Question

${\mu }_{obs}=\mathbf{\Sigma }{\mu }_i{x}_i$
where ${\mu }_i$ is the dipole moment of stable conformer and $x_i$ is
the mole fraction of that conformer.
(a) Write stable conformer for $Z-C{H}_2-C{H}_2-Zin$
Newman's projection.
If ${\mu }_{solution}=1.0D$ and mole fraction of anti form = 0.82,
find ${\mu }_{gauche}$
(b) Write most stable meso conformer of $(CHDY{)}_2.$ If
(i) $Y=C{H}_3$ about $C_2-C_3$ rotation and
(ii) Y=OH about $C_1-C_2$ rotation.

Answer 1

Mole fraction of anti form = 0.82
Mole fraction of gauche form = 0.18
${\mu }_{obs}=1D$
$\Rightarrow 1={\mu }_{anti}\times 0.82+{\mu }_{gauche}\times 0.18$
$\because {\mu }_{anti}=0$
$\Rightarrow 1={\mu }_{gauche}\times 0.18$
$\Rightarrow {\mu }_{gauche}=\frac{1}{0.18}=5.55D$
Structure (ii) is more stable than its anti conformer because of
intramolecular H-bonding.