Mechanisms

Question 1

Hydroboration-oxidation (BH₃)

Answer 1

stereo- Syn

OH(takes place of B)- anti-markovnikov

• concerted transition state
• oxidation (NaOH/H₂O₂)= removal of Br and replace with OH

Question 2

Hydrogenation (catalytic) (H₂)

Answer 2

Stereo-Syn

Regio- doesn’t matter b/c adding same thing to both sides

Question 3

Hydration (acid catalyzed)

Answer 3

H_3O converts to water which breaks double bond, forming carbocation. Water bonds to carbocation. Another water comes and steals H creating OH.

Stereo- both syn and anti

Regio- OH= markovnikov

Question 4

Halogenation (Br₂, etc.)

Answer 4

Forms bromonium ion from double bond. Other bromine attacks from backside to break triangle.

Stereo- anti

Regio- First Br= anti-markovnikov

Question 5

Oxymercuration-reduction

Answer 5

Stereo- anti

Regio- Hg(later H) = anti-markovnikov

Question 6

HBr addition (no solvent)

Answer 6

stero- both syn and anti

regio- Br = markovnikove

carbocation mechanism

Question 7

HBr (in peroxides- Free-radical addition)

Answer 7

stereo- both syn and anti

regio- Br = anti- markovnikov

• peroxide forms radicals, steals H from Hbr which makes Br radical
• Br radical attacks double bond, going less substituted
• Free radical carbo cation steals H from another HBr

Question 8

Ozonolysis

Answer 8

• Ozone attacks double bond forming malozonide (3 Os on top)
• malozonide rearranges (starts at c-c bond) to ozonide (2 top, 1 below)
• Malozonide with Me₂S (DMS) gives normal products (DMS taking one oxygen to become DMSO)
• Malozonide with (H₂O₂/H₂O) forms carboxylic acids by replacing H with OH

Question 9

Halohydrin formation (Br₂ in H₂O)

Answer 9

stereo- anti

regio- OH= markovnikov

Water backside attacks the bromonium ion, taking the spot that to other Br would have gone (but markovnikov)

Question 10

Formation of grignard reagents

Answer 10

• Mg Switches places with a halogen attached to an alkyl group so that the order is: alkyl group–mg–halogen

Question 11

Formation of Organolithium

Answer 11

Li displaces a halogen attached to an alkyl group so that you end up with: R-Li and Li-halogen

Question 12

Reactions with organometallic

Answer 12

Alkyl group steals H from water, Mg-halogen group or Li left with + charge, OH- left.

Question 13

H+ reaction

Answer 13

• Will react like acid/base reaction
• can cause carbocation shifts

Question 14

Free radical halogenation (in presence of light/heat)

Answer 14

• light split Cl_2, forming radicals
• Cl radical attacks H on H-R, forming R radical
• R radical attacks another Cl₂
• Two Cl radicals recombine to end cycle