Electrophilic Addition

Question 1

Stereochemistry in the hydroboration-oxidation sequence

Answer 1

Anti-markovnikov/syn addition of water (and Hydrogen) to a double bond

Question 2

CHCl3 + Strong Base

Answer 2

Forms trihalomethyl anion - which then loses a Cl to give a neutral carbene

Question 3

Alkene + Br2 (non-nucleophilic solvent)

Answer 3

Forms dibromide, with the 2 Br anti to each other

Question 4

Conjugated Diene + Br2

Answer 4

Will form the 1-2 or 1-4 product.

Question 5

Alkene’s + peroxyacids (MCPBA or peroxyacetic acid)

Answer 5

• Three membered cyclic ethers (epoxides) are formed.

- The stereochemistry of the alkene is maintained in the epoxide.

Question 6

Stereochemistry in Diels-Alder products

Answer 6

• The products retain stereochemistry of the dienophile (cis/trans)
• bulky groups tend to be endo (trans to the one carbon atom bridge) when carbon bridges are formed.

Question 7

Under which set of conditions are Diels-Alder reactions best carried out?

Answer 7

heating in hexane

Question 8

Alkene + Br2 (in alcohol)

Answer 8

Forms a Bromine ring, then the alcohol attacks this ring on the more positive side (attacks more substituted side)