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An alkyl group is formed by removing a hydrogen atom from a saturated hydrocarbon. How is an alkyl group named?
The NCERT states, 'An alkyl group is named by substituting ‘yl’ for ‘ane’ in the corresponding alkane.' For example, methane ($CH_4$) becomes methyl ($-CH_3$).
What is the primary rule for numbering the carbon atoms of the parent chain in a branched-chain alkane?
The NCERT text states, 'The carbon atoms of the parent chain are numbered...in such a way that the branched carbon atoms get the lowest possible numbers.' This ensures the lowest locant set for substituents.
When two or more identical substituent groups are present in a branched-chain alkane, how are they indicated in the IUPAC name?
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.'
Consider the compound: $CH_3–CH_2–CH(CH_2CH_3)–CH_2–CH(CH_3)–CH_2–CH_3$. What is the correct IUPAC name for this compound?
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).
Which of the following prefixes (used in naming branched alkyl groups) are NOT considered a part of the fundamental name for alphabetical arrangement?
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.
What is the IUPAC name for the following compound: $(CH_3)_3CCH_2C(CH_3)_3$?
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.
Which of the following statements about alkenes is INCORRECT?
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.
What is the IUPAC name for the compound $CH_2=CH–CH_2–CH_3$?
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.
In naming branched alkyl groups attached to a parent alkane, which carbon atom of the branch is numbered 1?
The NCERT states, 'However, the carbon atom of the branch that attaches to the root alkane is numbered 1 as exemplified below.'
When two substituents are found in equivalent positions on a parent chain, which substituent is given the lower number?
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.'
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