Organic Chemistry: Brominating Alkenes Flashcards

Questions and Answers

What is a chiral carbon?

A carbon with 3 different substituents

A carbon with 4 different substituents (correct)

A carbon in a ring structure

A carbon with 4 identical substituents

Which of the following best describes enantiomers?

A type of diastereomer

Molecules with chiral centers and non-superimposable mirror images (correct)

Identical molecules

Molecules that can freely rotate

What is a racemic mixture?

Equal amounts of enantiomers

What defines a meso compound?

Chiral centers with an internal plane of symmetry Signup and view all the answers

What occurs during electrophilic addition?

The pi bond is replaced by two sigma bonds Signup and view all the answers

Describe the Bromination process.

Bromine induces dipole, C-Br forms while Br-Br breaks, forming Br- ion that adds on opposite side. Signup and view all the answers

What is the physical state of trans-stilbene during bromination?

Solid Signup and view all the answers

What is the physical state of cis-stilbene during bromination?

Liquid Signup and view all the answers

What is the procedure for brominating cis-stilbene?

Put cis and acetic acid and pyrid tribrom and b chips to rbf, reflux, lower heat and cool, add water, remove condenser, cool in ice-water bath, vacuum filter and wash. Signup and view all the answers

What terms are used to differentiate stereoisomers?

Erythro and threo Signup and view all the answers

Study Notes

Key Concepts in Bromination of Alkenes

Chiral Carbons: A carbon atom that has four different substituents, leading to the possibility of stereoisomerism.
Enantiomers: Stereoisomers that are non-superimposable mirror images of each other, arising from chiral centers.
Racemic Mixture: A mixture that contains equal amounts of two enantiomers, resulting in no optical activity.

Stereochemical Aspects

Meso Compound: A molecule that contains chiral centers but also has an internal plane of symmetry, making it achiral overall.
Erythro and Threo: Terms used to differentiate stereoisomers based on their spatial arrangement, important in discussing stereochemistry.

Mechanism of Bromination

Electrophilic Addition: A process where a pi bond is converted into two sigma bonds; involves the formation of a carbocation intermediate after an electrophile attacks the alkene.
Bromination: Involves the generation of a bromonium ion when bromine reacts with an alkene; results in formation of trans vicinal dihalides through an anti-addition mechanism, yielding chiral carbons with R or S configurations.

Specific Reactions

Trans-Stilbene Bromination: A solid state reaction, highlighting the difference in physical properties in comparison to its cis counterpart.
Cis-Stilbene Bromination: Occurs in a liquid state, indicative of the differences in reactivity of cis and trans alkenes.
Cinnamic Acid Bromination: Another application of bromination that showcases variations in products based on the starting structure.

Experimental Procedure

General Steps: Combine cis stilbene with acetic acid and bromine in a round bottom flask, reflux, then cool, add water, vacuum filter, and wash the product. Repeat with trans stilbene for comparative analysis.
Silver Nitrate Results: Typically used for identifying the presence of bromine in reaction mixtures.

Yield and Analysis

Percent Yield of Cis and Trans: Measurements that evaluate the efficiency of the bromination reaction for both isomers.
Postlab and Prelab: Sections that typically involve analysis and preparatory work for conducting the experiment, encompassing safety, theoretical background, and expected outcomes.

Description

Test your knowledge on key concepts related to the bromination of alkenes with these flashcards. Learn about chiral carbons, enantiomers, and other important terms in stereochemistry. Perfect for organic chemistry study and review.