Ten alkyl halides were reacted with 2ml of 15% Nal-in-acetone solution: 1) 2-chl
ID: 858133 • Letter: T
Question
Ten alkyl halides were reacted with 2ml of 15% Nal-in-acetone solution:
1) 2-chlorobutane
2) 2-bromobutane
3)1-chlorobutane
4) 1-bromobutane
5) 2-chloro-2-methylpropane
6) crotyl chloride
7) benzyl chloride
8) bromobenzene
9) bromocyclohexane
10) bromocyclopentane
and another experiment used the same alkyl halides but with the reaction of 1% ethanolic silver nitrate solution.
These questions pertain to both experiments:
1) In the test tubes with sodium iodide in acetone and silver nitrate in ehtanol, why should 2-bromobutane react faster than 2-chlorobutane?
2) Why is benzyl chloride reactive in both tests, whereas bromobenzene is unreactive?
3) When benzyl chloride is treated with sodium iodide in acetone, it reacts much faster that 1-chlorobutane, even though both compounds are primary alkyl halides. Explain this rate difference.
4) 2-Chlorobutane reacts much more slowly than 2-chloro-2-methylpropane in the silver nitrate test. Explain this difference in reactivity.
5) Bromocyclopentane is more reactive thsn bromocyclohexane when heated with sodium iodide in acetone. Explain this difference in reactivity.
6) How do you expect the following series of compounds to compare in behavior in the two tests?:
CH3-CH=CH-CH2-Br
CH3-CH2-CH2-CH2-Br
Explanation / Answer
1) In the test tubes with sodium iodide in acetone and silver nitrate in ehtanol, why should 2-bromobutane react faster than 2-chlorobutane?
Ans: as Bromide ion is a better leaving group due to larger size as compard to chloride ion
2) Why is benzyl chloride reactive in both tests, whereas bromobenzene is unreactive?
Ans: benzyl chloride will give a stable carbocation (SN1) as well it is primary alkyl halide(SN2) while bromo benzne is neither a primary halide nor will give a stable cation.
in bromo benzen: For an SN2 reaction to occur, the nucleophile must attack from behind the carbon which is hindered by the bulky ring and An SN1 reaction cannot occur since the all the carbons in the benzene ring have sp2 hybridized orbitals. SN1 reaction cannot occur since the all the carbons in the benzene ring have sp2 hybridized orbitals.
3) When benzyl chloride is treated with sodium iodide in acetone, it reacts much faster that 1-chlorobutane, even though both compounds are primary alkyl halides. Explain this rate difference.
Ans: Benzyl chloride reacts faster because its transition state is more stable than the transition state of 1-chlorobutane.
4) 2-Chlorobutane reacts much more slowly than 2-chloro-2-methylpropane in the silver nitrate test. Explain this difference in reactivity.
Ans: 2-chloro,2-methyl propane is a teriary alkyl halide will give more stable carbocation
5) Bromocyclopentane is more reactive thsn bromocyclohexane when heated with sodium iodide in acetone. Explain this difference in reactivity.
Ans: bromocyclopentane is faster than bromocyclohexane because of ring strain, bond angles and conformations.
6) How do you expect the following series of compounds to compare in behavior in the two tests?:
CH3-CH=CH-CH2-Br ( will give SN1 easily , nitrate test, due to formation of stable carbocation stabilized by resonance)
CH3-CH2-CH2-CH2-Br
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