6. Ald/Ket I Flashcards
What happens if ald/ket react with water aka hydration rxn? Describe how they’re formed
geminal diols (1,1-diols)
1) H2O attacks carbonyl C –> carbonyl C single bonds w/ water, electroneg O and whatever R groups
2) electroneg O grabs H from bonded water –> carbonyl C is now singly bonded to 2 -OH’s and R groups
What happens if ald/ket react with alc and acid catalyst? Describe how they’re formed
hemiacetal/hemiketal
1) alc attacks carbonyl C –> carbonyl C single bonds w/ alc, electroneg O and whatever R groups
2) electroneg O grabs H from bonded alc –> carbonyl C is now singly bonded to -OH, -OR and R groups
What happens if hemiacetal/hemiketal react with alc and acid catalyst? What happens if ald/ket react with 2 alcs and acid catalyst? Describe mechanism
acetal/ketal. SN1 RXN
1) hemiacetal = protonated by acid catalyst —> C singly bonds with water, -OR, and 2 other R groups
2) water = good leaving group —> O from -OR makes 2x bond with C to kick out water (LOOKIE HERE IT’S A DEHYDRATION RXN)
3) alc attacks —> C singly bonds with alc, -OR, and 2 other R groups
4) bonded alc loses H by a base —> acetal
What happens if ald/ket react with primary amine vs secondary amine? What else do you need for this rxn to occur? What type of rxn is imine/enamine formation? Describe the mechanism
imine vs enamine; need an acid catalyst; dehydration
1) carbonyl O takes H from HA –> carbonyl C double bonds w/ OH
2) N from amine attacks carbonyl C –> carbonyl C single bonds w/ OH and amine
3) conjugate base takes H from amine
4) single bonded OH takes H from HA –> H2O on top
5) H2O = leaving group –> amine double bonds w/ ald/ket stem
6) conjugate base steals H from amine
What happens if ald/ket react with cyanohydrin?
1) CN- = nuc and the C backside attacks carbonyl C –> carbonyl C single bonds w/ electroneg O and CN
2) electroneg O steals H+ and becomes -OH
3) product: C single bonds w/ orig R groups, -OH at top and -CN at bottom
Describe mechanism for Strecker synthesis
1) ald/ket + ammonia in presence of H+ –> imine + H2O
2) imine + KCN in presence of H+ –> alpha amino nitrile
3) alpha amino nitrile + H3O+ –> alpha amino acid
Decarboxylation of beta keto acids result in what?
Keto/enol + CO2
Ald/ket with Grignard makes what?
Alc
Diols are common protecting groups for which functional groups?
Ald and ket
How do you know if a reagent will [O] -OH to ald/ket or CA intentionally?
If they really only want ald/ket, they will use a reagent specific for [O] to ald/ket. Otherwise, it’ll go straight to CA
Ald/ket + hydroxylamine vs hydrazine vs semicarbazide yields what?
Oximes (can also be made from quinone + hydroxylamine) vs hydrazone vs semicarbazones
Ald/ket reacts with diol to make what? What about reverse?
Acetals/ketals
Acetals/Ketals can be reverted back into ald/ket and diols by reacting with aq acid + heat => deprotection
How to convert ald/ket into alcs with NaBH4?
1) an H from BH4- attacks carbonyl C
2) carbonyl O and new H = single bond w/ carbonyl C
3) H2O or any H+ gets attacked by single carbonyl O
Order of increasing bpt b/w alcs, alkanes and ald/ket
alkanes < ald/ket < alcs
Hemiacetals/ketals = hard to isolate and tend to continue to acetal/ketals. Why?
Hemiacetals/ketals = unstable and hydroxyl group = rapidly protonated UNDER ACIDIC CONDITIONS (IE. EXCESS IN ACID —> straight to acetals/ketals)
