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Which of the following alkyl halides will undergo SN1 reaction most readily? - Chemistry

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प्रश्न

Which of the following alkyl halides will undergo SN1 reaction most readily?

विकल्प

  • \[\ce{(CH3)3C-F}\]

  • \[\ce{(CH3)3C-Cl}\]

  • \[\ce{(CH3)3C-Br}\]

  • \[\ce{(CH3)3C-I}\]

MCQ
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उत्तर

\[\ce{(CH3)3C-I}\]

Explanation:

\[\ce{(CH3)3C-I}\] will undergo SN1 reaction most readily as C-I bond is weakest, due to the large difference in the size of carbon and iodine.

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अध्याय 10: Haloalkanes and Haloarenes - Exercises [पृष्ठ १३७]

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एनसीईआरटी एक्झांप्लर Chemistry [English] Class 12
अध्याय 10 Haloalkanes and Haloarenes
Exercises | Q I. 17. | पृष्ठ १३७

संबंधित प्रश्न

How do you convert the following:

Ethanol to propanenitrile


 Give reasons for the following:

(CH3)3C–O–CH3 on reaction with HI gives (CH3)3C–I and CH3–OH as the main products and not (CH3)3C–OH and CH3–I.


Write the isomers of the compound having the formula C4H9Br.


Write the structure of the major organic product in the following reaction:

\[\ce{CH3CH2Br + KCN ->[aq.ethanol]}\]


Arrange the compounds of the following set in order of reactivity towards SN2 displacement:

1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 2-Bromo-3-methylbutane


AgCN reacts with haloalkanes to form isocyanide. Haloalkanes react with KCN to form alkyl cyanides as the main product. Why?


Arrange the following organic compounds in descending order of their reactivity towards SN1 reaction.

C6H5CH2Br, C6H5CH(C6H5)Br, C6H5CH(CH3)Br, C6H5C(CH3)(C6H5)Br


Which one is most reactive towards SN1 reaction?


Which of the following is an optically active compound?


Among the following, the dissociation constant is highest for:


Complete the following analogy:

Same molecular formula but different structures: A : : Non superimposable mirror images: B


Which of the following statements are correct about the kinetics of this reaction?

(i) The rate of reaction depends on the concentration of only (b).

(ii) The rate of reaction depends on concentration of both (a) and (b).

(iii) Molecularity of reaction is one.

(iv) Molecularity of reaction is two.


Ethylene chloride and ethylidene chloride are isomers. Identify the correct statements.

(i) Both the compounds form same product on treatment with alcoholic KOH.

(ii) Both the compounds form same product on treatment with aq.NaOH.

(iii) Both the compounds form same product on reduction.

(iv) Both the compounds are optically active.


When CH3CH2CHCl2 is treated NaNH2 product formed is:-


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Among the following compounds I - IV, which one forms a yellow precipitate on reacting sequentially with (i) NaOH (ii) dil. HNO3 (iii) AgNO3?

I II III IV

The decreasing order of reactivity of the following compounds towards nucleophilic substitution (SN2) is ______.






The following questions are case-based questions. Read the passage carefully and answer the questions that follow:

Nucleophilic Substitution:
Nucleophilic substitution reaction of haloalkane can be conducted according to both SN1 and SN2 mechanisms. SN1 is a two-step reaction, while SN2 is a single-step reaction. For any haloalkane, which mechanism is followed depends on factors such as the structure of haloalkane, properties of leaving group, nucleophilic reagent and solvent.

Influences of solvent polarity:
In SN1 reaction, the polarity of the system increases from the reactant to the transition state, because a polar solvent has a greater effect on the transition state than the reactant, thereby reducing activation energy and accelerating the reaction. In SN2 reaction, the polarity of the system generally does not change from the reactant to the transition state, and only charge dispersion occurs. At this time, the polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (SN1) of tertiary chlorobutane at 25°C in water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24).

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


Explain why Grignard reagents should be prepared under anhydrous conditions.


Which alkyl halide from the following pair would you expect to react more rapidly by an SN2 mechanism? Explain your answer.

\[\begin{array}{cc}\ce{CH3CH2CHCH3}\\\phantom{...}|\\\phantom{....}\ce{Br}\end{array}\] or \[\begin{array}{cc}\phantom{.....}\ce{CH3}\\\phantom{..}|\\\ce{H3C - C - Br}\\\phantom{..}|\\\phantom{....}\ce{CH3}\end{array}\]


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