up-down-kick carbonyl mechanism

Problem # 708

The overall mechanism for Fischer esterification is shown below. This isn't a real mechanism, just an outline.

Methanol (the nucleophile) attacks the carbonyl carbon, forming a tetrahedral intermediate, which then loses a water to reform the carbonyl. This mechanism is called nucleophilic acyl substitution.

 

Use curved arrows to draw a full mechanism for this reaction. I've included structures for you to use as a guide.

This reaction takes place under acidic conditions, so the mechanism you draw will be similar to those in problem 706.

Problem # 707

The overall mechanism for imine formation is shown below. (This isn't a real mechanism, just an outline)

 

Use curved arrows to draw the full mechanism for imine formation under acidic conditions. (I've added outlines of the intermediate structures for you to use as a guide). This mechanism is similar to that in problem 706 (carbonyl hydrate equilibria).

Problem # 706

Carbonyls are in equilibrium with their hydrate forms. This equilibrium happens in both acid and base.

Let's go through this equilibrium under acidic conditions. Draw a mechanism using curved arrows for each reaction below.

Remember that under acidic conditions, most species are either neutral or positively charged, and rarely negatively charged. So your structures will contain either ROH or ROH2+, but not RO-.

 

a) Carbonyl to Hydrate (acidic)

b) Hydrate to Carbonyl (acidic)

Problem # 705

Carbonyls are in equilibrium with their hydrate forms. This equilibrium happens in both acid and base.

Let's go through this equilibrium under basic conditions. Draw a mechanism using curved arrows for each reaction below.

Remember that under basic conditions, most species are either neutral or negatively charged, and rarely positively charged. So your structures will contain either ROH or RO-, but not ROH2+.

 

a) Carbonyl to Hydrate

Notice that no oxygen is ever positive during these basic mechanisms (always negative or neutral).

b) Hydrate to Carbonyl