Organic Chemistry Basics - Result Question 192
####45. $\mu _{obs}=\Sigma \mu _i x _i$
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 $Z-CH _2-CH _2-Z$ in Newman’s projection.
If $\mu _{\text {solution }}=1.0 D$ and mole fraction of anti form $=0.82$, find $\mu _{\text {gauche }}$
(b) Write most stable meso conformer of $(CHDY) _2$. If
(i) $Y=CH _3$ about $C _2-C _3$ rotation and
(ii) $Y=OH$ about $C _1-C _2$ rotation.
$(2005,6 M)$
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Solution:
- (a)
anti
gauche
Mole fraction of anti form $=0.82$
Mole fraction of gauche form $=0.18$
$$ \begin{array}{rlrl} & \mu _{obs} & =1 D \ \Rightarrow & 1 & =\mu _{\text {anti }} \times 0.82+\mu _{\text {gauche }} \times 0.18 \ \because & & \mu _{\text {anti }} & =0 \Rightarrow 1=\mu _{\text {gauche }} \times 0.18 \ \Rightarrow & & \mu _{\text {gauche }}=\frac{1}{0.18}=5.55 D \end{array} $$
(b)
(i)
(ii) Structure (ii) is more stable than its anti conformer because of intramolecular H-bonding.
