Question

What product(s) would you expect from the reaction of 1-methylcyclohexene with NBS?

Short answer

3-bromo-1-methylcyclohexene.

Step-by-step solution

Understanding the Reagents

The reaction involves 1-methylcyclohexene and N-bromosuccinimide (NBS). NBS is used for allylic bromination, where a bromine atom is introduced at the allylic position, which is the carbon adjacent to a double bond.

Identifying the Allylic Positions

1-methylcyclohexene has a double bond between two of its carbon atoms, forming a ring. The methyl group is attached to one of the carbons involved in the double bond, and so the carbon adjacent to the double bond, on the non-methyl side, is the allylic position.

Product Formation

During the reaction, the bromine from NBS will substitute a hydrogen atom at the allylic position. This leads to the formation of 3-bromo-1-methylcyclohexene as the major product.

Conclusion

The reaction of 1-methylcyclohexene with NBS results in the formation of 3-bromo-1-methylcyclohexene, where bromination occurs at the allylic position adjacent to the methyl-substituted carbon.

Key concepts

1-Methylcyclohexene

1-methylcyclohexene is an organic compound that features a cyclohexene ring with a methyl group attached to it. Imagine a hexagon made entirely of carbon atoms, and then one of these carbons also holds a little extra carbon branch—this is the methyl group. In this molecule, the carbon-carbon double bond plays an essential role in reactions. This bond is located in the ring and is adjacent to the methyl group, making

• 1-methylcyclohexene reactive at its allylic positions.
• The presence of the double bond allows for potential chemical transformations, such as bromination.

For students learning about organic chemistry, identifying this structure in a reaction is key to understanding where reactions, like allylic bromination, will occur.

N-Bromosuccinimide (NBS)

N-bromosuccinimide, commonly known as NBS, is a special reagent used predominantly for bromination reactions. Its primary function is to donate a bromine atom specifically during allylic or benzylic bromination, which means it targets carbon atoms adjacent to double bonds or aromatic rings.

• In the context of 1-methylcyclohexene, NBS will facilitate the addition of bromine to an allylic position.
• This reagent is particularly useful due to its selective nature, allowing it to introduce bromine without significantly affecting the molecule's more sensitive double bonds.

The application of NBS is fundamental for students to master when predicting the outcomes of reactions involving alkenes or aromatic compounds in organic chemistry.

Organic Reaction Mechanisms

Understanding organic reaction mechanisms involves tracing the step-by-step movement of electrons during a chemical transformation. When 1-methylcyclohexene undergoes allylic bromination with NBS, a specific sequence of events occurs. First, a radical is generated, often through the initiation by thermal or light energy, which then interacts with the alkene. This interaction mobilizes the formation of a bromine atom from NBS. Here are key points:

• The radical formation is a crucial step, making the reaction potent and encouraging the migration of bromine to the allylic position.
• Understanding the electron flow, through arrow pushing and radical movement, provides insight into why 3-bromo-1-methylcyclohexene is the major product.

Each step in a mechanism adds to the whole picture, helping students predict how substances will react and what products will result. Mastering these concepts is essential for anyone diving deeper into the study of organic chemistry or pursuing a related field.