In the following reaction sequence, X and Z, respectively are : CH3CH2CH2-OH + PCl5 CH3CH2CH2Cl + X + HCl [figure]
- X = POCl3; Z = [figure]
- X = POCl3; Z = CH3CH2CH2-Br
- X = H3PO3; Z = [figure]
- X = H3PO3; Z = CH3CH2CH2-Br
Answer
(2) X = POCl3; Z = CH3CH2CH2-Br
Solution
ROH + PCl5 RCl + POCl3 + HCl, so X = POCl3.
With alc. KOH and heat (Δ), CH3CH2CH2Cl undergoes dehydrohalogenation (β-elimination), so Y is propene, CH3-CH=CH2.
As per NCERT, in presence of benzoyl peroxide HBr adds to an unsymmetrical alkene against Markovnikov's rule (peroxide effect, free radical mechanism):
CH3-CH=CH2 + HBr (C6H5CO)2O2 CH3-CH2-CH2-Br
Hence Z is 1-bromopropane.
∴ X = POCl3; Z = CH3CH2CH2-Br
Answer: (2)