Atom affinity oxygen

Compared to the corresponding carbides the heats of oxygen chemisorption on metals are higher. For example, on metallic tungsten the heat of adsorption is 812 kJ/mole 02, while on metallic chromium it is 730 kJ/ mole 02n. These values are significantly higher that those of the carbides of the same metals (Table 16.2). Thus, carbon atoms, when implanted in the metal lattice, reduce the adsorption affinity of the metal atoms towards oxygen. 

Calix[4]arene derivatives with hard donating atoms, like oxygen, have a high affinity for hard alkaline and alkaline earth metal ions [101]. This type of calix[4]-arene derivatives will be described first. Subsequently, the calix[4]arene derivatives with soft donating atoms, like sulfur, will be discussed. These compounds have a preference for soft metal ions. 

The Benson mechanism can in principle be extended without major modifications to insertion reactions of other divalent species, such as oxygen and sulfur atoms. With oxygen, Yamaaaki and Cvetanovid have shown recently that 0( Z>) atoms preferentially insert, while 0( P) atoms abstract. This despite the fact that the singlet state hes some 48 kcal./ mole above the ground triplet state. On the other hand, sulfur atom reactions seem compatible with the proposed mechanism. Thus, if one attempts to apply it for the insertion of S( D) atoms, one finds that its predictions are consistent with the experimentally observed trend in the reaction rates. Here the transition state, due to the ionization potential and electron affinity of S( Z)) atoms being higher than those of alkyl radicals (9.2 and 2.2 e.v., respectively) could be formulated as... 

So far as oxygen is concerned, I admit that an atom of this body in combination exerts a powerful affinity upon a second atom of oxygen that is itself combined with another element. This affinity is modified by the electrical position of the elements to which the atoms of oxygen are respectively attached. The following explanations will make this conception understood. 

Here the whole four of hydrogen are not bound by a mutual affinity for each element of hydrogen can be substituted for one of chlorine in regular series, beginning with the first and ending with the last. The atoms of oxygen are, on the contrary, united in pairs (which will be more fully developed hereafter), and only for two atoms of oxygen two of chlorine can be substituted thus—... 

In the instance before us, it is a certain property of the oxygen which is the cause of the secondary combinate. This property is the affinity which one atom of oxygen in combination always exerts towards another atom of oxygen likewise in combination. 

This affinity is modified by the electric position of the element to which the respective atoms of oxygen are bound. From this property results the fact, that in organic combinates the atoms of oxygen are always found double. 

The main factors determining the efficiency of different oxides as catalysts for lower alkanes oxidation are the H-atom affinity of strong oxidizing surface sites and the oxygen binding energy. These thermochemical factors cause the rates and directions of free-radical reactions and, as a result, the catalytic activity and selectivity to certain products. 

The dissociation equilibnum of carbon dioxide may be obtained from Nernst s data (Lehrbuch, 5 Aufl, p 680) At iooo° absolute carbon dioxide at atmospheric pressure is dissociated to the extent of 1 58 x io-5 per cent, that is 1 mole of carbon dioxide yields a fraction 1 58 x io-7 mole of carbon monoxide and 1 58 x ro T gram-atoms of oxygen, or -5 1 x xo-7 mole of 02 Hence the affinity with which... 

In 1811 Berzelius said that the electricities must follow the same laws as hold for ponderable matter in respect of the proportions in which they combine with bodies — an adumbration of Faraday s laws. In his first account of Faraday s paper of 1834 (Series VII, see p. 116), Berzelius says the law that the same quantity of electricity produces the same amount of decomposition, although perhaps correct, had not been so fully proved as could be wished. That the same current should decompose water and fused lead chloride, and liberate equivalents of lead and hydrogen had been shown, but the acid in the water must have had an effect, and the idea that the same quantity of electricity could separate an atom of potassium from an atom of oxygen as would separate an atom of silver from an atom of oxygen was not probable, the force of affinity being so much larger in the first case. He also corrected Faraday s chemical results on sulphide of antimony. ... 

Figure 8.2 Plot of reaction efficiency and product-branching versus metal-ion-O-atom affinity for the reaction of 50 atomic cations reacting with molecular oxygen.

---