Chemistry MCQs for NEET — Practice Questions with Answers

The NCERT text states: 'Thus the absence of pure double bond in benzene accounts for the reluctance of benzene to show addition reactions under normal conditions, thus explaining the unusual behaviour of benzene.' This 'absence of pure double bond' is due to the delocalized $\pi$ electron system, which contributes to its enhanced stability. Therefore, option o3 is the correct explanation.

The NCERT text provides a list of common names: 'Methylbenzene (Toluene)'. Therefore, option o3 is correct.

The NCERT text says: 'Substituent of the base compound is assigned number 1 and then the direction of numbering is chosen such that the next substituent gets the lowest number.' This clarifies the numbering rule, making option o2 correct.

The NCERT text clearly states: 'For tri- or higher substituted benzene derivatives, these prefixes cannot be used and the compounds are named by identifying substituent positions on the ring by following the lowest locant rule.' Hence, option o3 is correct.

The NCERT text states: 'When a benzene ring is attached to an alkane with a functional group, it is considered as substituent, instead of a parent. The name for benzene as substituent is phenyl (C6H5-, also abbreviated as Ph).' Therefore, 'phenyl' is the correct name.

The NCERT text mentions: 'Aromatic hydrocarbons, despite having unsaturation, undergo mainly electrophilic substitution reactions. These undergo addition reactions only under special conditions.' This highlights the predominant reaction type for aromatic hydrocarbons, making option o3 correct.

The C-O bond in ethers can be cleaved by hydrogen halides. In the case of an alkyl-aryl ether like anisole, the cleavage occurs such that the halide attacks the alkyl group. The context states 'the attack by I- ion breaks O–CH3 bond to form CH3I. Phenols do not react further to give halides because the $sp^2$ hybridised carbon of phenol cannot undergo nucleophilic substitution reaction needed for conversion to the halide.' Thus, phenol and iodomethane are formed.

The NCERT text explicitly states, 'The alkoxy group (-OR) is ortho, para directing and activates the aromatic ring towards electrophilic substitution in the same way as in phenol.'

The context mentions, 'anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron (III) bromide catalyst. It is due to the activation of benzene ring by the methoxy group.' This activation makes the ring sufficiently electron-rich to react with the electrophile without a stronger catalyst.

Similar to phenols, where '-OH group directs the incoming group to ortho and para positions in the ring as these positions become electron rich due to the resonance effect caused by –OH group', the alkoxy group in ethers also shows a strong positive resonance effect, donating electron density to the ortho and para positions, thus activating them for electrophilic attack.