Nucleophilic substitution reactions of alkyl halides

Prelab Exercise Predict the outcomes of the two sets of experiments to be carried out with the eight halides used in the present experiment. 

In free radical reactions the covalent bond undergoes homolysis when it breaks 

A carbocation is often formed as a reactive intermediate in these reactions. This carbocation is sp hybridized and trigonal-planar in structure with a 

The alkyl (R) groups stabilize the positive charge of the carbocation by displacing or releasing electrons toward the positive charge. Delocalization of the chcu-ge over several atoms stabilizes the charge. 

Many organic reactions occur when a nucleophile (a species with an unshared pair of electrons) reacts with an alkyl halide to replace the halogen with the nucleophile. 

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Nucleophilic substitution reactions of alkyl halides are related to elimination reactions m that the halogen acts as a leaving group on carbon and is lost as an anion The... 

Representative Functional Group Transformations by Nucleophilic Substitution Reactions of Alkyl Halides... 

Alkylamines are, in principle, capable of being prepared by nucleophilic substitution reactions of alkyl halides with ammonia. 

How- does this reaction take place Although it appears superficially similar to the SN1 and S 2 nucleophilic substitution reactions of alkyl halides discussed in Chapter 11, it must be different because aryl halides are inert to both SN1 and Sj 2 conditions. S l reactions don t occur wdth aryl halides because dissociation of the halide is energetically unfavorable due to tire instability of the potential aryl cation product. S]sj2 reactions don t occur with aryl halides because the halo-substituted carbon of the aromatic ring is sterically shielded from backside approach. For a nucleophile to react with an aryl halide, it would have to approach directly through the aromatic ring and invert the stereochemistry of the aromatic ring carbon—a geometric impossibility. 

Ju and Varma envisioned that the nucleophilic substitution reaction of alkyl halides with amines may be accelerated by microwave energy because of their polar nature [88]. An environmentally friendly synthesis of tertiary amines via direct JV-alkylation of primary and secondary amines by alkyl halides under microwave irradiation was developed (Scheme 21), that pro-... 

The chemistry of amines is dominated by the nucleophilicity of the nitrogen atom. Amines form salts, participate in nucleophilic substitution reactions of alkyl halides and in nucleophilic addition reactions to carbonyl compounds. 

When substitution or elimination reactions are used in synthesis, care must be taken to choose reactants and reaction conditions that will maximize the yield of the desired product. In Section 10.4, you saw that nucleophilic substitution reactions of alkyl halides can lead to a wide variety of orgaiuc compounds. For example, ethers are synthesized by the reaction of an alkyl halide with an alkoxide ion. This reaction, discovered by Alexander Williamson in 1850, is still considered one of the best ways to synthesize an ether. 

Nitriles can also be prepared by nucleophilic substitution reactions of alkyl halides with sodium cyanide. Hydrolysis of the nitrile yields a carboxylic acid with a chain one carbon atom longer than the original alkyl halide ... 

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