As we will see in Chapter 15, the carbonyl group of...

As we will see in Chapter $15,$ the carbonyl group of aldehydes and ketones reacts with water to form a compound called a hydrate. The hydration of a carbonyl group is catalyzed by acid. Formaldehyde, for example, reacts as shown below. When dissolved in water, formaldehyde exists almost entirely as its hydrate. This aqueous solution is given the name formalin. The mechanism for this acid-catalyzed hydration is similar to the mechanism for the acid-catalyzed hydration of an alkene to give an alcohol and occurs by the following three steps. Step 1: Add a proton. Step 2: Make a new covalent bond between an electrophile (an electron-seeking species) and a nucleophile (an electron-donating species). Step 3: Take a proton away. Write an equation for each step and show by the use of curved arrows how each of these steps occurs. Show all bond-forming steps and bond-breaking steps.

As we will see in Chapter $15,$ the carbonyl group of aldehydes and ketones reacts with water to form a compound called a hydrate. The hydration of a carbonyl group is catalyzed by acid. Formaldehyde, for example, reacts as shown below. When dissolved in water, formaldehyde exists almost entirely as its hydrate. This aqueous solution is given the name formalin.
The mechanism for this acid-catalyzed hydration is similar to the mechanism for the acid-catalyzed hydration of an alkene to give an alcohol and occurs by the following three steps. Step 1: Add a proton. Step 2: Make a new covalent bond between an electrophile (an electron-seeking species) and a nucleophile (an electron-donating species). Step 3: Take a proton away. Write an equation for each step and show by the use of curved arrows how each of these steps occurs. Show all bond-forming steps and bond-breaking steps.

Key Concepts

Carbonyl Group Reactivity

Carbonyl compounds, such as aldehydes and ketones, contain a highly polarized carbon-oxygen double bond that renders the carbon electrophilic. This electrophilicity makes the carbonyl carbon susceptible to attack by nucleophiles. The reactivity of the carbonyl group is central to many organic transformations, including hydration, where the addition of water occurs.

Acid Catalysis

Acid catalysis involves the addition of a proton (H?) to a substrate, which in many organic reactions serves to increase the electrophilicity of a functional group or stabilize an intermediate. In the hydration of carbonyl compounds, the protonation of the oxygen increases the electrophilicity of the carbon, thereby facilitating the subsequent nucleophilic attack by water.

Nucleophilic Addition Reaction

Nucleophilic addition is a fundamental type of reaction in organic chemistry where a nucleophile, an electron-rich species, attacks an electrophilic center. In the context of hydrated carbonyl compounds, water acts as the nucleophile and attacks the protonated carbonyl carbon, forming a new covalent bond and leading to an intermediate that will eventually lose a proton.

Electrophile and Nucleophile Concepts

Electrophiles are electron-deficient species that seek electrons, while nucleophiles are electron-rich species that donate electrons. This interplay of electron flow underlies mechanisms such as the acid-catalyzed hydration of carbonyls, where a protonated carbonyl group (electrophile) is attacked by water (nucleophile).

Mechanistic Steps in Acid-Catalyzed Reactions

The acid-catalyzed hydration follows a three-step mechanism: protonation of the oxygen to activate the carbonyl group, nucleophilic attack by the water to form a new bond with the electrophilic carbon, and finally a deprotonation step where the excess proton is removed to yield a neutral hydrate. This stepwise process highlights the importance of both the protonation and deprotonation events in driving the reaction forward.

Transcript

00:01 In this video, we're going to be going over carbonyl chemistry, specifically how we convert a compound with a carbonyl group to a hydrate.

00:11 So these reactions are very common.

00:14 But before i begin, let me first go over what a carbonyl group it really is.

00:18 So a carbonyl is a carbon that is double bonded to an oxygen.

00:23 The important thing we have to remember is because of the difference in electronegativities, oxygen being a lot more electronegative than carbon.

00:31 We're going to have a intrinsic polarity in which carbon is partially positive, whereas oxygen is partially negative because it holds onto these electrons tighter, and it hogs them.

00:47 And so in light of this knowledge, let's go over this reaction.

00:52 So i'm converting formaldehyde, which is the most simple aldehyde to its hydrate in the presence of water as well as an acid.

01:03 Catalyst.

01:04 So this reaction occurs in three main steps.

01:07 First, we're going to protonate the carbonyl oxygen.

01:15 Then we're going to form a covalent bond between a nucleophile, as well as an electrophilic region within this formaldehyde.

01:30 And then we're going to deprotonate water at the end.

01:38 And this will be more clear as i draw this mechanism.

01:41 So first, let's draw formaldehyde again...