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SN1 Reaction - (Concept)
The general reaction occurs as follows:
- The mechanism occurs as follows:
- SN1 reactions are nucleophilic substitution reactions, involving a nucleophile replacing a leaving group.
- SN1 reactions are unimolecular. The rate of this reaction depends only on the concentration of one reactant and does not depend upon the strength of the nucleophile
- Rate determinig step depends on the stability of the intermediate carbocation which is obtained during the course of the reaction
- Since the mechanism involves the attack of nucleophile on an already formed carbocation, the strength of nucleophile is unimportant for the rate of the reaction
- The rate of formation of intermediate is independent of concentration of nucleophile and depends only on the concentration of reactants.
- Good ionising solvents (polar protic solvents) are required to carry out SN1 reaction as there has to be formation of ions
- Configuration of the product may be same or inverted and in cases where the leaving group departs from a chiral centre, racemisation occurs.
- If Nu- attacks on the same side from where X- leaves, then it is called 'Retention'.
- If Nu- attacks from the opposite side from where X- leaves, then it is called 'Inversion'.
- Racemic mixture is obtained when equal amount of retention and inversion products are formed in the reaction.
- Generally, partial racemisation is seen in the reactions as it both SN1 and SN2 are both competing
| Exam | Chapter |
| JEE MAIN | Organic Compounds containing Halogens |
A solution of (-) - 1-chloro - 1 - phenylethane in toluene racemises slowly in the presence of a small amount of SbCl5 ,due to the formation of :
| A. |
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| B. |
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| C. |
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| D. |
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The major product of the following reaction is :
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| B. |
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| C. |
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| D. |
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The increasing order of the reactivity of the following halides for the SN1 reaction is :
| A. |
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| B. |
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| C. |
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| D. |
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Consider the reaction sequence given below:
Which of the following statements is true:
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| B. |
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| C. |
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| D. |
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The mechanism of SN1 reaction is given as
A student writes general characteristics based on the given mechanism as :
(a) The reaction is favoured by weak nucleophiles.
(b) would be easily formed if the substituents are bulky
(c) The reaction is accompanied by racemization.
(d) The reaction is favoured by non-polar solvents.
Which observations are correct-
| A. |
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| B. |
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| D. |
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The decreasing order of reactivity of the following organic molecules towards solution is:
| A. |
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| B. |
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| D. |
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Which of the following compunds will form precipitate with aq. solution most readily?
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Which one of the following compounds is inactive towards reaction?
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| D. |
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Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono-substituted alkyl halide?
| A. |
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| B. |
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| C. |
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| D. |
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In nucleophilic substitution reaction , order of halogens as incoming (attacking) nucleophile is :
The order of halogens as departing nucleophile should be:
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| B. |
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| C. |
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| D. |
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Which one is most reactive towards SN1 reaction?
| A. |
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| B. |
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| D. |
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Number of moles of formed in the following reaction is _______
| A. |
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| B. |
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| D. |
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Decreasing order towards SN 1 reaction for the following compounds is:
| A. |
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| B. |
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| C. |
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| D. |
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Choose the halogen which is most reactive towards reaction in the given compounds (A, B, C, & D)
(A) 
(B) 
(C) 
(D) 
| A. |
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| B. |
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| C. |
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| D. |
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Identify the correct order of reactivity for the following pairs towards the respective mechanism
Choose the correct answer from the options given below:
| A. |
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| B. |
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| C. |
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| D. |
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2-Methyl propyl bromide reacts with and gives 'A' whereas on reaction with
it gives 'B'. The mechanism followed in these reactions and the products 'A' and 'B' respectively are :
| A. |
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| B. |
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| C. |
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| D. |
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Which among the following halide/s will not show $\mathrm{S}_{\mathrm{N}} 1$ reaction
(A)$\mathrm{H}_2 \mathrm{C}=\mathrm{CH}-\mathrm{CH}_2 \mathrm{Cl}$
(B) $\mathrm{CH}_3-\mathrm{CH}=\mathrm{CH}-\mathrm{Cl}$
Choose the most appropriate answer from the options given below :
| A. |
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| B. |
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| C. |
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| D. |
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Given below are two statements:
Statement - I : High concentration of strong nucleophilic reagent with secondary alkyl halides which do not have bulky substituents will follow $\mathrm{S}_{\mathrm{N}}{ }^2$ mechanism.
Statement - II : A secondary alkyl halide when treated with a large excess of ethanol follows $\mathrm{S}_{\mathrm{N}}{ }^1$ mechanism.
In the light of the above statements, choose the most appropriate from the options given below:
| A. |
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| B. |
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| C. |
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| D. |
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SN1 reactions are generally carried out in polar protic solvents (like water, alcohol, acetic acid, etc.).
