Primary alcohols can be dehydrated in an acid-catalyzed reaction. The mechanism is an E2 elimination since a primary carbocation is too unstable to be forme Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions NOC XT H3C CH3 H OH₂ H₂O H3C CH3 CH₂ H3O+ H₂0
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.
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Second picture shows instructions on how the arrows must be shown as.
![### Acid-Catalyzed Dehydration of Primary Alcohols
Primary alcohols can be dehydrated in an acid-catalyzed reaction. The mechanism follows an E2 elimination pathway since forming a primary carbocation is too unstable.
#### Step 1: Protonation of the Alcohol
The reaction starts with a primary alcohol and an acid (represented as \( \text{H}_3\text{O}^+ \)).
\[ \underset{\text{(hydrated structure)}}{\begin{aligned}
\text{CH}_3\text{CH}_2\text{CH}_2\text{OH} & \hspace{1em}+ \hspace{1em} \text{H}_3\text{O}^+ \\
\end{aligned}}
\hspace{0.5em} \longrightarrow \hspace{0.5em}
\underset{\text{(protonated hydroxyl group)}}{\begin{aligned}
\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}_2^+
\end{aligned}}
\]
#### Step 2: Formation of the Alkene and Removal of Water
In this step, the protonated alcohol (which is now a good leaving group) undergoes dehydration, resulting in the formation of an alkene. The electron movement can be explained through:
1. **Arrow-Pushing Mechanism**:
- The hydroxyl group \( \text{OH}_2^+ \) leaves as a water molecule.
- Simultaneously, a hydride shift occurs, leading to the formation of the double bond (alkene).
\[ \underset{\text{(protonated structure)}}{\begin{aligned}
\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}_2^+ \\
\end{aligned}}
\hspace{1em} \longrightarrow \hspace{1em}
{\begin{aligned}
\text{CH}_3\text{CH} = \text{CH}_2 \hspace{1em}+ \hspace{1em} \text{H}_3\text{O}^+ \hspace{1em}+ \hspace{1em} \text{H}_2\text{O}
\end{aligned}}](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc94cb5d1-997a-49d0-b0ef-9ec02bf0a187%2Fbaba55f3-03ef-4581-bb3f-efd337924a2f%2Fe2d8ped_processed.png&w=3840&q=75)
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