Understanding Organic Reactions

Reactions are at the heart of organic chemistry. An understanding of chemical processes has made possible the conversion of natural substances into new compounds with different, and sometimes superior, properties. Aspirin, ibuprofen, nylon, and polyethylene are all products of chemical reactions between substances derived from petroleum. 

Reactions are difficult to learn when each reaction is considered a unique and isolated event. Avoid this tendency. Virtually all chemical reactions are woven together by a few basic themes. After we learn the general principles, specific reactions then fit neatly into a general pattern. 

Often the solvent and temperature of a reaction are omitted from chemical equations, to further focus attention on the main substances involved in the reaction. 

Solvent. Although the solvent is often omitted in an equation for a chemical reaction, most organic reactions take place in a liquid solvent. Solvents solubilize key reaction components and serve as heat reservoirs to maintain a given temperature. Chapter 7 presents the two major types of reaction solvents and how they affect substitution reactions. 

Like other reactions, equations for organic reactions are usually drawn with a single reaction arrow (— ) between the starting material and product, but other conventions make these equations look different from those encountered in general chemistry. 

Why do certain reactions occur when two compounds are mixed together whereas others do not To answer this question we must learn how and why organic compounds react. 

Use curved arrows to show the movement of electrons. Full-headed arrows are used for electron pairs and half-headed arrows are used for single electrons. 

Reagents can be drawn either on the left side of an equation or over an arrow. Catalysts are drawn over or under an arrow. 

The higher the bond dissociation energy, the stronger the bond (6.4). 

Study Guide/Solutions Manual to accompany Organic Chemistry, 3rd Edition 

Breaking bonds generates reactive intermediates. Homolysis generates radicals with unpaired electrons. Heterolysis generates ions. 

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Rivail J L 1989 New Theoretical Ooncepts for Understanding Organic Reactions ed J Bertran and I G Cizmadia (Amsterdam Kluwer) p 219... 

Schlegel H B 1989. Some Practical Suggestions for Optimizing Geometries and Locating Transition States. In Bertran J and IG Csizmadia (Editors). New Theoretical Concepts for Understanding Organic Reactions. Dordrecht, Kluwer, pp. 33-53. 

New Theoretical Concepts for Understanding Organic Reactions J. Beilran, I. G. Csiz-madia, Eds., Kluwer, Dordrecht (1988). 

Much of the background needed to understand organic reactions has now been covered, and it s time to begin a systematic description of the major functional groups. Both in this chapter on alkenes and in future chapters on other... 

Bertran, J. In New Theoretical Concepts for Understanding Organic Reactions Csizmadia, I.G., Ed. Kluwer Academic Press Dordretch, 1989, p.231. 

Tucker, S. C. and Truhlar, D. G. 1989. Dynamical Formulation of Transition State Theory Variational Transition States and Semiclassical Tunneling , in New Theoretical Concepts for Understanding Organic Reactions, Bertran, J. and Czismadia, I. G., Eds., Kluwer Berlin, 291. 

H. B. Schlegel, Adv. Chem. Phys. 69, 249 (1987) H. B. Schlegel, in New Theoretical Concepts for Understanding Organic Reactions, edited by J. Bertrdn and I. G. Csizma-dia (Kluwer, Dordrecht, 1989)... 

Mezey, P. G. (1989) Topology ofmolecular shape and chirality, inBertran, J. and Csizmadia, I. G. (eds), New theoretical concepts for understanding organic reactions, Kluwer, Dordrecht, pp. 55-100. 

S. S. Shaik, in New Theoretical Concepts for Understanding Organic Reactions, J. Bertran and I. G. Csizmadia, Eds, NATO ASI Series, C267, Kluwer Academic Publishers, Norwell, MA, 1989, pp. 165-217. A Qualitative Valence Bond Model for Organic Reactions. 

Since an understanding of orbital theory is critical to understanding organic reaction mechanisms, review of the material presented in primary organic chemistry textbooks is essential. For the purposes of the discussions presented herein, recall that ground-state first-row elements (including C, N, and O) all possess one s orbital and three p orbitals. Figure 5.2 illustrates the shapes of s and p orbitals. 

The ability to construct Lewis structures is fundamental to writing or understanding organic reaction mechanisms. It is particularly important because lone pairs of electrons frequently are crucial to the mechanism but often are omitted from structures appearing in the chemical literature. 

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