Recent Reviews

A book entitled Emulsion Polymerization and its Use in Industry has recently appeared under the authorship of Yeliseyeva et al. It is available in the Russian language only as yet, although it is understood that there are plans for an English translation to be published. The appearance of an English translation will be greatly welcomed, as it should provide a convenient summary of the rather distinctive approach which has been adopted towards the subject by Russian workers. 

Some interest has been shown in recent years in emulsion polymerizations which occur in systems having non-aqueous dispersion media. A typical example would be the polymerization of methyl methacrylate in a medium such as dodecane, in the presence of a suitable colloid stabilizer. Industrial interest in such reactions and their products has waned somewhat following the increases in world oil prices and increasing sensitivity to the possibility of environmental pollution. However, these reactions and their products remain of considerable academic interest. The subject of non-aqueous polymer dispersions has recently been reviewed by Barrett, following the appearance of a book on dispersion polymerization.  

Although not a review of emulsion polymerization, it is convenient to note here the appearance of a collection of original papers on the subject in convenient book form under the editorship of Piirma and Gardon. These papers were first presented at an American Chemical Society Emulsion Polymers symposium held in April 1975. Taken together, they provide a representative cross-section of current problems in the subject, and also a convenient summary of the progress which had been made towards the solution of those i oblems at the time of publication. Several of these papers have since appeared elsewhere in the literature. 

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The surface forces apparatus (Section VI-3C) has revealed many features of surfactant adsorption and its effect on the forces between adsorbent surfaces [180,181]. A recent review of this work has been assembled by Parker [182]. 

There has been a surge of research activity in the physical chemistry of membranes, bilayers, and vesicles. In addition to the fundamental interest in cell membranes and phospholipid bilayers, there is tremendous motivation for the design of supported membrane biosensors for medical and pharmaceutical applications (see the recent review by Sackmann [64]). This subject, in particular its biochemical aspects, is too vast for full development here we will only briefly discuss some of the more physical aspects of these systems. The reader is referred to the general references and some additional reviews [65-69]. 

The various approaches to laser control of chemical reactions have been discussed in detail in several recent reviews [64. 65],... 

We smmnarize here only the main results of the theory and refer to a recent review [27] for details. The total number of adiabatically open channels is computed by searching for chaimel potential maxima V The... 

The treatment of equilibrium solvation effects in condensed-phase kmetics on the basis of TST has a long history and the literature on this topic is extensive. As the basic ideas can be found m most physical chemistry textbooks and excellent reviews and monographs on more advanced aspects are available (see, for example, the recent review article by Tnihlar et al [6] and references therein), the following presentation will be brief and far from providing a complete picture. 

A completely difierent approach to scattering involves writing down an expression that can be used to obtain S directly from the wavefunction, and which is stationary with respect to small errors in die waveftmction. In this case one can obtain the scattering matrix element by variational theory. A recent review of this topic has been given by Miller [32]. There are many different expressions that give S as a ftmctional of the wavefunction and, therefore, there are many different variational theories. This section describes the Kohn variational theory, which has proven particularly useftil in many applications in chemical reaction dynamics. To keep the derivation as simple as possible, we restrict our consideration to potentials of die type plotted in figure A3.11.1(c) where the waveftmcfton vanishes in the limit of v -oo, and where the Smatrix is a scalar property so we can drop the matrix notation. 

Two recent reviews recount subsequent research in the physics of neutral-atom cooling and trapping [3, 4],... 

In tills section we focus on tlie tlieory of stability of charged colloids. In section C2.6.5.1 it is shown how particles can be made to aggregate by adding sufficient electrolyte. The associated aggregation kinetics are discussed in section C2.6.5.2, and tlie stmcture of tlie aggregates in section C2.6.5.3. For more details, see tlie recent reviews [53, 54 and 55], or tlie colloid science textbooks [33, 39]. 

Interestingly, the need for a multiple electronic set, which we connect with the reciprocal relations, was also a keynote of a recent review ([46] and previous publications cited there and in [47]). Though the considerations relevant to this effect are not linked to the complex nature of the states (but rather to the stability of the adiabatic states in the real domain), we have included in Section HI a mention of, and some elaboration on, this topic. 

In this chapter, we look at the techniques known as direct, or on-the-fly, molecular dynamics and their application to non-adiabatic processes in photochemistry. In contrast to standard techniques that require a predefined potential energy surface (PES) over which the nuclei move, the PES is provided here by explicit evaluation of the electronic wave function for the states of interest. This makes the method very general and powerful, particularly for the study of polyatomic systems where the calculation of a multidimensional potential function is an impossible task. For a recent review of standard non-adiabatic dynamics methods using analytical PES functions see [1]. 

To add non-adiabatic effects to semiclassical methods, it is necessary to allow the trajectories to sample the different surfaces in a way that simulates the population transfer between electronic states. This sampling is most commonly done by using surface hopping techniques or Ehrenfest dynamics. Recent reviews of these methods are found in [30-32]. Gaussian wavepacket methods have also been extended to include non-adiabatic effects [33,34]. Of particular interest here is the spawning method of Martinez, Ben-Nun, and Levine [35,36], which has been used already in a number of direct dynamics studies. 

Decades of work have led to a profusion of LEERs for a variety of reactions, for both equilibrium constants and reaction rates. LEERs were also established for other observations such as spectral data. Furthermore, various different scales of substituent constants have been proposed to model these different chemical systems. Attempts were then made to come up with a few fundamental substituent constants, such as those for the inductive, resonance, steric, or field effects. These fundamental constants have then to be combined linearly to different extents to model the various real-world systems. However, for each chemical system investigated, it had to be established which effects are operative and with which weighting factors the frmdamental constants would have to be combined. Much of this work has been summarized in two books and has also been outlined in a more recent review [9-11]. 

In a recent review the pharmacophore identification programs Catalyst, DISCO, and GASP have been compared [83]. 

The bibliography for this chapter is perhaps the most difficult to write. The majority of references in this entire book pertain to organic molecules. The organic references listed here are just a few of the review references pertaining specifically to organic chemistry. This list is incomplete, but attempts to include recent reviews, which will reference earlier work. The listing for other classes of molecules are more complete. 

The Fischer cyclization is usually carried out with a protic or Lewis acid which functions both to facilitate the formation of the cnchydrazine by tautomerization and also to assist the N N bond breakage. The mechanistic basis of the Fischer cyclization has been discussed in recent reviews[l,2]. 

Butler recently reviewed the diazotization of heterocyclic amines (317). Reactions with nitrous acid yield in most cases N-exocyclic compounds. Since tertiary amines are usually regarded as inen to nitrosation, this... 

A detailed discussion of the properties of aerogels can be found ia several recent review articles (51—55) and the references thereia. This section provides a physical basis for these properties by focusiag on the microstmcture of an aerogel. The latent is to provide a bridge between the two previous sections, which discuss the preparative and dryiag parameters that affect microstmcture, and the next one, which oudines the potential appHcations made possible by unique stmctural features. The emphasis is on siUca aerogels because they have been the most extensively characteri2ed. 

Catalysis. Kistler explored the catalytic appHcations of aerogels ia the 1930s because of the unique pore characteristics of aerogels (24), but this area of research stayed dormant for about three decades until less tedious procedures to produce the materials were introduced (25,26). Three recent review articles summarize the flurry of research activities since then (63—65). Table 3 is a much abbreviated Hst of what has been cited in these three articles to demonstrate simply the wide range of catalytic materials and reactions that have been studied. 

Several early interpretations of the polymerization mechanism have been proposed (1,17,29—31). Because of the complexity of this polymerization and insoluble character of the products, key intermediates have not ordinarily been isolated, nor have the products been characterized. Later work, however, on the resinification of furfural (32,33) has provided a new insight on the polymerization mechanism, particularly with respect to thermal reaction at 100—250°C in the absence of air. Based on the isolation and characterization of two intermediate products (9) and (10), stmcture (11) was proposed for the final resin. This work also explains the color produced during resinification, which always is a characteristic of the final polymer (33). The resinification chemistry is discussed in a recent review (5). 

The chemistry of furfuryl alcohol polymerization has received much attention over the years. Several recent reviews have been written (5,6,54). Based on the accumulated data, furfuryl alcohol has to be considered a bifimctional monomer in the initial stage and its "normal" reactions give linear chains or oligomers containing essentially two repeating units (15,16) with (16) predominating. 

Uses. Furan is utilised as a chemical building block in the production of other industrial chemicals for use as pharmaceuticals, herbicides, stabili2ers, and fine chemicals. There are a great many references to the use of furan as an intermediate in these applications. For a recent review, see Reference 104. Several of the principal uses are described below. 

H. Strehlow, Rapid Reactions in Solution, VCH, Weinheim, Germany, 1992. Recent review of perturbation kinetics and magnetic resonance methods. 

Naphthenic acids have been the topic of numerous studies extending over many years. Originally recovered from the petroleum distillates to minimise corrosion of refinery equipment, they have found wide use as articles of commerce in metal naphthenates and other derivatives. A comprehensive overview of the uses of naphthenic acid and its derivatives can be found in References 1 and 2. A review of the extensive research on carboxyUc acids in petroleum conducted up to 1955 is available (3), as is a more recent review of purification, identification, and uses of naphthenic acid (4). 

Cychc polyarsines undergo a number of reactions with transition metal compounds to form complexes containing both As—As and As—metal bonds. The stmctural chemistry of these complexes has been the subject of a recent review (112). 

To date, the most extensively studied polyboron hydride compounds in BNCT research have been the icosahedral mercaptoborane derivatives Na2[B22H22SH] and Na [(B22H22S)2], which have been used in human trials with some, albeit limited, success. New generations of tumor-localizing boronated compounds are being developed. The dose-selectivity problem of BNCT has been approached using boron hydride compounds in combination with a variety of deUvery vehicles including boronated polyclonal and monoclonal antibodies, porphyrins, amino acids, nucleotides, carbohydrates, and hposomes. Boron neutron capture therapy has been the subject of recent reviews (254). 

The use of polychloroprene in solvent and latex adhesives has been the subject of a recent review (155). 

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