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प्रश्न
Elimination reactions (especially β-elimination) are as common as the nucleophilic substitution reaction in case of alkyl halides. Specify the reagents used in both cases.
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उत्तर
Alkyl halides undergo nucleophilic substitution as well as elimination (Beta-elimination) reaction. However, by proper choice of reagents and reaction conditions, a particular product can be obtained. Usually strong and bulky bases and high temperature favour elimination reactions while weaker and smaller bases and lower temperature favour substitution reactions. For example, ethyl bromide on heating with alcoholic KOH (which contain stronger base, \[\ce{C2H5O}\] ion) at about 473-523 K undergoes elimination to give ethene. But with aqueous \[\ce{KOH}\] at about 373 K, it gives ethanol.
\[\ce{CH3CH2Br ->[alc.KOH][473-523 K] CH2 = CH2 (Elimination)}\]
\[\ce{CH3CH2Br ->[aq.KOH][373 K] CH3CH2OH (Substitution)}\]
Nucleophilic substitution: Reagents used nucleophilies like \[\ce{- \overset{-}{O}H, NH3, \overset{-}{C} ≡ N;, AgCN:, O = N - O, \overset{-}{O}R}\]' etc. also, alc. \[\ce{KOH}\] at lower temperature (373 K) undergoes substitution reaction.
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संबंधित प्रश्न
Write the structure of an isomer of compound C4H9Br which is most reactive towards SN1 reaction
Which would undergo SN1 reaction faster in the following pair and why?
How do you convert the following:
Ethanol to propanenitrile
Write the structure of the major product in each of the following reaction :
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-Bromobutane, 1-Bromo-2, 2-dimethylpropane, 1-Bromo-2-methylbutane, 1-Bromo-3-methylbutane
How the following conversion can be carried out?
Ethyl chloride to propanoic acid.
Identify 'A' in the following reaction -
(a) 2- Bromo-2 methylbutane
(b) 1 -Bromo-2,2-dimethylpropane
(c) 1 - Bromo - 3 -methylbutane
(d) 1 - Bromo- 2 -methylpropane
Which of the following pairs is/are correctly matched?
| Reaction | Product | |
| I | RX + AgCN | RNC |
| II | RX + KCN | RCN |
| III | RX + KNO2 | \[\begin{array}{cc} \phantom{.......}\ce{O}\\ \phantom{.....}/\\ \ce{R - N}\phantom{....}\\ \phantom{.....}\backslash\backslash\\ \phantom{.......}\ce{O} \end{array}\] |
| IV | RX + AgNO2 | \[\ce{R-O-N=O}\] |
In the SN1 reaction, racemization takes place. It is due to:
Isopropyl chloride undergoes hydrolysis by:
Which of the following is an optically active compound?
An organic molecule necessarily shows optical activity if it ____________.
The increasing order of reactivity towards SN1 mechanism is:
(I) \[\begin{array}{cc}
\ce{CH3-CH-CH2-CH3}\\
|\phantom{........}\\
\ce{CH3}\phantom{.....}
\end{array}\]
(II) CH3CH2CH2Cl
(III) P–CH3O–C6H4–CH2Cl
Which of the statements are correct about above reaction?
(i) (a) and (e) both are nucleophiles.
(ii) In (c) carbon atom is sp3 hybridised.
(iii) In (c) carbon atom is sp2 hybridised.
(iv) (a) and (e) both are electrophiles.
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.
Chlorination of alkanes is an example of
When CH3CH2CHCl2 is treated NaNH2 product formed is:-
Complete the reaction with the main product formed:
