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Questions and Answers
What is the main role of LiAlH4 in the reduction of amides to amines?
What is the main role of LiAlH4 in the reduction of amides to amines?
Which type of product is predominantly obtained when reducing equatorial alcohols using LiAlH4?
Which type of product is predominantly obtained when reducing equatorial alcohols using LiAlH4?
In the reduction reactions involving LiAlH4, how does stereoselectivity manifest?
In the reduction reactions involving LiAlH4, how does stereoselectivity manifest?
What is the primary function of AlH3 in the reduction process depicted?
What is the primary function of AlH3 in the reduction process depicted?
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What characteristic distinguishes unhindered ketones in their reaction with LiAlH4?
What characteristic distinguishes unhindered ketones in their reaction with LiAlH4?
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Which reagent is preferred for the selective reduction of aldehydes and ketones without affecting esters or amides?
Which reagent is preferred for the selective reduction of aldehydes and ketones without affecting esters or amides?
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What is the major stereochemical outcome when reducing a carbonyl compound using NaBH4 in the presence of a chiral environment?
What is the major stereochemical outcome when reducing a carbonyl compound using NaBH4 in the presence of a chiral environment?
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In the presence of sodium borohydride and calcium chloride, what type of functional group reduction can occur selectively?
In the presence of sodium borohydride and calcium chloride, what type of functional group reduction can occur selectively?
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When sodium borohydride is reacted in ethanol, what is the outcome for the reduction of carbonyls?
When sodium borohydride is reacted in ethanol, what is the outcome for the reduction of carbonyls?
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What is the observed ratio of products when NaBH4 is used to reduce a specific compound compared to NaBH4 in the presence of CeCl3?
What is the observed ratio of products when NaBH4 is used to reduce a specific compound compared to NaBH4 in the presence of CeCl3?
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Study Notes
Reduction Using Lithium Aluminium Hydride (LiAlH4)
- LiAlH4 is a strong reducing agent effective in reducing amides to amines.
- Reduction reaction involves the conversion of amides (RCONR2) to amines (RNH2) with the help of LiAlH4.
- Stereoselectivity results in a mixture of products; unhindered ketones react more readily under LiAlH4.
Chemoselectivity of LiAlH4
- LiAlH4 can differentiate between functional groups; it reduces ketones and aldehydes significantly.
- The reaction ratios indicate selective formation, with different ratios observed for various substrates (example: 72:28 and 20:80 on different products).
Sodium Borohydride (NaBH4)
- NaBH4 displays greater chemoselectivity than LiAlH4.
- Predominantly reduces aldehydes and ketones while showing little reaction with esters and amides.
- Reaction conditions (EtOH at -15ºC) influence the reduction efficiency and selectivity.
Stereoselectivity with NaBH4
- Reaction conditions can lead to differing stereochemical outcomes. For instance, reactions can yield syn and anti isomers in defined ratios.
- Variations in temperature and solvents can shift selectivity significantly, affecting the overall product distribution.
Sodium Cyanoborohydride (NaBH3CN) and Sodium Triacetoxyborohydride (NaBH(OAc)3)
- NaBH3CN is a selective reducing agent with a notable ability to reduce carbonyl compounds while leaving aldehydes and ketones untouched at neutral pH.
- However, when the pH is adjusted to 3-4, reduction occurs efficiently.
Reductive Amination
- Iminium groups formed in acid media can be more readily reduced than carbonyls.
- This principle can be utilized in synthesizing amines via reductive amination using primary or secondary amines.
Borane and Derivatives
- Borane effectively reduces various functional groups such as carboxylic acids (RCOOH) and plays a significant role in organic synthesis.
- Specific outcomes depend on the functional group involved, illustrating a diverse reactivity profile with different carbonyl compounds.
Key Functional Group Reductions
- Common reductions include:
- Aldehyde (RCHO) to alcohol (RCH2OH)
- Ketones (R2C=O) to alcohols (RCH(OH)R)
- Nitriles (RCN) to amines (RNH2)
- Some functional groups, such as carboxylic acids, may reduce to alcohols while others (like acid chlorides and nitro compounds) remain unaffected.
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Description
Explore the reactions involving Lithium Aluminum Hydride (LiAlH4) and its applications in organic chemistry. This quiz covers key concepts related to reduction reactions and functional group transformations. Test your understanding of reaction mechanisms and product formation.
