Hexabromocyclododecane: properties, uses, and environmental effects

Hexabromocyclododecane

Chemical Formula: C12H18Br6

Molecular Weight: 641.70

3D Rendering using Chemitorium:

Functional Groups: bromo, cyclo

Shape and Geometric Features: The atom is always a 12-sided figure with six Br vertices. It takes the shape of an octagon that is connected to a hexagon on one side. In a three-dimensional rendering, the molecule takes on a more oval shape rather than the stricter appearance of the two-dimensional rendering.

Chiral Properties and Isomers:

Isomers:

Isomers are the addition or subtraction of electrons in the molecule. The below are the most common isomers of Hexabromocyclododecane. These are coded as alphahexabromocyclododecane, betabromocyclododecane, and gammabromocyclododecane. These indicate which portion of the Bromine in the molecule has been affected by the electron changes.

Chiral Diastereomers: -, ?-, and ?- HBCD

Chirality, by definition is a type of molecule that lacks an internal plane of symmetry. The chirality of Hexabromocyclododecane yields many pollutants which have an adverse affect on the environment (Wong 72). This is directly caused by the necessity to balance the chemicals comprising the molecule, which even in proper balance possesses levels of toxicity. The molecule, by lacking symmetry in its composition makes the creating of chiral diastereomers more prevalent than with other potential compounds.

Dynamic Structures of the Molecule:

Conformations:

Conformation refers to the interconversion of the isomers by rotation around singular bonds. Given the cyclical formulation of the Hexabromocyclododecane molecule, the conformation of the molecule can only be conducted through rotation and not through breaking and reforming of chemical bonds. No matter how the atoms are aligned, the rendering will always illustrate a similar-shaped figure, that of a circular conglomeration of atoms.

Ionization:

Ionization is the process of breaking down a compound into its elemental forms. For Hexabromocyclododecane this would be breaking down the molecule into twelve atoms of carbon, eighteen of hydrogen, and six of bromide which is the portion of the molecule which creates fire retardation.

Polarity of the Bonds and Polarity of the Molecule:

Since the geometric shape of the Hexabromocyclododecane molecule shows itself to be spherical and balanced, the compound has limited polarity. The polarity of the bonds themselves are similarly rounded and thus have limited polarity within the compound itself. Researchers have been able to determine that the compound has a depolarization effect on other materials. "The number of cells showing depolarization-evoked neurotransmitter release was markedly released following Hexabromocyclododecane exposure" (Dingemans).

Properties:

Appearance: white to off-white odorless solid or crystalline powder

Melting Point: 185-195?C

Boiling Point: 240? C

Density: 2.38 g/cm3

Solubility: 66µg/l

Soluble in acetone, benzene, toluene, methylene chloride, but insoluble in water and methanol. It is also soluble in ketone, and chlorinated and aromatic solvents.

Vapor Pressure: 4.7 x 10-7 Hg at 21? C

Stereochemistry: 16 stereoisomers

Reactivity:

"Halogenated aliphatic compounds, such as Hexabromocyclododecane, are moderately or very reactive. Reactivity generally decreases with increased degrees of substitution for halogen for hydrogen atoms. Materials in this group may be incompatible with strong oxidizing and reducing agents. Also, they may be incompatible with many amines, nitrides, azo/diazo compounds, alkali metals, and epoxides. Hexabromocyclododecane can react vigorously with oxidizing materials" (Chemical).

Stability:

Stability is determined by the isomer of Hexabromocyclododecane used, but has high stability overall in thermal situations. The molecule shows fine thermal stability while maintaining optimum performance.

Spectroscopy:

nucleus delta1 pattern integ. multiplicity and coupling constants

1.93 dtd 3.00 d 13.85 t 4.83 d 3.05

1.93 dtd 3.00 d 13.85 t 4.83 d 3.05

1.93 dtd 3.00 d 13.85 t 4.83 d 3.05

1.93 dddd 3.12 d 14.68 d 4.83 d 3.05 d 3.04

1.93 ddt 3.12 d 14.68 d 4.83 t 3.05

1.93 ddt 3.12 d 14.68 d 4.83 t 3.05

1.95 dtd 3.57 d 13.85 t 7.96 d 4.83

1.95 dtd 3.57 d 13.85 t 7.96 d 4.83

1.95 dtd 3.57 d 13.85 t 7.96 d 4.83

1.98 ddt 2.69 d 14.68 d 7.96 t 4.83

1.98 ddt 2.69 d 14.68 d 7.96 t 4.83

1.98 ddt 2.69 d 14.68 d 7.96 t 4.83

4.64 td 1.00 t 4.83 d 3.04

4.64 td 1.00 t 4.83 d 3.05

4.64 td 1.00 t 4.83 d 3.05

4.77 dt 1.00 d 7.96 t 4.83

4.77 dt 1.00 d 7.96 t 4.83

4.77 dt 1.00 d 7.96 t 4.83

This spectroscopy data indicates shows that with a larger number in the nucleus, the lower the integer of radiated energy. Also, the more components in the deltal pattern, the higher the integer produced. At integers of two and five, Hexabromocyclododecane releases the most energy.

Uses / Applications of the Molecule:

Hexabromocyclododecane is primarily used as a flame retardant. It is also used in the production of polystyrene foam. The product is used as flame resistant insulator in building construction. Besides making the building flame retardant, Hexabromocyclododecane insulation also acts as sound insulation and saves energy (Flame). It has been used in the textiles of furniture to make them less flammable and thus save lives. Various other products are infused with hexabromo-cyclododecane to increase their flame resistance. The four main products in which Hexabromocyclododecane is used are: Expandable Polystyrene (EPS), Extruded Polystyrene (XPS), High Impact Polystyrene (HIP), and Polymer dispersion for textiles (Arnot 43).

The product is an important component of the following products:

Flat and pile upholstered furniture

Upholstery seating in transportation, draperies, and wall coverings

Bed mattress ticking

Interior textiles such as blinds

Automobile interior textiles

Car cushions

Insulation boards used to prevent frost heaving of roads and railway embankments

Packaging material

Electrical and electronic equipment

Video cassette housings

Polyvinyl chloride wire, cable, and textile coating

Protective paint

(Environment Canada)

Polystyrene:

Synthesis and/or Isolation of the Molecule:

"Hexabromocyclododecane can be synthesized at a high yield in pure form by brominating 1, 5, 9-cyclododecatriene with bromine in a C4 -- C8 saturated aliphatic alcohol in the presence of a boron trifluoride complex, neutralizing the reaction mixture with a non-aqueous base, and recovering the resulting crystals of Hexabromocyclododecane" (Preparation).

Societal Issues:

There are both environmental and human health concerns related to Hexabromocyclododecane. The material can be released into the environment through the products themselves or from "fugitive emissions during its manufacture and use in subsequent products, and potentially from leaching in landfills, and from incinerator emissions" (Environment). "Occurrence in the environment, high persistence, potential for long-range air transport, and in addition for some of the substances, high bioaccumulation and high toxicity are reasons for concern relating to them" (Environment). According to Dr. Leo Morf, there are other emissions that should be of concern to the human population. These include:

Atmospheric emissions (gaseous and dust bound)

Atmospheric emissions (particulates)

Atmospheric emissions (unintended fires)

Emissions to hydrosphere (particulates)

Emissions to hydrosphere (unintended fires)

Emissions to soil (particulates)

Emissions to soil (unintended fires)

Releases to wastewater (washing of textiles)

Releases to wastewater (cleaning and mop water as well as release of dust sticking at textiles during washing)

Transport to MSWIPS (dust in vacuum cleaner bags

(Figure 1: Effects of Hexabromocyclododecane Emission, Arnot).

All these methods can allow harmful Hexabromocyclododecane into the human body and into the environment as well.

Environmental groups such as the Environmental Protection Agency (EPA) in the United States have been attempting to ban or at least curb the use of Hexabromocyclododecane in polystyrene foam. The end product is difficult to dispose of as it takes a long time to burn and, when it has burnt, releases the chemicals into the air. Additionally, Hexabromocyclododecane that is dumped into rivers and streams is highly toxic to the aquatic life in the vicinity (Arnot 5). Birds come along and eat the affected fish which creates a secondary toxicity, showing that the toxins can be transported through consumption meaning a danger to any humans to eat the fish or who eat the birds who have been affected (SVHC 27). In 2010, the EPA created an action plan to determine how to deal with the product. They wish to add Hexabromocyclododecane to their Concern List of Chemicals. They also wish to restrict the inclusion of the molecule in consumer goods under the Significant New Use Rule (SNUR). This requires any new product to get EPA approval before including the chemical in the product and should the EPA determine that there is no need or if the product is not anything important to mankind, they can make the decision to terminate production. The EPA also wants to make a rule wherein existing manufacturers using Hexabromocyclododecane could be shut down by the government agency. Hexabromo-cyclododecane is in the process of making it onto the Toxics Release Inventory (TRI) which would require manufacturers to take responsibility for creating a toxic material and put out reports about the production and the effects. Lastly, the EPA is conducting a Design for the Environment (DfE) assessment on Hexabromocyclododecane to encourage industries from stopping the use and manufacture of the chemical (Hexabromocyclododecane). The toxic components of the material can be taken in to the body orally, by inhalation, or through the skin (SVHC 27).

Hexabromocyclododecane can be absorbed into the human body and into the bloodstream. In 1986, 1993, and 2001 samples of breast milk were taken from nursing mothers in Sweden and tested for Hexabromocyclododecane (HBCDD but also abbreviated as HBCD by some). All samples contained the molecule. Milk and blood was also taken from mothers in Mexico and also found to contain HBCDD (Proposal 13). Similar tests were conducted in Japan where they produce HBCDD and use it on an average of 200 pounds per person. Levels of HBCDD in Japanese mothers were considerably higher than those found in the other women. The conclusion being that longer period of contact with Hexabromocyclododecane increases its presence in the body. In experimentation wherein groups of rats were injected with varying levels of HBCDD, it was found that there was a good chance that the higher-dosed animals would have more difficulty in reproducing and that their offspring would have greater difficulty in surviving the first few days after birth. In some of the male rats, the testes on male offspring were so small that the animal could never reproduce (Proposal 35). If similar tests were conducted on human beings, similar results might very well be discovered creating a direct link between HBCDD and certain deformities. Data alludes to the potential for HBCDD to affect the reproductive system, the liver, and the brain (SVHC 28).