Curved arrows illustrating reactions with

When two compounds react with each other to form new and different products, we try to understand how the reaction occurred. Every reaction involves the flow of electron density—electrons move to break bonds and form new bonds. Mechanisms illustrate how the electrons move during a reaction. The flow of electrons is shown with curved arrows for example. 

Each of the corners represents one pure component. The solid black dot indicates a first minimum-azeotrope. The curved surface illustrates the chemical equilibrium of reaction (1). As the second azeotrope, marked with a circle, lies on that surface, it is a so-called reactive azeotrope. The distillation information is included in the figure as well along the surface of the chemical equilibrium several reactive distillation lines are shown qualitatively. The arrows point towards the direction of decreasing temperatures. 

All reactions are accomplished via a flow of electron density (the motion of electrons). Acid-base reactions are no exception. The flow of electron density is illustrated with curved arrows ... 

Acids and bases Chapter 2 on acids and bases serves two purposes. It gives students experience with curved arrow notation using some familiar proton transfer reactions. It also illustrates how some fundamental concepts in organic structure affect a reaction, in this case an acid-base reaction. Since many mechanisms involve one or more acid-base reactions, 1 emphasize proton transfer reactions early and come back to this topic often throughout the text. 

Let us illustrate this important claim with a simple model showing how the reactivity pattern of the substrate, toluene 6 (Scheme 2.3), can be controlled by variations in reaction partners and external conditions. There are two reactions of 6 that proceed with the same stoichiometry (equations 1 and 2) but yield isomeric products benzyl bromide 7 and p-bromotoluene 8. Under the appropriate conditions it is possible to carry out each reaction selectively with almost complete exclusion of the alternate process. In order to understand how this can be accomplished, it is necessary to analyse the mechanisms of these conversions. The concise description of reaction mechanisms requires the use of special symbols such as the curved pronged or half-pronged arrows shown below. These arrows indicate the movement of an electron pair or a single electron, respectively, within the dynamics of a reaction process. 

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