Fill in the missing reagents or major products to complete the transformations. Be sure to pay careful attention to stereochemistry where appropriate. If the major product is a pair of enantiomer you may show one of them and indicate + enantiomer. If the products are diasteromers, show them both.
Reactive Intermediates
In chemistry, reactive intermediates are termed as short-lived, highly reactive atoms with high energy. They rapidly transform into stable particles during a chemical reaction. In specific cases, by means of matrix isolation and at low-temperature reactive intermediates can be isolated.
Hydride Shift
A hydride shift is a rearrangement of a hydrogen atom in a carbocation that occurs to make the molecule more stable. In organic chemistry, rearrangement of the carbocation is very easily seen. This rearrangement can be because of the movement of a carbocation to attain stability in the compound. Such structural reorganization movement is called a shift within molecules. After the shifting of carbocation over the different carbon then they form structural isomers of the previous existing molecule.
Vinylic Carbocation
A carbocation where the positive charge is on the alkene carbon is known as the vinyl carbocation or vinyl cation. The empirical formula for vinyl cation is C2H3+. In the vinyl carbocation, the positive charge is on the carbon atom with the double bond therefore it is sp hybridized. It is known to be a part of various reactions, for example, electrophilic addition of alkynes and solvolysis as well. It plays the role of a reactive intermediate in these reactions.
Cycloheptatrienyl Cation
It is an aromatic carbocation having a general formula, [C7 H7]+. It is also known as the aromatic tropylium ion. Its name is derived from the molecule tropine, which is a seven membered carbon atom ring. Cycloheptatriene or tropylidene was first synthesized from tropine.
Stability of Vinyl Carbocation
Carbocations are positively charged carbon atoms. It is also known as a carbonium ion.
attention to stereochemistry where appropriate. If the major product is a pair of enantiomer you may
show one of them and indicate + enantiomer. If the products are diasteromers, show them both.
![### Addition of HBr to Alkenes: Effect of Peroxides
This image pertains to the addition of hydrogen bromide (HBr) to an alkene in the presence and absence of peroxides.
#### Reaction without Peroxides
**Top Reaction:**
- Reactant: A cyclobutene with a single substituent on the ring.
- Reagent: HBr.
\[
\text{Cyclobutene derivative} + \text{HBr} \rightarrow \text{Product}
\]
In the absence of peroxides (ROOR), the reaction proceeds according to Markovnikov's rule, where the hydrogen atom from HBr attaches to the carbon of the double bond that has the greater number of hydrogen atoms, and the bromine attaches to the carbon with fewer hydrogen atoms.
#### Reaction with Peroxides
**Bottom Reaction:**
- Reactant: A cyclobutene with a single substituent on the ring.
- Reagent: HBr with peroxide (ROOR) catalyst.
\[
\text{Cyclobutene derivative} + \text{HBr} \xrightarrow{\text{ROOR}} \text{Product}
\]
When peroxides are present, the reaction follows the anti-Markovnikov addition rule due to the formation of free radicals. Here, the bromine atom attaches to the carbon of the double bond that has the greater number of hydrogen atoms, and the hydrogen atom attaches to the carbon with fewer hydrogen atoms.
### Summary
- **Without Peroxides:** Markovnikov addition of HBr to the alkene, resulting in the hydrogen atom adding to the more substituted carbon (carbon with fewer hydrogen atoms initially).
- **With Peroxides:** Anti-Markovnikov addition of HBr to the alkene due to radical formation, resulting in the bromine atom adding to the more substituted carbon.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Ff57d3743-5e44-4060-83da-5d90a37d31c6%2F2df4c2ed-cae2-4ee7-b379-404acf933aec%2Fjn7mcrp_processed.png&w=3840&q=75)
Trending now
This is a popular solution!
Step by step
Solved in 3 steps with 2 images
how do you know the first +HBR reaction is a pair of enantiomers? Can you draw both enantiomers with wedges and dashes? I thought the place where the Bromine attacked is not a chiral center, so how can there be enantiomers?
by Bartleby Expert
