Electrophilic Addition

Question 1

What reaction makes Alkane
What reaction makes Alkyl halide
Name reaction, what conduction need for it .

Answer 1

1) hydrogenation (add H2, with Pd\C)
2) addition of hydrogen halide

Question 2

What reaction makes alcohol
What reaction makes ether.
Name reaction, what condition you need for it .

Answer 2

1) acide-catalised hydration (H2SO4,H2O). Forms carbocation .
2) acid catalyses addition of alcohol (H2SO4,R-OH). Forms carbocation .

Question 3

What reaction makes alcohol (using B)
What reaction makes vicinal halide?.
Name reaction, what condition you need for it .

Answer 3

1)hydroboration-oxidation . (1.BH3, THF.2.H2O2,HO,H2O).
2) addition of halogens. (CH2Cl2)

Question 4

Explain Hydrogenation

Answer 4

+H2 (Pd/C). = alkane
Don’t need mechanism of intermediate .
It’s on metal, follow syn addition .
So, stereoselective.

Question 5

What is halohydrin

Answer 5

R+OH+X

Question 6

What reaction makes halohydrin ? What is halohydrine?
Name reaction, what condition you need for it .

Answer 6

Halohydrin formation . R +OH+X
(X2, H2O)

But If something else is used instead of H20, it will act as nucleophile in the second reaction . ex . CH3OH will create ether . Second halogen (NaCl) will add Cl instead of OH.

Question 7

Ragioselective

Answer 7

Several constitutional isomers are possible but one is formed.
1) check possible compounds formed. Sometimes it’s the same like with 2 butène and Jack. In this case it’s not ragioselective.
2) in case is 1-butène , 2 constitutional isomers can be formed but only one is formed(due to stability ) . It’s ragioselective .

All forming carbocations(markovnolov and antimarkovnolov rules ) are ragioselective.
For cyclic halonium ion reaction :
Yes for assymetrycal (halohydrin formation)
No for assymetrical (addition of halogens)

Question 8

Is it stereoselective.
What is stereoselective.

Answer 8

Two stereosimers (R and S) can be formed. But actually only one is formed.
When reagent without chiral center makes a product with one chiral center. The product is racemic mixture. (50/50) it is NOT stereoselective .

Question 9

Stereospecfic

Answer 9

Cis and trans version only form different products (R and S) enantiomers).
Those forming of halinium ion as intermediate . (Additional of halogens and halohydrin formation). Anti addition .
Cis form threo
Trans form erythro

Question 10

Stereoselective vs. Stereospecific

Answer 10

• Stereoselective:
The reaction prefers one stereoisomer over another, but both can form.
Think: “Preference.”
• Stereospecific:
The stereochemistry of the reactant determines the product — only one product forms from each specific stereoisomer.
Think: “Strict match.”

Quick Example:
• Stereoselective: Makes mostly R, some S.
• Stereospecific: R reactant gives S product (only).
Racemic mixture is not atereospecific

Question 11

Influence on stereoselectivity

Answer 11

1) 0 chiral centers > 1 chiral center. Racemic mixture. Not stereoselective if same substitutes , can be 1 meso
2) 1 chiral centers > 2 chiral centers .
Get 2 diastereisomers.
Stereospecofic and Stereoselective . Major one is not blocked by substitutes.
3) 0 chiral centers > 2 chiral senters. Depend on reaction
A) with carbocation formed as intermediate, 4 stereisomes
NOT stereoselective.
B) hydrogenation and hydroboration SYN edition
C) reaction that involve cyclic bromonium and chromonium,
Anti addition

Syn
Cis form erithro
Trans from threo

Anti addition
The contrary