CHAPT 6.2: Nucleophilic addition Flashcards Preview

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Flashcards in CHAPT 6.2: Nucleophilic addition Deck (7)
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Reactions of carbonyl compound

1. reaction of the carbonyl carbon : the carbonyl carbon is electron deficient as it is bonded to a highly electronegative oxygen atom. Therefore it is susceptible to attack by nucleophiles such as hydride(H-) and cyanide (CN-)
2. reaction at the alpha carbon


general mechanism

step 1:
- formation of new pi bond between Nu and the electrophile C of the C=O grp
- breaking of the pi bond to o resulting in formation of alkoxide intermediate
step 2: protonation of the alkoxide intermediate to give alcohol derivative


most commonly used metal hydrides

sodium borohydride (NaBH4) and lithium aluminium hydride (LiAlH4) . they contain polar metal-hydrogen bonds that serves as a sources of H- nucleophiles.


compare sodium borohydride (NaBH4) and lithium aluminium hydride (LiAlH4)

LiAlH4 is a stronger reducing agent than NaBH4
NaBH4 selectively reduces aldehydes and ketones in the presence of most other functional groups.
LiAlH4 reduces aldehydes and ketones as well as many other functional groups like carboxylic acid , amides etc


addition of cyanide (carboanion)

- forms cyanohydrin product
- CN is a versatile functional group as it can be converted to -COOH and CH2NH2 ( carboxylic acid and amine)


reagents for formation of COOH



reagents for formation of amine (CH2NH2)

(1) LiAlH4
(2) H2O
or H2/Ni