Question

The correct statement(s) about dipole moments of $R_{3}NO$ and $R_{3}PO$ is/are:

• A. Dipole moment of $R_{3}NO>$ dipole moment of $R_{3}PO$
• B. Dipole moment of $R_{3}NO<$ dipole moment of $R_{3}PO$
• C. Experimental dipole moment of $R_{3}PO>$ theoretical dipole moment of $R_{3}PO$
• D. Experimental dipole moment of $R_{3}PO<$ theoretical dipole moment of $R_{3}PO$

Answer 1

Answer: (A), (D)

The correct options are
A Dipole moment of $R_{3}NO>$ dipole moment of $R_{3}PO$
D Experimental dipole moment of $R_{3}PO<$ theoretical dipole moment of $R_{3}PO$


${\mu }_1>{\mu }_2\Rightarrow$ due to a higher difference in the electronegativities of $N$ and $C$ than those between $P$ and $C$.
${\mu }_1^{{}^{\prime }}>{\mu }_2^{{}^{\prime }}\Rightarrow$ because $2p_x=3d_{\pi }$ back bonding in the $P-O$ bond decreases its dipole moment hence $(R_{3}NO{)}_{\mu }>(R_{3}PO{)}_{\mu }$

Hence, experimental dipole moment of $R_{3}PO<$ theoretical dipole moment of $R_{3}PO$ due to back bonding from O to P.