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Example of Cross Aldol Condensation:
Reaction between Benzaldehyde and Acetophenone: The reaction between benzaldehyde and acetophenone undergo cross aldol condensation in presence of dil. NaOH. In this reaction benzaldehyde have no alpha hydrogen but acetophenone have alpha hydrogen so its undergo aldol condensation form β-hydroxy ketone. Furthermore, dehydration leads to the formation of the α, β – unsaturated ketone.
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Crossed Aldol Condensation
The condensation reaction between two different molecules of an aldehyde or ketone in a protic solvent such as water or alcohol constitutes the crossed aldol reaction. When condensation is between two different carbonyl compounds, it is called crossed aldol condensation. When both aldehydes have alpha hydrogens, both can form carbanions and can also act as carbanion acceptors.…
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Mechanism of Aldol Condensation
Step-1: In reverse order, The hydroxide ion deprotonates the aldehyde. Step-2: Here Enolate ion 1 adds to the unreacted aldehyde. Step-3: Alkoxide ion 2 is protonated by water. Step-4: A small amount of aldol is converted into enolate ion (4) by hydroxide ion. Step-5: Here Enolate Ion(4) loses a hydroxide ion. Step 1 to step…
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Aldol Condensation Reaction
Aldol Condensation can be defined as an organic reaction in which enolate ion reacts with a carbonyl compound to form β-hydroxy ketone or β-hydroxy aldehyde, followed by dehydration to give a conjugated enone. Aldol Condensation plays a vital role in organic synthesis, creating a path to form carbon-carbon bonds. The general reaction of aldol condensation is General Aldol…
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Aldol Condensation
What is Aldol Condensation? Aldol condensation occurs in aldehydes having α-hydrogen with a dilute base to give β-hydroxy aldehydes called aldols. This reaction is most commonly known as aldol condensation. If the condensation reaction occurs between two different carbonyl compounds it is called crossed aldol condensation.
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FAQs
What does Markovnikov’s rule predict? Markovnikov’s rule predicts the regiochemistry of the reaction when a protic acid (usually denoted by HX) is added to an unsymmetrically substituted alkene. It predicts that the halide part of the protic acid preferentially attaches itself to highly substituted carbon atoms whereas the hydrogen component of the protic acid preferentially…
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Hydroboration/Oxidation of Alkenes
When alkenes are treated with borane (BH3) in the presence of hydrogen peroxide or sodium hydroxide, an alcohol is obtained as the final product. In this electrophilic addition reaction, the boron atom acts as an electrophile. This reaction does not obey Markovnikov’s rule and can, therefore, be classified as an anti-Markovnikov reaction.
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Examples
The Hydration of Alkenes When alkenes are treated with certain aqueous acids (usually sulfuric acid), the resulting electrophilic addition reaction yields an alcohol as the product. The regioselectivity of such reactions can be predicted by Markownikoff’s rule. Therefore, these reactions can be classified as Markovnikov reactions. In the hydration of alkenes, the H+ ion acts as an electrophile…
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What is the Mechanism Behind Markovnikov`s Rule?
To understand this mechanism, let us consider the same example illustrated earlier, i.e. the addition reaction of hydrobromic acid with propene. The Mechanism of Markovnikov’s rule can be broken down into the following two steps. Step 1 The alkene is protonated and it gives rise to the more stable carbocation as shown below. From the illustration…
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Markovnikov`s Rule
Markovnikov’s Rule, also known as Markownikoff’s rule, can be used to describe the outcome of some chemical addition reactions. The Russian chemist Vladimir Vasilyevich Markovnikov first formulated this rule in 1865. What is Markovnikov’s Rule? When a protic acid (HX) is added to an asymmetric alkene, the acidic hydrogen attaches itself to the carbon having a…
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