Reagent Addition Results

Question 1

PBr₃ or PCl₃

Answer 1

Effect: Replaces an OH group with Br or Cl

Stereochemistry: Inverted from OH group’s

Solvent: H₂O

Mechanism: OH acts as a nucleophile attacking PBr₃ or PCl₃, Br or Cl acts as a LG. Then Br or Cl acts as nucleophile kicking out the HO-PBr₂ complex.

Question 2

Ammonia or an Amine (in presence of alkyl halide)

Answer 2

Effect: Replaces halide with a deprotonated amine

Stereochemistry: Inverted from halogen’s

Solvent: Any

Mechanism: Amine acts as a nucleophile attacking the carbon attached to the halide, kicking out the halide as a LG. A proton transfer follows to make the positively charged amine neutral again. The product (if extra hydrogens are available) can act as a nucleophile repeating the process with the excess alkyl halides.

Question 3

Alkyl Halide (in presence of aldehyde or ketone)

Answer 3

Effect: Akylates an alpha carbon

Stereochemistry: Inverted from halogen’s

Solvent: Strong Base (ex: NaOH)

Mechanism: Strong base deprotonates an alpha carbon, which acts as a nucleophile attacking the carbon attached to the alkyl halide, kicking out the halide as a LG.

Regioselectivity: LDA at Low temp → less substituted alpha carbon preferred. RO^- → more highly substituted alpha carbon preferred

Question 4

Molecular Halogen (in presence of aldehyde or ketone)

Answer 4

Effect: Replaces a alpha hydrogen with a halogen

Stereochemistry: Inverted from halogen’s

Solvent: Strong Base (e.g. NaOH) → every alpha carbon is halogenated. Acidic → One carbon is halogenated

Mechanism: Strong base performs a proton transfer on the alpha carbon. The deprotonated carbon then acts like a nucleophile attacking a halogen in a molecular halide, kicking out the other halogen atom as a LG

Question 5

Diazomethane (in presence of carboxylic acid)

Answer 5

Effect: Acidic H is replaced with a methyl group

Stereochemistry: Inverted from CH₂ group’s on diazomethane

Solvent: Any

Mechanism: Negatively charged carbon on Diazomethane acts as a nucleophile deprotonating the H on the OH group of carboxylic acid. The negatively charged O then acts as a nucleophile attacking the methyl group, kicking out N₂ as a LG

Question 6

RO^- (in presence of alkyl halide (includes intramolecularly)

Answer 6

Effect: Forms ethers (intermolecular → symmetric/asymmetric, but intramolecular → cyclic ether)

Stereochemistry: Inverted from the halogen’s

Solvent: Any

Mechanism: RO^- attacks the carbon attached to the halogen, kicking out the halogen as a LG

Question 7

Bases (in presence of epoxides)

Answer 7

Effect: base attaches to a carbon in the epoxide while opening it.

Stereochemistry: Inverted

Solvent: Basic or neutral

Mechanism: The base attacks the less substituted carbon on the epoxide ring, opening the ring. Solvent mediated proton transfer or acidic work up protonates the negatively charged oxygen

Question 8

Acid (in presence of epoxide)

Answer 8

Effect: Opens the epoxide and adds the conjugate base to the molecule

Stereochemistry: Inverted

Solvent: Acidic

Mechanism: The oxygen in the epoxide attacks the H on the acid, deprotonating the acid. The conjugate base then attacks the epoxide ring at the more substituted carbon, opening the ring

Question 9

Strong Base (in presence of Alkene)