variety of different classification schemes have been proposed. 

Development of weighted residual finite element schemes that can yield stable solutions for hyperbolic partial differential equations has been the subject of a considerable amount of research. The most successful outcome of these attempts is the development of the streamline upwinding technique by Brooks and Hughes (1982). The basic concept in the streamline upwinding is to modify the weighting function in the Galerkin scheme as... 

Anilines react with ct-haloacetophenones to give 2-arylindoles. In a typical procedure an W-phenacylaniline is heated with a tw o-fold excess of the aniline hydrobromide to 200-250°C[1]. The mechanism of the reaction was the subject of considerable investigation in the 1940s[2]. A crucial aspect of the reaction seems to be the formation of an imine of the acetophenone which can isomerize to an aldimine intermediate. This intermediate apparently undergoes cyclization more rapidly (path bl -> b2) than its precursor (Scheme 7.3). Only with very reactive rings, e.g, 3,5-dimethoxyaniline, has the alternative cydiz-ation (path al a2) to a 3-arylindole been observed and then only under modified reaction conditions[3],... 

Acetamidothiazole and its 4-alkyl derivatives react with chloro-sulfonic acid. The structure of the resulting products was a subject of controversy (172. 393-397). N-acetyl-A -(2-thiazolyl)-sulfamoyl chlorides (189) first proposed were then shown to be 2-acetamido-5-chloro-sulfonylthiazoles (190) (Scheme 120) (367. 368. 398). the latter assignment is based on infrared (368) and chemical evidence (367). 

Covalent synthesis of complex molecules involves the reactive assembly of many atoms into subunits with aid of reagents and estabUshed as well as innovative reaction pathways. These subunits are then subjected to various reactions that will assemble the target molecule. These reaction schemes involve the protection of certain sensitive parts of the molecule while other parts are being reacted. Very complex molecules can be synthesized in this manner. A prime example of the success of this approach is the total synthesis of palytoxin, a poisonous substance found in marine soft corals (35). Other complex molecules synthesized by sequential addition of atoms and blocks of atoms include vitamin potentially anticancer KH-1 adenocarcinoma antigen,... 

The mechanism of anionic polymerization of cyclosiloxanes has been the subject of several studies (96,97). The first kinetic analysis in this area was carried out in the early 1950s (98). In the general scheme of this process, the propagation/depropagation step involves the nucleophilic attack of the silanolate anion on the sUicon, which results in the cleavage of the siloxane bond and formation of the new silanolate active center (eq. 17). 

Relationships Between Objects, Processes, and Events. Relationships can be causal, eg, if there is water in the reactor feed, then an explosion can take place. Relationships can also be stmctural, eg, a distiUation tower is a vessel containing trays that have sieves in them or relationships can be taxonomic, eg, a boiler is a type of heat exchanger. Knowledge in the form of relationships connects facts and descriptions that are already represented in some way in a system. Relational knowledge is also subject to uncertainty, especiaUy in the case of causal relationships. The representation scheme has to be able to express this uncertainty in some way. 

Isothiazoles are reductively desulfurized by Raney nickel, e.g. as in Scheme 31 (72AHC(l4)l). 1,2,5-Thiadiazoles are subject to reductive cleavage by zinc in acid, sodium in alcohol, or Raney nickel, e.g. Scheme 32 (68AHC(9)107). 

The fundamental subject of this section is the transformation of A -pyrazolines into cyclopropanes (Buchner-Curtius and Kishner cyclopropane syntheses). The cyclopropane is often accompanied by alkenes (67HC(22)l). When applied to A -pyrazolines the reaction occurs via the A isomers (Scheme 37). 

Below, we analyse the likely fault levels of a system under different circuits and fault conditions for an easy understanding of the subject. It is a prerequisite to decide the level of fault, to select and design the right type of equipment, devices and components and the protective scheme for a particular network. 

This is a complex subject and requires detailed engineering and application of the various protection schemes for... 

LT installations may be subject to frequent load variations and inductive switchings. It will be more desirable in such cases to provide them with an automatic p.f. correction scheme than manual correction. It may be... 

The reaction between benzoyl peroxide and A,A-dimethylaniline has been the subject of many examinations over the years. The following mechanism of initiation is fairly well accepted in the polymerization of styrene. It seems likely that a similar mechanism is followed for other free-radical polymerizations (Scheme 5). 

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