Rideal

The determination of the amino group is often conveniently accomplished by converting it into the diazoderivative and replacing the nitrogen by chlorine as a rule the diazo-compound is not isolated. The following examplewill serve to illustrate the method  

The following example will illustrate the method of working Aniline (3.1 grams) 

Abnormal chloraurates of isopropylamine, piperidine, i-methylpiperidine, 2-5-dimethylpyrrplidine and quinoline have also been described, they have the 

The methods of acylation described for the determination of hydroxyl are also applicable to the amine 

Thiacctic acid readily yields acetyl derivatives with 

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J. T. Davies and E. K. Rideal, Interfacial Phenomerux, Academic Press, New York, 1961. 

To resume the brief historical sketch, the subject of monolayers developed rapidly during the interwar years, with the names of Langmuir, Adam, Harkins, and Rideal perhaps the most prominent the subject became one of precise and... 

It is known that even condensed films must have surface diffusional mobility Rideal and Tadayon [64] found that stearic acid films transferred from one surface to another by a process that seemed to involve surface diffusion to the occasional points of contact between the solids. Such transfer, of course, is observed in actual friction experiments in that an uncoated rider quickly acquires a layer of boundary lubricant from the surface over which it is passed [46]. However, there is little quantitative information available about actual surface diffusion coefficients. One value that may be relevant is that of Ross and Good [65] for butane on Spheron 6, which, for a monolayer, was about 5 x 10 cm /sec. If the average junction is about 10 cm in size, this would also be about the average distance that a film molecule would have to migrate, and the time required would be about 10 sec. This rate of Junctions passing each other corresponds to a sliding speed of 100 cm/sec so that the usual speeds of 0.01 cm/sec should not be too fast for pressurized film formation. See Ref. 62 for a study of another mechanism for surface mobility, that of evaporative hopping. 

The above situation led to the proposal by Rideal [202] of what has become an important alternative mechanism for surface reactions, illustrated by Eq. XVIII-33. Here, reaction takes place between chemisorbed atoms and a colliding or physical adsorbed molecule (see Ref. 203). 

Similar equations were written by Eley [204] for the exchange of N2 with N2 catalyzed by Fe or W, and mechanisms such as Eq. XVIII-33 have come to be known as Eley-Rideal mechanisms. Mechanisms such as that of Eq. XVIII-32 are now most commonly called Langmuir-Hinshelwood mechanisms (see... 

Some detailed calculations have been made by Tully [209] on the trajectories for Rideal-type processes. Thus the collision of an oxygen atom with a carbon atom bound to Pt results in a CO that departs with essentially all of the reaction energy as vibrational energy (see Ref. 210 for a later discussion). 

Studies to determine the nature of intermediate species have been made on a variety of transition metals, and especially on Pt, with emphasis on the Pt(lll) surface. Techniques such as TPD (temperature-programmed desorption), SIMS, NEXAFS (see Table VIII-1) and RAIRS (reflection absorption infrared spectroscopy) have been used, as well as all kinds of isotopic labeling (see Refs. 286 and 289). On Pt(III) the surface is covered with C2H3, ethylidyne, tightly bound to a three-fold hollow site, see Fig. XVIII-25, and Ref. 290. A current mechanism is that of the figure, in which ethylidyne acts as a kind of surface catalyst, allowing surface H atoms to add to a second, perhaps physically adsorbed layer of ethylene this is, in effect, a kind of Eley-Rideal mechanism. 

Derive the probable rate law for the reaction CO + j02 = CO2 as catalyzed by a metal surface assuming (a) an Eley-Rideal mechanism and (b) a Langmuir-Hinshelwood mechanism. 

Figure A3.9.1. Schematic illustrations of (a) the Langmuir-Hinshelwood and (b) Eley-Rideal mechanisms in gas-surface dynamics.

Rettner C T 1994 Reaction of an H-atom beam with Cl/Au(111)—dynamics of concurrent Eley-Rideal and Langmuir-Hinshelwood mechanisms J. Chem. Phys. 101 1529... 

Shalashilin D V, Jackson B and Persson M 1999 Eley-Rideal and hot atom reactions of H(D) atoms with D(H)-covered Cu(111) surfaces quasiclassical studies J. Chem. Phys. 110 11 038... 

Xi M and Bent B E 1993 Reaction of deuterium atoms with cyclohexane on Cu(111)—hydrogen abstraction reactions by Eley-Rideal mechanisms J. Phys. Chem. 97 4167... 

The first step consists of the molecular adsorption of CO. The second step is the dissociation of O2 to yield two adsorbed oxygen atoms. The third step is the reaction of an adsorbed CO molecule with an adsorbed oxygen atom to fonn a CO2 molecule that, at room temperature and higher, desorbs upon fomiation. To simplify matters, this desorption step is not included. This sequence of steps depicts a Langmuir-Hinshelwood mechanism, whereby reaction occurs between two adsorbed species (as opposed to an Eley-Rideal mechanism, whereby reaction occurs between one adsorbed species and one gas phase species). The role of surface science studies in fomuilating the CO oxidation mechanism was prominent. 

Mechanistic kinetic expressions are often used to represent the rate data obtained in laboratory studies, and to explain quantitatively the effects observed in the field. Several types of mechanisms have been proposed. These differ primarily in complexity, and on whether the mechanism assumes that one compound that is adsorbed on the catalyst surface reacts with the other compound in the gas phase, eg, the Eley-Rideal mechanism (23) or that both compounds are adsorbed on the catalyst surface before they react, eg, the Langmuir-Hinshelwood mechanism (25). 

Tj is the surface excess (Davies and Rideal, Jnteifacial Phenomena, 2d ed.. Academic, New York, 1963). For most purposes, it is sufficient to view Vj as the concentration of adsorbed component i at the surface in units of, say (g mol)/cm . R is the gas constant, T is the absolute temperature, Y is the surface tension, and a is the activity of component i. The minus sign shows that material which concentrates at the surface generally lowers the surface tension, and vice versa. This can sometimes be a guide in determining preliminarily what materials can be separated. 

The major surfactant in the foam may usually be considered to be present at the bubble surfaces in the form of an adsorbed monolayer with a substantially constant F, often of the order of 3 X 10" (g mol)/ cm", for a molecular weight of several hundred. On the other hand, trace materials follow the linear-adsorption isotherm Tj = KiCj if their concentration is low enough. For a wider range of concentration a Langmuir or other type of isotherm may be applicable (Davies and Rideal, loc. cit.). 

That department, the Department of Colloid Science in Cambridge University, was the creation and brainchild of Eric Rideal (1890-1974). In his own words, writing in 1947, some twenty years ago it was my duty to attempt to build up a... 

The department s input to undergraduate teaching was slight, and moreover it was geographically separated from the rest of Cambridge chemistry. In 1946, Rideal accepted an invitation to become director of the Royal Institution in London, taking some of his staff with him, and another professor of colloid science (Erancis... 

Rideal, E. (1970) Text of a talk, Sixty Years of Chemistry , presented on the occasion of the official opening of the West Wing, Unilever Research Laboratory, Port Sunlight, 20 July, 1970 (privately printed). 

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