7.5 Esters

• carboxylic acid derivatives are more reactive than esters.

• We can make acid halides using thionyl chloride.

• The carboxylic acid is first converted into an acid halide.

• Let's see what we can do to make this happen.
• If we try to make the nucleophilic, what will happen?

• carboxylic acids and alkoxide ion have strong bases.

• An ester wouldn't be produced again.

• We can try one more thing.
• We can try to make the electrophilic instead of the nucleophilic.

• The function of the acid is catalytic because it is not consumed during the reaction.

• The accepted mechanism for this reaction is a staple of any organic chemistry course, so let's explore it step-by-step.

• The mechanism has six steps, but there are only two core steps: attack and re-form.

• There are three moments at which the transfer steps occur.

• Two transfer steps are required.
• It wouldn't be appropriate to simply deprotonating the OH group without first deprotonating the OR group, because that would give an intermediate with two positive charges.
• We first deprotonate to remove the positive charge and then give the OH group a good leaving group.

• The reaction is called a Fischer esterification.
• The position of equilibrium can be affected by starting materials and products.

• We are going to spend some time on the reverse process.

• The reaction between a carboxylic acid and an alcohol is called a Fischer esterification.
• If a compound contains both functional groups, it is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556

• There is a COOH group and an OH group in this compound.

• The rest of the mechanism is similar to what we have already seen.
• The mechanism has two core steps, an attack and re-form.

• The first thing we need to do is make a carboxylic acid and alcohol.

We need acid catalysis, savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay savesay

• Now that we know how to make esters, let's focus on the reactions.
• We will look at two reactions in particular.

• Theacidic conditions should be familiar to you.
• The reverse of a Fischer esterification is what this reaction is about.

• We see the same pattern again and again.
• Look closely at the mechanism.
• The first two steps are attack and re-form.

• The only other steps in the mechanism are the ones that facilitate the reaction.
• One transfer is required in the beginning, two in the middle, and one at the end to deprotonate the carbonyl group.

• Under basic conditions, it is possible to hydrolyze an ester.

• We have two core steps, followed by a deprotonation.
• Under these conditions, the transfer of protons at the end is unavoidable.
• A carboxylic acid will be deprotonated.

• The formation of a carboxylate ion serves as a driving force.

• Basic conditions are used to hydrolyze an ester.

• Under strongly basic conditions, we just produced a carboxylic acid.

• We are starting with an acidic substance.
• The ester will be converted into a carboxylic acid and alcohol.