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Strong and Weak bases, SN2 Reaction, SN1 Reaction, Nucleophilic Substitution are considered the most difficult concepts.
75 Questions around this concept.
The major product obtained in the following reaction is :
Which of the following reactions is an example of nucleophilic substitution reaction?
In a face-centered cubic lattice atoms A are at the corner points and atoms B at the face-centered points. If atom B is missing from one of the face-centered points, the formula of the ionic compound is :
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Tertiary alkyl halides are practically inert to substitution by mechanism because of
The organic chloro compound, which shows complete stereochemical inversion during a reaction, is
In an SN 1 reaction on chiral centres, there is :
Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono-substituted alkyl halide?
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Which one is most reactive towards SN1 reaction?
In which of the following compounds. the C-Cl bond ionisation shall give most stable carbonium ion?
Which one of the following bases is not present in DNA?
Most common bases that we have use are alc.KOH and aqueous NaOH. In alc.KOH, we have EtO-(CH3-CH2-O-) as the base while in aqueous NaOH, the base is OH-. The strength of these two bases are given below:
CH3-CH2-O- > OH-
Because CH3-CH2- is the releasing group and hence it unstabilize the O-, thus it reacts faster and hence it is stronger base. The reactions occurs as follows:
For alc.KOH:
For aq.NaOH:
NOTE: Since, we have retention product and ionversion product both, therefore 'Partial racemisation' can occur.
Very stong base such as sodium or potassium amide react with aryl halide, even those without electron withdrawing substituents to give products corresponding to nucleophilic substitution of halide by the base.
Mechanism
Aryl halides are extremely less reactive towards nucleophilic substitution reactions due to the following reasons:
Chlorobenzene can be converted into phenol by heating in aqueous sodium hydroxide solution at a temperature of 623K and a pressure of 300 atmospheres.
The presence of an electron withdrawing group (-NO2 ) at ortho- and para-positions increases the reactivity of haloarenes.
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