Chemistry Class 11 NCERT Solutions: Chapter 12 Organic Chemistry Some Basic Principles and Techniques Part 3

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Q: 5. Which of the following represents the correct IUPAC name for the compounds concerned?

(A) Dimethylpentane or 2-Dimethylpentane

(B) Trimethyloctane or -Trimethyloctane

(D) 2-Chloro-4-methylpentane or 4-Chloro-2-methylpentane

(D) But-3-yn-1-ol or But -yen

Answer:

(A) The prefix di in the IUPAC name indicates that two identical substituent groups are present in the parent chain. Since two methyl groups are present in the C–2 of the parent chain of the given compound, the correct IPUAC name of the given compound is 2, 2–dimethylpentane.

(B) Locant number is lower than Hence; the IUPAC name of the given compound is trimethyloctane.

(C) If the substituents are present in the equivalent position of the parent chain, then the lower number is given to the one that comes first in the name according to the alphabetical order. Hence, the correct IUPAC name of the given compound is 2–chloro– 4–methylpentane.

(D) Two functional groups – alcoholic and alkyne – are present in the given compound. The principal functional group is the alcoholic group. Hence, the parent chain will be suffixed with ol. The alkyne group is present in the C–3 of the parent chain. Hence, the correct IUPAC name of the given compound is But–3–yn–1–ol.

Q: 6. Draw formulas for the first five members of each homologous series beginning with the following compounds.

(A)

(B)

(C)

Answer:

The first five members of each homologous series beginning with the given compounds are shown as follows:

(A)

: Methanoic acid

: Ethanoic acid

: Propanoic acid

: Butanoic acid

: Pentanoic acid

(B)

: Propanone

: Butanone

: Pentane – 2 – one

: Hexane – 2- one

Heptane – 2 – one

(C)

: Ethene

: Propene

: 1 – Butene

: 1 – Pentene

: 1 Hexene