Total number of compounds with Chiral carbon atoms from following is _________.

Solution

Chemistry ma’am · 3 steps

For each carbon with an H, list its four groups. If any two match, it is not chiral, so move on.

1. The test. A carbon is chiral when all four groups on it are different. A carbon in a C=O, a CH₂ or a CH₃ cannot qualify, so check only the CH carbons carrying a branch.

   Compound	Candidate carbon and its groups	Chiral?
   2-methylcyclohexanone	C-2: H, CH₃, C=O side of ring, CH₂ side of ring	yes
   cyclopentane-1,3-dione	every ring carbon is C=O or CH₂	no
   CH₃CH₂CH(NO₂)COOH	H, NO₂, COOH, C₂H₅	yes
   CH₃CH₂CHBrCH₂CH₃	H, Br, C₂H₅, C₂H₅: two ethyl groups	no
   CH₃CH(I)CH₂NO₂	H, I, CH₃, CH₂NO₂	yes
   CH₃CH₂CH(OH)CH₂OH	H, OH, CH₂OH, C₂H₅	yes
   CH₃CH(I)CH(I)C₂H₅	C-2 and C-3 both carry four different groups	yes, counted once

2. Count compounds. The question asks for compounds, not chiral carbons. The last compound has two chiral carbons but adds only 1 to the count.
3. So. The chiral compounds are 2-methylcyclohexanone, the nitro acid, the iodonitro compound, the diol and the diiodo compound, giving 5.

The common slip: 6. Counting chiral carbons instead of compounds gives 6, because the diiodo compound has two chiral centres but is only one compound.

The idea to keep. Write out all four groups on each suspect carbon. Ring carbons count as different when the two ring paths differ, and identical alkyl groups on both sides kill chirality.

Answer from the NTA final answer key. Solution by PrepWiser.