Ncert Solutions Chemistry Class 12th

This is a multiple choice answer as classified in NCERT Exemplar

The Correct Answer is Option (i).

A racemic mixture is one that contains two enantiomers in equal quantities but has no optical activity because the opposing optical rotations of the two enantiomers cancel each other out. The optically active reactant undergoes the S_N¹ reaction in order for a racemic mixture to form following nucleophilic substitution. Option (a) is a chiral carbon atom that will undergo the S_N¹ process, resulting in a racemic mixture. Option (b) does not include an asymmetric carbon, but option (c) has a secondary carbon asymmetric atom that is less reactive to an S_N¹ substitution. The right answer is (i).

This is a multiple choice answer as classified in NCERT Exemplar

The Correct Answer is Option (i).

When benzyl chloride is treated with aqueous sodium hydroxide, where -OH is the nucleophile, a nucleophilic substitution reaction occurs, resulting in the formation of benzyl alcohol. The benzene ring is resonance stabilised here, and this stability is extended to the connected methylene group, giving a positive charge to -CH₂, making the whole carbocation stable when the link between benzyl and bromide is broken. This is an S_N¹ reaction with two stages that is followed due to the stability of the carbocation. This is a coordinated reaction that takes place in two phases. The halide group first exits the carbocation, and then the nucleophile binds to the cation, producing alcohol. The right answer is (i).

This is a multiple choice answer as classified in NCERT Exemplar

The Correct Answer is Option (iv).

By electrophilic substitution, aromatic arenes react with chlorine in the presence of Lewis acid catalysts such as iron (III) chloride, yielding ortho and para isomers of haloarenes. (ii) and (iii) are both products of the reaction. Cl₂ forms a coordination complex with FeCl₃, creating the Cl + FeCl₄ - complex, which has a small positive charge on Cl and a negative charge on FeCl₄ - . This Cl⁺  then interacts with the aromatic double bonds of the toluene molecule to create an addition product, which is subsequently deprotonated to form a mixture of o-, p-, and m- chlorotoluene isomers. Because the m- isomer is highly unstable, the product is not accessible in the o- and p- forms.

This is a multiple choice answer as classified in NCERT Exemplar

The Correct Answer is Option (ii).

We may conclude from the given compound's common name that there are two -C₂H₅ groups and one -Br group linked to a CH₄ molecule. Bromomethane would be represented by the symbol CH₃-Br. Two ethyl groups can be replaced for the hydrogens in the methyl molecule to make diethylbromomethane (C₂H₅)CH (C₂H₅)Br. The longest parent chain must be identified in order to offer an IUPAC name. The parent chain is CH₃-CH₂-CH (Br)-CH₂-CH₃, with the -Br group from either side connected to the third carbon atom. Because the parent chain has five carbons, the molecule is termed 3-bromopentane.

This is a multiple choice answer as classified in NCERT Exemplar

The Correct Answer is Option (ii).

When an alkyl halide with -hydrogen atoms reacts with a base or a nucleophile, depending on the nature of the alkyl halide, the strength of the base or nucleophile, the size of the molecules, and the reaction circumstances, it can undergo a specific kind of reaction. A substitution or elimination process can be followed by an alkyl halide, as well as the two kinds of substitution, S_N¹ and S_N². Because the entering nucleophile cannot engage with the bulky substituents on or near the carbon atom, the main alkyl halide prefers the S_N²reaction. As a result, primary alkyl halides and methyl halides have the greatest proclivity for S_N² reactions.