NEET Practice Questions (MCQs) with Answers & Solutions

According to the NCERT, 'If two or more identical substituent groups are present then...prefixes such as di (for 2), tri (for 3), tetra (for 4)...are used. While writing the name of the substituents in alphabetical order, these prefixes, however, are not considered.'

The longest carbon chain contains 7 carbons (heptane). Numbering from the end that gives the lowest locants for substituents (right end in this case), the ethyl group is at carbon 3 and the methyl group is at carbon 5. Alphabetical order dictates ethyl before methyl. Hence, 3-ethyl-5-methylheptane. (Similar to example given of 3-ethyl-5-methylheptane not 5-ethyl-3-methylheptane).

The NCERT states: 'The prefixes sec- and tert- are not considered to be the part of the fundamental name.' It also states for identical substituents: 'While writing the name of the substituents in alphabetical order, these prefixes [di, tri, tetra], however, are not considered.' Therefore, both sec-, tert- and di-, tri- are not considered for alphabetical order.

The longest chain is 5 carbons (pentane). There are two methyl groups at carbon 2 and two methyl groups at carbon 4. So, it's 2,2,4,4-Tetramethylpentane, as confirmed in Problem 9.3 (i) example.

The general formula for alkenes is $C_nH_{2n}$. The general formula $C_nH_{2n+2}$ is for alkanes. The other statements are correct as per the NCERT text regarding alkenes.

The longest chain contains four carbons, making it a 'but'. The double bond starts at the first carbon. Hence, it is But-1-ene, as explicitly listed in the IUPAC names of alkenes table.

The NCERT states, 'However, the carbon atom of the branch that attaches to the root alkane is numbered 1 as exemplified below.'

As per NCERT Rule 5, 'If the two substituents are found in equivalent positions, the lower number is given to the one coming first in the alphabetical listing.'

The NCERT text clearly defines: 'Unsaturated hydrocarbons are those, which contain at least one carbon-carbon double or triple bond.'

Heptane is a straight-chain saturated hydrocarbon with only single C-C bonds, falling under the definition of an alkane. Propene is an alkene, Ethyne is an alkyne, and Benzene is an aromatic hydrocarbon.