Ethanol with halogenoalkanes

CH3CHICH3 + 2NH3 - CH3CH(NH3)CH3 + NH,I conditions heat excess of a concentrated solution of ammonia in ethanol with the halogenoalkane in a sealed tube. 

Nitriles can be prepared by the reaction of a halogenoalkane with KCN in aqueous ethanol. 

A primary carbon atom is attached to the functional group (-OH above) and also to at least two hydrogen atoms. Molecules with this arrangement are known as primary molecules. For example, ethanol is a primary alcohol, CH3CH2OH, while 1-chloropropane is a primary halogenoalkane, CH3CH2CH2CI. 

A close look at the nature of a nucleophile will emphasize that it shares common features with a Lewis hase (see Chapter 18). Indeed, a nucleophilic species can act as such a base if the reaction conditions are appropriate - it can remove a proton (H ion) from a halc enoalkane and thereby initiate an elimination reaction. In this type of reaction HX is eliminated from the halogenoalkane and an alkene is produced. It is essential to realize that, given the similarity of the reagents involved, the two processes of nucleophilic substitution and elimination are generally in competition with each other. If a primary halogenoalkane is reacted with aqueous alkali (OH (aq)) then the substitution reaction we have discussed earlier is favoured. However, if ethanolic alkali (OH (ethanol)) is used, then the elimination reaction is favoured. 

Nucleophilic substitution reactions are important in organic synthesis because the halogen atom on halogenoalkanes can be replaced by other functional groups. The reaction with potassium cyanide is a good illustration of this. The cyanide ion reacts to form a nitrile. For example, bromoethane reacts by an Sj42 mechanism with a solution of potassium cyanide in ethanol to form propanenitrile ... 

Sometimes in industry chemists need to make a new compound with one more carbon atom than the best available organic raw material (the starting compound). Therefore, if we can convert the starting compound to a halogenoalkane, we can then reflux with ethanolic KCN to make a nitrile. We now have an intermediate nitrile with the correct number of carbon atoms. 

If a halogenoalkane is heated with an excess of ammonia dissolved in ethanol under pressure, an amine is formed. 

Halogenoalkanes will also undergo elimination reactions when heated with ethanolic sodium hydroxide, forming alkenes. 

We also learnt in Chapter 16 (pages 219-220) about the formation of nitriles by reacting a halogenoalkane with the CN ion. To carry out the reaction, a solution of potassium cyanide, KCN, in ethanol is heated under reflux with the halogenoalkane ... 

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