Chapter 8 - More Molecules

Question 1

Hydrohalogenation (HBr, HCl, or HI)

Answer 1

Reaction Type: Electrophilic addition.
Regioselectivity: Markovnikov addition (halogen adds to the more substituted carbon).
Effect on Structure: Adds hydrogen and a halogen (X = Br, Cl, or I) across the double bond.
Anti-Markovnikov Addition: Achieved if ROOR (peroxides) are present, leading to radical mechanism.

Question 2

Acid-Catalyzed Hydration (H2O, H2SO4)

Answer 2

Reaction Type: Electrophilic addition.
Regioselectivity: Markovnikov addition (OH group adds to the more substituted carbon).
Effect on Structure: Adds H and OH across the double bond to form an alcohol.

Carbocation intermediates may lead to rearrangements.

Question 3

Oxymercuration-Demercuration (Hg(OAc)2, H2O / NaBH4)

Answer 3

Reaction Type: Addition reaction.
Regioselectivity: Markovnikov addition.
Effect on Structure: Adds H and OH across the double bond to form an alcohol without carbocation rearrangements.

Preferred when carbocation rearrangements are undesirable.

Question 4

Hydroboration-Oxidation (BH3∙THF / H2O2, NaOH)

Answer 4

Reaction Type: Addition reaction.
Regioselectivity: Anti-Markovnikov (OH group adds to the less substituted carbon).
Stereoselectivity: Syn addition (H and OH added on the same face of the alkene).
Effect on Structure: Produces alcohols from alkenes.

Question 5

Catalytic Hydrogenation (H2 / Pd, Pt, or Ni)

Answer 5

Reaction Type: Reduction.
Stereoselectivity: Syn addition (hydrogen atoms add to the same face of the alkene).
Effect on Structure: Converts alkenes to alkanes by saturating the double bond.

Question 6

Halogenation (Br2 or Cl2 in CCl4)

Answer 6

Reaction Type: Electrophilic addition.
Stereoselectivity: Anti addition (halogen atoms add to opposite faces of the alkene).
Effect on Structure: Produces vicinal dihalides.

Reaction proceeds via a halonium ion intermediate.

Question 7

Halohydrin Formation (Br2 or Cl2 in H2O)

Answer 7

Reaction Type: Electrophilic addition.
Regioselectivity: OH group adds to the more substituted carbon, halogen to the less substituted carbon.
Stereoselectivity: Anti addition.
Effect on Structure: Produces halohydrins (compounds with an -OH group and a halogen).

Question 8

Anti Dihydroxylation (RCO3H / H3O+)

Answer 8

Reaction Type: Oxidation.
Effect on Structure: Converts alkenes to 1,2-diols (two -OH groups) with anti addition.
Intermediate: Involves an epoxide that is opened by water.

Question 9

Syn Dihydroxylation (OsO4 / NaHSO3)

Answer 9

Reaction Type: Oxidation.
Effect on Structure: Converts alkenes to 1,2-diols (two -OH groups) with syn addition.

Alternative Reagent: KMnO4 (cold, dilute).

Question 10

Oxidative Cleavage (O3 / DMS or Zn/H2O)

Answer 10

Reaction Type: Ozonolysis.
Effect on Structure: Breaks double bonds to form carbonyl compounds (aldehydes or ketones).

Can identify the position of double bonds in complex alkenes.

Question 11

Oxidative Cleavage (KMnO4, hot, concentrated)

Answer 11

Reaction Type: Oxidation.
Effect on Structure: Breaks double bonds to form carboxylic acids (if hydrogen is present on the double-bonded carbon) or ketones.