Question

CHM 2210 Homework 14 "I have GOT to get me one of these!" C.1. What is the major organic product from the reaction of 2-methyl 2- butene with HBr? A. (S)-2-bromo-3-methyl butane Cz-bromo-2-methyl butane B. (R)-2-bromo-3-methyl butane D. racemic mix of A and B 2.2. What is the major organic product from the reaction of 2-methyl 2- butene with HBr in the presence of hydrogen peroxide? A. 2,3-dibromo-2-methyl butane B. (E)-1-bromo-2-methyl 2-butene C. 2-bromo-2-methyl butane 02-bromo-3-methyl butane 3. Show the mechanism for one reaction from the questions 1 and 2. 4. Briefly explain why a difference in the mechanisms in the reactions in questions 1 and 2 cause a change in the products. H2SO. + 5. What is the major organic product from the following reaction? OH OH OH D. OH OH Reference: 8.4 - 8.5 (348 359), 10.10 (464 - 468)
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Answer 1

1) The reaction follows markovnikov's addition , that is negative part of the reagent goes to the carbon containing least number of hydrogen atom.

CH3 СН2 CH3 – C=CH-CH3 + H By – CH3-C- CH2 - CH3 2-methyl-2- Butene 2-Bromo-2-methylbutane

so the major product is 2-Bromo-2-methyl butane.

2) This reaction follows anti Markovnikov's addition, here the negative part of the reagent goes to the carbon containing more number of hydrogen atoms.

CH3 CH3-C = CH-CH3 H₂ Oz - + H By 2 2-methyl-2- Butene CH3-C- CH - CH₂ H Br 2-Bromo - 3-methyl butane

3) Mechanism

Mechanism of Reaction (1) [Mar kounikov's addition] Hor V HBT → 2-methyl 2-Butene 2- bromo-2-methyl butane Mechanism of Reaction (2) Lanti- Markownikow's addition] HONOH be, 28H Hot H-By H0H+ Bå Br Bito - ty - + H By 2-Bromo-3-methyl butane

4) The first reaction acts as an ionic reagent and it is the Br- reacts with the double bond of the alkene.

The second reaction is a radical reaction. Hydrogen peroxide acts as the radical initiator.

The first reaction follows markovnikov's addition , that is negative part of the reagent goes to the carbon containing least number of hydrogen atom.

The second reaction follows anti Markovnikov's addition, here the negative part of the reagent goes to the carbon containing more number of hydrogen atoms.

5)

1 +420 H2SO4, r ton 3,3-dimethyl-1- butene 2,3-dimethyl-2-butanol