Skip to main content
Ch.8 - Reactions of Alkenes
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.8 - Reactions of AlkenesProblem 13b
Chapter 8, Problem 13b

Predict the major products of the following reactions. Include stereochemistry where applicable.
(b) trans-4,4-dimethylpent-2-ene + BH3⋅THF then H2O2, OH–

Verified step by step guidance
1
Step 1: Recognize the reaction type. The given reaction involves hydroboration-oxidation, which is a two-step process used to convert alkenes into alcohols. This reaction proceeds with anti-Markovnikov regioselectivity and syn addition of hydrogen and hydroxyl groups.
Step 2: Analyze the structure of the starting material. The starting alkene is trans-4,4-dimethylpent-2-ene. Note the trans configuration of the substituents around the double bond and the presence of bulky methyl groups at the 4th carbon.
Step 3: In the first step, BH3⋅THF reacts with the alkene. Boron adds to the less substituted carbon of the double bond (anti-Markovnikov addition), while hydrogen adds to the more substituted carbon. This occurs via syn addition, meaning both groups add to the same face of the double bond.
Step 4: In the second step, the boron group is replaced by a hydroxyl group through oxidation using H2O2 and OH-. The hydroxyl group retains the same stereochemistry as the boron group, resulting in an alcohol product with syn stereochemistry.
Step 5: Predict the major product. The major product will be a syn addition alcohol formed at the less substituted carbon of the double bond. Consider the stereochemistry of the trans starting material and ensure the product reflects the correct spatial arrangement of substituents.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
7m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hydroboration-Oxidation

Hydroboration-oxidation is a two-step reaction process used to convert alkenes into alcohols. In the first step, BH3 adds to the double bond of the alkene, forming a trialkylborane intermediate. The second step involves oxidation with hydrogen peroxide (H2O2) and hydroxide (OH-), resulting in the formation of an alcohol. This reaction is notable for its anti-Markovnikov selectivity, meaning that the hydroxyl group attaches to the less substituted carbon.
Recommended video:
Guided course
06:38
General properties of hydroboration-oxidation.

Stereochemistry

Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In reactions involving alkenes, stereochemistry is crucial because the addition of reagents can lead to different stereoisomers. For the hydroboration-oxidation of trans-4,4-dimethylpent-2-ene, the stereochemical outcome must be considered, particularly whether the resulting alcohol will have a specific configuration (cis or trans) based on the addition mechanism.
Recommended video:
1:38
Polymer Stereochemistry Concept 1

Regioselectivity

Regioselectivity is the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In the context of hydroboration-oxidation, regioselectivity is important because the reaction favors the formation of the less substituted alcohol due to the anti-Markovnikov addition of boron. Understanding regioselectivity helps predict the major product of the reaction, which is essential for accurately determining the outcome of the given reaction involving trans-4,4-dimethylpent-2-ene.
Recommended video:
Guided course
05:09
Heck Reaction
Related Practice
Textbook Question

When (E)-3-methylhex-3-ene undergoes hydroboration–oxidation, two isomeric products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the relationship between these isomers? What is the relationship between the products formed from (Z)-3-methylhex-3-ene and those formed from (E)-3-methylhex-3-ene?

2376
views
Textbook Question

Show how you would accomplish the following synthetic conversions.

c. 2-bromo-2,4-dimethylpentane → 2,4-dimethylpentan-3-ol

1416
views
Textbook Question

Predict the major products of the following reactions. Include stereochemistry where applicable.

(c)

1978
views
1
comments
Textbook Question

Predict the major products of the following reactions. Include stereochemistry where applicable.

(a) 1−methylcyclohexene + BH3⋅THF then H2O2, OH–

2334
views
Textbook Question

In the hydroboration of 1-methylcyclopentene shown in Solved Problem 8-3, the reagents are achiral, and the products are chiral. The product is a racemic mixture of trans-2-­methylcyclopentanol, but only one enantiomer is shown. Show how the other enantiomer is formed.

1473
views
Textbook Question

When (Z)-3-methylhex-3-ene undergoes hydroboration–oxidation, two isomeric ­products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the relationship between these isomers?

1421
views