Preparation of Aldehydes from Nitriles and Esters (using DIBAL-H)
Nitriles and esters can be selectively reduced to aldehydes using diisobutylaluminium hydride (DIBAL-H).
What is Preparation of Aldehydes from Nitriles and Esters (using DIBAL-H)?
A bulky organoaluminium compound used as a reducing agent, particularly for selective reductions at low temperatures.
Key formula / rule: Reduction of Nitrile to Aldehyde
Key points
- To understand the selective reducing action of DIBAL-H on nitriles and esters.
- To be able to predict the products of DIBAL-H reduction of nitriles and esters followed by hydrolysis.
- To appreciate the importance of reaction conditions in controlling the outcome of reduction reactions.
- To differentiate DIBAL-H from other common reducing agents.
Common exam trap
Using DIBAL-H at room temperature, leading to over-reduction.
Definitions
- Term
Diisobutylaluminium hydride (DIBAL-H)
- Meaning
A bulky organoaluminium compound used as a reducing agent, particularly for selective reductions at low temperatures.
- Term
Selective Reduction
- Meaning
A reduction reaction that specifically reduces one functional group in the presence of others, or reduces a functional group to a specific oxidation state without further reduction.
- Term
Imine
- Meaning
A functional group with the structure R₂C=NR', where R is an organic group and R' can be hydrogen or an organic group.
- Term
Hemiacetal
- Meaning
A compound containing both a hydroxyl (-OH) group and an alkoxy (-OR) group attached to the same carbon atom.
Learning objectives
To understand the selective reducing action of DIBAL-H on nitriles and esters.
To be able to predict the products of DIBAL-H reduction of nitriles and esters followed by hydrolysis.
To appreciate the importance of reaction conditions in controlling the outcome of reduction reactions.
To differentiate DIBAL-H from other common reducing agents.
Formulae
- Name
Reduction of Nitrile to Aldehyde
- Note
Intermediate is an imine-aluminium complex.
- Expression
R-C≡N + DIBAL-H → [R-CH=N-Al(i-Bu)₂] → (H₃O⁺) → R-CHO
- Name
Reduction of Ester to Aldehyde
- Note
Intermediate is a hemiacetal-aluminium complex.
- Expression
R-COOR' + DIBAL-H → [R-CH(OAl(i-Bu)₂)OR'] → (H₃O⁺) → R-CHO
Prerequisites
Understanding of functional groups (nitriles, esters, aldehydes, amines, alcohols).
Knowledge of basic organic reaction mechanisms.
Familiarity with common reducing agents and their reactivity.
Understanding of reaction conditions like temperature and stoichiometry.
Common mistakes
Using DIBAL-H at room temperature, leading to over-reduction.
Incorrect stoichiometry of DIBAL-H.
Incomplete hydrolysis of the intermediate complex.
Confusing DIBAL-H with stronger reducing agents like LiAlH₄.
Keywords
DIBAL-H
Nitrile reduction
Ester reduction
Aldehyde synthesis
Selective reduction
Organoaluminium compounds
Low temperature reactions
Organic synthesis
NEETIM
HEMIACETAL
Practice preview
Consider the reaction: R-COOR' + DIBAL-H (low temp) -> Intermediate --(H2O)--> Product. What is the structure of the 'Product'?…
medium
A chemist wants to synthesize an aldehyde from an ester using DIBAL-H. They observe that the reaction produces a significant amount of the corresponding primary alcohol. Which of the following modifications would be MOST…
hard
Which of the following statements is INCORRECT regarding the use of DIBAL-H in organic synthesis?…
medium