How many chiral carbon atoms are present in 2-Iodo-3, 4, 5-trimethylhexane ?

Question

TestHub · Accepted Answer

The structure of 2-iodo-3,4,5-trimethylhexane is $C H_{3} - C H (I) - C H (C H_{3}) - C H (C H_{3}) - C H (C H_{3}) - C H_{3}$ .

Let us examine each carbon atom in the principal chain for chirality by checking if it is bonded to four different groups:

$C_{1}$ : Bonded to three identical hydrogen atoms, hence achiral.

$C_{2}$ : Bonded to $- H$ , $- I$ , $- C H_{3}$ , and $- C H (C H_{3}) C H (C H_{3}) C H (C H_{3})_{2}$ . All four groups are different, making $C_{2}$ a chiral center.

$C_{3}$ : Bonded to $- H$ , $- C H_{3}$ , $- C H (I) C H_{3}$ , and $- C H (C H_{3}) C H (C H_{3})_{2}$ . All four groups are different, making $C_{3}$ a chiral center.

$C_{4}$ : Bonded to $- H$ , $- C H_{3}$ , $- C H (C H_{3})_{2}$ , and $- C H (C H_{3}) C H (I) C H_{3}$ . All four groups are different, making $C_{4}$ a chiral center.

$C_{5}$ : Bonded to $- H$ , $- C H_{3}$ , $- C H_{3}$ (from $C_{6}$ ), and $- C H (C H_{3}) C H (C H_{3}) C H (I) C H_{3}$ . Since it is bonded to two identical methyl groups, $C_{5}$ is achiral.

$C_{6}$ : Bonded to three identical hydrogen atoms, hence achiral.

The methyl substituents on $C_{3}$ , $C_{4}$ , and $C_{5}$ are also bonded to three identical hydrogen atoms and are achiral.

Thus, there are exactly $3$ chiral carbon atoms ( $C_{2}$ , $C_{3}$ , and $C_{4}$ ).

Answer: $3$

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