NEET Practice Questions (MCQs) with Answers & Solutions

The NCERT text states: 'The delocalised $\pi$ electron cloud is attracted more strongly by the nuclei of the carbon atoms than the electron cloud localised between two carbon atoms. Therefore, presence of delocalised $\pi$ electrons in benzene makes it more stable than the hypothetical cyclohexatriene.' This confirms option o3.

The NCERT text states the characteristics of aromaticity: '(i) Planarity (ii) Complete delocalisation of the $\pi$ electrons in the ring (iii) Presence of (4n + 2) $\pi$ electrons in the ring where n is an integer (n = 0, 1, 2, . . .). This is often referred to as Hückel Rule.' The presence of a benzene ring is often associated with aromatic compounds, but not a universal rule for aromaticity itself, as 'non-benzenoids' can also be aromatic. Thus, option o4 is not a strict criterion.

The NCERT text specifies: 'In the trivial system of nomenclature the terms ortho (o), meta (m) and para (p) are used as prefixes to indicate the relative positions 1,2;1,3 and 1,4 respectively.' This matches option o2.

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.

According to the NCERT text, 'Growth, at a cellular level, is principally a consequence of increase in the amount of protoplasm.' (Chapter: PLANT_GROWTH_AND_DEVELOPMENT, Section 13.1.2).