Aldehyde and Ketone Reactions

How do you form a carbonyl?

oxidize an alcohol

what oxidizing agent will not over oxidize a primary alcohol?

Pyridinium Chlorochromate (PCC)

will not make 1° alcohol into carboxylic acid

oxidation of a primary alcohol

PCC: aldehyde

all other oxidizing agents: carboxylic acid

oxidation of secondary alcohol

ketone

oxidation of tertiary alcohol

NO REACTION

what are the reactive portions of a carbonyl?

1. have very acidic α protons (when proton removed, electrons can delocalize into pi system, addition reaction

2. electrophilic carbonyl carbon → nucleophile attack

Hydride reduction (ketone or aldehyde products, solvent)

NaBH₄ or LiAlH₄,

aldehyde→ primary alcohol

ketone→secondary alcohol

cannot form tertiary alcohol

how do you recognize nucleophilic addition reactions?

a pi bond is broken and two sigma bonds in product result

Organometallic Reagents purpose?

used for nucleophilic addition

Gringard and Lithium reagents.

Grignard formation

Important to form it and react it in aprotic solvent (basic) to prevent unwanted protonation

Grignard addition

need to do in steps.

form alkoxide intermediate than do acidic workup to protonate alcohol

important uses of Grignard reagents!

can form a tertiary alcohol (cannot do with hydride reduction)

What is the purpose of a protecting group?

To prevent unintended reactions, such as a gringard reacting with an alcohol or carboxylic acid or amino group. remove the reactive nature of protic groups.

What must you do with protic groups after reacting?

need to neutralize with HCL

Mesylate and Tosylates

1. good for protecting group

2. turn a bad LG (-OH) into a good leaving group to make easier for nucleophilic addition/substitution

acetals and hemiacetals: synthesis

synthesized via nucleophilic addition reaction to aldehydes and ketones.

form when aldehydes or ketones react with alcohols in presence of acid.

Acetal formation mechanism

**** ACID CATALYZED****

goes through step with hemiacetal

series of protonations and de-protonations

cyanohydrin formation

must have acid in order for -OH to be protonated to leave.

imine formation (what type of amine?)

acid catalyzed

pH around 5 (weakly acidic conditions)

**must be a primary amine reacting with carbonyl to form imine