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Organic Chemistry
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- making mono, di, and tri substituted alkenes. Tetrasubstituted products are difficult to prepare due to steric hindrance in the TS
- desulfurization, therefore we have an alternative to the Wolff-Kishner/Clemmenson reductions
- unstabilized (no resonance) reactants produces cis (Z) product favored (kinetic), stabilized forms trans, E product favored (thermodynamic)
- amine attacks carbonyl group, oxygen protonated to remove negative charge, deprotonation gives a carbinolamine (H taken from the N), OH group protonated into a good leaving group, water leaves, C=N double bond forms, intermediate deprotonated to generate enamine
- imine formation (Hydrazone), which can be reduced under strongly basic conditions (KOH/H2O)
- Hydrazine (N2H4) attacks a carbonyl via the imine formation mechanism shown earlier, forming a hydrazone which is structurally similar to an imine
- HCN is highly toxic, so KCN/HCl is typically employed. Nitriles are precursors to amines/carboxylic acids
- converts a carbonyl group into a new C=C double bond where no bond existed before
- must be acid catalyzed (protonation of the carbonyl group activates it such that it will react with the weak nucleophile, ROH)
- one of the protons is removed (resonance-stabilized intermediate), intermediate protonated, another proton removed, nitrogen gas expelled (carbanion), carbanion protonated
- nucleophilic attack on carbonyl carbon, proton transfer, asymmetric ketone gives chirality center (enantiomers)
- strong nucleophile attacks, then oxygen gets protonated, or oxygen gets protonated and then weak nucleophile attacks
- so that the less hindered end of the double bond comes from the ylide
- carbonyl carbon has a partial positive charge and will react as an electrophile; the oxygen atom has a partial negative charge and is nucleophilic
- acetals are hydrolyzed by addition of dilute acid. Excess water favors the formation of the ketone/aldehyde
- aldehyde carbon is number 1 (so no locant), if the aldehyde group attached to a ring, the suffix carbaldehyde is used
- Betaine formation, oxaphosphetane formation, oxaphosphetane collapses, forming carbonyl (ketone or aldehyde) and PPh3O
- the hydroxide ion (strong nucleophile) attacks the carbonyl group (electrophile). Protonation of the intermediate gives the hydrate
- for water (weak nucleophile) to attack, the carbonyl group must first be activated by protonation, deprotonation then gives the hydrate
- adding a nucleophile and H to the C=O, electrophilic C is sp2 and planar, so is attacked from top/bottom giving an sp3 carbon