Clemmensen Reduction / NaBH4 & LiAlH4 / Acidity of a-hydrogens / a-halogenation
Clemmensen
reduction is a chemical reaction described as a reduction of ketones (or
aldehydes) to alkanes using zinc amalgam and concentrated hydrochloric acid.
This reaction is named after Erik Christian Clemmensen, a
Danish chemist.
NaBH4 & LiAlH4 reduction. The most common sources of the hydride nucleophile are lithium aluminium hydride (LiAlH4) and sodium borohydride (NaBH4). Note! The hydride anion is not present during this reaction; rather, these reagents serve as a source of hydride due to the presence of a polar metal-hydrogen bond. Because aluminium is less electronegative than boron, the Al-H bond in LiAlH4 is more polar, thereby, making LiAlH4 a stronger reducing agent.
Acidity of a-hydrogens.
Why are the alpha hydrogens of aldehydes and ketones so acidic?
Due to the acidic property of α-hydrogen in aldehydes and ketones, the compounds undergo different types of reactions. The acidic property of α-hydrogen in aldehydes and ketones is because of the high electron-withdrawing capacity of the carbonyl group and resonance stabilization of the conjugate base
a-halogenation of saturated aldehydes and ketones usually occurs exclusively by replacement of hydrogens alpha to the carbonyl group: The reagents that commonly are used to halogenate carbonyl compounds are those that are used to halogenate alkanes (e.g. Cl2, Br2, SO2Cl2, and N-bromoamides
NaBH4 & LiAlH4 reduction. The most common sources of the hydride nucleophile are lithium aluminium hydride (LiAlH4) and sodium borohydride (NaBH4). Note! The hydride anion is not present during this reaction; rather, these reagents serve as a source of hydride due to the presence of a polar metal-hydrogen bond. Because aluminium is less electronegative than boron, the Al-H bond in LiAlH4 is more polar, thereby, making LiAlH4 a stronger reducing agent.
Acidity of a-hydrogens.
Why are the alpha hydrogens of aldehydes and ketones so acidic?
Due to the acidic property of α-hydrogen in aldehydes and ketones, the compounds undergo different types of reactions. The acidic property of α-hydrogen in aldehydes and ketones is because of the high electron-withdrawing capacity of the carbonyl group and resonance stabilization of the conjugate base
a-halogenation of saturated aldehydes and ketones usually occurs exclusively by replacement of hydrogens alpha to the carbonyl group: The reagents that commonly are used to halogenate carbonyl compounds are those that are used to halogenate alkanes (e.g. Cl2, Br2, SO2Cl2, and N-bromoamides
Ulasan
Catat Ulasan