Kinds of Organic Reactions

Organic chemical reactions can be organized broadly in two ways—by wIkU kinds of reactions occur and by how those reactions occur, l.et s look first at the kinds of reactions that take place. 1here arc four gcMieral types of organic reactions additions, eliminations, snhstitntions, and reammgenients. 

I Addition reactions occur when two reactants add together to form a single product with no atoms left over. An example that we ll be studying soon 

I Elimination reactions are, in a sen.se, the opposite of addition reactions. They occur when a single reactant splits into two products, often with formation of a small molecule such as water or HBr. An example is the acid-catalyzed reaction of an alcohol to yield water and an alkene. 

I Substitution reactions occur when two reactants exchange parts to give two new products. An example is the reaction of an alkane with Cb m the presence of ultraviolet light to yield an alkyl chloride. A Cl atom from Cb substi tutes for an H atom of the alkane, and two new products result. 

I Rearrangement reactions occur when a single reactant undergoes a reorganization of bonds and atoms to yield an isomeric product. An example is the conversion of the alkene I-butene into its constitutional isomer 2-butene by treatment with an acid cataivst. 

An example of an addition reaction that we ll be studying soon is the reac tion of an alkene, such as ethylene, with HBr to yield an alkyl bromide  

Elimination reactions are, in a sense, the opposite of addition reac tions. Eliminations occur when a single reactant splits into two products  

An example of an elimination reaction is the reaction of an alkyl halide with base to yield an acid and an alkene  

Like other compounds, organic molecules undergo acid-base and oxidation-reduction reactions, as discussed in Chapters 2 and 4. Organic molecules also undergo substitution, elimination, and addition reactions. 

In a general substitution reaction, Y replaces Z on a carbon atom. Substitution reactions involve o bonds one o bond breaks and another forms at the same carbon atom. The most common examples of substitution occur when Z is hydrogen or a heteroatom that is more electronegative than carbon. 

Bimination is a reaction in which elements of the starting material are lost and a jr bond is formed. 

In an elimination reaction, two groups X and Y are removed from a starting material. Two a bonds are broken, and a it bond is formed between adjacent atoms. The most common examples of elimination occur when X = H and Y is a heteroatom more electronegative than carbon. 

In an addition reaction, new groups X and Y are added to a starting material. Ait bond is broken and two o bonds are formed. 

Eiimination is a reaction in which eiements of the starting materiai are iost and a jc bond is formed. 

To understand both organic and biological chemistry, it s necessary to know not just what occurs, but also why and how chemical reactions take place. In this chapter, we ll start with an overview of the fundamental kinds of organic reactions, we ll see why reactions occur, and we ll see how reactions can be described. Once this background is out of the way, we ll then be ready to begin studying the details of organic chemistry. 

Thomson W Click Organic Interactive to classify organic reactions by examining reactants and products. 

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Problem 29.8 Look at the entire glycolysis pathway and make a list of the kinds of organic reactions that take place—nucleophilic acyl substitutions, aldol reactions, ElcB reactions, and so forth. 

We can use these bromine compounds to illustrate one kind of organic reaction. Ethyl bromide is not particularly reactive but it does react with bases such as NaOH or NH3. If we mix ethyl bromide and aqueous sodium hydroxide solution and heat the mixture for an hour or so, we find that sodium bromide and ethanol are formed. 

As an aside, benzotrifluoride is a slightly polar, non-Lewis basic solvent that has favorable properties for many kinds of organic reactions. A. Ogawa, D. P. Curran, Benzotrifluoride A useful alternative solvent for organic reactions currently conducted in dichloro-methane and related solvents , J. Org Chem. 1997, 62, 450. 

What kind of organic reactions can be carried out on encapsulated guests ... 

We shall now explain all this in one section using frontier molecular orbitals. Of all the kinds of organic reactions, pericyclic ones are the most tightly controlled by orbitals, and the development of the ideas we are about to expound is one of the greatest triumphs of modern theoretical chemistry. It is a beautiful and satisfying set of ideas based on very simple principles. 

Ethylammonium nitrate (entry 18 in Table 3-1) was shown in 1914 to have m.p. 12 °C and was hence the first room temperature ionic Hquid [156] this was followed in 1967 by tetra- -hexylammonium benzoate with m.p. —50 °C (entry 26) [169], Ambient-temperature ionic liquids based on l-alkyl-3-methylimidazolium salts (entries 19-24) were first reported by Wilkes et al. in 1982 as tetrachloroaluminates [162a], Replacement of this moisture-sensitive anion by the tetrafluoroborate ion and other anions led, in 1992, to air- and water-stable, room temperature ionic liquids [162b], which have since found increasing application as reaction media for various kinds of organic reactions, mainly owing to the work of Seddon [167, 190] and Hussey [187], Suitably selected... 

Tetmalkylammoniurin salt.s. R4N X, are ii ed as catalysts for many different kinds of organic reactions. As an example, imagine an experiment in which cydobexene is dissolved in chlcrofonn and treated with aqueous... 

Having now learned how to write and identify some common kinds of organic reactions, we can turn to a discussion of reaction mechanism. 

Chapters 7-10 have introduced three basic kinds of organic reactions nucleophilic substitution, P elimination, and addition. In the process, many specific reagents have been discussed and the stereochemistry that results from many different mechanisms has been examined. How can we keep track of all the reactions ... 

What kind of organic reaction can form fluoromethane, CH3F, from methane ... 

The transfer of an inorganic ion such as OH from one phase to another is called phase transfer, and the tetraalkylammonium salt is referred t as a phase-transfer catalyst. Many different kinds of organic reactions, includ ing oxidations, reductions, carbonyl-group alkylations, and 8 2 reaction an subject to phase-transfer catalysis, often with considerable improvements ii yield. 8 2 reactions are particularly good candidates for phase-transfi-catalysis because inorganic nucleophiles can be transferred from an aqut ous (protic) phase to an organic (aprotic) phase, where they are much mort reactive. For example ... 

A Summary of the Kinds of Organic Reactions A Summary of Organic Reaction Mechanisms Problems 653... 

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