Experiment= synthesis of n-butyl bromide, using n-butyl alcohol, NaBr, H2SO4. A) An ether and an alkene are formed as by-products in this reaction. Draw the structures of these by-products and give mechanisms for their formation.
I believe the two products are dibutyl ether and 1-butene? I know each of their line structures, but I don't know about the mechanisms? Any Help?
Actually, primary alcohols undergo a E2 mechanism to form the alkene.
I believe the 1-butene forms by an SN1 mechanism and the dibutyl ether forms by E1 mechanism, but I am still not sure which are the nucleophiles, electrophiles, leaving group, etc.?
The alkene would be formed via an E1 mechanism because it is formed by an elimination reaction in a dehydration reaction between n-butyl alcohol, a primary alcohol, and sulfuric acid, an obviously strong acid. The ether would be formed via Williamson ether synthesis, which is an SN2 mechanism. I think that the person who answered this question originally should have read the question carefully before answering. If you don't know what you are talking about then please don't answer and lead someone down the wrong path. People who come here are looking to understand how things work, so if you don't know yourself then don't give a bs answer.
burn
The person who first answered the question was the same person who posted it. Way to be a hypocrite and complain about people not reading carefully.
Sure! To successfully draw the structures of the by-products and provide mechanisms for their formation, we need to understand the reaction conditions involved in the synthesis of n-butyl bromide using n-butyl alcohol, NaBr, and H2SO4.
The synthesis of n-butyl bromide from n-butyl alcohol occurs through an SN2 substitution reaction. Let's break down the process step by step:
Step 1: Protonation of n-butyl alcohol
In the presence of an acid catalyst (H2SO4), n-butyl alcohol (CH3(CH2)3OH) gets protonated. One of the oxygen atoms from the alcohol picks up a proton from the acid. This protonation makes the oxygen atom a better leaving group.
Step 2: Formation of a carbocation intermediate
After protonation, water molecules present in the reaction mixture can act as a nucleophile and attack the positively charged carbon atom, leading to the formation of a carbocation intermediate. In this case, the water molecule attacks the carbon atom adjacent to the protonated oxygen.
Step 3: Nucleophilic substitution to form n-butyl bromide
In the final step, bromide ions (Br-) from NaBr act as nucleophiles. They attack the carbocation intermediate formed in the previous step, displacing the protonated water molecule. This results in the formation of n-butyl bromide (CH3(CH2)3Br) as the desired product.
Now let's think about the formation of the by-products:
By-Product 1: Dibutyl ether (C8H18O)
Dibutyl ether is formed via an acid-catalyzed dehydration reaction. Let's break down the mechanism:
Step 1: Protonation of n-butyl alcohol
Similar to the synthesis of n-butyl bromide, n-butyl alcohol undergoes protonation in the presence of the acid catalyst (H2SO4). This generates a protonated n-butyl alcohol molecule.
Step 2: Removal of water molecule
The protonated n-butyl alcohol molecule can lose a molecule of water. This occurs when the protonated oxygen atom acts as a leaving group and forms a carbocation.
Step 3: Nucleophilic attack by another alcohol molecule
In the last step, another molecule of n-butyl alcohol can act as a nucleophile and attack the carbocation intermediate created in the second step. This creates a new carbon-oxygen bond, resulting in the formation of dibutyl ether.
By-Product 2: 1-butene (C4H8)
1-butene is formed via an acid-catalyzed dehydration reaction as well. Here's the mechanism:
Step 1: Protonation of n-butyl alcohol
As with the previous reactions, n-butyl alcohol undergoes protonation in the presence of the acid catalyst (H2SO4), creating a protonated n-butyl alcohol molecule.
Step 2: Removal of water molecule and formation of a double bond
Similar to the mechanism for the formation of dibutyl ether, the protonated n-butyl alcohol molecule can eliminate a molecule of water. This leads to the formation of a carbocation that has a double bond between adjacent carbon atoms.
Step 3: Protonation of the double bond
The double bond in the carbocation intermediate created in the previous step can now be protonated. This results in the formation of 1-butene.
To summarize:
- Dibutyl ether (C8H18O) is formed via an acid-catalyzed dehydration reaction involving n-butyl alcohol, with the protonated alcohol acting as an electrophile and another alcohol molecule acting as a nucleophile.
- 1-butene (C4H8) is formed via an acid-catalyzed dehydration reaction involving n-butyl alcohol as well, with the protonated alcohol generating a carbocation that undergoes a double bond formation.
It's important to keep in mind that these explanations provide a basic understanding of the mechanisms involved. For a more detailed and accurate analysis, consulting reliable organic chemistry textbooks or scientific literature is recommended.