Pentachlorocyclopropane
[CAS# 6262-51-7]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Cyclic hydrocarbon
• Name: Pentachlorocyclopropane
• Synonyms: 1,1,2,2,3-pentachlorocyclopropane
• Molecular Formula: C₃HCl₅
• Molecular Weight: 214.31
• CAS Registry Number: 6262-51-7
• EC Number: 613-064-5
• SMILES: C1(C(C1(Cl)Cl)(Cl)Cl)Cl

Properties

• Solubility: 187.5 mg/L (25 ºC water)
• Density: 1.8±0.1 g/cm³, Calc.^*
• Index of Refraction: 1.552, Calc.^*
• Melting point: 19.99 ºC
• Boiling Point: 165.05 ºC, 182.2±35.0 ºC (760 mmHg), Calc.^*
• Flash Point: 66.4±23.3 ºC, Calc.^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H315-H319-H335
• Precautionary Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

Discovory and Applicatios

Pentachlorocyclopropane is a halogenated cyclopropane compound with the molecular formula C₃Cl₅. It consists of a three-membered cyclopropane ring substituted with five chlorine atoms, making it a highly chlorinated and strained ring system. The compound has been studied primarily in the context of pesticide chemistry and organochlorine compound research. Due to its structural similarity to various halogenated pesticides, it has attracted attention for both its synthesis and its transformation pathways in environmental systems.

The compound was developed during the mid-20th century when intensive research efforts were directed toward the synthesis of chlorinated hydrocarbons with potential insecticidal or pesticidal properties. The discovery of pentachlorocyclopropane was associated with attempts to explore novel cyclopropane derivatives for agricultural use, particularly in the development of soil fumigants and pest control agents. Although pentachlorocyclopropane itself did not find widespread commercial application as an active pesticide ingredient, it served as a model compound for studying the reactivity and environmental fate of highly chlorinated cyclopropanes.

Pentachlorocyclopropane has been synthesized through chlorination of cyclopropane derivatives under conditions that promote substitution with multiple chlorine atoms. The reaction typically involves free radical chlorination using chlorine gas under ultraviolet light or thermal activation, allowing the stepwise replacement of hydrogen atoms with chlorine. Alternatively, more selective chlorination strategies using reagents such as sulfuryl chloride or antimony pentachloride have been explored to minimize byproducts and achieve higher yields of the desired pentachlorinated product.

In environmental chemistry, pentachlorocyclopropane is of interest due to its stability and resistance to degradation. Like many organochlorine compounds, it exhibits low water solubility and high lipid solubility, characteristics that can lead to bioaccumulation in ecosystems. However, specific data on the environmental persistence and toxicology of pentachlorocyclopropane are limited compared to more widely studied compounds such as DDT or hexachlorocyclohexane. Its structural features, especially the combination of ring strain and heavy halogenation, make it a compound of interest in mechanistic studies of dechlorination and photodegradation processes.

In laboratory studies, pentachlorocyclopropane has been used to explore the behavior of polyhalogenated cyclopropanes under various chemical and physical conditions. Its ring strain, combined with electron-withdrawing chlorine substituents, renders it susceptible to ring-opening reactions under nucleophilic or reductive conditions. Such reactions can produce trichlorinated acyclic products or dehalogenated derivatives, depending on the reagents and conditions employed.

From a structural chemistry standpoint, pentachlorocyclopropane is notable for its unique electronic and geometric properties. The cyclopropane ring itself is characterized by significant angle strain due to the 60° bond angles, which deviate substantially from the ideal tetrahedral angle of 109.5°. The addition of five chlorine atoms further affects the molecule’s geometry and electron distribution, contributing to its reactivity and influencing its interactions with other chemical species. Spectroscopic techniques such as nuclear magnetic resonance (NMR) and mass spectrometry have been employed to study its structure and fragmentation patterns.

Although not used as a commercial pesticide, pentachlorocyclopropane continues to be referenced in the scientific literature for its role in understanding the behavior of chlorinated ring systems and its relevance in the historical context of organochlorine research. It serves as a representative compound in discussions of halogenated hydrocarbon chemistry, environmental contaminant modeling, and synthetic transformations involving strained ring systems. Its study contributes to the broader knowledge of the reactivity and stability of chlorinated organic compounds in both laboratory and environmental settings.

References

1989 New Aspects of Highly Strained Ring Chemistry. Strain and Its Implications in Organic Chemistry.
DOI: 10.1007/978-94-009-0929-8_25

2005 Pentachlorocyclopropane/Base Complexes: Matrix Isolation Infrared Spectroscopic and Density Functional Study of C-H- - -N Hydrogen Bonds. The Journal of Physical Chemistry A, 109(34).
DOI: 10.1021/jp0581781

2019 Thermal cyclopropyl�allyl rearrangement of gem-chlorofluorocyclopropanes under gas-phase pyrolysis conditions. Formation of chlorofluoroalkenes and 2-fluorobuta-1,3-dienes. Russian Chemical Bulletin, 68(7).
DOI: 10.1007/s11172-019-2567-3