05 Aldehydes and Ketones: Nucleophilic Addition Free Online FlashCards

Why is the carbonyl carbon electrophilic?

The bond is polarized: oxygen is partially negative, while the carbonyl carbon is partially positive and electrophilic.

What happens when a nucleophile attacks a carbonyl?

The nucleophile attacks the carbonyl carbon, and the C=O π electrons move onto oxygen, forming a tetrahedral alkoxide intermediate.

What does a Grignard reagent contribute to a carbonyl addition?

Its carbon acts as a nucleophile and bonds to the carbonyl carbon, creating a new carbon–carbon bond.

What class of alcohol forms when a Grignard reagent adds to formaldehyde?

After workup, formaldehyde gives a primary alcohol.

Why is acidic workup added only after organometallic addition?

Water or acid would quench the organometallic reagent. Keep the reaction anhydrous, then add water or dilute acid during workup.

What product forms when a primary amine reacts with a carbonyl?

A primary amine reacts reversibly with an aldehyde or ketone to form an imine and water.

Why is imine formation commonly carried out under mildly acidic conditions?

Mild acid helps convert the hydroxyl group into water, which can leave. Strong acid protonates the amine and reduces its nucleophilicity.

What product generally forms when a secondary amine reacts with a carbonyl?

A secondary amine generally forms an enamine when an α-hydrogen is available; the product has a C=C bond next to nitrogen.

Why are aldehydes generally more reactive than ketones?

Aldehydes are generally more reactive because they are less crowded and have fewer electron-donating alkyl groups.

How does magnesium assist a Grignard addition?

Magnesium coordinates to the carbonyl oxygen, helping activate the carbonyl for attack by the reagent’s carbon.

What class of alcohol forms from a Grignard addition to an aldehyde other than formaldehyde?

After workup, another aldehyde gives a secondary alcohol.

What class of alcohol forms from a Grignard addition to a ketone?

After workup, a ketone gives a tertiary alcohol.