N-butyl alcohol and bromide reaction

In summary, n-butyl alcohol is reacted with potassium bromide in the presence of concentrated sulphuric acid and water to yield 1-bromobutane via an SN2 mechanism. The sulphuric acid serves as a catalyst to protonate the hydroxyl group and create a good leaving group, while water acts as a solvent and weak nucleophile.
  • #1
kellyN
2
0

Homework Statement



n-butyl alcohol was reacted with potassium bromide in the presence of concentrated sulphuric acid and water.

1) Is hydrobromic acid involved in this reaction? If yes, how so?
2) Is this reaction SN1 or SN2? What is the mechanism?
3) What is the purpose of the sulphuric acid and water?

Homework Equations



-

The Attempt at a Solution



1) I believe HBr is involved, even though it's not added. Perhaps the bromide from potassium bromide and the hydrogen ion from sulphuric form HBr.
2) This is an SN2 reaction (substrate is a primary carbon). The hydroxyl group of the n-butyl alcohol undergoes protonation with HBr, while the nucleophilic Br- does a backside attack on the carbon atom which is attached to the alcohol group. The leaving group is the water molecule while n-butyl alcohol is converted into 1-bromobutane.
3) Sulphuric acid serves as a catalyst? Or to provide the hydrogen ions for protonation.. or for the formation of HBr? Quite confused over this question. Water seemingly serves as a solvent, but it's a protic solvent, which means that it will slow the reaction down. Why is this so?


Any help would be greatly appreciated. Thanks in advance.
 
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  • #2
kellyN said:
1) I believe HBr is involved, even though it's not added. Perhaps the bromide from potassium bromide and the hydrogen ion from sulphuric form HBr.
Yes, in an acidic environment, your nucleophile will be neutral (in a basic environment, it'll be an anion). The sulfuric acid protonates the KBr to give HBr.

kellyN said:
2) This is an SN2 reaction (substrate is a primary carbon). The hydroxyl group of the n-butyl alcohol undergoes protonation with HBr, while the nucleophilic Br- does a backside attack on the carbon atom which is attached to the alcohol group. The leaving group is the water molecule while n-butyl alcohol is converted into 1-bromobutane.
Yes, it's SN2. The rest looks fine.

kellyN said:
3) Sulphuric acid serves as a catalyst? Or to provide the hydrogen ions for protonation.. or for the formation of HBr? Quite confused over this question. Water seemingly serves as a solvent, but it's a protic solvent, which means that it will slow the reaction down. Why is this so?
The sulfuric acid pushes the hydroxyl equilibrium toward protonated hydroxyl, setting up water as a good leaving group. HBr is a pretty decent nucleophile in water, given that the hydrogen bonding to HBr is quite a bit weaker than in other acids like HCl or HF.
 

1. What is the chemical equation for the reaction between N-butyl alcohol and bromide?

The chemical equation for the reaction between N-butyl alcohol and bromide is C4H9OH + HBr → C4H9Br + H2O.

2. What type of reaction is the reaction between N-butyl alcohol and bromide?

The reaction between N-butyl alcohol and bromide is a substitution reaction, specifically an SN2 reaction, where the bromide ion replaces the hydroxyl group on the alcohol.

3. What are the major products of the reaction between N-butyl alcohol and bromide?

The major products of the reaction between N-butyl alcohol and bromide are n-butyl bromide and water. This is because the bromide ion replaces the hydroxyl group on the alcohol to form the new compound, while the hydrogen from the hydroxyl group combines with the remaining oxygen to form water.

4. What are the conditions necessary for the reaction between N-butyl alcohol and bromide to occur?

The reaction between N-butyl alcohol and bromide occurs in the presence of a strong acid, such as hydrobromic acid, and at elevated temperatures. This is because the acid protonates the alcohol, making it a better leaving group, and the elevated temperatures help to overcome the energy barrier for the reaction to occur.

5. What are the main uses of N-butyl alcohol and bromide reaction in industry?

The N-butyl alcohol and bromide reaction is commonly used in the production of n-butyl bromide, which is an important intermediate in the synthesis of various organic compounds such as pharmaceuticals, pesticides, and fragrances. It is also used as a solvent and in organic synthesis reactions. Additionally, n-butyl bromide can be converted to other useful compounds such as n-butyl chloride and n-butyl acetate.

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