Exam 2 - Orgo 2: Reagents

LiAlH4, then H2O

Reduces a ketone or aldehyde (C=O) to an alcohol. Ketone gives a secondary alcohol, aldehyde gives a primary alcohol.

H2, Pt

Reduces C=O to an alcohol. Also reduces C=C bonds first if present.

RMgBr (Grignard), then H3O+

Adds R to the carbonyl carbon, forming a new C-C bond. Ketone gives a tertiary alcohol, aldehyde gives a secondary alcohol.

RLi, then H3O+

Works like a Grignard: adds R to the carbonyl carbon to give an alcohol with a new C-C bond.

HCN

Adds to a ketone or aldehyde to make a cyanohydrin (carbon with OH and C≡N). CN- attacks the carbonyl carbon.

Ph3P=CHR (Wittig ylide)

Converts C=O into C=C, forming an alkene. Ph3P=O is the byproduct.

1 R'OH, H+

Adds to a ketone or aldehyde to make a hemiacetal (one OH and one OR on the same carbon).

2 R'OH, H+

Converts a ketone or aldehyde into an acetal (two OR groups on the same carbon, no OH).

Ethylene glycol, H+

Converts a ketone or aldehyde into a cyclic acetal with a 5-membered ring (1,3-dioxolane).

Propane-1,3-diol, H+

Converts a ketone or aldehyde into a cyclic acetal with a 6-membered ring (1,3-dioxane).

RNH2 (primary amine), H+

Converts a ketone or aldehyde into an imine (C=N).

R2NH (secondary amine), H+

Converts a ketone or aldehyde into an enamine (C=C-N). The nitrogen has no H to lose, so an alpha H is removed instead.

R-Br + Mg, ether

Makes the Grignard reagent, RMgBr. Reactivity is R-I > R-Br > R-Cl >> R-F.

R-Br + 2 Li, Et2O

Makes the organolithium reagent, RLi.

H3O+ (after a Grignard or LAH)

Workup step. Protonates the alkoxide (O-) to give the neutral alcohol.