Alkenes

Question 0

1. Hg(OAc)2, HOEt (alkoxymercuration)

2. NaBH4 (reduction)*

Answer 0

Alkene -> Ether

Notes: Mercurinium ion intermediate, prevents rearrangement, Mark product
opening these three membered rings depends on bond strength, NOT sterics - look at resonance and amt of substitution

Question 1

1. Hg(OAc)2, H2O (oxymercuration) 2. NaBH4 (reduction)*

Answer 1

Alkene -> Alcohol

Notes: Mercurinium ion intermediate, prevents rearrangement, Mark product
only large atoms like mercury can form these types of three membered rings - these mercury compounds are very nasty!

Question 2

1.BH3, THF (hydroboration)* 2.H2O2, NaOH (oxidation)

Answer 2

Alkene -> Alcohol

Notes: Anti-Mark Product, no rearrangement, intermediate exists as trialkylborane, O and H syn addition. Won Nobel Prize!

Question 3

HBr or HCl

Answer 3

Alkene -> Vicinal Hydride, Bromide

Notes: Equal parts syn and anti addition, carbocation intermediate

Question 4

H2, Pd/C

Answer 4

Alkene -> Vicinal Dihydride (Alkane)

Notes: Syn addition

Question 5

Br2 or Cl2

Answer 5

Alkene -> Vicinal Dihalide

Notes: Anti addition due to halonium ion intermediate, Mark Product

Question 6

Br2, excess H2O

Answer 6

Alkene -> Halohydrin (vicinal halide and alcohol)

Notes: Anti addition due to cyclic bromonium ion intermediate, Mark product

Question 7

H2O, H+ catalyst

Answer 7

Alkene -> Alcohol

Notes: Carbocation intermediate, watch for rearrangement, Mark product

Question 8

mCPBA

Answer 8

Alkene -> Epoxide

Notes: No added carbons - just epoxide where alkene used to be, the pKa of mCPBA is about 8

Question 9

Dichlorocarbene

Answer 9

Alkene -> Epoxide-esque product, CCl2 bonded to carbon chain

Question 10

Carbenoid H2C(I)(ZnI)

Answer 10

Alkene -> Epoxide-esque product

Notes: ZnI and I fall off, CH2 bonded to carbon chain

Question 11

1. O3

2. Me2S (or H2/Pd or Zn/H2O)

Answer 11

Alkene -> Ketone and Aldehyde

Notes: Split double bond down the middle, aldehyde goes on less substituted carbon

Question 12

1. O3

2. H2O2

Answer 12

Alkene -> Ketone and Carboxylic Acid

Notes: Split double bond down the middle, carboxylic acid goes on less substituted carbon (-H turns into -OH)

Question 13

1. KMnO4, KOH, heat

Answer 13

Alkene -> Ketone and Carboxylic Acid

Notes: MCAT ONLY!

Question 14

1. OsO4 2. NaHSO4, H2O

Answer 14

Alkene -> Syn Diol

Notes: syn addition of alcohols - OsO4 has 4 oxygens, each of which is double bonded to osmium, and forms a five member ring when reacted with an alkene. OsO4 is volitile, toxic, and turn whites of eyes black

Question 15

1. KMnO4 2. NaOH, H2O

Answer 15

Alkene -> Syn Diol

Notes: MCAT ONLY!