Draw the structure of the product formed in the reaction.

Draw the structure of the product formed in the following reaction.

Answer

General guidance

Concepts and reason
• A condensation reaction is a type of chemical reaction, which has a huge importance in organic synthesis. • The reaction undergoes the formation of a carbon-carbon double bond. An aldol condensation reaction is a type of condensation reaction in which two aldehydes have a α-hydrogen atom reacting with each other to form a product called aldol. • The first step is the aldol reaction in which the enolate ion formed then reacts with another molecule of the aldehyde. • The dehydration of product of an aldol reaction forms αβ-unsaturated carbonyl molecules (aldol). This is known as an aldol condensation reaction. • In a base catalyzed aldol reaction, the base deprotonates the acidic hydrogen on a α-carbon atom to form the enolate. • An enolate are good nucleophile and carbonyl is a good electrophile, so the enolate reacts with the carbonyl carbon of another aldehyde.

Fundamentals

The mechanism of an aldol condensation contains two steps. The first part is an aldol reaction; the second part is a dehydration elimination reaction. First, the base abstracts the proton to form a carbanion, and then it attacks the carbonyl group of another compound to form an oxy anion. This compound undergoes hydrolysis and forms an aldol, followed by dehydration which will give an aldol product. Mechanism:- OH
ha
base
RCHH
4
HzCR—C—H
H—ő—
—
—CHYR
RCH,
H.
enolate
B hydroxyl aldehyde
dehydration
H20 + 1—7—Ç=g—CHYR
aßunsaturated alde

Step-by-step

Step 1 of 3

Q-1220,
NaOH, ethanol
heat
enolate ion

Sodium hydroxide abstracts the acidic proton from an α-carbon atom of 2-phenylacetaldehyde to form the enolate and water as a byproduct. Hydroxide is not a good base to enolize an aldehyde, so the amount of enolate ion formed is less.

Step 2 of 3

:0
Ін
I
IO
3-hydroxy-2,4-diphenylbutanal

The enolate ion formed in the first step reacts with the 2-phenylacetaldehyde that is not enolized. Each enolate ion attacks the 2-phenylacetaldehyde to form 4-oxo-1,3-diphenylbutan-2-olate (alkoxide ion). This is then protonated by the water molecules formed in the first step. The product 3-hydroxyl-2,4-diphenylbutanal is called the aldol.

Step 3 of 3

I
-HO
Quay
3-hydroxy-2,4-diphenylbutanal
(E)-2,4-diphenylbut-2-enal

aux al
NaOH, ethanol
heat


Hydroxide formed from the sodium hydroxide again removes an acidic α-hydrogen bond to form the enolate ion of an aldol product. The negative charge on the carbon of an enolate ion is used to form the carbon-carbon double bond. This causes the displacement of the leaving group and regenerates hydroxide, giving 2, 4-diphenylbut-2-enal.

Answer

aux al
NaOH, ethanol
heat

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