Which of the following compounds has a plane of symmetry?
$R = -CH(Cl)-CH_3$
$S = -CH(Cl)-Br$

Among the structures shown below,which has the lowest potential energy?

Which one among the following carbocations has the longest half-life?

The correct statement$(s)$ concerning the structures $E, F$ and $G$ is (are):
$E$: $CH_3CH_2CH(CH_3)COCH_3$
$F$: $CH_3CH_2C(OH)=C(CH_3)_2$ (enol form)
$G$: $CH_3CH_2C(CH_3)=C(OH)CH_3$ (enol form)
$(A)$ $E, F$ and $G$ are resonance structures
$(B)$ $E, F$ and $E, G$ are tautomers
$(C)$ $F$ and $G$ are geometrical isomers
$(D)$ $F$ and $G$ are diastereomers

Which of the following molecules is (are) chiral?

Which of the following structures has an $R$-configuration at the chiral center?