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प्रश्न
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.
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उत्तर
(i) The rate of reaction depends on the concentration of only (b).
(iii) Molecularity of reaction is one.
Explanation:
SN1 occurs in two steps. I, the polarized \[\ce{C - Cl}\] bond undergoes slow cleavage to produce a carbonation and a chloride ion. The carbocation thus formed is then attacked by nucleophile in step II to complete the substitution reaction. Step I is the slowest and reversible. It involves the \[\ce{C - Cl}\] bond breaking for which the energy is obtained through salvation of halide ion with the proton of protic solvent. Since the rate of reaction depends upon the slowest step, the rate of reaction depends only on the concentration of alkyl halide and not on the concentration of hydroxide ion. So, the rate-determining step is unimolecular.
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संबंधित प्रश्न
Which alkyl halide from the following pair would you expect to react more rapidly by an SN2 mechanism? Explain your answer.
CH3CH2CH2CH2Br or \[\begin{array}{cc}
\ce{CH3CH2CHCH3}\\
\phantom{...}|\\
\phantom{....}\ce{Br}\
\end{array}\]
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
Out of C6H5CH2Cl and C6H5CHClC6H5, which is more easily hydrolysed by aqueous KOH.
How the following conversion can be carried out?
Ethyl chloride to propanoic acid.
SN1 reactions are accompanied by racemization in optically active alkyl halides.
In the reaction, \[\ce{R - X + NaOR' -> ROR’ + X}\] ( – ve ion). The main product formed is:
The order of reactivities of the following alkyl halides for an SN2 reaction is:
Which among MeX, RCH2X, R2CHX and R3CX is most reactive towards SN2 reaction?
The correct order of increasing the reactivity of C–X bond towards nucleophile in following compounds.
(I)
(II)
(CH3)3CCl
(III)
(CH3)2CHCl
(IV)
Assertion: KCN reacts with methyl chloride to give methyl isocyanide.
Reason: CN– is an ambident nucleophile.
Compound ‘A’ with molecular formula \[\ce{C4H9Br}\] is treated with aq. \[\ce{KOH}\] solution. The rate of this reaction depends upon the concentration of the compound ‘A’ only. When another optically active isomer ‘B’ of this compound was treated with aq. \[\ce{KOH}\] solution, the rate of reaction was found to be dependent on concentration of compound and \[\ce{KOH}\] both.
(i) Write down the structural formula of both compounds ‘A’ and ‘B’.
(ii) Out of these two compounds, which one will be converted to the product with inverted configuration.
Match the reactions given in Column I with the types of reactions given in Column II.
| Column I | Column II | |
| (i) |  |
(a) Nucleophilic aromatic substitution |
| (ii) | \[\begin{array}{cc} \ce{CH3 - CH = CH2 + HBr -> CH3 - CH - CH3}\\ \phantom{............................}|\phantom{}\\ \phantom{.............................}\ce{Br}\phantom{} \end{array}\] |
(b) Electrophilic aromatic substitution |
| (iii) |  |
(c) Saytzeff elimination |
| (iv) |  |
(d) Electrophilic addition |
| (v) | \[\begin{array}{cc} \ce{CH3 CH2 CH CH3 ->[alc.KOH] CH3 CH = CH CH3}\\ \phantom{}|\phantom{..........................}\\ \phantom{}\ce{Br}\phantom{........................} \end{array}\] |
(e) Nucleophilic substitution (SN1) |
When CH3CH2CHCl2 is treated NaNH2 product formed is:-
The major product formed in the following reaction is:
Assertion (A) : Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R) : Bond enthalpy of C-I bond is less than that of C-Cl bond.
An organic compound A with the molecular formula (+) C4H9Br undergoes hydrolysis to form (+) C4H9OH. Give the structure of A and write the mechanism of the reaction.
Identify the product in the following reaction: 
Acetic anhydride from acetic acid
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 \[\begin{array}{cc}\phantom{.....}\ce{CH3}\\\phantom{..}|\\\ce{H3C - C - Br}\\\phantom{..}|\\\phantom{....}\ce{CH3}\end{array}\]
