Q79 / 180 · NEET 2016 (Phase 2) · Chemistry

The correct increasing order of trans-effect of the following species is

A
${NH}_{3} > {CN}^{-} > {Br}^{-} > C_{6} H_{5}^{-}$
Correct answer
B
${CN}^{-} > C_{6} H_{5}^{-} > {Br}^{-} > {NH}_{3}$
C
${Br}^{-} > {CN}^{-} > {NH}_{3} > C_{6} H_{5}^{-}$
D
${CN}^{-} > {Br}^{-} > C_{6} H_{5}^{-} > {NH}_{3}$

Solution

The trans effect is the increased lability of ligands that are trans to certain other ligands, which can thus be regarded as trans-directing ligands. It is attributed to electronic effects and it is most notable in square planar complexes, although it can also be observed for octahedral complexes.
${CN}^{-} > C_{6} H_{5}^{-} > {Br}^{-} > {NH}_{3}$

Hence, the correct answer is option: 'B'.

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