Structural and stereoisomerism should be considered when answering this question.
A mixture of 1-chlorobutane and 2-chlorobutane is heated with an excess of \(\mathrm{NaOH}\) in ethanol.
How many different organic molecules will be produced?
Correct Answer: \( \boxed{\mathrm{C}} \)
Ethanolic \(\mathrm{NaOH}\) promotes elimination.
Therefore, the different organic molecules are:
Total different molecules \(=3\). Therefore, the correct answer is (C).
An organic ion containing a carbon atom with a negative charge is called a carbanion.
An organic ion containing a carbon atom with a positive charge is called a carbocation.
The reaction between \(\mathrm{NaOH(aq)}\) and 1-bromobutane proceeds by an \(\mathrm{S_N2}\) mechanism.
What is the first step in the mechanism?
Correct Answer: \( \boxed{\mathrm{A}} \)
An \(\mathrm{S_N2}\) reaction occurs in a single step.
The hydroxide ion acts as a nucleophile and attacks the carbon atom bonded to bromine, which has a partial positive charge due to the polar \(\mathrm{C-Br}\) bond.
Bond formation and bond breaking occur simultaneously without forming a carbocation intermediate.
Therefore, the correct answer is (A).
2-chloropropane and 2-bromopropane react separately with aqueous \(\mathrm{NaOH}\).
Which row is correct?
| Comparison of rates of reaction | Explanation of the difference in reaction rates | |
|---|---|---|
| A | 2-chloropropane reacts faster | chlorine is more reactive than bromine |
| B | 2-chloropropane reacts faster | the \(\mathrm{C-Cl}\) bond is more polar than the \(\mathrm{C-Br}\) bond |
| C | 2-bromopropane reacts faster | the first ionisation energy of bromine is lower than chlorine’s |
| D | 2-bromopropane reacts faster | the \(\mathrm{C-Br}\) bond is weaker than the \(\mathrm{C-Cl}\) bond |
Correct Answer: \( \boxed{\mathrm{D}} \)
Hydrolysis of halogenoalkanes involves breaking the carbon-halogen bond.
The \(\mathrm{C-Br}\) bond is weaker than the \(\mathrm{C-Cl}\) bond, so it requires less energy to break.
As a result, 2-bromopropane reacts faster with aqueous \(\mathrm{NaOH}\) than 2-chloropropane.
Therefore, the correct answer is (D).
