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Aqueous Chlorination of D-Limonene
Albert T Lebedev1,2, Elena A Detenchuk1, Tomas B Latkin3
1Organic Chemistry Department, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russia.
Molecules (Basel, Switzerland)
|May 14, 2022
Summary
Aqueous chlorination of limonene forms polychlorinated compounds, with haloforms appearing at high chlorine levels. These reaction products are less toxic than limonene itself.
Area of Science:
- Environmental Chemistry
- Organic Chemistry
- Water Treatment
Background:
- Limonene is a widespread natural and industrial monocyclic terpene found in the environment and consumer products.
- It can be present in water supplies and swimming pools, leading to potential exposure during aqueous chlorination processes.
Purpose of the Study:
- To investigate the reaction products and mechanisms of aqueous chlorination of D-limonene.
- To assess the toxicity of the chlorination byproducts compared to the parent compound.
Main Methods:
- Laboratory experiments involving the aqueous chlorination of D-limonene.
- Analysis of reaction products using electron ionization mass spectrometry.
- Toxicity assessment using the bioluminescence test on *Vibrio fischeri*.
Main Results:
- The primary reaction involves electrophilic addition of hypochlorous acid (HOCl) to limonene's double bonds, following Markovnikov's rule.
- Major products result from the addition of two HOCl molecules, followed by a cascade of addition-elimination reactions yielding polychlorinated species.
- Haloforms, including brominated variants, form at limonene/active chlorine ratios above 1:10.
- Chlorination byproducts exhibited lower toxicity than limonene in *V. fischeri* bioluminescence tests.
Conclusions:
- Aqueous chlorination of limonene leads to complex polychlorinated compounds and haloforms.
- The reaction pathway is characterized by electrophilic addition and subsequent elimination reactions.
- The study indicates that limonene chlorination byproducts may be less toxic than limonene itself.
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