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प्रश्न
Arrange the following compounds in increasing order of reactivity towards SN2 reaction.
2-Bromopentane, 1-Bromopentane, 2-Bromo-2-methylbutane
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उत्तर
SN2 reaction involves the formation of transition state. Therefore, reactivity towards SN2 depends upon the steric hindrance:
Due to the presence of 2 methyl group in 2-Bromo-2-methylbutane it is least reactive towards SN2 reactions, 2-bromopentane is moderately reactive while 1-bromopentane is most reactive.
2-Bromo-2-methylbutane < 2-Bromopentane < 1-Bromopentane
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संबंधित प्रश्न
Discuss the mechanism of alkaline hydrolysis of bromomethane.
Which would undergo SN2 reaction faster in the following pair and why ?
Write the structure of the major product in each of the following reaction :
Which of the following is an example of SN2 reaction?
Which of the following is a chiral compound?
Which of the following undergoes nucleophilic substitution exclusively by SN1 mechanism?
Which of the following compound will undergo racemisation when reacts with aq. KOH?
(i)
(ii)
CH3CH2CH2Cl
(iii)
\[\begin{array}{cc}
\ce{CH3}\phantom{..}\\
|\phantom{....}\\
\ce{CH3-CH-CH2Cl}
\end{array}\]
(iv)
\[\begin{array}{cc}
\phantom{..}\ce{H}\\
\phantom{..}|\\
\ce{CH3-C-Cl}\\
\phantom{..}|\\
\phantom{.....}\ce{C2H5}
\end{array}\]
Complete the reaction with the main product formed:
The following questions are case-based questions. Read the passage carefully and answer the questions that follow:
|
Nucleophilic Substitution: Influences of solvent polarity: The reaction rate (SN2) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. Hence the level of solvent polarity has an influence on both SN1 and SN2 reactions but with different results. Generally speaking, a weak polar solvent is favourable for SN2 reaction, while a strong polar solvent is favourable for SN1. Generally speaking, the substitution reaction of tertiary haloalkane is based on SN1 mechanism in solvents with a strong polarity (for example ethanol containing water). |
Answer the following questions:
(a) Why racemisation occurs in SN1? (1)
(b) Why is ethanol less polar than water? (1)
(c) Which one of, the following in each pair is more reactive towards SN2 reaction? (2)
(i) CH3 – CH2 – I or CH3CH2 – Cl
(ii)
OR
(c) Arrange the following in the increasing order of their reactivity towards SN1 reactions: (2)
(i) 2-Bromo-2-methylbutane, 1-Bromo-pentane, 2-Bromo-pentane
(ii) 1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 2-Bromo-3- methylbutane
Discuss the mechanism of alkaline hydrolysis of methyl bromide.
