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I immersed a semi dry green leaf in glass of concentrated NaCl solution . I left it in mild sunlight for around 3 hours . Solution before was clear but afterwards it became reddish brown and the color of leaf turned brown. I want to know why this happened? Please help.

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It is most likely the $\ce{Na+}$ is formed a complex salt with chlorophyll (bulky group) subsequently displacing $\ce{Mg+}$ cation, even though $\ce{Na+}$ doesn't have extra electronic shells for complex ion stabilisation, instead the chlorophyll (through the $\ce{N}$ atoms with lone pairs) provided extra stabilisation of the positively charged $\ce{Na+}$ cation.

Chlorine dissociated from $\ce{NaCl}$ to form aqueous chloride ions $\ce{Cl-(aq)}$ forming a typically greenish-brown solution you noticed during your experiment.

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  • $\begingroup$ Are you saying that chloride ion is greenish brown? If so, why is a sodium chloride solution not brown? $\endgroup$ – jerepierre Feb 27 '17 at 21:35
  • $\begingroup$ Not necessarily, because when isolated it exist as pale greenish-brown gas, however due to the presence of different molecules and aqueous environment several solvents are present together with the chloride ions, and may inhibit the Chloride ions to explicitly show it's typical greenish-brown colour, remember other minor products are also present in solution with the Cl- ions. Also to note in the leaves there is also Fe³+ ions , subsequently can be attributed to the overall color of solution, if we to extract all the "impurities" to leave only chloride ions we would get a color close to green $\endgroup$ – xavier_fakerat Feb 27 '17 at 21:56
  • $\begingroup$ NaCl would not be green because of the lack of "outer shells with vast electrons" so would not get excited to 3d states where it absorbs light, emit some to produce color like what transition elements do. For our complex solution above, the chlorophyll group ( with N lone pairs of electrons) allowed the complex salt to be activated hence emit some light energy to produce color. $\endgroup$ – xavier_fakerat Feb 27 '17 at 22:06

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