13.8 Reactions of Alcohols: Substitution and Elimination

• We will focus on the reactions of alcohols now that we know how to make them.

• We have already seen substitution and elimination.
• Let's start our review with elimination reactions.
• There are two types of elimination reactions: E1 and E2.

• In this reaction, acidic conditions are used to convert the OH group into an excellent leaving group.
• For a review of this mechanism, see Chapter 10.
• The E1 mechanism involves an intermediate carbocation, so it works well with a tertiary alcohol.

• We can't use an E1 reaction on primary alcohols.
• We use an E2 reaction.
• OH is still a terrible leaving group.
• The problem was solved in an E1 reaction with the OH group.
• We will need to convert the OH group into a better leaving group in an E2 reaction.
• The strongly basic conditions that are required in order to perform an E2 process are incompatible with the use of a protons source.

• It was used to favor elimination over substitution.
• We can use either an E1 process or an E2 process to convert alcohol into alkene.

• The OH group is not a good leaving group if we want to perform a substitution reaction with an alcohol.
• The OH needs to be converted into a better leaving group.
• There are many ways to do that.

• An S 1 process can be used with tertiary alcohol.

• A carbocation would be too unstable to form in this reaction.
• After converting the OH group into a better leaving group, the leaving group is expelled when the nucleophile attacks.

• The reaction works well with HBr, but it doesn't work well with HCl.
• Chloride is less polarizable than bromide.
• chloride is not as nucleophilic as bromide.

• A substitution reaction can be done by converting an OH group into a better leaving group.

• The first three steps convert a bad leaving group into a good leaving group.

• SO is produced as a side product.

• The reaction will be pushed to completion if the gas is free to leave.

• It might seem like a new reaction.

• N reaction where the OH group is converted into a better leaving group and then chloride functions as the nucleophile.
• This reaction is the same as converting the OH group into a tosylate and then attacking with chloride.

• We are looking at the reactions of alcohols.
• The details of familiar reactions have been the focus of this section so far.

• We must perform an elimination reaction to form an alkene.
• Specific regiochemistry is required to eliminate this problem.
• The less substituted alkene is called the Hofmann product.
• An OH group is a bad leaving group.
• The OH group needs to be converted into a better leaving group.