Which compound in the following pair will react faster in SN2 reaction with OH−? (CH3)3CCl or CH3Cl - Chemistry

प्रश्न

Which compound in the following pair will react faster in S_N2 reaction with OH⁻?

(CH₃)₃CCl or CH₃Cl

रासायनिक समीकरण/संरचनाएँ

लघु उत्तरीय

उत्तर

$\begin{array}{cc} CH_{3} \\ | \\ CH_{3} - C - Cl \\ | \\ CH_{3} \end{array}$ or CH₃ — Cl

The S_N2 mechanism involves the attack of the nucleophile at the atom bearing the leaving group. But, in case of (CH₃)₃CCl, the attack of the nucleophile at the carbon atom is hindered because of the presence of bulky substituents on that carbon atom bearing the leaving group. On the other hand, there are no bulky substituents on the carbon atom bearing the leaving group in CH₃Cl. Hence, CH₃Cl reacts faster than (CH₃)₃CCl in S_N2 reaction with OH⁻.

shaalaa.com

Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions

क्या इस प्रश्न या उत्तर में कोई त्रुटि है?

Q 9.2 Q 9.1 Q 10.1

अध्याय 10: Haloalkanes and Haloarenes - Exercises [पृष्ठ ३११]

APPEARS IN

एनसीईआरटी Chemistry [English] Class 12

अध्याय 10 Haloalkanes and Haloarenes
Exercises | Q 9.2 | पृष्ठ ३११

संबंधित प्रश्न

Given reasons: C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH₃–Cl.

In the following pair of halogen compounds, which compound undergoes a faster S_N1 reaction?

Write the isomers of the compound having the formula C₄H₉Br.

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

$CH_{3} CH (Br) CH_{2} CH_{3} + NaOH \overset{water}{\to}$

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

$CH_{3} CH_{2} CH_{2} OH + SOCl_{2} ⟶$

C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH₃–Cl.

Given reasons: S_N1 reactions are accompanied by racemization in optically active alkyl halides.

Identify 'A' in the following reaction -

(a) 2- Bromo-2 methylbutane

(b) 1 -Bromo-2,2-dimethylpropane

(d) 1 - Bromo- 2 -methylpropane

What is the action of the following on ethyl bromide:
silver acetate

Answer the following question.
Write one stereochemical difference between S_N1 and S_N2 reactions.

Which among MeX, RCH₂X, R₂CHX and R₃CX is most reactive towards S_N2 reaction?

Identify X and Y in the following sequence:

$C_{2} H_{5} Br \overset{X}{\to} Product \overset{Y}{\to} C_{3} H_{7} NH_{2}$

The increasing order of nucleophilicity would be:

Which of the following compound will undergo racemisation when reacts with aq. KOH?

(i)

(ii)

CH₃CH₂CH₂Cl

(iii)

$\begin{array}{cc} CH_{3} \\ | \\ CH_{3} - CH - CH_{2} Cl \end{array}$

(iv)

$\begin{array}{cc} H \\ | \\ CH_{3} - C - Cl \\ | \\ C_{2} H_{5} \end{array}$

In which reaction mechanism carbocation is formed?

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:
Nucleophilic substitution reaction of haloalkane can be conducted according to both S_N1 and S_N2 mechanisms. S_N1 is a two-step reaction, while S_N2 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 S_N1 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 S_N2 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 (S_N1) of tertiary chlorobutane at 25°C in water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24).

The reaction rate (S_N2) 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 S_N1 and S_N2 reactions but with different results. Generally speaking, a weak polar solvent is favourable for S_N2 reaction, while a strong polar solvent is favourable for S_N1. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_N1 mechanism in solvents with a strong polarity (for example ethanol containing water).

Answer the following questions:

(a) Why racemisation occurs in S_N1? (1)

(b) Why is ethanol less polar than water? (1)

(c) Which one of, the following in each pair is more reactive towards S_N2 reaction? (2)

(i) CH₃ – CH₂ – I or CH₃CH₂ – Cl

(ii)

(c) Arrange the following in the increasing order of their reactivity towards S_N1 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 S_N2 mechanism of methyl bromide using aqueous KOH.

Which compound in the following pair will react faster in SN2 reaction with OH−? (CH3)3CCl or CH3Cl - Chemistry

Advertisements

Advertisements

प्रश्न

उत्तर

APPEARS IN

संबंधित प्रश्न

Select a course

Which compound in the following pair will react faster in SN2 reaction with OH−? (CH3)3CCl or CH3Cl - Chemistry

Advertisements

Advertisements

प्रश्न

उत्तरShow Solution

APPEARS IN

संबंधित प्रश्न

Select a course

उत्तर