L3 Carbonyl reductions with borohydrides Flashcards
What are the two reagents of choice for reduction of carbonyls into aldehydes and ketones?
NaBH4
LiAlH4
What are the features of sodium borohydride?
Safe
Easy to handle
Mild
What are the features of lithium aluminium hydride?
Powerful
Potentially hazardous
What is the issue with using NaBH4 as your reducing agent?
The preparations involve aqueous work up
How does the borohydride interact with the carbonyl?
The electrons in the B-H sigma bond have good overlap with the carbonyl pi* bond
They are energetically well matched
In theory, how many nucleophilic hydride ions can NaBH4 donate?
4
What conditions are required for NaBH4 reduction?
1) NaBH4/EtOH
2) H3O+
As LiAlH4 is more reactive than NaBH4, what other compounds can it reduce?
Less reactive carbonyl compounds such as esters or amides
What will LiAlH4 reduce an ester to?
An alcohol
What will LiAlH4 reduce an amide to?
Amine
Why is LiAlH4 dangerous?
It reacts with H2O to product H2 and heat, so anhydrous, dry organic solvents are needed
What solvents are needed tor LiAlH4 reduction?
Et2O or THF
Dry
