NEET Chemistry: Chemistry - Organic Chemistry questions with solutions

Q1. While numbering carbon atoms of long carbon chain numbering should be done in such a manner that substitution gets

1. lowest possible number
2. highest possible number
3. some middle number
4. none of the above

Answer: lowest possible number

In IUPAC nomenclature, carbon chains are numbered to give substituents the lowest possible numbers. This makes the name unambiguous and follows the lowest-locant rule.

Q2. when compound \( \mathbf{C} \) is treated with \( \boldsymbol{B} \boldsymbol{r}_{2} / \boldsymbol{C} \boldsymbol{C l}_{4} \)

1. a meso dibromide is formed.
2. four stereo-isomers of dibromides are fromed.
3. racemic mixture of dibromides are formed.
4. a pair of enantiomers of dibromides in unequal amount is formed.

Answer: racemic mixture of dibromides are formed.

Bromination with Br2/CCl4 proceeds by anti addition through a bromonium ion. When the starting alkene is achiral and the new stereocenters are formed from either face equally, the products are a racemic mixture of enantiomers.

Q3. The IUPAC name of the given compound is :

1. 3-cyclopropane-1-propene
2. 3-cyclopropyl-1-propene
3. 3-cyclopropyl-2-propene
4. 3-cyclopropane-2-propene

Answer: 3-cyclopropyl-1-propene

The parent chain is propene because it contains the double bond and is the main carbon chain. The three-membered ring is attached as a cyclopropyl substituent at carbon 3, giving 3-cyclopropyl-1-propene.

Q4. The IUPAC name of the compound is:

1. 2 - Methyl -4 - hexanamine
2. 5- Methyl - 3 - hexanamine
3. 2 - Methyl -4 - amino hexane
4. \( 5- \) Methyl -3 - amino hexane

Answer: 2 - Methyl -4 - hexanamine

The amino group is the principal functional group, so it must be named with the suffix "-anamine" and given the lowest possible number. Numbering the hexane chain accordingly places the amino group at C-4 and the methyl substituent at C-2, giving 2-methyl-4-hexanamine.