Question 18.3: Determining Chirality Lactic acid can be isolated from sour ......
Determining Chirality
Lactic acid can be isolated from sour milk. Is lactic acid chiral?
\begin{matrix} \underset{\mid}{O}H \underset{\mid\mid}{O}\\ \underset{3}{C}H_3—\underset{2}{C}H—\underset{1}{C}—OH\\ Lactic acid\end{matrix}
ANALYSIS A molecule is chiral if it contains one C atom bonded to four different groups. Identify any C atoms that meet this condition.
To find out if lactic acid is chiral, list the groups attached to each carbon atom:
\begin{matrix} \underset{\mid}{O}H \underset{\mid\mid}{O}\\ \underset{3}{C}H_3—\underset{2}{C}H—\underset{1}{C}—OH\\ Lactic acid\end{matrix}
Next, look at the lists to see if any carbon atom is attached to four different groups. Of the three carbons, carbon 2 has four different groups, and lactic acid is therefore chiral.