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JEE Advanced levelSingle correct optionDifficulty 3 of 3cc162

Square planar exists as isomers X and Y. Only X reacts with oxalic acid, replacing both to give , whereas Y does not (the bidentate oxalate can only span adjacent positions). Which statement is correct?

  1. AX is the trans isomer with a non-zero dipole moment, and Y is the cis isomer with zero dipole moment.
  2. BX is the cis isomer with zero dipole moment, and Y is the trans isomer with a non-zero dipole moment.
  3. CX is the cis isomer with a non-zero dipole moment, and Y is the trans isomer with zero dipole moment.
  4. DX and Y are optical isomers and differ only in the direction of rotation of plane-polarised light.

Answer: C

Oxalate spans a bite of about , so it can chelate only if the two being replaced are cis. X is therefore cis, with the bond dipoles adding to a net dipole. In trans-Y the dipoles are opposed and cancel, giving zero dipole moment. Neither is chiral because each has the molecular plane as a mirror plane.
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